Internet DRAFT - draft-ietf-alto-path-vector
draft-ietf-alto-path-vector
ALTO K. Gao
Internet-Draft Sichuan University
Intended status: Experimental Y. Lee
Expires: 21 September 2022 Samsung
S. Randriamasy
Nokia Bell Labs
Y.R. Yang
Yale University
J. Zhang
Tongji University
20 March 2022
An ALTO Extension: Path Vector
draft-ietf-alto-path-vector-25
Abstract
This document is an extension to the base Application-Layer Traffic
Optimization (ALTO) protocol. It extends the ALTO Cost Map and ALTO
Property Map services so that an application can decide which
endpoint(s) to connect based on not only numerical/ordinal cost
values but also fine-grained abstract information of the paths. This
is useful for applications whose performance is impacted by specified
components of a network on the end-to-end paths, e.g., they may infer
that several paths share common links and prevent traffic bottlenecks
by avoiding such paths. This extension introduces a new abstraction
called Abstract Network Element (ANE) to represent these components
and encodes a network path as a vector of ANEs. Thus, it provides a
more complete but still abstract graph representation of the
underlying network(s) for informed traffic optimization among
endpoints.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
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This Internet-Draft will expire on 21 September 2022.
Copyright Notice
Copyright (c) 2022 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
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Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Requirements Languages . . . . . . . . . . . . . . . . . . . 6
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6
4. Requirements and Use Cases . . . . . . . . . . . . . . . . . 7
4.1. Design Requirements . . . . . . . . . . . . . . . . . . . 7
4.2. Sample Use Cases . . . . . . . . . . . . . . . . . . . . 10
4.2.1. Exposing Network Bottlenecks . . . . . . . . . . . . 11
4.2.2. Resource Exposure for CDN and Service Edge . . . . . 15
5. Path Vector Extension: Overview . . . . . . . . . . . . . . . 17
5.1. Abstract Network Element (ANE) . . . . . . . . . . . . . 18
5.1.1. ANE Entity Domain . . . . . . . . . . . . . . . . . . 19
5.1.2. Ephemeral and Persistent ANEs . . . . . . . . . . . . 19
5.1.3. Property Filtering . . . . . . . . . . . . . . . . . 20
5.2. Path Vector Cost Type . . . . . . . . . . . . . . . . . . 20
5.3. Multipart Path Vector Response . . . . . . . . . . . . . 21
5.3.1. Identifying the Media Type of the Root Object . . . . 22
5.3.2. References to Part Messages . . . . . . . . . . . . . 22
6. Specification: Basic Data Types . . . . . . . . . . . . . . . 23
6.1. ANE Name . . . . . . . . . . . . . . . . . . . . . . . . 23
6.2. ANE Entity Domain . . . . . . . . . . . . . . . . . . . . 23
6.2.1. Entity Domain Type . . . . . . . . . . . . . . . . . 23
6.2.2. Domain-Specific Entity Identifier . . . . . . . . . . 23
6.2.3. Hierarchy and Inheritance . . . . . . . . . . . . . . 23
6.2.4. Media Type of Defining Resource . . . . . . . . . . . 23
6.3. ANE Property Name . . . . . . . . . . . . . . . . . . . . 24
6.4. Initial ANE Property Types . . . . . . . . . . . . . . . 24
6.4.1. Maximum Reservable Bandwidth . . . . . . . . . . . . 24
6.4.2. Persistent Entity ID . . . . . . . . . . . . . . . . 25
6.4.3. Examples . . . . . . . . . . . . . . . . . . . . . . 25
6.5. Path Vector Cost Type . . . . . . . . . . . . . . . . . . 26
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6.5.1. Cost Metric: ane-path . . . . . . . . . . . . . . . . 26
6.5.2. Cost Mode: array . . . . . . . . . . . . . . . . . . 27
6.6. Part Resource ID and Part Content ID . . . . . . . . . . 27
7. Specification: Service Extensions . . . . . . . . . . . . . . 27
7.1. Notations . . . . . . . . . . . . . . . . . . . . . . . . 27
7.2. Multipart Filtered Cost Map for Path Vector . . . . . . . 28
7.2.1. Media Type . . . . . . . . . . . . . . . . . . . . . 28
7.2.2. HTTP Method . . . . . . . . . . . . . . . . . . . . . 28
7.2.3. Accept Input Parameters . . . . . . . . . . . . . . . 28
7.2.4. Capabilities . . . . . . . . . . . . . . . . . . . . 29
7.2.5. Uses . . . . . . . . . . . . . . . . . . . . . . . . 30
7.2.6. Response . . . . . . . . . . . . . . . . . . . . . . 30
7.3. Multipart Endpoint Cost Service for Path Vector . . . . . 34
7.3.1. Media Type . . . . . . . . . . . . . . . . . . . . . 34
7.3.2. HTTP Method . . . . . . . . . . . . . . . . . . . . . 34
7.3.3. Accept Input Parameters . . . . . . . . . . . . . . . 34
7.3.4. Capabilities . . . . . . . . . . . . . . . . . . . . 35
7.3.5. Uses . . . . . . . . . . . . . . . . . . . . . . . . 35
7.3.6. Response . . . . . . . . . . . . . . . . . . . . . . 35
8. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 39
8.1. Sample Setup . . . . . . . . . . . . . . . . . . . . . . 39
8.2. Information Resource Directory . . . . . . . . . . . . . 39
8.3. Multipart Filtered Cost Map . . . . . . . . . . . . . . . 42
8.4. Multipart Endpoint Cost Service Resource . . . . . . . . 43
8.5. Incremental Updates . . . . . . . . . . . . . . . . . . . 48
8.6. Multi-cost . . . . . . . . . . . . . . . . . . . . . . . 50
9. Compatibility with Other ALTO Extensions . . . . . . . . . . 52
9.1. Compatibility with Legacy ALTO Clients/Servers . . . . . 53
9.2. Compatibility with Multi-Cost Extension . . . . . . . . . 53
9.3. Compatibility with Incremental Update . . . . . . . . . . 53
9.4. Compatibility with Cost Calendar . . . . . . . . . . . . 53
10. General Discussions . . . . . . . . . . . . . . . . . . . . . 54
10.1. Constraint Tests for General Cost Types . . . . . . . . 54
10.2. General Multi-Resource Query . . . . . . . . . . . . . . 54
11. Security Considerations . . . . . . . . . . . . . . . . . . . 55
12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 57
12.1. ALTO Cost Metric Registry . . . . . . . . . . . . . . . 57
12.2. ALTO Cost Mode Registry . . . . . . . . . . . . . . . . 58
12.3. ALTO Entity Domain Type Registry . . . . . . . . . . . . 58
12.4. ALTO Entity Property Type Registry . . . . . . . . . . . 59
12.4.1. New ANE Property Type: Maximum Reservable
Bandwidth . . . . . . . . . . . . . . . . . . . . . . 59
12.4.2. New ANE Property Type: Persistent Entity ID . . . . 60
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 60
13.1. Normative References . . . . . . . . . . . . . . . . . . 60
13.2. Informative References . . . . . . . . . . . . . . . . . 61
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 64
Appendix B. Revision Logs (To be removed before publication) . . 64
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B.1. Changes since -20 . . . . . . . . . . . . . . . . . . . . 64
B.2. Changes since -19 . . . . . . . . . . . . . . . . . . . . 65
B.3. Changes since -18 . . . . . . . . . . . . . . . . . . . . 65
B.4. Changes since -17 . . . . . . . . . . . . . . . . . . . . 65
B.5. Changes since -16 . . . . . . . . . . . . . . . . . . . . 65
B.6. Changes since -15 . . . . . . . . . . . . . . . . . . . . 65
B.7. Changes since -14 . . . . . . . . . . . . . . . . . . . . 65
B.8. Changes since -13 . . . . . . . . . . . . . . . . . . . . 66
B.9. Changes since -12 . . . . . . . . . . . . . . . . . . . . 66
B.10. Changes since -11 . . . . . . . . . . . . . . . . . . . . 66
B.11. Changes since -10 . . . . . . . . . . . . . . . . . . . . 66
B.12. Changes since -09 . . . . . . . . . . . . . . . . . . . . 67
B.13. Changes since -08 . . . . . . . . . . . . . . . . . . . . 67
B.14. Changes Since Version -06 . . . . . . . . . . . . . . . . 67
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 68
1. Introduction
Network performance metrics are crucial to assess the Quality of
Experience (QoE) of applications. The ALTO protocol allows Internet
Service Providers (ISPs) to provide guidance, such as topological
distance between different end hosts, to overlay applications. Thus,
the overlay applications can potentially improve the perceived QoE by
better orchestrating their traffic to utilize the resources in the
underlying network infrastructure.
Existing ALTO Cost Map (Section 11.2.3 of [RFC7285]) and Endpoint
Cost Service (Section 11.5 of [RFC7285]) provide only cost
information on an end-to-end path defined by its <source,
destination> endpoints: The base protocol [RFC7285] allows the
services to expose the topological distances of end-to-end paths,
while various extensions have been proposed to extend the capability
of these services, e.g., to express other performance metrics
[I-D.ietf-alto-performance-metrics], to query multiple costs
simultaneously [RFC8189], and to obtain the time-varying values
[RFC8896].
While the existing extensions are sufficient for many overlay
applications, the QoE of some overlay applications depends not only
on the cost information of end-to-end paths, but also on particular
components of a network on the paths and their properties. For
example, job completion time, which is an important QoE metric for a
large-scale data analytics application, is impacted by shared
bottleneck links inside the carrier network as link capacity may
impact the rate of data input/output to the job. We refer to such
components of a network as Abstract Network Elements (ANE).
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Predicting such information can be very complex without the help of
ISPs, for example, [BOXOPT] has shown that finding the optimal
bandwidth reservation for multiple flows can be NP-hard without
further information than whether a reservation succeeds. With proper
guidance from the ISP, an overlay application may be able to schedule
its traffic for better QoE. In the meantime, it may be helpful as
well for ISPs if applications could avoid using bottlenecks or
challenging the network with poorly scheduled traffic.
Despite the claimed benefits, ISPs are not likely to expose raw
details on their network paths: first for the sake of topology hiding
requirement, second because it may increase volume and computation
overhead, and last because applications do not necessarily need all
the network path details and are likely not able to understand them.
Therefore, it is beneficial for both ISPs and applications if an ALTO
server provides ALTO clients with an "abstract network state" that
provides the necessary information to applications, while hiding the
network complexity and confidential information. An "abstract
network state" is a selected set of abstract representations of
Abstract Network Elements traversed by the paths between <source,
destination> pairs combined with properties of these Abstract Network
Elements that are relevant to the overlay applications' QoE. Both an
application via its ALTO client and the ISP via the ALTO server can
achieve better confidentiality and resource utilization by
appropriately abstracting relevant Abstract Network Elements. Server
scalability can also be improved by combining Abstract Network
Elements and their properties in a single response.
This document extends [RFC7285] to allow an ALTO server to convey
"abstract network state", for paths defined by their <source,
destination> pairs. To this end, it introduces a new cost type
called "Path Vector" following the cost metric registration specified
in [RFC7285] and the updated cost mode registration specified in
[I-D.bw-alto-cost-mode]. A Path Vector is an array of identifiers
that identifies an Abstract Network Element, which can be associated
with various properties. The associations between ANEs and their
properties are encoded in an ALTO information resource called Unified
Property Map, which is specified in
[I-D.ietf-alto-unified-props-new].
For better confidentiality, this document aims to minimize
information exposure of an ALTO server when providing Path Vector
service. In particular, this document enables and recommends that
first ANEs are constructed on demand, and second an ANE is only
associated with properties that are requested by an ALTO client. A
Path Vector response involves two ALTO Maps: the Cost Map that
contains the Path Vector results and the up-to-date Unified Property
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Map that contains the properties requested for these ANEs. To
enforce consistency and improve server scalability, this document
uses the "multipart/related" content type defined in [RFC2387] to
return the two maps in a single response.
As a single ISP may not have the knowledge of the full Internet paths
between arbitrary endpoints, this document is mainly applicable 1)
when there is a single ISP between the requested source and
destination PIDs or endpoints, for example, ISP-hosted CDN/edge,
tenant interconnection in a single public cloud platform, etc.; or 2)
when the Path Vectors are generated from end-to-end measurement data.
2. Requirements Languages
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
When the words appear in lower case, they are to be interpreted with
their natural language meanings.
3. Terminology
This document extends the ALTO base protocol [RFC7285] and the
Unified Property Map extension [I-D.ietf-alto-unified-props-new]. In
addition to the terms defined in these documents, this document also
uses the following additional terms:
Abstract Network Element (ANE): An abstract representation for a
component in a network that handles data packets and whose
properties can potentially have an impact on the end-to-end
performance of traffic. An ANE can be a physical device such as a
router, a link or an interface, or an aggregation of devices such
as a subnetwork or a data center.
The definition of Abstract Network Element is similar to Network
Element defined in [RFC2216] in the sense that they both provide
an abstract representation of specific components of a network.
However, they have different criteria on how these particular
components are selected. Specifically, a Network Element requires
the components to be capable of exercising QoS control, while
Abstract Network Element only requires the components to have an
impact on the end-to-end performance.
ANE Name: A string that uniquely identifies an ANE in a specific
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scope. An ANE can be constructed either statically in advance or
on demand based on the requested information. Thus, different
ANEs may only be valid within a particular scope, either ephemeral
or persistent. Within each scope, an ANE is uniquely identified
by an ANE Name, as defined in Section 6.1. Note that an ALTO
client must not assume ANEs in different scopes but with the same
ANE Name refer to the same component(s) of the network.
Path Vector: Path Vector, or ANE Path Vector, refers to a JSON array
of ANE Names. It is a generalization of BGP path vector. While
standard BGP path vector (Section 5.1.2 of [RFC4271]) specifies a
sequence of autonomous systems for a destination IP prefix, the
Path Vector defined in this extension specifies a sequence of ANEs
either for a source Provider-Defined Identifier (PID) and a
destination PID as in the CostMapData (11.2.3.6 in [RFC7285]), or
for a source endpoint and a destination endpoint as in the
EndpointCostMapData object (Section 11.5.1.6 of [RFC7285]).
Path Vector resource: An ALTO information resource (Section 8.1 of
[RFC7285]) which supports the extension defined in this document.
Path Vector cost type: A special cost type, which is specified in
Section 6.5. When this cost type is present in an IRD entry, it
indicates that the information resource is a Path Vector resource.
When this cost type is present in a Filtered Cost Map request or
an Endpoint Cost Service request, it indicates each cost value
must be interpreted as a Path Vector.
Path Vector request: The POST message sent to an ALTO Path Vector
resource.
Path Vector response: A Path Vector response refers to the
multipart/related message returned by a Path Vector resource.
4. Requirements and Use Cases
4.1. Design Requirements
This section gives an illustrative example of how an overlay
application can benefit from the extension defined in this document.
Assume that an application has control over a set of flows, which may
go through shared links/nodes and share bottlenecks. The application
seeks to schedule the traffic among multiple flows to get better
performance. The constraints of feasible rate allocations of those
flows will benefit the scheduling. However, Cost Maps as defined in
[RFC7285] can not reveal such information.
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Specifically, consider a network as shown in Figure 1. The network
has 7 switches (sw1 to sw7) forming a dumb-bell topology. Switches
"sw1", "sw2", "sw3" and "sw4" are access switches, and sw5-sw7 form
the backbone. End hosts eh1 to eh4 are connected to access switches
sw1 to sw4 respectively. Assume that the bandwidth of link eh1 ->
sw1 and link sw1 -> sw5 is 150 Mbps, and the bandwidth of the other
links is 100 Mbps.
+-----+
| |
--+ sw6 +--
/ | | \
PID1 +-----+ / +-----+ \ +-----+ PID2
eh1__| |_ / \ ____| |__eh2
192.0.2.2 | sw1 | \ +--|--+ +--|--+ / | sw2 | 192.0.2.3
+-----+ \ | | | |/ +-----+
\_| sw5 +---------+ sw7 |
PID3 +-----+ / | | | |\ +-----+ PID4
eh3__| |__/ +-----+ +-----+ \____| |__eh4
192.0.2.4 | sw3 | | sw4 | 192.0.2.5
+-----+ +-----+
bw(eh1--sw1) = bw(sw1--sw5) = 150 Mbps
bw(eh2--sw2) = bw(eh3--sw3) = bw(eh4--sw4) = 100 Mbps
bw(sw1--sw5) = bw(sw3--sw5) = bw(sw2--sw7) = bw(sw4--sw7) = 100 Mbps
bw(sw5--sw6) = bw(sw5--sw7) = bw(sw6--sw7) = 100 Mbps
Figure 1: Raw Network Topology
The base ALTO topology abstraction of the network is shown in
Figure 2. Assume the cost map returns an hypothetical cost type
representing the available bandwidth between a source and a
destination.
+----------------------+
{eh1} | | {eh2}
PID1 | | PID2
+------+ +------+
| |
| |
{eh3} | | {eh4}
PID3 | | PID4
+------+ +------+
| |
+----------------------+
Figure 2: Base Topology Abstraction
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Now assume the application wants to maximize the total rate of the
traffic among a set of <source, destination> pairs, say "eh1 -> eh2"
and "eh1 -> eh4". Let "x" denote the transmission rate of "eh1 ->
eh2" and "y" denote the rate of "eh1 -> eh4". The objective function
is
max(x + y).
With the ALTO Cost Map, the cost between PID1 and PID2 and between
PID1 and PID4 will both be 100 Mbps. The client can get a capacity
region of
x <= 100 Mbps,
y <= 100 Mbps.
With this information, the client may mistakenly think it can achieve
a maximum total rate of 200 Mbps. However, this rate is infeasible,
as there are only two potential cases:
* Case 1: "eh1 -> eh2" and "eh1 -> eh4" take different path segments
from "sw5" to "sw7". For example, if "eh1 -> eh2" uses path "eh1
-> sw1 -> sw5 -> sw6 -> sw7 -> sw2 -> eh2" and "eh1 -> eh4" uses
path "eh1 -> sw1 -> sw5 -> sw7 -> sw4 -> eh4", then the shared
bottleneck links are "eh1 -> sw1" and "sw1 -> sw5". In this case,
the capacity region is:
x <= 100 Mbps
y <= 100 Mbps
x + y <= 150 Mbps
and the real optimal total rate is 150 Mbps.
* Case 2: "eh1 -> eh2" and "eh1 -> eh4" take the same path segment
from "sw5" to "sw7". For example, if "eh1 -> eh2" uses path "eh1
-> sw1 -> sw5 -> sw7 -> sw2 -> eh2" and "eh1 -> eh4" also uses
path "eh1 -> sw1 -> sw5 -> sw7 -> sw4 -> eh4", then the shared
bottleneck link is "sw5 -> sw7". In this case, the capacity
region is:
x <= 100 Mbps
y <= 100 Mbps
x + y <= 100 Mbps
and the real optimal total rate is 100 Mbps.
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Clearly, with more accurate and fine-grained information, the
application can gain a better prediction of its traffic and may
orchestrate its resources accordingly. However, to provide such
information, the network needs to expose abstract information beyond
the simple cost map abstraction. In particular:
* The ALTO server must expose abstract information about the network
paths that are traversed by the traffic between a source and a
destination beyond a simple numerical value, which allows the
overlay application to distinguish between Cases 1 and 2 and to
compute the optimal total rate accordingly.
* The ALTO server must allow the client to distinguish the common
ANE shared by "eh1 -> eh2" and "eh1 -> eh4", e.g., "eh1 - sw1" and
"sw1 - sw5" in Case 1.
* The ALTO server must expose abstract information on the properties
of the ANEs used by "eh1 -> eh2" and "eh1 -> eh4". For example,
an ALTO server can either expose the available bandwidth between
"eh1 - sw1", "sw1 - sw5", "sw5 - sw7", "sw5 - sw6", "sw6 - sw7",
"sw7 - sw2", "sw7 - sw4", "sw2 - eh2", "sw4 - eh4" in Case 1, or
expose 3 abstract elements "A", "B" and "C", which represent the
linear constraints that define the same capacity region in Case 1.
In general, we can conclude that to support the multiple flow
scheduling use case, the ALTO framework must be extended to satisfy
the following additional requirements:
AR1: An ALTO server must provide the ANEs that are important to
assess the QoE of the overlay application on the path of a
<source, destination> pair.
AR2: An ALTO server must provide information to identify how ANEs
are shared on the paths of different <source, destination> pairs.
AR3: An ALTO server must provide information on the properties that
are important to assess the QoE of the application for ANEs.
The extension defined in this document specifies a solution to expose
such abstract information.
4.2. Sample Use Cases
While the multiple flow scheduling problem is used to help identify
the additional requirements, the extension defined in this document
can be applied to a wide range of applications. This section
highlights some use cases that are reported.
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4.2.1. Exposing Network Bottlenecks
An important use case of the Path Vector extension is to expose
network bottlenecks. Applications which need to perform large scale
data transfers can benefit from being aware of the resource
constraints exposed by this extension even if they have different
objectives. One such example is the Worldwide LHC Computing Grid
(WLCG), the largest example of a distributed computation
collaboration in the research and education world.
Figure 3 illustrates an example of using ALTO Path Vector as an
interface between the job optimizer for a data analytics system and
the network manager. In particular, we assume the objective of the
job optimizer is to minimize the job completion time.
In such a setting, the network-aware job optimizer (e.g., [CLARINET])
takes a query and generates multiple query execution plans (QEP). It
can encode the QEPs as Path Vector requests that are send to an ALTO
server. The ALTO server obtains the routing information for the
flows in a QEP and finds links, routers, or middleboxes (e.g., a
stateful firewall) that can potentially become bottlenecks of the QEP
(e.g., see [NOVA] and [G2] for mechanisms to identify bottleneck
links under different settings). The resource constraint information
is encoded in a Path Vector response and returned to the ALTO client.
With the network resource constraints, the job optimizer may choose
the QEP with the optimal job completion time to be executed. It must
be noted that the ALTO framework itself does not offer the capability
to control the traffic. However, certain network managers may offer
ways to enforce resource guarantees, such as on-demand tunnels (e.g.,
[SWAN]), demand vector (e.g., [HUG], [UNICORN]), etc. The traffic
control interfaces and mechanisms are out of the scope of this
document.
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Data schema Queries
| |
\ /
+-------------+ +-----------------+
| ALTO Client | <===============> | Job Optimizer |
+-------------+ +-----------------+
PV | ^ PV |
Request | | Response |
| | On-demand resource |
(Data | | (Network allocation, demand |
Transfer | | Resource vector, etc. |
Intents) | | Constraints) (Non-ALTO interfaces)|
v | v
+-------------+ +-----------------+
| ALTO Server | <===============> | Network Manager |
+-------------+ +-----------------+
/ | \
| | |
WAN DC1 DC2
Figure 3: Example Use Case for Data Analytics
Another example is as illustrated in Figure 4. Consider a network
consisting of multiple sites and a non-blocking core network, i.e.,
the links in the core network have sufficient bandwidth that they
will not become the bottleneck of the data transfers.
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On-going transfers New transfer requests
\----\ |
| |
v v
+-------------+ +---------------+
| ALTO Client | <===========> | Data Transfer |
+-------------+ | Scheduler |
^ | ^ | PV request +---------------+
| | | \--------------\
| | \--------------\ |
| v PV response | v
+-------------+ +-------------+
| ALTO Server | | ALTO Server |
+-------------+ +-------------+
|| ||
+---------+ +---------+
| Network | | Network |
| Manager | | Manager |
+---------+ +---------+
. .
. _~_ __ . . .
. ( )( ) .___
~v~v~ /--( )------------( )
( )-----/ ( ) ( )
~w~w~ ~^~^~^~ ~v~v~
Site 1 Non-blocking Core Site 2
Figure 4: Example Use Case for Cross-site Bottleneck Discovery
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Site 1:
[c]
.
........................................> [d]
+---+ 10 Gbps +---+ 10 Gbps +----+ 50 Gbps
| A |---------| B |---------| GW |--------- Core
+---+ +---+ +----+
...................
. .
. v
[a] [b]
Site 2:
[d] <........................................ [c]
+---+ 5 Gbps +---+ 10 Gbps +----+ 20 Gbps
| X |--------| Y |---------| GW |--------- Core
+---+ +---+ +----+
....................
. .
. v
[e] [f]
Figure 5: Example: Three Flows in Two Sites
With the Path Vector extension, a site can reveal the bottlenecks
inside its own network with necessary information (such as link
capacities) to the ALTO client, instead of providing the full
topology and routing information, or no bottleneck information at
all. The bottleneck information can be used to analyze the impact of
adding/removing data transfer flows, e.g., using the [G2] framework.
For example, assume hosts "a", "b", "c" are in site 1 and hosts "d",
"e", "f" are in site 2, and there are 3 flows in two sites: "a -> b",
"c -> d", "e -> f". For these flows, site 1 returns:
a: { b: [ane1] },
c: { d: [ane1, ane2, ane3] }
ane1: bw = 10 Gbps (link: A->B)
ane2: bw = 10 Gbps (link: B->GW)
ane3: bw = 50 Gbps (link: GW->Core)
and site 2 returns:
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c: { d: [anei, aneii, aneiii] }
e: { f: [aneiv] }
anei: bw = 5 Gbps (link Y->X)
aneii: bw = 10 Gbps (link GW->Y)
aneiii: bw = 20 Gbps (link Core->GW)
aneiv: bw = 10 Gbps (link Y->GW)
With the information, the data transfer scheduler can use algorithms
such as the theory on bottleneck structure [G2] to predict the
potential throughput of the flows.
4.2.2. Resource Exposure for CDN and Service Edge
A growing trend in today's applications (2021) is to bring storage
and computation closer to the end users for better QoE, such as
Content Delivery Network (CDN), AR/VR, and cloud gaming, as reported
in various documents (e.g., [SEREDGE] and [MOWIE]). Internet Service
Providers may deploy multiple layers of CDN caches, or more generally
service edges, with different latency and available resources
including number of CPU cores, memory, and storage.
For example, Figure 6 illustrates a typical edge-cloud scenario where
memory is measured in Gigabytes (G) and storage is measured in
Terabytes (T). The "on-premise" edge nodes are closest to the end
hosts and have the smallest latency, and the site-radio edge node and
access central office (CO) have larger latency but more available
resources.
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+-------------+ +----------------------+
| ALTO Client | <==========> | Application Provider |
+-------------+ +----------------------+
PV | ^ PV |
Request | | Response | Resource allocation,
| | | service establishment,
(End hosts | | (Edge nodes | etc.
and cloud | | and metrics) |
servers) | | |
v | v
+-------------+ +---------------------+
| ALTO Server | <=========> | Cloud-Edge Provider |
+-------------+ +---------------------+
____________________________________/\___________
/ \
| (((o |
|
/_\ _~_ __ __
a (/\_/\) ( ) ( )~( )_
\ /------( )---------( )----\\---( )
_|_ / (______) (___) ( )
|_| -/ Site-radio Access CO (__________)
/---\ Edge Node 1 | Cloud DC
On premise |
/---------/
(((o /
| /
Site-radio /_\ /
Edge Node 2(/\_/\)-----/
/(_____)\
___ / \ ---
b--|_| -/ \--|_|--c
/---\ /---\
On premise On premise
Figure 6: Example Use Case for Service Edge Exposure
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a: { b: [ane1, ane2, ane3, ane4, ane5],
c: [ane1, ane2, ane3, ane4, ane6],
DC: [ane1, ane2, ane3] }
b: { c: [ane5, ane4, ane6], DC: [ane5, ane4, ane3] }
ane1: latency=5ms cpu=2 memory=8G storage=10T
(on premise, a)
ane2: latency=20ms cpu=4 memory=8G storage=10T
(Site-radio Edge Node 1)
ane3: latency=100ms cpu=8 memory=128G storage=100T
(Access CO)
ane4: latency=20ms cpu=4 memory=8G storage=10T
(Site-radio Edge Node 2)
ane5: latency=5ms cpu=2 memory=8G storage=10T
(on premise, b)
ane6: latency=5ms cpu=2 memory=8G storage=10T
(on premise, c)
Figure 7: Example Service Edge Query Results
With the extension defined in this document, an ALTO server can
selectively reveal the CDNs and service edges that reside along the
paths between different end hosts and/or the cloud servers, together
with their properties such as capabilities (e.g., storage, GPU) and
available Service Level Agreement (SLA) plans. See Figure 7 for an
example where the query is made for sources [a, b] and destinations
[b, c, DC]. Here each ANE represents a service edge and the
properties include access latency, available resources, etc. Note
the properties here are only used for illustration purposes and are
not part of this extension.
With the service edge information, an ALTO client may better conduct
CDN request routing or offload functionalities from the user
equipment to the service edge, with considerations on customized
quality of experience.
5. Path Vector Extension: Overview
This section provides a non-normative overview of the Path Vector
extension defined in this document. It is assumed that the readers
are familiar with both the base protocol [RFC7285] and the Unified
Property Map extension [I-D.ietf-alto-unified-props-new].
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To satisfy the additional requirements listed in Section 4.1, this
extension:
1. introduces the concept of Abstract Network Element (ANE) as the
abstraction of components in a network whose properties may have
an impact on the end-to-end performance of the traffic handled by
those components,
2. extends the Cost Map and Endpoint Cost Service to convey the ANEs
traversed by the path of a <source, destination> pair as Path
Vectors, and
3. uses the Unified Property Map to convey the association between
the ANEs and their properties.
Thus, an ALTO client can learn about the ANEs that are important to
assess the QoE of different <source, destination> pairs by
investigating the corresponding Path Vector value (AR1), identify
common ANEs if an ANE appears in the Path Vectors of multiple
<source, destination> pairs (AR2), and retrieve the properties of the
ANEs by searching the Unified Property Map (AR3).
5.1. Abstract Network Element (ANE)
This extension introduces ANE as an indirect and network-agnostic way
to specify a component or an aggregation of components of a network
whose properties have an impact on the end-to-end performance for
application traffic between endpoints.
ANEs allow ALTO servers to focus on common properties of different
types of network components. For example, the throughput of a flow
can be constrained by different components in a network: the capacity
of a physical link, the maximum throughput of a firewall, the
reserved bandwidth of an MPLS tunnel, etc. See the example below,
assume the throughput of the firewall is 100 Mbps and the capacity
for link (A, B) is also 100 Mbps, they result in the same constraint
on the total throughput of f1 and f2. Thus, they are identical when
treated as an ANE.
f1 | ^ f1
| | ----------------->
+----------+ +---+ +---+
| Firewall | | A |-----| B |
+----------+ +---+ +---+
| | ----------------->
v | f2 f2
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When an ANE is defined by an ALTO server, it is assigned an
identifier by the ALTO server, i.e., a string of type ANEName as
specified in Section 6.1, and a set of associated properties.
5.1.1. ANE Entity Domain
In this extension, the associations between ANE and the properties
are conveyed in a Unified Property Map. Thus, ANEs must constitute an
entity domain (Section 5.1 of [I-D.ietf-alto-unified-props-new]), and
each ANE property must be an entity property (Section 5.2 of
[I-D.ietf-alto-unified-props-new]).
Specifically, this document defines a new entity domain called "ane"
as specified in Section 6.2 and defines two initial properties for
the ANE entity domain.
5.1.2. Ephemeral and Persistent ANEs
By design, ANEs are ephemeral and not to be used in further requests
to other ALTO resources. More precisely, the corresponding ANE names
are no longer valid beyond the scope of a Path Vector response or the
incremental update stream for a Path Vector request. Compared with
globally unique ANE names, ephemeral ANE has several benefits
including better privacy of the ISP's internal structure and more
flexible ANE computation.
For example, an ALTO server may define an ANE for each aggregated
bottleneck link between the sources and destinations specified in the
request. For requests with different sources and destinations, the
bottlenecks may be different but can safely reuse the same ANE names.
The client can still adjust its traffic based on the information but
is difficult to infer the underlying topology with multiple queries.
However, sometimes an ISP may intend to selectively reveal some
"persistent" network components which, opposite to being ephemeral,
have a longer life cycle. For example, an ALTO server may define an
ANE for each service edge cluster. Once a client chooses to use a
service edge, e.g., by deploying some user-defined functions, it may
want to stick to the service edge to avoid the complexity of state
transition or synchronization, and continuously query the properties
of the edge cluster.
This document provides a mechanism to expose such network components
as persistent ANEs. A persistent ANE has a persistent ID that is
registered in a Property Map, together with their properties. See
Section 6.2.4 and Section 6.4.2 for more detailed instructions on how
to identify ephemeral ANEs and persistent ANEs.
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5.1.3. Property Filtering
Resource-constrained ALTO clients (see Section 4.1.2 of [RFC7285])
may benefit from the filtering of Path Vector query results at the
ALTO server, as an ALTO client may only require a subset of the
available properties.
Specifically, the available properties for a given resource are
announced in the Information Resource Directory as a new capability
called "ane-property-names". The properties selected by a client as
being of interest are specified in the subsequent Path Vector queries
using the filter called 'ane-property-names'. The response includes
and only includes the selected properties for the ANEs in the
response.
The "ane-property-names" capability for Cost Map and for Endpoint
Cost Service is specified in Section 7.2.4 and Section 7.3.4
respectively. The "ane-property-names" filter for Cost Map and
Endpoint Cost Service is specified in Section 7.2.3 and Section 7.3.3
accordingly.
5.2. Path Vector Cost Type
For an ALTO client to correctly interpret the Path Vector, this
extension specifies a new cost type called the Path Vector cost type.
The Path Vector cost type must convey both the interpretation and
semantics in the "cost-mode" and "cost-metric" respectively.
Unfortunately, a single "cost-mode" value cannot fully specify the
interpretation of a Path Vector, which is a compound data type. For
example, in programming languages such as C++ where there existed a
JSON array type named JSONArray, a Path Vector will have the type of
JSONArray<ANEName>.
Instead of extending the "type system" of ALTO, this document takes a
simple and backward compatible approach. Specifically, the "cost-
mode" of the Path Vector cost type is "array", which indicates the
value is a JSON array. Then, an ALTO client must check the value of
the "cost-metric". If the value is "ane-path", it means that the
JSON array should be further interpreted as a path of ANENames.
The Path Vector cost type is specified in Section 6.5.
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5.3. Multipart Path Vector Response
For a basic ALTO information resource, a response contains only one
type of ALTO resources, e.g., Network Map, Cost Map, or Property Map.
Thus, only one round of communication is required: An ALTO client
sends a request to an ALTO server, and the ALTO server returns a
response, as shown in Figure 8.
ALTO client ALTO server
|-------------- Request ---------------->|
|<------------- Response ----------------|
Figure 8: A Typical ALTO Request and Response
The extension defined in this document, on the other hand, involves
two types of information resources: Path Vectors conveyed in an
InfoResourceCostMap (defined in Section 11.2.3.6 of [RFC7285]) or an
InfoResourceEndpointCostMap (defined in Section 11.5.1.6 of
[RFC7285]), and ANE properties conveyed in an InfoResourceProperties
(defined in Section 7.6 of [I-D.ietf-alto-unified-props-new]).
Instead of two consecutive message exchanges, the extension defined
in this document enforces one round of communication. Specifically,
the ALTO client must include the source and destination pairs and the
requested ANE properties in a single request, and the ALTO server
must return a single response containing both the Path Vectors and
properties associated with the ANEs in the Path Vectors, as shown in
Figure 9. Since the two parts are bundled together in one response
message, their orders are interchangeable. See Section 7.2.6 and
Section 7.3.6 for details.
ALTO client ALTO server
|------------- PV Request -------------->|
|<----- PV Response (Cost Map Part) -----|
|<--- PV Response (Property Map Part) ---|
Figure 9: The Path Vector Extension Request and Response
This design is based on the following considerations:
1. ANEs may be constructed on demand, and potentially based on the
requested properties (See Section 5.1 for more details). If
sources and destinations are not in the same request as the
properties, an ALTO server either cannot construct ANEs on-
demand, or must wait until both requests are received.
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2. As ANEs may be constructed on demand, mappings of each ANE to its
underlying network devices and resources can be specific to the
request. In order to respond to the Property Map request
correctly, an ALTO server must store the mapping of each Path
Vector request until the client fully retrieves the property
information. The "stateful" behavior may substantially harm the
server scalability and potentially lead to Denial-of-Service
attacks.
One approach to realize the one-round communication is to define a
new media type to contain both objects, but this violates modular
design. This document follows the standard-conforming usage of
"multipart/related" media type defined in [RFC2387] to elegantly
combine the objects. Path Vectors are encoded in an
InfoResourceCostMap or an InfoResourceEndpointCostMap, and the
Property Map is encoded in an InfoResourceProperties. They are
encapsulated as parts of a multipart message. The modular
composition allows ALTO servers and clients to reuse the data models
of the existing information resources. Specifically, this document
addresses the following practical issues using "multipart/related".
5.3.1. Identifying the Media Type of the Root Object
ALTO uses media type to indicate the type of an entry in the
Information Resource Directory (IRD) (e.g., "application/alto-
costmap+json" for Cost Map and "application/alto-endpointcost+json"
for Endpoint Cost Service). Simply putting "multipart/related" as
the media type, however, makes it impossible for an ALTO client to
identify the type of service provided by related entries.
To address this issue, this document uses the "type" parameter to
indicate the root object of a multipart/related message. For a Cost
Map resource, the "media-type" field in the IRD entry is "multipart/
related" with the parameter "type=application/alto-costmap+json"; for
an Endpoint Cost Service, the parameter is "type=application/alto-
endpointcost+json".
5.3.2. References to Part Messages
As the response of a Path Vector resource is a multipart message with
two different parts, it is important that each part can be uniquely
identified. Following the designs of [RFC8895], this extension
requires that an ALTO server assigns a unique identifier to each part
of the multipart response message. This identifier, referred to as a
Part Resource ID (See Section 6.6 for details), is present in the
part message's "Content-ID" header. By concatenating the Part
Resource ID to the identifier of the Path Vector request, an ALTO
server/client can uniquely identify the Path Vector Part or the
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Property Map part.
6. Specification: Basic Data Types
6.1. ANE Name
An ANE Name is encoded as a JSON string with the same format as that
of the type PIDName (Section 10.1 of [RFC7285]).
The type ANEName is used in this document to indicate a string of
this format.
6.2. ANE Entity Domain
The ANE entity domain associates property values with the Abstract
Network Elements in a Property Map. Accordingly, the ANE entity
domain always depends on a Property Map.
It must be noted that the term "domain" here does not refer to a
network domain. Rather, it is inherited from the "entity domain"
defined in Sec 3.2 in [I-D.ietf-alto-unified-props-new] that
represents the set of valid entities defined by an ALTO information
resource (called the defining information resource).
6.2.1. Entity Domain Type
The Entity Domain Type is "ane".
6.2.2. Domain-Specific Entity Identifier
The entity identifiers are the ANE Names in the associated Property
Map.
6.2.3. Hierarchy and Inheritance
There is no hierarchy or inheritance for properties associated with
ANEs.
6.2.4. Media Type of Defining Resource
The defining resource for entity domain type "ane" MUST be a Property
Map, i.e., the media type of defining resources is:
application/alto-propmap+json
Specifically, for ephemeral ANEs that appear in a Path Vector
response, their entity domain names MUST be exactly ".ane" and the
defining resource of these ANEs is the Property Map part of the
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multipart response. Meanwhile, for any persistent ANE whose defining
resource is a Property Map resource, its entity domain name MUST have
the format of "PROPMAP.ane" where PROPMAP is the resource ID of the
defining resource. Persistent entities are "persistent" because
standalone queries can be made by an ALTO client to their defining
resource(s) when the connection to the Path Vector service is closed.
For example, the defining resource of an ephemeral ANE whose entity
identifier is ".ane:NET1" is the Property Map part that contains this
identifier. The defining resource of a persistent ANE whose entity
identifier is "dc-props.ane:DC1" is the Property Map with the
resource ID "dc-props".
6.3. ANE Property Name
An ANE Property Name is encoded as a JSON string with the same format
as that of Entity Property Name (Section 5.2.2 of
[I-D.ietf-alto-unified-props-new]).
6.4. Initial ANE Property Types
Two initial ANE property types are specified, "max-reservable-
bandwidth" and "persistent-entity-id".
Note that these property types do not depend on any information
resource. As such, the EntityPropertyName MUST only have the
EntityPropertyType part.
6.4.1. Maximum Reservable Bandwidth
The maximum reservable bandwidth property ("max-reservable-
bandwidth") stands for the maximum bandwidth that can be reserved for
all the traffic that traverses an ANE. The value MUST be encoded as
a non-negative numerical cost value as defined in Section 6.1.2.1 of
[RFC7285] and the unit is bit per second (bps). If this property is
requested by the ALTO client but not present for an ANE in the server
response, it MUST be interpreted as that the property is not defined
for the ANE.
This property can be offered in a setting where the ALTO server is
part of a network system that provides on-demand resource allocation
and the ALTO client is part of a user application. One existing
example is [NOVA]: the ALTO server is part of an SDN controller and
exposes a list of traversed network elements and associated link
bandwidth to the client. The encoding in [NOVA] differs from the
Path Vector response defined in this document that the Path Vector
part and Property Map part are put in the same JSON object.
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In such a framework, the ALTO server exposes resource (e.g.,
reservable bandwidth) availability information to the ALTO client.
How the client makes resource requests based on the information and
how the resource allocation is achieved respectively depend on
interfaces between the management system and the users or a higher-
layer protocol (e.g., SDN network intents or MPLS tunnels), which are
out of the scope of this document.
6.4.2. Persistent Entity ID
The persistent entity ID property is the entity identifier of the
persistent ANE which an ephemeral ANE presents (See Section 5.1.2 for
details). The value of this property is encoded with the format
EntityID defined in Section 5.1.3 of
[I-D.ietf-alto-unified-props-new].
In this format, the entity ID combines:
* a defining information resource for the ANE on which a
"persistent-entity-id" is queried, which is the Property Map
resource defining the ANE as a persistent entity, together with
the properties;
* the persistent name of the ANE in that Property Map.
With this format, the client has all the needed information for
further standalone query properties on the persistent ANE.
6.4.3. Examples
To illustrate the use of "max-reservable-bandwidth", consider the
following network with 5 nodes. Assume the client wants to query the
maximum reservable bandwidth from H1 to H2. An ALTO server may split
the network into two ANEs: "ane1" that represents the subnetwork with
routers A, B, and C, and "ane2" that represents the subnetwork with
routers B, D and E. The maximum reservable bandwidth for "ane1" is
15 Mbps (using path A->C->B) and the maximum reservable bandwidth for
"ane2" is 20 Mbps (using path B->D->E).
20 Mbps 20 Mbps
10 Mbps +---+ +---+ +---+
/----| B |---| D |----| E |---- H2
+---+/ +---+ +---+ +---+
H1 ----| A | 15 Mbps|
+---+\ +---+
\----| C |
15 Mbps +---+
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To illustrate the use of "persistent-entity-id", consider the
scenario in Figure 6. As the life cycle of service edges are
typically long, they may contain information that is not specific to
the query. Such information can be stored in an individual unified
property map and later be accessed by an ALTO client.
For example, "ane1" in Figure 7 represents the on-premise service
edge closest to host a. Assume the properties of the service edges
are provided in a unified property map called "se-props" and the ID
of the on-premise service edge is "9a0b55f7-7442-4d56-8a2c-
b4cc6a8e3aa1", the "persistent-entity-id" of "ane1" will be "se-
props.ane:9a0b55f7-7442-4d56-8a2c-b4cc6a8e3aa1". With this
persistent entity ID, an ALTO client may send queries to the "se-
props" resource with the entity ID ".ane:9a0b55f7-7442-4d56-8a2c-
b4cc6a8e3aa1".
6.5. Path Vector Cost Type
This document defines a new cost type, which is referred to as the
Path Vector cost type. An ALTO server MUST offer this cost type if
it supports the extension defined in this document.
6.5.1. Cost Metric: ane-path
The cost metric "ane-path" indicates the value of such a cost type
conveys an array of ANE names, where each ANE name uniquely
represents an ANE traversed by traffic from a source to a
destination.
An ALTO client MUST interpret the Path Vector as if the traffic
between a source and a destination logically traverses the ANEs in
the same order as they appear in the Path Vector.
When the Path Vector procedures defined in this document are in use,
an ALTO server using the "ane-path" cost metric and the "array" cost
mode (see Section 6.5.2) MUST return as the cost value a JSON array
of ANEName and the client MUST also check that each element contained
in the array is an ANEName (Section 6.1). Otherwise, the client MUST
discard the response and SHOULD follow the instructions in
Section 8.3.4.3 of [RFC7285] to handle the error.
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6.5.2. Cost Mode: array
The cost mode "array" indicates that every cost value in the response
body of a (Filtered) Cost Map or an Endpoint Cost Service MUST be
interpreted as a JSON array object. While this cost mode can be
applied to all cost metrics, additional specifications will be needed
to clarify the semantics of the array cost mode when combined with
cost metrics other than 'ane-path'.
6.6. Part Resource ID and Part Content ID
A Part Resource ID is encoded as a JSON string with the same format
as that of the type ResourceID (Section 10.2 of [RFC7285]).
Even though the client-id assigned to a Path Vector request and the
Part Resource ID MAY contain up to 64 characters by their own
definition, their concatenation (see Section 5.3.2) MUST also conform
to the same length constraint. The same requirement applies to the
resource ID of the Path Vector resource, too. Thus, it is
RECOMMENDED to limit the length of resource ID and client ID related
to a Path Vector resource to 31 characters.
A Part Content ID conforms to the format of msg-id as specified in
[RFC2387] and [RFC5322]. Specifically, it has the following format:
"<" PART-RESOURCE-ID "@" DOMAIN-NAME ">"
PART-RESOURCE-ID: PART-RESOURCE-ID has the same format as the Part
Resource ID. It is used to identify whether a part message is a
Path Vector or a Property Map.
DOMAIN-NAME: DOMAIN-NAME has the same format as dot-atom-text
specified in Section 3.2.3 of [RFC5322]. It must be the domain
name of the ALTO server.
7. Specification: Service Extensions
7.1. Notations
This document uses the same syntax and notations as introduced in
Section 8.2 of RFC 7285 [RFC7285] to specify the extensions to
existing ALTO resources and services.
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7.2. Multipart Filtered Cost Map for Path Vector
This document introduces a new ALTO resource called multipart
Filtered Cost Map resource, which allows an ALTO server to provide
other ALTO resources associated with the Cost Map resource in the
same response.
7.2.1. Media Type
The media type of the multipart Filtered Cost Map resource is
"multipart/related" and the required "type" parameter MUST have a
value of "application/alto-costmap+json".
7.2.2. HTTP Method
The multipart Filtered Cost Map is requested using the HTTP POST
method.
7.2.3. Accept Input Parameters
The input parameters of the multipart Filtered Cost Map are supplied
in the body of an HTTP POST request. This document extends the input
parameters to a Filtered Cost Map, which is defined as a JSON object
of type ReqFilteredCostMap in Section 4.1.2 of RFC 8189 [RFC8189],
with a data format indicated by the media type "application/alto-
costmapfilter+json", which is a JSON object of type
PVReqFilteredCostMap:
object {
[EntityPropertyName ane-property-names<0..*>;]
} PVReqFilteredCostMap : ReqFilteredCostMap;
with fields:
ane-property-names: A list of selected ANE properties to be included
in the response. Each property in this list MUST match one of the
supported ANE properties indicated in the resource's "ane-
property-names" capability (Section 7.2.4). If the field is not
present, it MUST be interpreted as an empty list.
Example: Consider the network in Figure 1. If an ALTO client wants
to query the "max-reservable-bandwidth" between PID1 and PID2, it can
submit the following request.
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POST /costmap/pv HTTP/1.1
Host: alto.example.com
Accept: multipart/related;type=application/alto-costmap+json,
application/alto-error+json
Content-Length: 201
Content-Type: application/alto-costmapfilter+json
{
"cost-type": {
"cost-mode": "array",
"cost-metric": "ane-path"
},
"pids": {
"srcs": [ "PID1" ],
"dsts": [ "PID2" ]
},
"ane-property-names": [ "max-reservable-bandwidth" ]
}
7.2.4. Capabilities
The multipart Filtered Cost Map resource extends the capabilities
defined in Section 4.1.1 of [RFC8189]. The capabilities are defined
by a JSON object of type PVFilteredCostMapCapabilities:
object {
[EntityPropertyName ane-property-names<0..*>;]
} PVFilteredCostMapCapabilities : FilteredCostMapCapabilities;
with fields:
ane-property-names: Defines a list of ANE properties that can be
returned. If the field is not present, it MUST be interpreted as
an empty list, indicating the ALTO server cannot provide any ANE
property.
This extension also introduces additional restrictions for the
following fields:
cost-type-names: The "cost-type-names" field MUST include the Path
Vector cost type, unless explicitly documented by a future
extension. This also implies that the Path Vector cost type MUST
be defined in the "cost-types" of the Information Resource
Directory's "meta" field.
cost-constraints: If the "cost-type-names" field includes the Path
Vector cost type, "cost-constraints" field MUST be "false" or not
present unless specifically instructed by a future document.
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testable-cost-type-names (Section 4.1.1 of [RFC8189]): If the "cost-
type-names" field includes the Path Vector cost type and the
"testable-cost-type-names" field is present, the Path Vector cost
type MUST NOT be included in the "testable-cost-type-names" field
unless specifically instructed by a future document.
7.2.5. Uses
This member MUST include the resource ID of the network map based on
which the PIDs are defined. If this resource supports "persistent-
entity-id", it MUST also include the defining resources of persistent
ANEs that may appear in the response.
7.2.6. Response
The response MUST indicate an error, using ALTO protocol error
handling, as defined in Section 8.5 of [RFC7285], if the request is
invalid.
The "Content-Type" header of the response MUST be "multipart/related"
as defined by [RFC2387] with the following parameters:
type: The type parameter is mandatory and MUST be "application/alto-
costmap+json". Note that [RFC2387] permits both parameters with
and without the double quotes.
start: The start parameter is as defined in [RFC2387] and is
optional. If present, it MUST have the same value as the
"Content-ID" header of the Path Vector part.
boundary: The boundary parameter is as defined in Section 5.1.1 of
[RFC2046] and is mandatory.
The body of the response MUST consist of two parts:
* The Path Vector part MUST include "Content-ID" and "Content-Type"
in its header. The "Content-Type" MUST be "application/alto-
costmap+json". The value of "Content-ID" MUST have the same
format as the Part Content ID as specified in Section 6.6.
The body of the Path Vector part MUST be a JSON object with the
same format as defined in Section 11.2.3.6 of [RFC7285] when the
"cost-type" field is present in the input parameters and MUST be a
JSON object with the same format as defined in Section 4.1.3 of
[RFC8189] if the "multi-cost-types" field is present. The JSON
object MUST include the "vtag" field in the "meta" field, which
provides the version tag of the returned CostMapData. The
resource ID of the version tag MUST follow the format of
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resource-id '.' part-resource-id
where "resource-id" is the resource Id of the Path Vector
resource, and "part-resource-id" has the same value as the PART-
RESOURCE-ID in the "Content-ID" of the Path Vector part. The
"meta" field MUST also include the "dependent-vtags" field, whose
value is a single-element array to indicate the version tag of the
network map used, where the network map is specified in the "uses"
attribute of the multipart Filtered Cost Map resource in IRD.
* The Unified Property Map part MUST also include "Content-ID" and
"Content-Type" in its header. The "Content-Type" MUST be
"application/alto-propmap+json". The value of "Content-ID" MUST
have the same format as the Part Content ID as specified in
Section 6.6.
The body of the Unified Property Map part is a JSON object with
the same format as defined in Section 7.6 of
[I-D.ietf-alto-unified-props-new]. The JSON object MUST include
the "dependent-vtags" field in the "meta" field. The value of the
"dependent-vtags" field MUST be an array of VersionTag objects as
defined by Section 10.3 of [RFC7285]. The "vtag" of the Path
Vector part MUST be included in the "dependent-vtags". If
"persistent-entity-id" is requested, the version tags of the
dependent resources that may expose the entities in the response
MUST also be included.
The PropertyMapData has one member for each ANEName that appears
in the Path Vector part, which is an entity identifier belonging
to the self-defined entity domain as defined in Section 5.1.2.3 of
[I-D.ietf-alto-unified-props-new]. The EntityProps for each ANE
has one member for each property that is both 1) associated with
the ANE, and 2) specified in the "ane-property-names" in the
request. If the Path Vector cost type is not included in the
"cost-type" field or the "multi-cost-type" field, the "property-
map" field MUST be present and the value MUST be an empty object
({}).
A complete and valid response MUST include both the Path Vector part
and the Property Map part in the multipart message. If any part is
NOT present, the client MUST discard the received information and
send another request if necessary.
According to [RFC2387], the Path Vector part, whose media type is the
same as the "type" parameter of the multipart response message, is
the root object. Thus, it is the element the application processes
first. Even though the "start" parameter allows it to be placed
anywhere in the part sequence, it is RECOMMENDED that the parts
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arrive in the same order as they are processed, i.e., the Path Vector
part is always put as the first part, followed by the Property Map
part. When doing so, an ALTO server MAY choose not to set the
"start" parameter, which implies the first part is the root object.
Example: Consider the network in Figure 1. The response of the
example request in Section 7.2.3 is as follows, where "ANE1"
represents the aggregation of all the switches in the network.
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HTTP/1.1 200 OK
Content-Length: 859
Content-Type: multipart/related; boundary=example-1;
type=application/alto-costmap+json
--example-1
Content-ID: <costmap@alto.example.com>
Content-Type: application/alto-costmap+json
{
"meta": {
"vtag": {
"resource-id": "filtered-cost-map-pv.costmap",
"tag": "fb20b76204814e9db37a51151faaaef2"
},
"dependent-vtags": [
{
"resource-id": "my-default-networkmap",
"tag": "75ed013b3cb58f896e839582504f6228"
}
],
"cost-type": { "cost-mode": "array", "cost-metric": "ane-path" }
},
"cost-map": {
"PID1": { "PID2": ["ANE1"] }
}
}
--example-1
Content-ID: <propmap@alto.example.com>
Content-Type: application/alto-propmap+json
{
"meta": {
"dependent-vtags": [
{
"resource-id": "filtered-cost-map-pv.costmap",
"tag": "fb20b76204814e9db37a51151faaaef2"
}
]
},
"property-map": {
".ane:ANE1": { "max-reservable-bandwidth": 100000000 }
}
}
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7.3. Multipart Endpoint Cost Service for Path Vector
This document introduces a new ALTO resource called multipart
Endpoint Cost Service, which allows an ALTO server to provide other
ALTO resources associated with the Endpoint Cost Service resource in
the same response.
7.3.1. Media Type
The media type of the multipart Endpoint Cost Service resource is
"multipart/related" and the required "type" parameter MUST have a
value of "application/alto-endpointcost+json".
7.3.2. HTTP Method
The multipart Endpoint Cost Service resource is requested using the
HTTP POST method.
7.3.3. Accept Input Parameters
The input parameters of the multipart Endpoint Cost Service resource
are supplied in the body of an HTTP POST request. This document
extends the input parameters to an Endpoint Cost Service, which is
defined as a JSON object of type ReqEndpointCost in Section 4.2.2 of
[RFC8189], with a data format indicated by the media type
"application/alto-endpointcostparams+json", which is a JSON object of
type PVReqEndpointCost:
object {
[EntityPropertyName ane-property-names<0..*>;]
} PVReqEndpointcost : ReqEndpointcostMap;
with fields:
ane-property-names: This document defines the "ane-property-names"
in PVReqEndpointcost as the same as in PVReqFilteredCostMap. See
Section 7.2.3.
Example: Consider the network in Figure 1. If an ALTO client wants
to query the "max-reservable-bandwidth" between eh1 and eh2, it can
submit the following request.
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POST /ecs/pv HTTP/1.1
Host: alto.example.com
Accept: multipart/related;type=application/alto-endpointcost+json,
application/alto-error+json
Content-Length: 227
Content-Type: application/alto-endpointcostparams+json
{
"cost-type": {
"cost-mode": "array",
"cost-metric": "ane-path"
},
"endpoints": {
"srcs": [ "ipv4:192.0.2.2" ],
"dsts": [ "ipv4:192.0.2.18" ]
},
"ane-property-names": [ "max-reservable-bandwidth" ]
}
7.3.4. Capabilities
The capabilities of the multipart Endpoint Cost Service resource are
defined by a JSON object of type PVEndpointcostCapabilities, which is
defined as the same as PVFilteredCostMapCapabilities. See
Section 7.2.4.
7.3.5. Uses
If this resource supports "persistent-entity-id", it MUST also
include the defining resources of persistent ANEs that may appear in
the response.
7.3.6. Response
The response MUST indicate an error, using ALTO protocol error
handling, as defined in Section 8.5 of [RFC7285], if the request is
invalid.
The "Content-Type" header of the response MUST be "multipart/related"
as defined by [RFC7285] with the following parameters:
type: The type parameter MUST be "application/alto-
endpointcost+json" and is mandatory.
start: The start parameter is as defined in Section 7.2.6.
boundary: The boundary parameter is as defined in Section 5.1.1 of
[RFC2046] and is mandatory.
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The body MUST consist of two parts:
* The Path Vector part MUST include "Content-ID" and "Content-Type"
in its header. The "Content-Type" MUST be "application/alto-
endpointcost+json". The value of "Content-ID" MUST have the same
format as the Part Content ID as specified in Section 6.6.
The body of the Path Vector part MUST be a JSON object with the
same format as defined in Section 11.5.1.6 of [RFC7285] when the
"cost-type" field is present in the input parameters and MUST be a
JSON object with the same format as defined in Section 4.2.3 of
[RFC8189] if the "multi-cost-types" field is present. The JSON
object MUST include the "vtag" field in the "meta" field, which
provides the version tag of the returned EndpointCostMapData. The
resource ID of the version tag MUST follow the format of
resource-id '.' part-resource-id
where "resource-id" is the resource Id of the Path Vector
resource, and "part-resource-id" has the same value as the PART-
RESOURCE-ID in the "Content-ID" of the Path Vector part.
* The Unified Property Map part MUST also include "Content-ID" and
"Content-Type" in its header. The "Content-Type" MUST be
"application/alto-propmap+json". The value of "Content-ID" MUST
have the same format as the Part Content ID as specified in
Section 6.6.
The body of the Unified Property Map part MUST be a JSON object
with the same format as defined in Section 7.6 of
[I-D.ietf-alto-unified-props-new]. The JSON object MUST include
the "dependent-vtags" field in the "meta" field. The value of the
"dependent-vtags" field MUST be an array of VersionTag objects as
defined by Section 10.3 of [RFC7285]. The "vtag" of the Path
Vector part MUST be included in the "dependent-vtags". If
"persistent-entity-id" is requested, the version tags of the
dependent resources that may expose the entities in the response
MUST also be included.
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The PropertyMapData has one member for each ANEName that appears
in the Path Vector part, which is an entity identifier belonging
to the self-defined entity domain as defined in Section 5.1.2.3 of
[I-D.ietf-alto-unified-props-new]. The EntityProps for each ANE
has one member for each property that is both 1) associated with
the ANE, and 2) specified in the "ane-property-names" in the
request. If the Path Vector cost type is not included in the
"cost-type" field or the "multi-cost-type" field, the "property-
map" field MUST be present and the value MUST be an empty object
({}).
A complete and valid response MUST include both the Path Vector part
and the Property Map part in the multipart message. If any part is
NOT present, the client MUST discard the received information and
send another request if necessary.
According to [RFC2387], the Path Vector part, whose media type is the
same as the "type" parameter of the multipart response message, is
the root object. Thus, it is the element the application processes
first. Even though the "start" parameter allows it to be placed
anywhere in the part sequence, it is RECOMMENDED that the parts
arrive in the same order as they are processed, i.e., the Path Vector
part is always put as the first part, followed by the Property Map
part. When doing so, an ALTO server MAY choose not to set the
"start" parameter, which implies the first part is the root object.
Example: Consider the network in Figure 1. The response of the
example request in Section 7.3.3 is as follows.
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HTTP/1.1 200 OK
Content-Length: 845
Content-Type: multipart/related; boundary=example-1;
type=application/alto-endpointcost+json
--example-1
Content-ID: <ecs@alto.example.com>
Content-Type: application/alto-endpointcost+json
{
"meta": {
"vtag": {
"resource-id": "ecs-pv.ecs",
"tag": "ec137bb78118468c853d5b622ac003f1"
},
"dependent-vtags": [
{
"resource-id": "my-default-networkmap",
"tag": "677fe5f4066848d282ece213a84f9429"
}
],
"cost-type": { "cost-mode": "array", "cost-metric": "ane-path" }
},
"cost-map": {
"ipv4:192.0.2.2": { "ipv4:192.0.2.18": ["ANE1"] }
}
}
--example-1
Content-ID: <propmap@alto.example.com>
Content-Type: application/alto-propmap+json
{
"meta": {
"dependent-vtags": [
{
"resource-id": "ecs-pv.ecs",
"tag": "ec137bb78118468c853d5b622ac003f1"
}
]
},
"property-map": {
".ane:ANE1": { "max-reservable-bandwidth": 100000000 }
}
}
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8. Examples
This section lists some examples of Path Vector queries and the
corresponding responses. Some long lines are truncated for better
readability.
8.1. Sample Setup
----- L1
/
PID1 +----------+ 10 Gbps +----------+ PID3
192.0.2.0/28+-+ +------+ +---------+ +--+192.0.2.32/28
| | MEC1 | | | | 2001:db8::3:0/16
| +------+ | +-----+ |
PID2 | | | +----------+
192.0.2.16/28+-+ | | NET3
| | | 15 Gbps
| | | \
+----------+ | -------- L2
NET1 |
+----------+
| +------+ | PID4
| | MEC2 | +--+192.0.2.48/28
| +------+ | 2001:db8::4:0/16
+----------+
NET2
Figure 10: Examples of ANE Properties
In this document, Figure 10 is used to illustrate the message
contents. There are 3 sub-networks (NET1, NET2 and NET3) and two
interconnection links (L1 and L2). It is assumed that each sub-
network has sufficiently large bandwidth to be reserved.
8.2. Information Resource Directory
To give a comprehensive example of the extension defined in this
document, we consider the network in Figure 10. Assume that the ALTO
server provides the following information resources:
* "my-default-networkmap": A Network Map resource which contains the
PIDs in the network.
* "filtered-cost-map-pv": A Multipart Filtered Cost Map resource for
Path Vector, which exposes the "max-reservable-bandwidth" property
for the PIDs in "my-default-networkmap".
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* "ane-props": A filtered Unified Property resource that exposes the
information for persistent ANEs in the network.
* "endpoint-cost-pv": A Multipart Endpoint Cost Service for Path
Vector, which exposes the "max-reservable-bandwidth" and the
"persistent-entity-id" properties.
* "update-pv": An Update Stream service, which provides the
incremental update service for the "endpoint-cost-pv" service.
* "multicost-pv": A Multipart Endpoint Cost Service with both Multi-
Cost and Path Vector.
Below is the Information Resource Directory of the example ALTO
server. To enable the extension defined in this document, the "path-
vector" cost type (Section 6.5) is defined in the "cost-types" of the
"meta" field, and is included in the "cost-type-names" of resources
"filtered-cost-map-pv" and "endpoint-cost-pv".
{
"meta": {
"cost-types": {
"path-vector": {
"cost-mode": "array",
"cost-metric": "ane-path"
},
"num-rc": {
"cost-mode": "numerical",
"cost-metric": "routingcost"
}
}
},
"resources": {
"my-default-networkmap": {
"uri": "https://alto.example.com/networkmap",
"media-type": "application/alto-networkmap+json"
},
"filtered-cost-map-pv": {
"uri": "https://alto.example.com/costmap/pv",
"media-type": "multipart/related;
type=application/alto-costmap+json",
"accepts": "application/alto-costmapfilter+json",
"capabilities": {
"cost-type-names": [ "path-vector" ],
"ane-property-names": [ "max-reservable-bandwidth" ]
},
"uses": [ "my-default-networkmap" ]
},
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"ane-props": {
"uri": "https://alto.example.com/ane-props",
"media-type": "application/alto-propmap+json",
"accepts": "application/alto-propmapparams+json",
"capabilities": {
"mappings": {
".ane": [ "cpu" ]
}
}
},
"endpoint-cost-pv": {
"uri": "https://alto.exmaple.com/endpointcost/pv",
"media-type": "multipart/related;
type=application/alto-endpointcost+json",
"accepts": "application/alto-endpointcostparams+json",
"capabilities": {
"cost-type-names": [ "path-vector" ],
"ane-property-names": [
"max-reservable-bandwidth", "persistent-entity-id"
]
},
"uses": [ "ane-props" ]
},
"update-pv": {
"uri": "https://alto.example.com/updates/pv",
"media-type": "text/event-stream",
"uses": [ "endpoint-cost-pv" ],
"accepts": "application/alto-updatestreamparams+json",
"capabilities": {
"support-stream-control": true
}
},
"multicost-pv": {
"uri": "https://alto.exmaple.com/endpointcost/mcpv",
"media-type": "multipart/related;
type=application/alto-endpointcost+json",
"accepts": "application/alto-endpointcostparams+json",
"capabilities": {
"cost-type-names": [ "path-vector", "num-rc" ],
"max-cost-types": 2,
"testable-cost-type-names": [ "num-rc" ],
"ane-property-names": [
"max-reservable-bandwidth", "persistent-entity-id"
]
},
"uses": [ "ane-props" ]
}
}
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}
8.3. Multipart Filtered Cost Map
The following examples demonstrate the request to the "filtered-cost-
map-pv" resource and the corresponding response.
The request uses the "path-vector" cost type in the "cost-type"
field. The "ane-property-names" field is missing, indicating that
the client only requests for the Path Vector but not the ANE
properties.
The response consists of two parts. The first part returns the array
of ANEName for each source and destination pair. There are two ANEs,
where "L1" represents the interconnection link L1, and "L2"
represents the interconnection link L2.
The second part returns an empty Property Map. Note that the ANE
entries are omitted since they have no properties (See Section 3.1 of
[I-D.ietf-alto-unified-props-new]).
POST /costmap/pv HTTP/1.1
Host: alto.example.com
Accept: multipart/related;type=application/alto-costmap+json,
application/alto-error+json
Content-Length: 153
Content-Type: application/alto-costmapfilter+json
{
"cost-type": {
"cost-mode": "array",
"cost-metric": "ane-path"
},
"pids": {
"srcs": [ "PID1" ],
"dsts": [ "PID3", "PID4" ]
}
}
HTTP/1.1 200 OK
Content-Length: 855
Content-Type: multipart/related; boundary=example-1;
type=application/alto-costmap+json
--example-1
Content-ID: <costmap@alto.example.com>
Content-Type: application/alto-costmap+json
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{
"meta": {
"vtag": {
"resource-id": "filtered-cost-map-pv.costmap",
"tag": "d827f484cb66ce6df6b5077cb8562b0a"
},
"dependent-vtags": [
{
"resource-id": "my-default-networkmap",
"tag": "c04bc5da49534274a6daeee8ea1dec62"
}
],
"cost-type": {
"cost-mode": "array",
"cost-metric": "ane-path"
}
},
"cost-map": {
"PID1": {
"PID3": [ "L1" ],
"PID4": [ "L1", "L2" ]
}
}
}
--example-1
Content-ID: <propmap@alto.example.com>
Content-Type: application/alto-propmap+json
{
"meta": {
"dependent-vtags": [
{
"resource-id": "filtered-cost-map-pv.costmap",
"tag": "d827f484cb66ce6df6b5077cb8562b0a"
}
]
},
"property-map": {
}
}
8.4. Multipart Endpoint Cost Service Resource
The following examples demonstrate the request to the "endpoint-cost-
pv" resource and the corresponding response.
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The request uses the Path Vector cost type in the "cost-type" field,
and queries the Maximum Reservable Bandwidth ANE property and the
Persistent Entity property for two IPv4 source and destination pairs
(192.0.2.34 -> 192.0.2.2 and 192.0.2.34 -> 192.0.2.50) and one IPv6
source and destination pair (2001:db8::3:1 -> 2001:db8::4:1).
The response consists of two parts. The first part returns the array
of ANEName for each valid source and destination pair. As one can
see in Figure 10, flow 192.0.2.34 -> 192.0.2.2 traverses NET2, L1 and
NET1, and flows 192.0.2.34 -> 192.0.2.50 and 2001:db8::3:1 ->
2001:db8::4:1 traverse NET2, L2 and NET3.
The second part returns the requested properties of ANEs. Assume
NET1, NET2 and NET3 has sufficient bandwidth and their "max-
reservable-bandwidth" values are set to a sufficiently large number
(50 Gbps in this case). On the other hand, assume there are no prior
reservation on L1 and L2, and their "max-reservable-bandwidth" values
are the corresponding link capacity (10 Gbps for L1 and 15 Gbps for
L2).
Both NET1 and NET2 have a mobile edge deployed, i.e., MEC1 in NET1
and MEC2 in NET2. Assume the ANEName for MEC1 and MEC2 are "MEC1"
and "MEC2" and their properties can be retrieved from the Property
Map "ane-props". Thus, the "persistent-entity-id" property of NET1
and NET3 are "ane-props.ane:MEC1" and "ane-props.ane:MEC2"
respectively.
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POST /endpointcost/pv HTTP/1.1
Host: alto.example.com
Accept: multipart/related;
type=application/alto-endpointcost+json,
application/alto-error+json
Content-Length: 362
Content-Type: application/alto-endpointcostparams+json
{
"cost-type": {
"cost-mode": "array",
"cost-metric": "ane-path"
},
"endpoints": {
"srcs": [
"ipv4:192.0.2.34",
"ipv6:2001:db8::3:1"
],
"dsts": [
"ipv4:192.0.2.2",
"ipv4:192.0.2.50",
"ipv6:2001:db8::4:1"
]
},
"ane-property-names": [
"max-reservable-bandwidth",
"persistent-entity-id"
]
}
HTTP/1.1 200 OK
Content-Length: 1432
Content-Type: multipart/related; boundary=example-2;
type=application/alto-endpointcost+json
--example-2
Content-ID: <ecs@alto.example.com>
Content-Type: application/alto-endpointcost+json
{
"meta": {
"vtags": {
"resource-id": "endpoint-cost-pv.ecs",
"tag": "bb6bb72eafe8f9bdc4f335c7ed3b10822a391cef"
},
"cost-type": {
"cost-mode": "array",
"cost-metric": "ane-path"
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}
},
"endpoint-cost-map": {
"ipv4:192.0.2.34": {
"ipv4:192.0.2.2": [ "NET3", "L1", "NET1" ],
"ipv4:192.0.2.50": [ "NET3", "L2", "NET2" ]
},
"ipv6:2001:db8::3:1": {
"ipv6:2001:db8::4:1": [ "NET3", "L2", "NET2" ]
}
}
}
--example-2
Content-ID: <propmap@alto.example.com>
Content-Type: application/alto-propmap+json
{
"meta": {
"dependent-vtags": [
{
"resource-id": "endpoint-cost-pv.ecs",
"tag": "bb6bb72eafe8f9bdc4f335c7ed3b10822a391cef"
},
{
"resource-id": "ane-props",
"tag": "bf3c8c1819d2421c9a95a9d02af557a3"
}
]
},
"property-map": {
".ane:NET1": {
"max-reservable-bandwidth": 50000000000,
"persistent-entity-id": "ane-props.ane:MEC1"
},
".ane:NET2": {
"max-reservable-bandwidth": 50000000000,
"persistent-entity-id": "ane-props.ane:MEC2"
},
".ane:NET3": {
"max-reservable-bandwidth": 50000000000
},
".ane:L1": {
"max-reservable-bandwidth": 10000000000
},
".ane:L2": {
"max-reservable-bandwidth": 15000000000
}
}
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}
Under certain scenarios where the traversal order is not crucial, an
ALTO server implementation may choose to not follow strictly the
physical traversal order and may even obfuscate the order
intentionally to preserve its own privacy or conform to its own
policies. For example, an ALTO server may choose to aggregate NET1
and L1 as a new ANE with ANE name "AGGR1", and aggregate NET2 and L2
as a new ANE with ANE name "AGGR2". The "max-reservable-bandwidth"
of "AGGR1" takes the value of L1, which is smaller than that of NET1,
and the "persistent-entity-id" of "AGGR1" takes the value of NET1.
The properties of "AGGR2" are computed in a similar way and the
obfuscated response is as shown below. Note that the obfuscation of
Path Vector responses is implementation-specific and is out of the
scope of this document, and developers may refer to Section 11 for
further references.
HTTP/1.1 200 OK
Content-Length: 1263
Content-Type: multipart/related; boundary=example-2;
type=application/alto-endpointcost+json
--example-2
Content-ID: <ecs@alto.example.com>
Content-Type: application/alto-endpointcost+json
{
"meta": {
"vtags": {
"resource-id": "endpoint-cost-pv.ecs",
"tag": "bb975862fbe3422abf4dae386b132c1d"
},
"cost-type": {
"cost-mode": "array",
"cost-metric": "ane-path"
}
},
"endpoint-cost-map": {
"ipv4:192.0.2.34": {
"ipv4:192.0.2.2": [ "NET3", "AGGR1" ],
"ipv4:192.0.2.50": [ "NET3", "AGGR2" ]
},
"ipv6:2001:db8::3:1": {
"ipv6:2001:db8::4:1": [ "NET3", "AGGR2" ]
}
}
}
--example-2
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Content-ID: <propmap@alto.example.com>
Content-Type: application/alto-propmap+json
{
"meta": {
"dependent-vtags": [
{
"resource-id": "endpoint-cost-pv.ecs",
"tag": "bb975862fbe3422abf4dae386b132c1d"
},
{
"resource-id": "ane-props",
"tag": "bf3c8c1819d2421c9a95a9d02af557a3"
}
]
},
"property-map": {
".ane:AGGR1": {
"max-reservable-bandwidth": 10000000000,
"persistent-entity-id": "ane-props.ane:MEC1"
},
".ane:AGGR2": {
"max-reservable-bandwidth": 15000000000,
"persistent-entity-id": "ane-props.ane:MEC2"
},
".ane:NET3": {
"max-reservable-bandwidth": 50000000000
}
}
}
8.5. Incremental Updates
In this example, an ALTO client subscribes to the incremental update
for the multipart Endpoint Cost Service resource "endpoint-cost-pv".
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POST /updates/pv HTTP/1.1
Host: alto.example.com
Accept: text/event-stream
Content-Type: application/alto-updatestreamparams+json
Content-Length: 112
{
"add": {
"ecspvsub1": {
"resource-id": "endpoint-cost-pv",
"input": <ecs-input>
}
}
}
Based on the server-side process defined in [RFC8895], the ALTO
server will send the "control-uri" first using Server-Sent Event
(SSE), followed by the full response of the multipart message.
HTTP/1.1 200 OK
Connection: keep-alive
Content-Type: text/event-stream
event: application/alto-updatestreamcontrol+json
data: {"control-uri": "https://alto.example.com/updates/streams/123"}
event: multipart/related;boundary=example-3;
type=application/alto-endpointcost+json,ecspvsub1
data: --example-3
data: Content-ID: <ecsmap@alto.example.com>
data: Content-Type: application/alto-endpointcost+json
data:
data: <endpoint-cost-map-entry>
data: --example-3
data: Content-ID: <propmap@alto.example.com>
data: Content-Type: application/alto-propmap+json
data:
data: <property-map-entry>
data: --example-3--
When the contents change, the ALTO server will publish the updates
for each node in this tree separately, based on Section 6.7.3 of
[RFC8895].
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event: application/merge-patch+json, ecspvsub1.ecsmap@alto.example.com
data: <Merge patch for endpoint-cost-map-update>
event: application/merge-patch+json, ecspvsub1.propmap@alto.example.com
data: <Merge patch for property-map-update>
8.6. Multi-cost
The following examples demonstrate the request to the "multicost-pv"
resource and the corresponding response.
The request asks for two cost types: the first is the Path Vector
cost type, and the second is a numerical routing cost. It also
queries the Maximum Reservable Bandwidth ANE property and the
Persistent Entity property for two IPv4 source and destination pairs
(192.0.2.34 -> 192.0.2.2 and 192.0.2.34 -> 192.0.2.50) and one IPv6
source and destination pair (2001:db8::3:1 -> 2001:db8::4:1).
The response consists of two parts. The first part returns a
JSONArray that contains two JSONValue for each requested source and
destination pair: the first JSONValue is a JSONArray of ANENames,
which is the value of the Path Vector cost type, and the second
JSONValue is a JSONNumber which is the value of the routing cost.
The second part contains a Property Map that maps the ANEs to their
requested properties.
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POST /endpointcost/mcpv HTTP/1.1
Host: alto.example.com
Accept: multipart/related;
type=application/alto-endpointcost+json,
application/alto-error+json
Content-Length: 433
Content-Type: application/alto-endpointcostparams+json
{
"multi-cost-types": [
{ "cost-mode": "array", "cost-metric": "ane-path" },
{ "cost-mode": "numerical", "cost-metric": "routingcost" }
],
"endpoints": {
"srcs": [
"ipv4:192.0.2.34",
"ipv6:2001:db8::3:1"
],
"dsts": [
"ipv4:192.0.2.2",
"ipv4:192.0.2.50",
"ipv6:2001:db8::4:1"
]
},
"ane-property-names": [
"max-reservable-bandwidth",
"persistent-entity-id"
]
}
HTTP/1.1 200 OK
Content-Length: 1350
Content-Type: multipart/related; boundary=example-4;
type=application/alto-endpointcost+json
--example-4
Content-ID: <ecs@alto.example.com>
Content-Type: application/alto-endpointcost+json
{
"meta": {
"vtags": {
"resource-id": "endpoint-cost-pv.ecs",
"tag": "84a4f9c14f9341f0983e3e5f43a371c8"
},
"multi-cost-types": [
{ "cost-mode": "array", "cost-metric": "ane-path" },
{ "cost-mode": "numerical", "cost-metric": "routingcost" }
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]
},
"endpoint-cost-map": {
"ipv4:192.0.2.34": {
"ipv4:192.0.2.2": [[ "NET3", "AGGR1" ], 3],
"ipv4:192.0.2.50": [[ "NET3", "AGGR2" ], 2]
},
"ipv6:2001:db8::3:1": {
"ipv6:2001:db8::4:1": [[ "NET3", "AGGR2" ], 2]
}
}
}
--example-4
Content-ID: <propmap@alto.example.com>
Content-Type: application/alto-propmap+json
{
"meta": {
"dependent-vtags": [
{
"resource-id": "endpoint-cost-pv.ecs",
"tag": "84a4f9c14f9341f0983e3e5f43a371c8"
},
{
"resource-id": "ane-props",
"tag": "be157afa031443a187b60bb80a86b233"
}
]
},
"property-map": {
".ane:AGGR1": {
"max-reservable-bandwidth": 10000000000,
"persistent-entity-id": "ane-props.ane:MEC1"
},
".ane:AGGR2": {
"max-reservable-bandwidth": 15000000000,
"persistent-entity-id": "ane-props.ane:MEC2"
},
".ane:NET3": {
"max-reservable-bandwidth": 50000000000
}
}
}
9. Compatibility with Other ALTO Extensions
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9.1. Compatibility with Legacy ALTO Clients/Servers
The multipart Filtered Cost Map resource and the multipart Endpoint
Cost Service resource has no backward compatibility issue with legacy
ALTO clients and servers. Although these two types of resources
reuse the media types defined in the base ALTO protocol for the
accept input parameters, they have different media types for
responses. If the ALTO server provides these two types of resources,
but the ALTO client does not support them, the ALTO client will
ignore the resources without incurring any incompatibility problem.
9.2. Compatibility with Multi-Cost Extension
The extension defined in this document is compatible with the multi-
cost extension [RFC8189]. Such a resource has a media type of either
"multipart/related; type=application/alto-costmap+json" or
"multipart/related; type=application/alto-endpointcost+json". Its
"cost-constraints" field must either be "false" or not present and
the Path Vector cost type must be present in the "cost-type-names"
capability field but must not be present in the "testable-cost-type-
names" field, as specified in Section 7.2.4 and Section 7.3.4.
9.3. Compatibility with Incremental Update
This extension is compatible with the incremental update extension
[RFC8895]. ALTO clients and servers MUST follow the specifications
given in Sections 5.2 and 6.7.3 of [RFC8895] to support incremental
updates for a Path Vector resource.
9.4. Compatibility with Cost Calendar
The extension specified in this document is compatible with the Cost
Calendar extension [RFC8896]. When used together with the Cost
Calendar extension, the cost value between a source and a destination
is an array of Path Vectors, where the k-th Path Vector refers to the
abstract network paths traversed in the k-th time interval by traffic
from the source to the destination.
When used with time-varying properties, e.g., maximum reservable
bandwidth, a property of a single ANE may also have different values
in different time intervals. In this case, if such an ANE has
different property values in two time intervals, it MUST be treated
as two different ANEs, i.e., with different entity identifiers.
However, if it has the same property values in two time intervals, it
MAY use the same identifier.
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This rule allows the Path Vector extension to represent both changes
of ANEs and changes of the ANEs' properties in a uniform way. The
Path Vector part is calendared in a compatible way, and the Property
Map part is not affected by the calendar extension.
The two extensions combined together can provide the historical
network correlation information for a set of source and destination
pairs. A network broker or client may use this information to derive
other resource requirements such as Time-Block-Maximum Bandwidth,
Bandwidth-Sliding-Window, and Time-Bandwidth-Product (TBP) (See
[SENSE] for details).
10. General Discussions
10.1. Constraint Tests for General Cost Types
The constraint test is a simple approach to query the data. It
allows users to filter the query result by specifying some boolean
tests. This approach is already used in the ALTO protocol.
[RFC7285] and [RFC8189] allow ALTO clients to specify the
"constraints" and "or-constraints" tests to better filter the result.
However, the current syntax can only be used to test scalar cost
types, and cannot easily express constraints on complex cost types,
e.g., the Path Vector cost type defined in this document.
In practice, developing a bespoke language for general-purpose
boolean tests can be a complex undertaking, and it is conceivable
that there are some existing implementations already (the authors
have not done an exhaustive search to determine whether there are
such implementations). One avenue to develop such a language may be
to explore extending current query languages like XQuery [XQuery] or
JSONiq [JSONiq] and integrating these with ALTO.
Filtering the Path Vector results or developing a more sophisticated
filtering mechanism is beyond the scope of this document.
10.2. General Multi-Resource Query
Querying multiple ALTO information resources continuously is a
general requirement. Enabling such a capability, however, must
address general issues like efficiency and consistency. The
incremental update extension [RFC8895] supports submitting multiple
queries in a single request, and allows flexible control over the
queries. However, it does not cover the case introduced in this
document where multiple resources are needed for a single request.
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This extension gives an example of using a multipart message to
encode the responses from two specific ALTO information resources: a
Filtered Cost Map or an Endpoint Cost Service, and a Property Map. By
packing multiple resources in a single response, the implication is
that servers may proactively push related information resources to
clients.
Thus, it is worth looking into the direction of extending the SSE
mechanism as used in the incremental update extension [RFC8895], or
upgrading to HTTP/2 [I-D.ietf-httpbis-http2bis] and HTTP/3
[I-D.ietf-quic-http], which provides the ability to multiplex queries
and to allow servers proactively send related information resources.
Defining a general multi-resource query mechanism is out of the scope
of this document.
11. Security Considerations
This document is an extension of the base ALTO protocol, so the
Security Considerations [RFC7285] of the base ALTO protocol fully
apply when this extension is provided by an ALTO server.
The Path Vector extension requires additional scrutiny on three
security considerations discussed in the base protocol:
confidentiality of ALTO information (Section 15.3 of [RFC7285]),
potential undesirable guidance from authenticated ALTO information
(Section 15.2 of [RFC7285]), and availability of ALTO service
(Section 15.5 of [RFC7285]).
For confidentiality of ALTO information, a network operator should be
aware that this extension may introduce a new risk: the Path Vector
information, when used together with sensitive ANE properties such as
capacities of bottleneck links, may make network attacks easier. For
example, as the Path Vector information may reveal more fine-grained
internal network structures than the base protocol, an attacker may
identify the bottleneck link and start a distributed denial-of-
service (DDoS) attack involving minimal flows to conduct the in-
network congestion. Given the potential risk of leaking sensitive
information, the Path Vector extension is mainly applicable in
scenarios where 1) the ANE structures and ANE properties do not
impose security risks to the ALTO service provider, e.g., not
carrying sensitive information, or 2) the ALTO server and client have
established a reliable trust relationship, for example, operated in
the same administrative domain, or managed by business partners with
legal contracts.
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Three risk types are identified in Section 15.3.1 of [RFC7285]: (1)
Excess disclosure of the ALTO service provider's data to an
unauthorized ALTO client; (2) Disclosure of the ALTO service
provider's data (e.g., network topology information or endpoint
addresses) to an unauthorized third party; and (3) Excess retrieval
of the ALTO service provider's data by collaborating ALTO clients.
To mitigate these risks, an ALTO server MUST follow the guidelines in
Section 15.3.2 of [RFC7285]. Furthermore, an ALTO server MUST follow
the following additional protections strategies for risk types (1)
and (3).
For risk type (1), an ALTO server MUST use the authentication methods
specified in Section 15.3.2 of [RFC7285] to authenticate the identify
of an ALTO client, and apply access control techniques to restrict
unprivileged ALTO clients from retrieving sensitive Path Vector
information. For settings where the ALTO server and client are not
in the same trust domain, the ALTO server should reach agreements
with the ALTO client on protecting the confidentiality before
granting the access to Path Vector service with sensitive
information. Such agreements may include legal contracts or Digital
Right Management (DRM) techniques. Otherwise, the ALTO server MUST
NOT offer the Path Vector service carrying sensitive information to
the clients unless the potential risks are fully assessed and
mitigated.
For risk type (3), an ALTO service provider must be aware that
persistent ANEs may be used as "landmarks" in collaborative
inferences. Thus, they should only be used when exposing public
service access points (e.g., API gateways, CDNi) and/or when the
granularity is coarse-grained (e.g., when an ANE represents an AS, a
data center or a WAN). Otherwise, an ALTO server MUST use dynamic
mappings from ephemeral ANE names to underlying physical entities.
Specifically, for the same physical entity, an ALTO server SHOULD
assign a different ephemeral ANE name when the entity appears in the
responses to different clients or even for different request from the
same client. A RECOMMENDED assignment strategy is to generate ANE
names from random numbers.
Further, to protect the network topology from graph reconstruction
(e.g., through isomorphic graph identification [BONDY]), the ALTO
server SHOULD consider protection mechanisms to reduce information
exposure or obfuscate the real information. When doing so, the ALTO
server must be aware that information reduction/obfuscation may lead
to potential Undesirable Guidance from Authenticated ALTO Information
risk (Section 15.2 of [RFC7285]).
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Thus, implementations of ALTO servers involving reduction or
obfuscation of the Path Vector information SHOULD consider reduction/
obfuscation mechanisms that can preserve the integrity of ALTO
information, for example, by using minimal feasible region
compression algorithms [NOVA] or obfuscation protocols
[RESA][MERCATOR]. However, these obfuscation methods are
experimental and their practical applicability of these methods to
the generic capability provided by this extension is not fully
assessed. The ALTO server MUST carefully verify that the deployment
scenario satisfies the security assumptions of these methods before
applying them to protect Path Vector services with sensitive network
information.
For availability of ALTO service, an ALTO server should be cognizant
that using Path Vector extension might have a new risk: frequent
requesting for Path Vectors might consume intolerable amounts of the
server-side computation and storage, which can break the ALTO server.
For example, if an ALTO server implementation dynamically computes
the Path Vectors for each request, the service providing Path Vectors
may become an entry point for denial-of-service attacks on the
availability of an ALTO server.
To mitigate this risk, an ALTO server may consider using
optimizations such as precomputation-and-projection mechanisms
[MERCATOR] to reduce the overhead for processing each query. Also,
an ALTO server may also protect itself from malicious clients by
monitoring the behaviors of clients and stopping serving clients with
suspicious behaviors (e.g., sending requests at a high frequency).
The ALTO service providers must be aware that providing incremental
updates of the "max-reservable-bandwidth" may provide information
about other consumers of the network. For example, a change of the
value may indicate one or more reservations has been made or changed.
To mitigate this risk, an ALTO server can batch the updates and/or
add a random delay before publishing the updates.
12. IANA Considerations
12.1. ALTO Cost Metric Registry
This document registers a new entry to the ALTO Cost Metric Registry,
as instructed by Section 14.2 of [RFC7285]. The new entry is as
shown below in Table 1.
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+============+====================+=========================+
| Identifier | Intended Semantics | Security Considerations |
+============+====================+=========================+
| ane-path | See Section 6.5.1 | See Section 11 |
+------------+--------------------+-------------------------+
Table 1: ALTO Cost Metric Registry
12.2. ALTO Cost Mode Registry
This document registers a new entry to the ALTO Cost Mode Registry,
as instructed by Section 4 of [I-D.bw-alto-cost-mode]. The new entry
is as shown below in Table 2.
+============+====================+
| Identifier | Intended Semantics |
+============+====================+
| array | See Section 6.5.2 |
+------------+--------------------+
Table 2: ALTO Cost Mode Registry
12.3. ALTO Entity Domain Type Registry
This document registers a new entry to the ALTO Domain Entity Type
Registry, as instructed by Section 12.2 of
[I-D.ietf-alto-unified-props-new]. The new entry is as shown below
in Table 3.
+============+============+=============+===================+=======+
| Identifier |Entity | Hierarchy & |Media Type of |Mapping|
| |Identifier | Inheritance |Defining Resoucrce |to ALTO|
| |Encoding | | |Address|
| | | | |Type |
+============+============+=============+===================+=======+
| ane |See Section | None |application/alto- |false |
| |6.2.2 | |propmap+json | |
+------------+------------+-------------+-------------------+-------+
Table 3: ALTO Entity Domain Type Registry
Identifier: See Section 6.2.1.
Entity Identifier Encoding: See Section 6.2.2.
Hierarchy: None
Inheritance: None
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Media Type of Defining Resource: See Section 6.2.4.
Mapping to ALTO Address Type: This entity type does not map to ALTO
address type.
Security Considerations: In some usage scenarios, ANE addresses
carried in ALTO Protocol messages may reveal information about an
ALTO client or an ALTO service provider. Applications and ALTO
service providers using addresses of ANEs will be made aware of
how (or if) the addressing scheme relates to private information
and network proximity, in further iterations of this document.
12.4. ALTO Entity Property Type Registry
Two initial entries "max-reservable-bandwidth" and "persistent-
entity-id" are registered to the ALTO Domain "ane" in the "ALTO
Entity Property Type Registry", as instructed by Section 12.3 of
[I-D.ietf-alto-unified-props-new]. The two new entries are shown
below in Table 4 and their details can be found in Section 12.4.1 and
Section 12.4.2.
+==========================+====================+===================+
| Identifier | Intended | Media Type of |
| | Semantics | Defining Resource |
+==========================+====================+===================+
| max-reservable-bandwidth | See Section | application/alto- |
| | 6.4.1 | propmap+json |
+--------------------------+--------------------+-------------------+
| persistent-entity-id | See Section | application/alto- |
| | 6.4.2 | propmap+json |
+--------------------------+--------------------+-------------------+
Table 4: Initial Entries for ane Domain in the ALTO Entity
Property Types Registry
12.4.1. New ANE Property Type: Maximum Reservable Bandwidth
Identifier: "max-reservable-bandwidth"
Intended Semantics: See Section 6.4.1.
Media Type of Defining Resource: application/alto-propmap+json
Security Considerations: This property is essential for applications
such as large-scale data transfers or overlay network
interconnection to make better choice of bandwidth reservation.
It may reveal the bandwidth usage of the underlying network and
can potentially be leveraged to reduce the cost of conducting
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denial-of-service attacks. Thus, the ALTO server MUST consider
protection mechanisms including only providing the information to
authorized clients, and information reduction and obfuscation as
introduced in Section 11.
12.4.2. New ANE Property Type: Persistent Entity ID
Identifier: "persistent-entity-id"
Intended Semantics: See Section 6.4.2.
Media Type of Defining Resource: application/alto-propmap+json
Security Considerations: This property is useful when an ALTO server
wants to selectively expose certain service points whose detailed
properties can be further queried by applications. The entity IDs
may consider sensitive information about the underlying network,
and an ALTO server should follow the security considerations in
Section 11 of [I-D.ietf-alto-unified-props-new].
13. References
13.1. Normative References
[I-D.bw-alto-cost-mode]
Boucadair, M. and Q. Wu, "A Cost Mode Registry for the
Application-Layer Traffic Optimization (ALTO) Protocol",
Work in Progress, Internet-Draft, draft-bw-alto-cost-mode-
01, 4 March 2022, <https://datatracker.ietf.org/doc/html/
draft-bw-alto-cost-mode-01>.
[I-D.ietf-alto-unified-props-new]
Roome, W., Randriamasy, S., Yang, Y. R., Zhang, J. J., and
K. Gao, "An ALTO Extension: Entity Property Maps", Work in
Progress, Internet-Draft, draft-ietf-alto-unified-props-
new-24, 28 February 2022,
<https://datatracker.ietf.org/doc/html/draft-ietf-alto-
unified-props-new-24>.
[RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part Two: Media Types", RFC 2046,
DOI 10.17487/RFC2046, November 1996,
<https://www.rfc-editor.org/rfc/rfc2046>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/rfc/rfc2119>.
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[RFC2387] Levinson, E., "The MIME Multipart/Related Content-type",
RFC 2387, DOI 10.17487/RFC2387, August 1998,
<https://www.rfc-editor.org/rfc/rfc2387>.
[RFC5322] Resnick, P., Ed., "Internet Message Format", RFC 5322,
DOI 10.17487/RFC5322, October 2008,
<https://www.rfc-editor.org/rfc/rfc5322>.
[RFC7285] Alimi, R., Ed., Penno, R., Ed., Yang, Y., Ed., Kiesel, S.,
Previdi, S., Roome, W., Shalunov, S., and R. Woundy,
"Application-Layer Traffic Optimization (ALTO) Protocol",
RFC 7285, DOI 10.17487/RFC7285, September 2014,
<https://www.rfc-editor.org/rfc/rfc7285>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.
[RFC8189] Randriamasy, S., Roome, W., and N. Schwan, "Multi-Cost
Application-Layer Traffic Optimization (ALTO)", RFC 8189,
DOI 10.17487/RFC8189, October 2017,
<https://www.rfc-editor.org/rfc/rfc8189>.
[RFC8895] Roome, W. and Y. Yang, "Application-Layer Traffic
Optimization (ALTO) Incremental Updates Using Server-Sent
Events (SSE)", RFC 8895, DOI 10.17487/RFC8895, November
2020, <https://www.rfc-editor.org/rfc/rfc8895>.
[RFC8896] Randriamasy, S., Yang, R., Wu, Q., Deng, L., and N.
Schwan, "Application-Layer Traffic Optimization (ALTO)
Cost Calendar", RFC 8896, DOI 10.17487/RFC8896, November
2020, <https://www.rfc-editor.org/rfc/rfc8896>.
13.2. Informative References
[BONDY] Bondy, J.A. and R.L. Hemminger, "Graph reconstruction—a
survey", Journal of Graph Theory, Volume 1, Issue 3, pp
227-268 , 1977, <https://doi.org/10.1002/jgt.3190010306>.
[BOXOPT] Xiang, Q., Yu, H., Aspnes, J., Le, F., Kong, L., and Y.R.
Yang, "Optimizing in the dark: Learning an optimal
solution through a simple request interface", Proceedings
of the AAAI Conference on Artificial Intelligence 33,
1674-1681 , 2019,
<https://doi.org/10.1609/aaai.v33i01.33011674>.
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[CLARINET] Viswanathan, R., Ananthanarayanan, G., and A. Akella,
"CLARINET: WAN-Aware Optimization for Analytics Queries",
In 12th USENIX Symposium on Operating Systems Design and
Implementation (OSDI 16), USENIX Association, Savannah,
GA, 435-450 , 2016,
<https://dl.acm.org/doi/abs/10.5555/3026877.3026911>.
[G2] Ros-Giralt, J., Bohara, A., Yellamraju, S., Langston,
M.H., Lethin, R., Jiang, Y., Tassiulas, L., Li, J., Tan,
Y., and M. Veeraraghavan, "On the Bottleneck Structure of
Congestion-Controlled Networks", Proceedings of the ACM on
Measurement and Analysis of Computing Systems, Volume 3,
Issue 3, pp 1-31 , 2019,
<https://dl.acm.org/doi/10.1145/3366707>.
[HUG] Chowdhury, M., Liu, Z., Ghodsi, A., and I. Stoica, "HUG:
Multi-Resource Fairness for Correlated and Elastic
Demands", 13th USENIX Symposium on Networked Systems
Design and Implementation (NSDI 16) (Santa Clara, CA,
2016), 407-424. , 2016,
<https://dl.acm.org/doi/10.5555/2930611.2930638>.
[I-D.ietf-alto-performance-metrics]
Wu, Q., Yang, Y. R., Lee, Y., Dhody, D., Randriamasy, S.,
and L. M. C. Murillo, "ALTO Performance Cost Metrics",
Work in Progress, Internet-Draft, draft-ietf-alto-
performance-metrics-26, 2 March 2022,
<https://datatracker.ietf.org/doc/html/draft-ietf-alto-
performance-metrics-26>.
[I-D.ietf-httpbis-http2bis]
Thomson, M. and C. Benfield, "HTTP/2", Work in Progress,
Internet-Draft, draft-ietf-httpbis-http2bis-07, 24 January
2022, <https://datatracker.ietf.org/doc/html/draft-ietf-
httpbis-http2bis-07>.
[I-D.ietf-quic-http]
Bishop, M., "Hypertext Transfer Protocol Version 3
(HTTP/3)", Work in Progress, Internet-Draft, draft-ietf-
quic-http-34, 2 February 2021,
<https://datatracker.ietf.org/doc/html/draft-ietf-quic-
http-34>.
[JSONiq] "The JSON Query language", 2020,
<https://www.jsoniq.org/>.
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[MERCATOR] Xiang, Q., Zhang, J., Wang, X., Liu, Y., Guok, C., Le, F.,
MacAuley, J., Newman, H., and Y.R. Yang, "Toward Fine-
Grained, Privacy-Preserving, Efficient Multi-Domain
Network Resource Discovery", IEEE/ACM IEEE Journal on
Selected Areas of Communication 37(8): 1924-1940, 2019,
<https://doi.org/10.1109/JSAC.2019.2927073>.
[MOWIE] Zhang, Y., Li, G., Xiong, C., Lei, Y., Huang, W., Han, Y.,
Walid, A., Yang, Y.R., and Z. Zhang, "MoWIE: Toward
Systematic, Adaptive Network Information Exposure as an
Enabling Technique for Cloud-Based Applications over 5G
and Beyond", In Proceedings of the Workshop on Network
Application Integration/CoDesign, ACM, Virtual Event USA,
20-27. , 2020, <https://doi.org/10.1145/3405672.3409489>.
[NOVA] Gao, K., Xiang, Q., Wang, X., Yang, Y.R., and J. Bi, "An
objective-driven on-demand network abstraction for
adaptive applications", IEEE/ACM Transactions on
Networking (TON) Vol 27, no. 2 (2019): 805-818., 2019,
<https://doi.org/10.1109/IWQoS.2017.7969117>.
[RESA] Xiang, Q., Zhang, J., Wang, X., Liu, Y., Guok, C., Le, F.,
MacAuley, J., Newman, H., and Y.R. Yang, "Fine-grained,
multi-domain network resource abstraction as a fundamental
primitive to enable high-performance, collaborative data
sciences", Proceedings of the Super Computing 2018,
5:1-5:13 , 2019, <https://doi.org/10.1109/SC.2018.00008>.
[RFC2216] Shenker, S. and J. Wroclawski, "Network Element Service
Specification Template", RFC 2216, DOI 10.17487/RFC2216,
September 1997, <https://www.rfc-editor.org/rfc/rfc2216>.
[RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
Border Gateway Protocol 4 (BGP-4)", RFC 4271,
DOI 10.17487/RFC4271, January 2006,
<https://www.rfc-editor.org/rfc/rfc4271>.
[SENSE] "Software Defined Networking (SDN) for End-to-End
Networked Science at the Exascale", 2019,
<https://www.es.net/network-r-and-d/sense/>.
[SEREDGE] Contreras, L., Baliosian, J., Martı́nez-Julia, P., and J.
Serrat, "Computing at the Edge: But, what Edge?", In
proceedings of the NOMS 2020 - 2020 IEEE/IFIP Network
Operations and Management Symposium. pp. 1-9. , 2020,
<https://doi.org/10.1109/NOMS47738.2020.9110342>.
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[SWAN] Hong, C., Kandula, S., Mahajan, R., Zhang, M., Gill, V.,
Nanduri, M., and R. Wattenhofer, "Achieving High
Utilization with Software-driven WAN", In Proceedings of
the ACM SIGCOMM 2013 Conference on SIGCOMM (SIGCOMM '13),
ACM, New York, NY, USA, 15-26. , 2013,
<http://doi.acm.org/10.1145/2486001.2486012>.
[UNICORN] Xiang, Q., Chen, S., Gao, K., Newman, H., Taylor, I.,
Zhang, J., and Y.R. Yang, "Unicorn: Unified Resource
Orchestration for Multi-Domain, Geo-Distributed Data
Analytics", 2017 IEEE SmartWorld, Ubiquitous Intelligence
Computing, Advanced Trusted Computed, Scalable Computing
Communications, Cloud Big Data Computing, Internet of
People and Smart City Innovation
(SmartWorld/SCALCOM/UIC/ATC/CBDCom/IOP/SCI) (Aug. 2017),
1-6. , 2017,
<https://doi.org/10.1016/j.future.2018.09.048>.
[XQuery] "XQuery 3.1: An XML Query Language", 2017,
<https://www.w3.org/TR/xquery-31/>.
Appendix A. Acknowledgments
The authors would like to thank discussions with Andreas Voellmy,
Erran Li, Haibin Song, Haizhou Du, Jiayuan Hu, Qiao Xiang, Tianyuan
Liu, Xiao Shi, Xin Wang, and Yan Luo. The authors thank Greg
Bernstein, Dawn Chen, Wendy Roome, and Michael Scharf for their
contributions to earlier drafts.
The authors would also like to thank Tim Chown, Luis Contreras, Roman
Danyliw, Benjamin Kaduk, Erik Kline, Suresh Krishnan, Murray
Kucherawy, Warren Kumari, Danny Lachos, Francesca Palombini, Eric
Vyncke, Samuel Weiler, and Qiao Xiang whose feedback and suggestions
are invaluable to improve the practicability and conciseness of this
document, and Mohamed Boucadair, Martin Duke, Vijay Gurbani, Jan
Seedorf, and Qin Wu who provide great support and guidance.
Appendix B. Revision Logs (To be removed before publication)
B.1. Changes since -20
Reivision -21
* changes the normative requirement on protecting confidentiality of
PV information with softer language
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B.2. Changes since -19
Revision -20
* changes the IANA registry information
* adopts the comments from IESG reviews
B.3. Changes since -18
Revision -19
* adds detailed examples for use cases
* clarify terms with ambiguous meanings
B.4. Changes since -17
Revision -18
* changes the specification for content-id to conform to [RFC2387]
and [RFC5322]
* adds IPv6 examples
B.5. Changes since -16
Revision -17
* adds items for media type of defining resources in IANA
considerations
B.6. Changes since -15
Revision -16
* resolves the compatibility with the Multi-Cost extension (RFC
8189)
* adds media types of defining resources for ANE property types (for
IANA registration)
B.7. Changes since -14
Revision -15
* fixes the IDNits warnings,
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* fixes grammar issues,
* addresses the comments in the AD review.
B.8. Changes since -13
Revision -14
* addresses the comments in the chair review,
* fixes most issues raised by IDNits.
B.9. Changes since -12
Revision -13
* changes the abstract based on the chairs' reviews
* integrates Richard's responds to WGLC reviews
B.10. Changes since -11
Revision -12
* clarifies the definition of ANEs in a similar way as how Network
Elements is defined in [RFC2216]
* restructures several paragraphs that are not clear (Sec 3, Path
Vector bullet, Sec 4.2, Sec 5.1.3, Sec 6.2.4, Sec 6.4.2, Sec 9.3)
* uses "ALTO Entity Domain Type Registry"
B.11. Changes since -10
Revision -11
* replaces "part" with "components" in the abstract;
* identifies additional requirements (AR) derived from the flow
scheduling example, and introduces how the extension addresses the
additional requirements
* fixes the inconsistent use of "start" parameter in multipart
responses;
* specifies explicitly how to handle "cost-constraints";
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* uses the latest IANA registration mechanism defined in
[I-D.ietf-alto-unified-props-new];
* renames "persistent-entities" to "persistent-entity-id";
* makes "application/alto-propmap+json" as the media type of
defining resources for the "ane" domain;
* updates the examples;
* adds the discussion on ephemeral and persistent ANEs.
B.12. Changes since -09
Revision -10
* revises the introduction which
- extends the scope where the PV extension can be applied beyond
the "path correlation" information
* brings back the capacity region use case to better illustrate the
problem
* revises the overview to explain and defend the concepts and
decision choices
* fixes inconsistent terms, typos
B.13. Changes since -08
This revision
* fixes a few spelling errors
* emphasizes that abstract network elements can be generated on
demand in both introduction and motivating use cases
B.14. Changes Since Version -06
* We emphasize the importance of the path vector extension in two
aspects:
1. It expands the problem space that can be solved by ALTO, from
preferences of network paths to correlations of network paths.
2. It is motivated by new usage scenarios from both application's
and network's perspectives.
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* More use cases are included, in addition to the original capacity
region use case.
* We add more discussions to fully explore the design space of the
path vector extension and justify our design decisions, including
the concept of abstract network element, cost type (reverted to
-05), newer capabilities and the multipart message.
* Fix the incremental update process to be compatible with SSE -16
draft, which uses client-id instead of resource-id to demultiplex
updates.
* Register an additional ANE property (i.e., persistent-entities) to
cover all use cases mentioned in the draft.
Authors' Addresses
Kai Gao
Sichuan University
No.24 South Section 1, Yihuan Road
Chengdu
610000
China
Email: kaigao@scu.edu.cn
Young Lee
Samsung
South Korea
Email: younglee.tx@gmail.com
Sabine Randriamasy
Nokia Bell Labs
Route de Villejust
91460 Nozay
France
Email: sabine.randriamasy@nokia-bell-labs.com
Yang Richard Yang
Yale University
51 Prospect Street
New Haven, CT
United States of America
Email: yry@cs.yale.edu
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Jingxuan Jensen Zhang
Tongji University
4800 Caoan Road
Shanghai
201804
China
Email: jingxuan.n.zhang@gmail.com
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