Internet DRAFT - draft-zhang-alto-bgp-ls
draft-zhang-alto-bgp-ls
ALTO WG J. Zhang
Internet-Draft Tongji University
Intended status: Informational K. Gao
Expires: 14 January 2021 Sichuan University
LM. Contreras
Telefonica
A. Escribano
Alten
P. Cano
UST Global
F. Cano
Telefonica
13 July 2020
Considerations of Deploying ALTO using BGP - Link State (BGP-LS)
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draft-zhang-alto-bgp-ls-01
Abstract
This document discusses the requirements and deployment
considerations of providing Application-Layer Traffic Optimization
(ALTO) information in the inter-domain scenario using Border Gateway
Protocol - Link State (BGP-LS) extension.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
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
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
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."
This Internet-Draft will expire on 14 January 2021.
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Copyright Notice
Copyright (c) 2020 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/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
extracted from this document must include Simplified BSD License text
as described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. New Problem Statement and Working Items . . . . . . . . . . . 3
3. Background . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.1. ALTO Inter-domain Deployment Problem . . . . . . . . . . 4
3.2. BGP-LS Background and Benefits for ALTO . . . . . . . . . 4
3.3. ALTO Deployment Problem using BGP-LS . . . . . . . . . . 5
4. Requirements for Deploying ALTO in the Inter-domain Scenario
using BGP-LS . . . . . . . . . . . . . . . . . . . . . . 6
4.1. Basic Requirements . . . . . . . . . . . . . . . . . . . 6
4.2. BGP-LS specific Requirements . . . . . . . . . . . . . . 6
5. ALTO Deployment Considerations using BGP-LS . . . . . . . . . 7
5.1. Provisioning of Topology Information . . . . . . . . . . 7
5.2. Provisioning of Routing Information . . . . . . . . . . . 7
5.3. Provisioning of Performance Metric Information . . . . . 7
6. Configuration Interfaces of Map Calculation . . . . . . . . . 7
6.1. Configuration Interface of Network Map Calculation . . . 7
6.2. Configuration Interface of Cost Map Calculation . . . . . 8
6.3. Configuration Examples . . . . . . . . . . . . . . . . . 9
7. Test Scenarios . . . . . . . . . . . . . . . . . . . . . . . 14
7.1. Test Environment Setup . . . . . . . . . . . . . . . . . 14
7.2. Test Approach . . . . . . . . . . . . . . . . . . . . . . 14
7.3. Test Results . . . . . . . . . . . . . . . . . . . . . . 14
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 14
8.1. Normative References . . . . . . . . . . . . . . . . . . 14
8.2. Informative References . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15
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1. Introduction
The major component of the Application-Layer Traffic Optimization
(ALTO) [RFC7285] deployment is the network information collection.
[RFC7971] discussed multiple options to collect the network
information from the inter-domain networks.
To collection the related network information for ALTO, the following
high-level questions should be considered:
* Can the ALTO service realistically discover that information?
* Is the distribution of that information allowed by the operators
of that service?
* Is it information that a client cannot find easily some other way?
The Border Gateway Protocol - Link State (BGP-LS) extension [RFC7752]
is one of the popular options and has been deployed in many
Autonomous Systems (ASes) in recent years [TODO: Need some
reference].
BGP-LS enables ALTO server to provide underlay inter-domain topology
information using the link-state information in IGP domains.
To leverage BGP-LS to generate ALTO information effectively, some
requirements for deployment should be considered.
This document discusses these requirements and the corresponding
deployment considerations.
Additionally, this document describes some inter-domain scenarios to
test the deployment.
2. New Problem Statement and Working Items
This document was initially written to summarize ALTO deployment
consideration using BGP-LS. However, authors are finding new
interesting practical problems when pushing the deployment to large-
scale ISP networks.
Authors identify two problems:
Problem 1: how to efficiently obtain fine-grained global ALTO
information from multiple networks?
Problem 2: how to efficiently reconstruct and disseminate the ALTO
information upon dynamics?
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Considering the scale of the ISP carrier networks and the frequency
of network dynamicity, the previous design cannot survive. We have
to target a systemtic design to support (1) distributed information
collection, and (2) calculation and incremental information
recomputation.
Thus, authors propose a hierarchical architecture to deploy ALTO
servers. To make the deployment in different small networks
compatible with each other, the interfaces to allow interoperations
between different ALTO servers are required. Although we can design
and implement those interfaces outside the scope of ALTO, we believe
making ALTO provide this capability by itself can be a more coherent
approach and also have more potential benefits.
We are still heavily working on the initial specification. No more
details are added in the current document. But we have already done
a paper submission to talk about the initial design. For people
interested in this work, please feel free to contact us.
3. Background
3.1. ALTO Inter-domain Deployment Problem
[RFC7971] discusses considerations of ALTO deployment in different
network scenarios. The inter-domain network is the most common
scenario to deploy ALTO.
In practice, the following approaches are used to collect information
from the network:
* Interior Gateway Protocols (IGPs, e.g., OSPF, IS-IS): intra-domain
topology, link weights
* Border Gateway Protocol (BGP): inter-domain topology, prefixes, AS
numbers, AS distances, or other BGP metrics
* Network Management Protocols (NMPs, e.g., SNMP, Netconf): latency,
utilization, bandwidth
3.2. BGP-LS Background and Benefits for ALTO
BGP-LS [RFC7752] is designed to allow a BGP speaker to advertise the
link state database (LSDB) or traffic engineering database (TED) of
its connected IGP area.
BGP-LS defines a new address family, link state, in the BGPv4
framework [RFC4271].
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Using BGP-LS, the ALTO server can communicate to only BGP speakers to
collect all those information.
3.3. ALTO Deployment Problem using BGP-LS
A simple deployment solution is to connect the ALTO server as a BGP
reflector client of every BGP speakers in the network. However, this
solution is expensive and redundant. And because of the BGP updates,
the ALTO server could receive a lot of inconsistent redundant
informaiton. To avoid the redundancy and inconsistency of the
collected information, a deployment solution should be minimal.
To understand what is a minimal solution to deploy ALTO using BGP-LS,
the following questions are raised:
* Is it necessary to connect the ALTO server to every AS within a
BGP session?
* Does the session between the ALTO server and each AS have to
enable BGP-LS?
* If using BGP-LS, can the number of necessary BGP sessions be
reduced?
The following example shows a minimal deployment in a simple example
topology.
Consider the following AS-level topology as an example. Assuming all
the BGP sessions between ASes have enabled BGP-LS, the BGP speaker on
AS B can received the IGP topologies from all the three ASes. Thus,
to make sure the ALTO server collect all the inter-domain and intra-
domain topology information, the minimal deployment could be to set
up the the ALTO server as a BGP reflector of the BGP speaker on AS B.
+--------+ +--------+ +---------+
| AS A |---| AS B |---| AS C |
+--------+ +--------+ +---------+
| BGP / BGP-LS
| /
| /
+-------------+
| ALTO Server |
+-------------+
Figure 1: Example AS-level Topology
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However, it is not enough for collecting the routing information. As
the BGP is a destination-based routing protocol, AS B could not
receive the routing information between endpoints from AS A and AS C.
To get the missing routing information, the ALTO server should also
connect read the BGP RIB of AS A or AS C at least.
As the result, the minimal solution is to establish a BGP session to
AS B with BGP-LS and another BGP session to AS A (or AS C) without
BGP-LS.
The following part of this document will discuss how to achieve the
minimal ALTO deployment using BPG-LS in detail. Specifically, two
questions are required to be answered:
* Which BGP speakers are required to be connected to the ALTO
server?
* Which BGP sessions are required to enable BGP-LS?
4. Requirements for Deploying ALTO in the Inter-domain Scenario using
BGP-LS
4.1. Basic Requirements
The following basic requirements are required by ALTO inter-domain
deployment in any case.
Req 1: The ALTO server MUST be able to collect topology information
from multiple IGP areas.
Req 2: The ALTO server MUST be able to collect routing information
for any pairs of endpoints.
Req 3: The ALTO server MUST be able to collect performance metrics
across routes.
4.2. BGP-LS specific Requirements
The following additional requirements are required by ALTO deployment
when using BGP-LS.
Req 4: The ALTO server SHOULD only communicate with necessary BGP
speakers.
Req 5: The ALTO server SHOULD only enable BGP-LS advertisement in
necessary BGP sessions between BGP speakers.
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5. ALTO Deployment Considerations using BGP-LS
This section discusses some deployment considerations about how to
address the basic requirements (Req 1-3) when satisfying the BGP-LS
specific requirements (Req 4-5).
5.1. Provisioning of Topology Information
As BGP-LS advertisement cannot be propagated to remote the remote
ASes, each BGP speaker can only discover directly peered IGP
topologies using BGP-LS.
To satisfy Req 4, the ALTO server should only communicate to transit
networks or IXPs using BGP-LS. As the IGP topology of a stub network
can always be discovered by its peered transit networks or IXPs, so
it is not necessary to communicate with the stub network.
Specifically, the ALTO server should find a minimal BGP speaker set
whose peered networks can cover all IGP domains.
5.2. Provisioning of Routing Information
As BGP is a destination-based routing protocol, a stub network can
receive all the inter-domain routing information from all the
reachable destinations via BGP.
Thus, to satisfy Req 4, the ALTO server should only communicate to
stub networks using BGP, as the inter-domain routing information from
the transit networks is not necessary.
Assuming the ALTO server has already collected the complete topology
information using BGP-LS, the ALTO server will have the LSDB of every
IGP domain.
To satisfy Req 5, all the BGP sessions connected to the stub networks
do not have to enable BGP-LS.
5.3. Provisioning of Performance Metric Information
TBD.
6. Configuration Interfaces of Map Calculation
6.1. Configuration Interface of Network Map Calculation
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rw network-map-config* [resource-id]
+--rw resource-id alto-types:resource-id
+--rw description? string
+--rw (params)
| +--:(bgp)
| +--rw bgp-params
| +--rw bgp-rib* [rib-id]
| +--rw rib-id rib:rib-id
| +--rw topology-id? topology:topology-id
| +--rw bgp-ls? boolean
+--rw (algorithm)
+--:(first-hop-cluster)
+--rw first-hop-cluster-algorithm
+--rw inspect-igp boolean
To generate a network map, one or more BGP RIBs that could provide
the topology information MUST specified. Each BGP RIB MAY include a
pre-computed topology from the RIB, and an option indicating if the
BPG-LS is enabled.
The "inspect-igp" option in the "first-hop-cluster-algorithm" field
indicates if the ALTO server exposes information about the IGP
topologies. If it is true, the ALTO server will inspect all the IGP
topolgies from the BGP RIBs that enalbe BGP-LS (whose "bgp-ls" option
is true).
6.2. Configuration Interface of Cost Map Calculation
rw cost-map-config* [resource-id]
+--rw resource-id alto-types:resource-id
+--rw description? string
+--rw dependent-network-map alto-types:resource-id
+--rw (general-params)
| +--:(bgp)
| +--rw bgp-params
| +--rw alternative-bgp-rib* [rib-id]
| +--rw rib-id rib:rib-id
| +--rw topology-id? topology:topology-id
| +--rw bgp-ls? boolean
+--rw cost-type* [cost-mode,cost-metric]
+rw cost-mode alto-types:cost-mode
+rw cost-metric alto-types:cost-metric
+rw (params)?
To generate a cost map, besides the dependent network map, one or
more alternative BGP RIBs could be specified to provide necessary
routing information to the ALTO server.
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6.3. Configuration Examples
Example Network
.----------------------------. .------------.
| 1.1.1.0/24 6.6.6.0/24 | | 8.8.8.0/24 |
| | | | | | |
| +-+--+ +-+--+ | | +-+--+ |
| | R1 +--------+ R6 | | .------------. | | R8 | |
| +-+--+ +-+--+ | | 3.3.3.0/24 | | +-+--+ |
| | | | | | | | | |
| | +-+--+ | | +-+--+ | | +-+--+ |
| +-----------+ R2 +- - -|- - | -+ R3 +- - | -|- -+ R7 | |
| +----+ | | +++--+ | | +----+ |
| | | | .. | | |
| +-+--+ | | ..AS 200 | | AS 300 |
| 5.5.5.0/24------+ R5 | | `------------' `------------'
| +-+--+ | ..
| | | ..
| AS 100 +-+--+ | ..
| | R4 +- - -|- - - - +.
| +-+--+ | .
`----------------------------' .
. .
. .
. +--------+----+
+- - - - -+ ALTO Server |
+-------------+
R2 - R3: BGP-LS
R4 - R3: BGP-LS
R7 - R3: BGP-LS
R3 - ALTO: BGP-LS
R4 - ALTO: BGP
Figure 2
Config a network map:
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POST /restconf/config/alto-maps/network-map-config/bgp-networkmap
HOST: alto-config.example.com
Content-Type: application/json
Content-Length: TBD
{
"network-map-config": {
"resource-id": "bgp-networkmap",
"bgp-params": {
"bgp-rib": [
{
"rib-id": "as200-r3",
"bgp-ls": true
}
]
},
"first-hop-cluster-algorithm": {
"inspect-igp": true
}
}
}
Test to fetch the network map:
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GET /alto/networkmap/example
HOST: alto.example.com
HTTP/1.1 200 OK
Content-Length: TBD
Content-Type: application/alto-networkmap+json
{
"meta": {
"vtag": {
"resource-id": "bgp-networkmap",
"tag": "da65eca2eb7a10ce8b059740b0b2e3f8eb1d4785"
}
},
{
"network-map": {
"PID100.R1": {
"ipv4": [ "1.1.1.0/24" ]
},
"PID100.R5": {
"ipv4": [ "5.5.5.0/24" ]
},
"PID100.R6": {
"ipv4": [ "6.6.6.0/24" ]
},
"PID200.R3": {
"ipv4": [ "3.3.3.0/24" ]
},
"PID300.R8": {
"ipv4": [ "8.8.8.0/24" ]
}
}
}
}
Config a cost map:
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POST /restconf/config/alto-maps/cost-map-config/bgp-costmap
HOST: alto-config.example.com
Content-Type: application/json
Content-Length: TBD
{
"cost-map-config": {
"resource-id": "bgp-costmap",
"dependent-network-map": "bgp-networkmap",
"bgp-params": {
"alternative-bgp-rib": [
{
"rib-id": "as100-r4",
"bgp-ls": false
}
]
},
"cost-type": [
{
"cost-mode": "numerical",
"cost-metric": "hopcount"
}
]
}
}
Test to fetch the cost map:
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GET /alto/costmap/bgp-costmap
HOST: alto.example.com
HTTP/1.1 200 OK
Content-Length: TBD
Content-Type: application/alto-costmap+json
{
"meta": {
"vtag": {
"resource-id": "bgp-costmap",
"tag": "c0ce023b8678a7b9ec00324673b98e54656d1f6d"
},
"dependent-vtags": [
{
"resource-id": "bgp-networkmap",
"tag": "da65eca2eb7a10ce8b059740b0b2e3f8eb1d4785"
}
],
"cost-type": {
"cost-mode": "numerical",
"cost-metric": "hopcount"
}
},
"cost-map": {
"PID100.R1": {
"PID100.R1": 1, "PID100.R5": 3, "PID100.R6": 2,
"PID200.R3": 3, "PID300.R8": 5
},
"PID100.R5": {
"PID100.R1": 3, "PID100.R5": 1, "PID100.R6": 3,
"PID200.R3": 3, "PID300.R8": 5
},
"PID100.R6": {
"PID100.R1": 2, "PID100.R5": 3, "PID100.R6": 1,
"PID200.R3": 3, "PID300.R8": 5
},
"PID200.R3": {
"PID100.R1": 3, "PID100.R5": 3, "PID100.R6": 3,
"PID200.R3": 1, "PID300.R8": 3
},
"PID300.R8": {
"PID100.R1": 5, "PID100.R5": 5, "PID100.R6": 5,
"PID200.R3": 3, "PID300.R8": 1
}
}
}
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7. Test Scenarios
7.1. Test Environment Setup
7.2. Test Approach
7.3. Test Results
8. References
8.1. Normative References
[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/info/rfc2119>.
[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/info/rfc4271>.
[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/info/rfc7285>.
[RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and
S. Ray, "North-Bound Distribution of Link-State and
Traffic Engineering (TE) Information Using BGP", RFC 7752,
DOI 10.17487/RFC7752, March 2016,
<https://www.rfc-editor.org/info/rfc7752>.
[RFC7971] Stiemerling, M., Kiesel, S., Scharf, M., Seidel, H., and
S. Previdi, "Application-Layer Traffic Optimization (ALTO)
Deployment Considerations", RFC 7971,
DOI 10.17487/RFC7971, October 2016,
<https://www.rfc-editor.org/info/rfc7971>.
[RFC8571] Ginsberg, L., Ed., Previdi, S., Wu, Q., Tantsura, J., and
C. Filsfils, "BGP - Link State (BGP-LS) Advertisement of
IGP Traffic Engineering Performance Metric Extensions",
RFC 8571, DOI 10.17487/RFC8571, March 2019,
<https://www.rfc-editor.org/info/rfc8571>.
8.2. Informative References
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[I-D.ietf-alto-cost-calendar]
Randriamasy, S., Yang, Y., WU, Q., Lingli, D., and N.
Schwan, "Application-Layer Traffic Optimization (ALTO)
Cost Calendar", Work in Progress, Internet-Draft, draft-
ietf-alto-cost-calendar-21, 17 March 2020,
<http://www.ietf.org/internet-drafts/draft-ietf-alto-cost-
calendar-21.txt>.
[I-D.ietf-alto-incr-update-sse]
Roome, W. and Y. Yang, "ALTO Incremental Updates Using
Server-Sent Events (SSE)", Work in Progress, Internet-
Draft, draft-ietf-alto-incr-update-sse-22, 20 March 2020,
<http://www.ietf.org/internet-drafts/draft-ietf-alto-incr-
update-sse-22.txt>.
[I-D.ietf-alto-path-vector]
Gao, K., Randriamasy, S., Yang, Y., and J. Zhang, "ALTO
Extension: Path Vector", Work in Progress, Internet-Draft,
draft-ietf-alto-path-vector-10, 9 March 2020,
<http://www.ietf.org/internet-drafts/draft-ietf-alto-path-
vector-10.txt>.
[I-D.ietf-alto-unified-props-new]
Roome, W., Randriamasy, S., Yang, Y., Zhang, J., and K.
Gao, "Unified Properties for the ALTO Protocol", Work in
Progress, Internet-Draft, draft-ietf-alto-unified-props-
new-11, 9 March 2020, <http://www.ietf.org/internet-
drafts/draft-ietf-alto-unified-props-new-11.txt>.
[I-D.wang-idr-bgpls-inter-as-topology-ext]
Wang, A. and H. Chen, "BGP-LS Extension for Inter-AS
Topology Retrieval", Work in Progress, Internet-Draft,
draft-wang-idr-bgpls-inter-as-topology-ext-02, 13 August
2018, <http://www.ietf.org/internet-drafts/draft-wang-idr-
bgpls-inter-as-topology-ext-02.txt>.
[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/info/rfc8189>.
Authors' Addresses
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Jingxuan Jensen Zhang
Tongji University
4800 Cao'An Hwy
Shanghai
201804
China
Email: jingxuan.zhang@tongji.edu.cn
Kai Gao
Sichuan University
No.24 South Section 1, Yihuan Road
Chengdu
610000
China
Email: kaigao@scu.edu.cn
Luis M. Contreras
Telefonica
Ronda de la Comunicacion, s/n
28050 Madrid
Spain
Email: luismiguel.contrerasmurillo@telefonica.com
Anais Escribano
Alten
Carrer de Josep Pla, 2
08019 Barcelona
Spain
Email: anais.escribano@alten.es
Patricia Cano
UST Global
Ramirez de Arellano 29
28043 Madrid
Spain
Email: Patricia.Diez@ust-global.com
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Francisco Cano
Telefonica
Avenida del Conocimiento, 12
18016 Granada
Spain
Email: franciscojose.canohila@telefonica.com
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