Internet DRAFT - draft-seedorf-cdni-request-routing-alto
draft-seedorf-cdni-request-routing-alto
CDNI J. Seedorf
Internet-Draft HFT Stuttgart - Univ. of Applied Sciences
Intended status: Standards Track Y. Yang
Expires: January 3, 2018 Tongji/Yale
K. Ma
Ericsson
J. Peterson
Neustar
July 2, 2017
Content Delivery Network Interconnection (CDNI) Request Routing: CDNI
Footprint and Capabilities Advertisement using ALTO
draft-seedorf-cdni-request-routing-alto-10
Abstract
The Content Delivery Networks Interconnection (CDNI) WG is defining a
set of protocols to inter-connect CDNs, to achieve multiple goals
such as extending the reach of a given CDN to areas that are not
covered by that particular CDN. One componet that is needed to
achieve the goal of CDNI is the CDNI Request Routing Footprint &
Capabilities Advertisement interface (FCI) [RFC7336]. [RFC8008] has
defined precisely the semantics of FCI and provided guidelines on the
FCI protocol, but the exact protocol is explicitly outside the scope
of that document. In this document, we define an FCI protocol using
the Application Layer Traffic Optimization (ALTO) protocol.
Status of This Memo
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This Internet-Draft will expire on January 3, 2018.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Background . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1. Semantics of FCI Advertisment . . . . . . . . . . . . . . 4
2.2. ALTO Background and Benefits . . . . . . . . . . . . . . 5
3. CDNI FCI ALTO Service . . . . . . . . . . . . . . . . . . . . 7
3.1. Server Response Encoding . . . . . . . . . . . . . . . . 8
3.1.1. Media Type . . . . . . . . . . . . . . . . . . . . . 8
3.1.2. Meta Information . . . . . . . . . . . . . . . . . . 8
3.1.3. Data Information . . . . . . . . . . . . . . . . . . 8
3.2. Protocol Errors . . . . . . . . . . . . . . . . . . . . . 8
3.3. Examples . . . . . . . . . . . . . . . . . . . . . . . . 8
3.3.1. Basic Example . . . . . . . . . . . . . . . . . . . . 8
3.3.2. Incremental FCI Update Example . . . . . . . . . . . 9
3.3.3. FCI Using ALTO Network Map Example . . . . . . . . . 9
4. Security Considerations . . . . . . . . . . . . . . . . . . . 9
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
6.1. Normative References . . . . . . . . . . . . . . . . . . 10
6.2. Informative References . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction
Many Network Service Providers (NSPs) are currently considering or
have already started to deploy Content Delivery Networks (CDNs)
within their networks. As a consequence of this development, there
is a need for interconnecting these local CDNs. Content Delivery
Networks Interconnection (CDNI) has the goal of standardizing
protocols to enable such interconnection of CDNs [RFC6707].
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The CDNI problem statement [RFC6707] defines four interfaces to be
standardized within the IETF for CDN interconnection:
o CDNI Request Routing Interface
o CDNI Metadata Interface
o CDNI Logging Interface
o CDNI Control Interface
The main purpose of the CDNI Request Routing Interface is described
in [RFC6707] as follows: "The CDNI Request Routing interface enables
a Request Routing function in an Upstream CDN to query a Request
Routing function in a Downstream CDN to determine if the Downstream
CDN is able (and willing) to accept the delegated Content Request.
It also allows the Downstream CDN to control what should be returned
to the User Agent in the redirection message by the upstream Request
Routing function." On a high level, the scope of the CDNI Request
Routing Interface therefore contains two main tasks:
o determining if the downstream CDN is willing to accept a delegated
content request;
o redirecting the content request coming from an upstream CDN to the
proper entry point or entity in the downstream CDN.
Correspondingly, the request routing interface is broadly divided
into two functionalities:
o CDNI FCI: the advertisement from a dCDN to a uCDN or a query from
a uCDN to a dCDN for the uCDN to decide whether to redirect
particular user requests to that dCDN;
o CDNI RI: the synchronous operation of actually redirecting a user
request.
This document focuses solely on CDNI FCI, with a goal to specify a
new Application Layer Traffic Optimization (ALTO) [RFC7285] service
called 'CDNI/FCI Service', to transport and update CDNI FCI JSON
objects, which are defined in a separate document in [RFC8008].
Throughout this document, we use the terminology for CDNI defined in
[RFC6707] and [RFC8008].
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2. Background
The design of CDNI FCI transport using ALTO depends on understanding
of both FCI semantics and ALTO. Hence, we start with a review of
both.
2.1. Semantics of FCI Advertisment
The CDNI document on "Footprint and Capabilities Semantics" [RFC8008]
defines the semantics for the CDNI FCI. It thus provides guidance on
what Footprint and Capabilities mean in a CDNI context and how a
protocol solution should in principle look like. The definitions in
[RFC8008] depend on [RFC8006]. Here we briefly summarize key related
points of [RFC8008] and [RFC8006]. For a detailed discussion, the
reader is referred to the RFCs.
o Footprint and capabilities are tied together and cannot be
interpreted independently from each other. In such cases, i.e.
where capabilities must be expressed on a per footprint basis, it
may be beneficial to combine footprint and capabilities
advertisement. [RFC8008] integrates footprint and capabilities
with an approach of "capabilities with footprint restrictions".
o Given that a large part of Footprint and Capabilities
Advertisement will actually happen in contractual agreements, the
semantics of CDNI Footprint and Capabilities advertisement refer
to answering the following question: what exactly still needs to
be advertised by the CDNI FCI? For instance, updates about
temporal failures of part of a footprint can be useful information
to convey via the CDNI request routing interface. Such
information would provide updates on information previously agreed
in contracts between the participating CDNs. In other words, the
CDNI FCI is a means for a dCDN to provide changes/updates
regarding a footprint and/or capabilities it has prior agreed to
serve in a contract with a uCDN. Hence, server push and
incremental encoding will be necessary techniques.
o Multiple types of footprints are defined in [RFC8006]:
* List of ISO Country Codes
* List of AS numbers
* Set of IP-prefixes
A 'set of IP-prefixes' must be able to contain full IP addresses,
i.e., a /32 for IPv4 and a /128 for IPv6, and also IP prefixes
with an arbitrary prefix length. There must also be support for
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multiple IP address versions, i.e., IPv4 and IPv6, in such a
footprint.
o For all of these mandatory-to-implement footprint types,
footprints can be viewed as constraints for delegating requests to
a dCDN: A dCDN footprint advertisement tells the uCDN the
limitations for delegating a request to the dCDN. For IP prefixes
or ASN(s), the footprint signals to the uCDN that it should
consider the dCDN a candidate only if the IP address of the
request routing source falls within the prefix set (or ASN,
respectively). The CDNI specifications do not define how a given
uCDN determines what address ranges are in a particular ASN.
Similarly, for country codes a uCDN should only consider the dCDN
a candidate if it covers the country of the request routing
source. The CDNI specifications do not define how a given uCDN
determines the country of the request routing source. Multiple
footprint constraints are additive, i.e. the advertisement of
different types of footprint narrows the dCDN candidacy
cumulatively.
o The following capabilities are defined as 'base' capabilities,
i.e. ones that are needed in any case and therefore constitute
mandatory capabilities to be supported by the CDNI FCI:
* Delivery Protocol (e.g., HTTP vs. RTMP)
* Acquisition Protocol (for acquiring content from a uCDN)
* Redirection Mode (e.g., DNS Redirection vs. HTTP Redirection as
discussed in [RFC7336])
* Capabilities related to CDNI Logging (e.g., supported logging
mechanisms)
* Capabilities related to CDNI Metadata (e.g., authorization
algorithms or support for proprietary vendor metadata)
2.2. ALTO Background and Benefits
Application Layer Traffic Optimization (ALTO) [RFC7285] is an
approach for guiding the resource provider selection process in
distributed applications that can choose among several candidate
resources providers to retrieve a given resource. By conveying
network layer (topology) information, an ALTO server can provide
important information to "guide" the resource provider selection
process in distributed applications. Usually, it is assumed that an
ALTO server conveys information these applications cannot measure
themselves [RFC5693].
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Originally, ALTO was motivated by the huge amount of cross-ISP
traffic generated by P2P applications [RFC5693]. Recently, however,
ALTO is also being considered for improving the request routing in
CDNs [I-D.jenkins-alto-cdn-use-cases]. In this context, it has also
been proposed to use ALTO for selecting an entry-point in a
downstream NSP's network (see section 3.4 "CDN delivering Over-The-
Top of a NSP's network" in [I-D.jenkins-alto-cdn-use-cases]). Also,
the CDNI problem statement explicitly mentions ALTO as a candidate
protocol for "algorithms for selection of CDN or Surrogate by
Request-Routing systems" [RFC6707].
The following reasons make ALTO a suitable candidate protocol for
downstream CDN selection as part of CDNI request routing and in
particular for an FCI protocol:
o CDN request routing is done at the application layer. ALTO is a
protocol specifically designed to improve application layer
traffic (and application layer connections among hosts on the
Internet) by providing additional information to applications that
these applications could not easily retrieve themselves. For
CDNI, this is exactly the case: a uCDN wants to improve
application layer CDN request routing by using dedicated
information (provided by a dCDN) that the uCDN could not easily
obtain otherwise.
o The semantics of an ALTO network map are an exact match for the
needed information to convey a footprint by a downstream CDN, in
particular if such a footprint is being expressed by IP-prefix
ranges.
o Security: ALTO maps can be signed and hence provide inherent
integrity protection (see Section 4)
o RESTful-Design: The ALTO protocol has undergone extensive
revisions in order to provide a RESTful design regarding the
client-server interaction specified by the protocol. A CDNI FCI
interface based on ALTO would inherit this RESTful design.
o Error-handling: The ALTO protocol has undergone extensive
revisions in order to provide sophisticated error-handling, in
particular regarding unexpected cases. A CDNI FCI interface based
on ALTO would inherit this thought-through and mature error-
handling.
o Filtered network map: The ALTO Map Filtering Service (see
[RFC7285] for details) would allow a uCDN to query only for parts
of an ALTO map.
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o Server-initiated Notifications and Incremental Updates: In case
the footprint or the capabilities of a downstream CDN change
abruptly (i.e. unexpectedly from the perspective of an upstream
CDN), server initiated notifications would enable a dCDN to
directly inform an upstream CDN about such changes. Consider the
case where - due to failure - part of the footprint of the dCDN is
not functioning, i.e. the CDN cannot serve content to such clients
with reasonable QoS. Without server-initiated notifications, the
uCDN might still use a very recent network and cost map from dCDN,
and therefore redirect request to dCDN which it cannot serve.
Similarly, the possibility for incremental updates would enable
efficient conveyance of the aforementioned (or similar) status
changes by the dCDN to the uCDN. The newest design of ALTO
supports server pushed incremental updates
[I-D.ietf-alto-incr-update-sse].
o Content Availability on Hosts: A dCDN might want to express CDN
capabilities in terms of certain content types (e.g. codecs/
formats, or content from certain content providers). The new
endpoint property for ALTO would enable a dCDN to make available
such information to an upstream CDN. This would enable a uCDN to
determine if a given dCDN actually has the capabilities for a
given request with respect to the type of content requested.
o Resource Availability on Hosts or Links: The capabilities on links
(e.g. maximum bandwidth) or caches (e.g. average load) might be
useful information for an upstream CDN for optimized downstream
CDN selection. For instance, if a uCDN receives a streaming
request for content with a certain bitrate, it needs to know if it
is likely that a dCDN can fulfill such stringent application-level
requirements (i.e. can be expected to have enough consistent
bandwidth) before it redirects the request. In general, if ALTO
could convey such information via new endpoint properties, it
would enable more sophisticated means for downstream CDN selection
with ALTO.
3. CDNI FCI ALTO Service
The ALTO protocol is based on an ALTO Information Service Framework
which consists of several services, where all ALTO services are
'provided through a common transport protocol, messaging structure
and encoding, and transaction model' [RFC7285]. The ALTO protocol
specification [RFC7285] defines several such services, e.g. the ALTO
map service.
This document defines a new ALTO Service called 'CDNI Footprint &
Capabilities Advertisement Service' which conveys JSON objects of
media type 'application/cdni'. This media type and JSON object
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format is defined in [RFC8006] and [RFC8008]; this document specifies
how to transport such JSON objects via the ALTO protocol with the
ALTO 'CDNI Footprint & Capabilities Advertisement Service'.
3.1. Server Response Encoding
3.1.1. Media Type
The media type of the CDNI FCI Map is 'application/cdni'.
3.1.2. Meta Information
The 'meta' field of a FCI response MUST include 'vtag', which is an
ALTO Version Tag of the retrieved FCIMapData according to [RFC7285]
(Section 10.3.). It thus contains a 'resource-id' attribute, and a
'tag' is an identifier string.
3.1.3. Data Information
The data component of a CDNI FCI resource is named 'cdni-fcimap'
which is a JSON object defined by [RFC8008]. This JSON object is
derived from ResponseEntityBase as specified in the ALTO protocol
[RFC7285] (Section 8.4.).
3.2. Protocol Errors
Protocol errors are handled as specified in the ALTO protocol
[RFC7285] (Section 8.5.).
3.3. Examples
3.3.1. Basic Example
The following example shows an CDNI FCI response as in [RFC8008],
however with meta-information as defined in Section 3.1.2 of this
document.
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GET /fcimap HTTP/1.1
Host: alto.example.com
Accept: application/cdni,application/alto-error+json
HTTP/1.1 200 OK
Content-Length: 439
Content-Type: application/cdni
{
"meta" : {
"vtag": {
"resource-id": "my-default-fcimap",
"tag": "da65eca2eb7a10ce8b059740b0b2e3f8eb1d4785"
}
},
"cdni-fcimap": {
"capabilities": [
{
"capability-type": "FCI.DeliveryProtocol",
"capability-value": {
"delivery-protocols": [
"http/1.1",
]
},
"footprints": [
<Footprint objects>
]
}
]
}
}
3.3.2. Incremental FCI Update Example
3.3.3. FCI Using ALTO Network Map Example
4. Security Considerations
One important security consideration is the proper authentication of
advertisement information provided by a downstream CDN. The ALTO
protocol provides a specification for a signature of ALTO information
(see 8.2.2. of [RFC7285]. ALTO thus provides a proper means for
protecting the integrity of FCI information.
More Security Considerations will be discussed in a future version of
this document.
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5. Acknowledgements
The authors would like to thank Kevin Ma, Daryl Malas, and Matt
Caulfield for their timely reviews and invaluable comments.
Jan Seedorf is partially supported by the GreenICN project (GreenICN:
Architecture and Applications of Green Information Centric
Networking), a research project supported jointly by the European
Commission under its 7th Framework Program (contract no. 608518) and
the National Institute of Information and Communications Technology
(NICT) in Japan (contract no. 167). The views and conclusions
contained herein are those of the authors and should not be
interpreted as necessarily representing the official policies or
endorsements, either expressed or implied, of the GreenICN project,
the European Commission, or NICT.
6. References
6.1. Normative References
[RFC5693] Seedorf, J. and E. Burger, "Application-Layer Traffic
Optimization (ALTO) Problem Statement", RFC 5693,
DOI 10.17487/RFC5693, October 2009,
<http://www.rfc-editor.org/info/rfc5693>.
[RFC6707] Niven-Jenkins, B., Le Faucheur, F., and N. Bitar, "Content
Distribution Network Interconnection (CDNI) Problem
Statement", RFC 6707, DOI 10.17487/RFC6707, September
2012, <http://www.rfc-editor.org/info/rfc6707>.
[RFC6770] Bertrand, G., Ed., Stephan, E., Burbridge, T., Eardley,
P., Ma, K., and G. Watson, "Use Cases for Content Delivery
Network Interconnection", RFC 6770, DOI 10.17487/RFC6770,
November 2012, <http://www.rfc-editor.org/info/rfc6770>.
[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,
<http://www.rfc-editor.org/info/rfc7285>.
[RFC7336] Peterson, L., Davie, B., and R. van Brandenburg, Ed.,
"Framework for Content Distribution Network
Interconnection (CDNI)", RFC 7336, DOI 10.17487/RFC7336,
August 2014, <http://www.rfc-editor.org/info/rfc7336>.
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[RFC7337] Leung, K., Ed. and Y. Lee, Ed., "Content Distribution
Network Interconnection (CDNI) Requirements", RFC 7337,
DOI 10.17487/RFC7337, August 2014,
<http://www.rfc-editor.org/info/rfc7337>.
[RFC8006] Niven-Jenkins, B., Murray, R., Caulfield, M., and K. Ma,
"Content Delivery Network Interconnection (CDNI)
Metadata", RFC 8006, DOI 10.17487/RFC8006, December 2016,
<http://www.rfc-editor.org/info/rfc8006>.
[RFC8008] Seedorf, J., Peterson, J., Previdi, S., van Brandenburg,
R., and K. Ma, "Content Delivery Network Interconnection
(CDNI) Request Routing: Footprint and Capabilities
Semantics", RFC 8008, DOI 10.17487/RFC8008, December 2016,
<http://www.rfc-editor.org/info/rfc8008>.
6.2. Informative References
[I-D.ietf-alto-incr-update-sse]
Roome, W. and Y. Yang, "ALTO Incremental Updates Using
Server-Sent Events (SSE)", draft-ietf-alto-incr-update-
sse-07 (work in progress), July 2017.
[I-D.jenkins-alto-cdn-use-cases]
Niven-Jenkins, B., Watson, G., Bitar, N., Medved, J., and
S. Previdi, "Use Cases for ALTO within CDNs", draft-
jenkins-alto-cdn-use-cases-03 (work in progress), June
2012.
[I-D.ma-cdni-capabilities]
Ma, K. and J. Seedorf, "CDNI Footprint & Capabilities
Advertisement Interface", draft-ma-cdni-capabilities-09
(work in progress), April 2016.
Authors' Addresses
Jan Seedorf
HFT Stuttgart - Univ. of Applied Sciences
Schellingstrasse 24
Stuttgart 70174
Germany
Phone: +49-0711-8926-2801
Email: jan.seedorf@hft-stuttgart.de
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Y.R. Yang
Tongji/Yale University
51 Prospect Street
New Haven, CT 06511
United States of America
Email: yry@cs.yale.edu
URI: http://www.cs.yale.edu/~yry/
Kevin J. Ma
Ericsson
43 Nagog Park
Acton, MA 01720
United States of America
Phone: +1-978-844-5100
Email: kevin.j.ma@ericsson.com
Jon Peterson
NeuStar
1800 Sutter St Suite 570
Concord, CA 94520
United States of America
Email: jon.peterson@neustar.biz
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