CDNI WG S. Previdi, Ed.
Internet-Draft F. Le Faucheur
Intended status: Standards Track Cisco Systems, Inc.
Expires: April 26, 2012 A. Guillou
SFR
J. Medved
Juniper Networks, Inc.
October 24, 2011
CDNI Footprint Advertisement
draft-previdi-cdni-footprint-advertisement-00
Abstract
This document describes the use of BGP for Content Delivery Networks
(CDNs) in order to advertise information about footprint and
connectivity to footprint in the context of CDNI.
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 RFC 2119 [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 http://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 April 26, 2012.
Copyright Notice
Copyright (c) 2011 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
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Provisions Relating to IETF Documents
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publication of this document. Please review these documents
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. CDNI Mesh and MP-BGP . . . . . . . . . . . . . . . . . . . . . 3
3. CDNI Information . . . . . . . . . . . . . . . . . . . . . . . 4
3.1. Footprint Information . . . . . . . . . . . . . . . . . . 5
3.2. Connectivity Information . . . . . . . . . . . . . . . . . 5
4. CDNI MP-BGP . . . . . . . . . . . . . . . . . . . . . . . . . 6
4.1. CDNI MP-BGP Footprint Information and Advertisements . . . 6
4.1.1. CDNI Footprint Attributes: Footprint Identifier . . . 6
4.1.2. CDNI Footprint Attributes: Origin_AS_PATH . . . . . . 7
4.1.3. Multihomed Prefixes . . . . . . . . . . . . . . . . . 7
4.2. CDNI MP-BGP Connectivity Information and Advertisements . 8
4.2.1. CDNI Connectivity Prefix . . . . . . . . . . . . . . . 8
4.2.2. CDNI Connectivity Attribute: Connected Footprints . . 8
4.2.3. CDNI Connectivity Advertisement Attributes:
Origin_AS_PATH . . . . . . . . . . . . . . . . . . . . 9
5. CDNI Topology Example . . . . . . . . . . . . . . . . . . . . 9
6. CDNI MP-BGP Operations . . . . . . . . . . . . . . . . . . . . 10
6.1. Internal and External MP-BGP Sessions . . . . . . . . . . 10
6.2. CDNI MP-BGP NLRI . . . . . . . . . . . . . . . . . . . . . 11
6.2.1. CDNI Footprint NLRI and Attributes . . . . . . . . . . 11
6.2.2. CDNI Connectivity NLRI and Attributes . . . . . . . . 11
7. Example of CDNI Mesh . . . . . . . . . . . . . . . . . . . . . 12
7.1. CDNI Footprint Information and Advertisements . . . . . . 13
7.2. Connectivity Information and Advertisements . . . . . . . 15
8. Compliance with CDNI Requirements . . . . . . . . . . . . . . 16
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
10. Security Considerations . . . . . . . . . . . . . . . . . . . 16
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 17
12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17
12.1. Normative References . . . . . . . . . . . . . . . . . . . 17
12.2. Informative References . . . . . . . . . . . . . . . . . . 17
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17
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1. Introduction
The IETF CDN Interconnection (CDNI) Working Group is chartered to
develop specifications for interconnecting standalone CDNs so that
their collective CDN footprint can be leveraged for the end-to-end
delivery of content from Content Service Providers (CSPs) to End
Users.
[I-D.jenkins-cdni-problem-statement] outlines the problem area that
the CDNI working group is chartered to address.
[I-D.bertrand-cdni-use-cases] discusses the use cases for CDN
Interconnection and [I-D.davie-cdni-framework] discusses the
technology framework for the CDNI solution and interfaces.
When an upstream CDN (uCDN) receives a request from a user, it has to
determine what is the downstream CDN (dCDN) to which the request is
to be redirected. This CDN selection decision can take into account
various criteria such as administrative preferences (for example
based on the commercial arrangements between the uCDN and candidate
dCDNs including associated request handling costs) and/or such as
whether candidate CDNs are have caches that are topologically close
to the user and capable of handling that request. Therefore, as
discussed in section "Dynamic Footprint Discovery" of
[I-D.davie-cdni-framework], there are situations where being able to
dynamically discover the set of requests that a given dCDN is willing
and able to serve is beneficial. As also discussed in
[I-D.davie-cdni-framework], this information could be potentially
provided by the dCDN in response to a query by the uCDN, or the
information (or its changes) could be spontaneously advertised by the
dCDN.
The proposal outlined in this document makes use of Multiprotocol-BGP
(MP-BGP [RFC4760]) in order for CDNs and/or ISPs to advertise their
footprint information as well as for CDNs to advertise their
connectivity to these footprints. In addition CDNs use MP-BGP
advertisements to represent their interconnectivity.
2. CDNI Mesh and MP-BGP
CDNI enables CDNs to communicate in order to deliver content in a
collaborative mode. In this document, we refer to a CDNI Mesh as the
set of CDNs participating into CDNI and using MP-BGP sessions between
them in accordance with the approach defined in this document. A
CDNI Mesh has no requirements in terms of topology, i.e.: the mesh
can be partial, full or hierarchical.
CDNI Mesh will make use of Multiprotocol-BGP (MP-BGP [RFC4760]) for
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the exchange of footprint and connectivity information.
We define a new Address Family (CDNI-AF, TBD) and a new NLRI that
will carry either CDN Footprint or CDN Connectivity advertisements.
The NLRI will have a NLRI type (i.e.: CDNI-footprint and CDNI-
connectivity) so to distinguish footprint and connectivity
advertisements.
The advantage of using a separate address family is to isolate CDNI
information from regular BGP-4 Internet information so to not
compromise in any way the security and reliability of the current BGP
information exchange used for IP network layer routing.
The advantage of having separate footprint and connectivity
information is that a CDN needs not originate (and update) footprint
information each time there's a change in the way a CDN is connected
to other CDNs. E.g.: if all footprint information was to be
exchanged between CDNs, it would consist of a very large amount of
prefixes advertised (and re-advertised) each time a CDNI
interconnection changes in the CDNI Mesh.
When an existing CDN connection is removed or when a new connection
between two CDNs is established, the only advertisements that need to
be updated are the ones concerning the connectivity.
While the footprint information is expected to be relatively stable,
the CDN Mesh (i.e.: the connectivity between CDNs) and the
connectivity between the CDN and the footprints may be impacted by
network events. Also, the connectivity between CDNs may be affected
by the CDN selection policy which may be modified relatively
frequently.
CDNI Connectivity advertisements allow the CDNI Mesh to scale by
adapting easily to topology changes. In fact, just a few number of
connectivity advertisements are used by each CDN which makes the CDNI
MP-BGP scheme very scalable.
3. CDNI Information
The CDNI Information is of two types:
Footprint Information, stored in the CDNI (MP-BGP) Footprint
Database.
Connectivity Information, stored in the CDNI (MP-BGP) Connectivity
Information Database.
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3.1. Footprint Information
Footprint Information (FI). The CDN Footprint Information refers to
the set of prefixes (with all their BGP attributes) that the CDN is
capable of, and willing to deliver content to in a given region and
or in a given Autonomous System. Note that a CDN may be capable and
willing to serve content to more than one footprint.
Example: if CDN-A delivers content to ISP-A users, then CDN-A
footprint consists of all prefixes owned and connected to ISP-A.
Footprint Information is therefore inferred from the BGP-4 Internet
database. It is assumed that the CDN will have a BGP-4 feed with
Internet prefixes that are necessary in order for the CDNI Mesh to
operate and from which it will be able to derive the different
footprints.
The CDN will maintain a database with footprint information that is
separate from the regular IP BGP database. The CDNI footprint
information database uses the CDNI-AF MP-BGP address family.
In addition, a CDN may want to advertise to other CDNs part or all of
its footprint information. For example, a CDN may want to give a
better granularity of the prefixes of its footprint (e.g.: longer
masks) or may want to add more attributes (e.g.: communities and
extended communities) to its footprint information. Therefore the
CDN is capable of originating Footprint Advertisements (from its CDNI
Footprint Database) and send them to its neighbors of the CDNI-Mesh.
The CDNI Footprint Information Database includes footprint
information inferred by the BGP-4 (Internet) database as well as
footprint information explicitely advertised by neighboring CDNs.
3.2. Connectivity Information
Connectivity Information refers to how the CDN is connected to a
footprint (and to which footprints). This information needs to be
advertised by the CDN to the rest of the CDNI Mesh so that every CDN
knows which CDN is connected to which footprints.
It has to be noted that by "connectivity" we do not intend physical
direct connectivity between the CDN and the footprint but rather the
ability to deliver content to the footprint. Connectivity
Advertisements are sent through MP-BGP and using CDNI-AF
advertisements.
Connectivity Information is stored in the CDNI Connectivity Database
which contains the information originated by the CDN and the
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information received from the other CDNs in the CDNI Mesh.
4. CDNI MP-BGP
This section describes the CDNI Footprint and Connectivity
Information in the CDNI MP-BGP databases. Two databases are used:
CDNI Footprint Database that contains footprint that is either
derived from BGP-4 Internet table or received from other CDN
through CDNI Footprint Advertisements.
CDNI Connectivity Database that contains the advertisements made
by each CDN describing how they are connected to footprints.
4.1. CDNI MP-BGP Footprint Information and Advertisements
Footprint information first comprises IP prefixes as known in the
BGP-4 database and that need to be translated into the CDNI-AF format
and stored in the CDNI Footprint database. BGP-4 information is
inserted in the CDNI Footprint database and all BGP attributes of
each original route are preserved (e.g.: AS_PATH, MED, Communities,
Extended Communities). In addition, a CDN may add more attributes to
the CDNI Footprint database routes.
As discussed earlier, a CDN may want to explicitly advertise
footprint information to the CDNI-Mesh (as explained in Section 3.1).
When it does so, this information is also incorporated by the in its
CDNI Footprint database by a CDN receiving these advertisments.
However, it is expected that a CDN acquires most of the footprint
information from the BGP-4 Internet table. So we expect limited
usage of footprint advertisements between CDNs.
For example, a CDN (or ISP) may originate MP-BGP footprint
advertisement including a Community attribute representing the
location of the prefixes or the type of user connectivity (e.g.:
fiber vs. cable vs. dsl vs Mobile3G vs Mobile 4G). Alternatively,
such information could be delivered initially by the ISP in the BGP-4
database.
4.1.1. CDNI Footprint Attributes: Footprint Identifier
Footprints are associated to Autonomous Systems. Therefore, the
identifier of a footprint is its Autonomous System Number (ASN).
When the CDN creates the CDNI Footprint database, it will assign to
each prefix, a new (TBD) Extended Community carrying the Footprint
Identifier.
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Footprint Identifier is derived from the Autonomous System Number
(ASN) of the original route. When inferring the CDNI footprint
information from the regular BGP-4 Internet database, the footprint
identifier is derived from the first ASN in the AS_PATH of the
prefix.
The role of the Footprint Identifier is to group all prefixes part of
the same footprint under a unique identifier. This allows a CDN to
claim connectivity to the footprint by just specifying the FI rather
than each individual prefix of the footprint.
Footprint Identifier may also be used in order to describe a finer
granularity than the ASN. Example: a CDN or an ISP participating
into the CDNI Mesh, may want to originate footprint advertisement
with a Footprint Identifier describing a region of its footprint
(e.g.: an ISP may have multiple peering points in different locations
and may want to partition its footprint so to represent geographical
groups.)
For that purpose multiple Footprint Identifiers are used (e.g.: a
footprint representing Los Angeles area and another footprint
representing New York City area). These two footprints MUST be
understood as part of the same ISP but representing different groups
of prefixes.
Using separate Footprint Identifiers (one for LA prefixes and one for
NYC prefixes) allows the CDNI Mesh to handle the footprints
separately even if they belong to the same ISP. Footprint Identifier
MUST be unique across the CDNI Mesh and therefore are numbered using
the ISP AS numbers followed by additional bit space allowing more
footprint identifiers per ISP.
4.1.2. CDNI Footprint Attributes: Origin_AS_PATH
A new MP-BGP attribute (TBD) is defined and called Origin_AS_PATH.
This attribute contains the prefix AS_PATH value that is present on
the CDNI footprint database.
The Origin_AS_PATH is used when a CDN originates a CDNI Footprint
Advertisement. The AS_PATH of the new advertisement follows the BGP
rules (i.e.: it is created with the CDN ASN and further updated at
each AS hop) while the Origin_AS_PATH contains the AS_PATH of the
original prefix.
4.1.3. Multihomed Prefixes
In some cases, a given prefix may be part of different footprint if
it represents a customer connected to two separate ISPs. In some
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cases it is useful to preserve this information and allow both
prefixes advertisements in the BGP database. However, due to BGP
Path Selection rules, when a BGP speaker receives two or more
advertisements for the same prefix, it selects one and ignore the
others.
In order to prevent this to happen a Route Distinguisher may be used
in the advertisement so that, from a BGP selection perspective, the
prefix advertisements are not considered being equal.
4.2. CDNI MP-BGP Connectivity Information and Advertisements
Once footprint information is known in the CDNI Mesh, each CDN should
advertise its connectivity to the footprints it has access to. The
CDN maintains a MP-BGP CDNI Connectivity Database with entries
describing its connectivity to footprints.
4.2.1. CDNI Connectivity Prefix
When a CDN wants to advertise its footprint connectivity it
originates a MP-BGP advertisement containing a prefix and a set of
attributes. The prefix it uses MUST be a prefix in the address space
owned by the CDN. A CDN willing to advertise different set of
footprints connectivity may use different prefix advertisements each
with its set of attributes.
The Connectivity prefix(es) the CDN originates may contain any
standard MP-BGP attribute and it MUST contain a newly defined
attribute: Connected Footprints.
4.2.2. CDNI Connectivity Attribute: Connected Footprints
Connected Footprints attribute describes the set of Footprint
Identifiers (FIs) the CDN claims connectivity to.
The Connected Footprint attribute (CF) is a set of Footprint
Identifiers which means a set of Extended Communities as defined in
Section 4.1.1.
The propagation of CDN Connectivity advertisements throughout the
CDNI Mesh is done according to standard MP-BGP rules and the inter-
CDN connectivity will be reflected in the MP-BGP attributes (e.g.:
AS_PATH will describe the different CDNs the advertisement traversed
during its propagation in the CDNI Mesh thus describing the inter-CDN
connectivity).
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4.2.3. CDNI Connectivity Advertisement Attributes: Origin_AS_PATH
The CDNI Connectivity Advertisement contains a new (TBD) attribute
called Origin_AS_PATH that contains the AS_PATH value describing the
distance (expressed in AS Hop Count) between the CDN and the
advertised connected footprint.
This attribute will allow remote CDNs to understand how this CDN is
distant (or close, in terms of AS hop count) to the footprint.
The regular AS_PATH attribute of the Connectivity Advertisement is
updated during its propagation in the CDNI Mesh so to prevent BGP
message loops (according to BGP rules).
5. CDNI Topology Example
The figure below gives an example how CDNs collaborate and how they
create their CDNI Footprint and Connectivity databases.
+-------------------------------------------+
| CDNI (partial or full) Mesh |
/\ +-------------------------------------------+
|| | | | |
|| +-------+ +-------+ +-------+ +-------+
connectivity | CDN 1 | | CDN 2 | | CDN 3 | | CDN 4 |
advertisements +-------+ +-------+ +-------+ +-------+
| | ___/ \ / |
_____________________|___________|____/_______|_____/____|_____
| | / | / |
/\ +-------+ +-------+ +-------+ +-------+
|| | ASN 1 | | ASN 2 | | ASN 3 | | ASN 4 |
|| +-------+ +-------+ +-------+ +-------+
footprint | | | |
advertisements +-------------------------------------------+
| Internet |
+-------------------------------------------+
Figure 1: Footprint and Connectivity Advertisements
In the figure above 4 CDNs are connected to a set of 4 different
footprints. Each CDN is capable of inferring the footprint
information from the BGP-4 Internet table and will create a CDNI
Footprint Database where a Footprint Identifier will be assigned to
each prefix of the footprints. The Footprint Identifier to each
prefix will be assigned based on the ASN of the prefix.
In addition, each CDN advertises its connectivity to the footprint.
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All CDNI information (footprint and connectivity) is then known in
the entire CDNI Mesh.
6. CDNI MP-BGP Operations
Connectivity advertisements and, when necessary, Footprint
Advertisements consist of MP-BGP update messages CDNs advertise to
the CDNI Mesh (following standard MP-BGP propagation rules).
Footprint consists of prefixes known in the CDNI Footprint Database
(MP-BGP). CDNs advertises these prefixes and can use standard BGP
attribute to attach more information to these prefixes. In addition
a new Extended Community Type is defined so to convey the Footprint
Identifier that associate each prefix to a given footprint.
Connectivity advertisements are originated using one or more prefixes
the CDN will use in order to convey the description of its
connectivity to a footprint. The prefix has the solely purpose to
convey the connectivity information of the CDN (i.e.: the prefix
itself is not to be used for routing or selection purposes). The
footprint connectivity of a CDN is expressed in the Extended
Community Attribute type "Connected Footprint" which consists of the
set of Footprint Identifiers the CDN is connected/have access to.
The Extended Community being additive, more than one Footprint
Identifier is allowed in the CDN Connectivity advertisement.
Also, the Origin_AS_PATH attribute reflects how the CDN is
effectively distance/close to the footprint from a network layer
perspective.
MP-BGP sessions are established between CDNs. MP-BGP requires an
Autonomous System (AS) number that is unique across all CDNs.
Therefore each CDN participating into the CDNI Mesh MUST have a
unique AS number.
6.1. Internal and External MP-BGP Sessions
CDNs establish external MP-BGP sessions with each others. The MP-BGP
session has to be established using the BGP Capabilities specifying
the speaker is capable of MP-BGP and for the CDNI Address Family. In
each of the CDNs at least one MP-BGP speaker will be available
ensuring connectivity to the CDNI Mesh.
Internal MP-BGP sessions can be used inside a CDN for propagating
footprint and connectivity advertisements. Same mechanisms such as
route reflectors and/or confederations can be used internally to a
CDN.
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A CDN that is operated by an ISP may use the same ASN than the one
currently used by the ISP.
6.2. CDNI MP-BGP NLRI
Two types of CDNI NLRIs are defined: footprint and connectivity.
6.2.1. CDNI Footprint NLRI and Attributes
This CDNI NLRI Type (TBD) describes footprint information which
consists of an IPv4 or IPv6 address prefix. CDNI Footprint
Advertisement includes following information (note well that in this
section we do not aim to describe in details the format of the NLRI
bur rather focus on the kind of information it should contain):
RD:ipv4 or RD:ipv6 addresses
BGP attributes such as: AS_PATH, NEXT_HOP, MED,
Community, ExtCommunity.
Origin_AS_PATH
Footprint Identifiers
where:
RD is the Route Distinguisher of the route. When used, it allows to
distinguish among multiple advertisements of the same prefix (for the
multihomed case). The RD is present in CDNI NLRI using CDNI-AF with
SAFI value set to 128.
Origin_AS_PATH contains the AS_PATH value that is present in the CDNI
Footprint Database for this prefix.
Footprint Identifier describes to which footprint this prefix belongs
to. The footprint Identifier represents the ASN of origin of the
prefix.
Footprint NLRIs are propagated in the CDNI Mesh according to standard
MP-BGP rules and MP-BGP attributes such as AS_PATH, NEXT_HOP, MED,
Local Preference, etc, are updated and used according to the standard
MP-BGP mechanisms. For example, AS_PATH is updated and checked so to
avoid messaging loops.
6.2.2. CDNI Connectivity NLRI and Attributes
The CDNI Connectivity NLRI Type (TBD) describes how the CDN connects
to a given footprint. Each CDN originates one or more prefixes whose
purpose is to convey attributes describing how the CDN can reach the
footprint. The Connectivity advertisment includes following
information:
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RD:ipv4 or RD:ipv6 addresses
BGP attributes such as: AS_PATH, NEXT_HOP, MED,
Community, ExtCommunity.
Origin_AS_PATH
Connected Footprints
where:
RD is the Route Distinguisher of the route. When used, it allows to
distinguish among multiple advertisements of the same prefix (for the
multihomed case). The RD is present in CDNI NLRI using CDNI-AF with
SAFI value set to 128. It has to be noted that the CDNI
Advertisements makes no use of the route distinguisher and therefore
it has to be set to all zero.
BGP attributes convey information related to the connectivity of the
CDN to the footprint.
Origin_AS_PATH contains the AS_PATH that describes how the CDN is
connected to the footprint (i.e.: what is the AS hop count).
Connected Footprints describe which footprints the CDN has
connectivity to.
7. Example of CDNI Mesh
In this section an example of a CDNI Mesh is described as well as the
CDNI Information that will be originated.
+-------------------------------------------+
| CDNI (partial or full) Mesh |
+-------------------------------------------+
| | | |
+-------+ +-------+ +-------+ +-------+
| CDN 1 | | CDN 2 | | CDN 3 | | CDN 4 |
| | | AS600 | | AS700 | | / |
| | +-------+ +-------+ |/ |
| | | ____/ | /| |
| | | / | / | |
| | +-------+ +-------+ | |
| AS100 |---| AS200 |---| AS300 |---| AS400 |
+-------+ +-------+ +-------+ +-------+
| | | |
192.168.10/24 | 192.168.30/24 |
| |
192.168.20/24 192.168.40/24
Figure 2: CDNI Mesh Example
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We assume different Autonomous Systems (representing different ISPs)
with their own prefix space. We also assume four CDNs that are, for
some of them, on their own AS while others share the AS of their ISP
(which describe the case where the CDN is managed by the ISP). The
Internet is represented by the interconnectivity of the Autonomous
System.
7.1. CDNI Footprint Information and Advertisements
Footprint information will be inferred by each CDN from the BGP-4
database. For example, the CDNI Footprint Database in CDN4, located
in Autonomous System 400, is as follows:
IPv4 prefix: 192.168.10/24
AS_PATH: 300 200 100
CDNI Footprint Identifier: 100:000
IPv4 prefix: 192.168.20/24
AS_PATH: 300 200
CDNI Footprint Identifier: 200:000
IPv4 prefix: 192.168.30/24
AS_PATH: 300
CDNI Footprint Identifier: 300:000
IPv4 prefix: 192.168.40/24
AS_PATH:
CDNI Footprint Identifier: 400:000
where:
IPv4 Prefix is the footprint prefix information.
AS_PATH is the existing BGP AS_PATH attribute (from the BGP-4
database) containing the set of ASNs the update has traversed in the
Internet.
CDNI Footprint Identifier represents the footprint as a whole. All
prefixes part of the same footprint will share the same Footprint
Identifier. For CDNI purposes, CDN4 may want to advertise more
information about the inferred footprint so to tell the CDNI Mesh
more information about location of the footprint. For example, part
of the address space 192.168.40/24 is located in NYC, part is located
in Chicago and part in LA. CDN4 may originate new CDNI Footprint
Information such as:
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IPv4 prefix: 192.168.40.64/26
AS_PATH:
CDNI Footprint Identifier: 400:001
IPv4 prefix: 192.168.40.128/26
AS_PATH:
CDNI Footprint Identifier: 400:002
IPv4 prefix: 192.168.40.192/26
AS_PATH:
CDNI Footprint Identifier: 400:003
When CDN4 sends out the above advertisements, it will have to update
both the AS_PATH attribute (in order to prevent BGP message loops as
well as the Origin-AS_PATH attribute so to preserve the original
AS_PATH. Therefore the advertisements CDN4 will send out will be as
follows:
IPv4 prefix: 192.168.40.64/26
AS_PATH: 400
CDNI Footprint Identifier: 400:001
Origin_AS_PATH 400
IPv4 prefix: 192.168.40.128/26
AS_PATH: 400
CDNI Footprint Identifier: 400:002
Origin_AS_PATH 400
IPv4 prefix: 192.168.40.192/26
AS_PATH: 400
CDNI Footprint Identifier: 400:002
Origin_AS_PATH 400
When the advertisement is received by the CDNI Mesh neighbors it will
also be propagated. For example, CDN3 may receive these
advertisements and send them to CDN2. At CDN2 the advertisements
will contain following information:
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IPv4 prefix: 192.168.40.64/26
AS_PATH: 300 400
CDNI Footprint Identifier: 400:001
Origin_AS_PATH 400
IPv4 prefix: 192.168.40.128/26
AS_PATH: 300, 400
CDNI Footprint Identifier: 400:002
Origin_AS_PATH 400
IPv4 prefix: 192.168.40.192/26
AS_PATH: 300 400
CDNI Footprint Identifier: 400:002
Origin_AS_PATH 400
where the AS_PATH attributes reflect the path taken by the
advertisement in the CDNI-Mesh while the Origin_AS_PATH reflects the
AS_PATH the prefix had at its point of origin (ASN 400).
7.2. Connectivity Information and Advertisements
Connectivity advertisements have the dual purpose of describing the
CDN connectivity to the footprint and the connectivity to other CDNs.
For example, CDN4 connectivity advertisement will describe the
footprint connectivity to Footprint Identifiers 400:001, 400:002 and
400:003. The following is the advertisement CDN4 will send to its
MP-BGP neighbors:
IPv4 prefix: 192.168.4.4/32
AS_PATH: 400
Connected footprints: 400:001, 400:002, 400:003
where:
IPv4 Prefix is the IPv4 address identifying the CDN (or part of it)
in the CDNI Mesh.
AS_PATH contains the AS numbers this update traversed (including the
AS where this connectivity advertisement has been originated).
Connected Footprints contains the set of footprint identifiers this
CDN is directly connected to.
*** Editor's Note: a mechanism in order to express preference or
costs to footprints is needed: either through a ranking sequence or
through explicit preference cost or weight.
Alternatively, CDN4 may want to advertise 3 distinct Connectivity
Advertisements for each of the footprints its connected to:
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IPv4 prefix: 192.168.4.1/32
AS_PATH: 400
Connected footprints: 400:001
IPv4 prefix: 192.168.4.2/32
AS_PATH: 400
Connected footprints: 400:002
IPv4 prefix: 192.168.4.3/32
AS_PATH: 400
Connected footprints: 400:003
Each prefix will carry a different Footprint Identifier so that CDN4
can separate these advertisements.
Each CDN may also advertise a set of communities representing the
capabilities of the CDN. It is possible for a transit CDN to
manipulate the set of communities during its propagation. Example: a
CDN, prior to propagate the connectivity advertisement of another
CDN, may strip one or more capabilities from the original
advertisement. This will allow to enforce a given path selection by
upstream CDNs.
8. Compliance with CDNI Requirements
[I-D.ietf-cdni-requirements] outlines the requirements for the
solution and interfaces to be specified by the CDNI working group.
This section identifies the relevant requirements from that document
and discusses compliance by the solution proposed in this document.
[Editor's Note: Text is to be added when requirements-03 is
available. This needs to discuss the requirements labeled R27, R28,
R29 and R30 as of requirements-02].
9. IANA Considerations
none
10. Security Considerations
This draft does not affect the BGP security model.
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11. Acknowledgements
The authors would like to recognize Bruce Davie for his
contributions.
12. References
12.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4760] Bates, T., Chandra, R., Katz, D., and Y. Rekhter,
"Multiprotocol Extensions for BGP-4", RFC 4760,
January 2007.
12.2. Informative References
[I-D.bertrand-cdni-use-cases]
Bertrand, G., Stephan, E., Watson, G., Burbridge, T.,
Eardley, P., and K. Ma, "Use Cases for Content Delivery
Network Interconnection", draft-bertrand-cdni-use-cases-02
(work in progress), July 2011.
[I-D.davie-cdni-framework]
Davie, B. and L. Peterson, "Framework for CDN
Interconnection", draft-davie-cdni-framework-00 (work in
progress), July 2011.
[I-D.ietf-cdni-requirements]
Leung, K. and Y. Lee, "Content Distribution Network
Interconnection (CDNI) Requirements",
draft-ietf-cdni-requirements-01 (work in progress),
October 2011.
[I-D.jenkins-cdni-problem-statement]
Niven-Jenkins, B., Faucheur, F., and N. Bitar, "Content
Distribution Network Interconnection (CDNI) Problem
Statement", draft-jenkins-cdni-problem-statement-02 (work
in progress), March 2011.
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Authors' Addresses
Stefano Previdi (editor)
Cisco Systems, Inc.
Via Del Serafico 200
Rome 00191
IT
Email: sprevidi@cisco.com
Francois Le Faucheur
Cisco Systems, Inc.
Greenside, 400 Avenue de Roumanille
Sophia Antipolis 06410
FR
Email: flefauch@cisco.com
Allan Guillou
SFR
40-42 Quai du Point du Jour
Boulogne-Billancourt 92659
FR
Email: allan.guillou@sfr.com
Jan Medved
Juniper Networks, Inc.
1194 N. Mathilda Ave.
Sunnyvale, CA 94089
US
Email: jmedved@juniper.net
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