North-Bound Distribution of Link-State and TE Information using BGP
draft-ietf-idr-ls-distribution-02
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft that was ultimately published as RFC 7752.
|
|
|---|---|---|---|
| Authors | Hannes Gredler , Jan Medved , Stefano Previdi , Adrian Farrel , Saikat Ray | ||
| Last updated | 2013-02-25 | ||
| Replaces | draft-gredler-idr-ls-distribution | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Formats | |||
| Reviews |
GENART Last Call review
(of
-10)
by Alexey Melnikov
Ready w/nits
RTGDIR Early review
(of
-05)
by Acee Lindem
Has issues
|
||
| Additional resources | Mailing list discussion | ||
| Stream | WG state | WG Document | |
| Document shepherd | (None) | ||
| IESG | IESG state | Became RFC 7752 (Proposed Standard) | |
| Consensus boilerplate | Unknown | ||
| Telechat date | (None) | ||
| Responsible AD | (None) | ||
| Send notices to | (None) |
draft-ietf-idr-ls-distribution-02
Inter-Domain Routing H. Gredler
Internet-Draft Juniper Networks, Inc.
Intended status: Standards Track J. Medved
Expires: August 28, 2013 S. Previdi
Cisco Systems, Inc.
A. Farrel
Juniper Networks, Inc.
S. Ray
Cisco Systems, Inc.
February 24, 2013
North-Bound Distribution of Link-State and TE Information using BGP
draft-ietf-idr-ls-distribution-02
Abstract
In a number of environments, a component external to a network is
called upon to perform computations based on the network topology and
current state of the connections within the network, including
traffic engineering information. This is information typically
distributed by IGP routing protocols within the network
This document describes a mechanism by which links state and traffic
engineering information can be collected from networks and shared
with external components using the BGP routing protocol. This is
achieved using a new BGP Network Layer Reachability Information
(NLRI) encoding format. The mechanism is applicable to physical and
virtual links. The mechanism described is subject to policy control.
Applications of this technique include Application Layer Traffic
Optimization (ALTO) servers, and Path Computation Elements (PCEs).
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/.
Gredler, et al. Expires August 28, 2013 [Page 1]
Internet-Draft Link-State Info Distribution using BGP February 2013
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 August 28, 2013.
Copyright Notice
Copyright (c) 2013 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
(http://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.
Gredler, et al. Expires August 28, 2013 [Page 2]
Internet-Draft Link-State Info Distribution using BGP February 2013
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Motivation and Applicability . . . . . . . . . . . . . . . . . 5
2.1. MPLS-TE with PCE . . . . . . . . . . . . . . . . . . . . . 5
2.2. ALTO Server Network API . . . . . . . . . . . . . . . . . 7
3. Carrying Link State Information in BGP . . . . . . . . . . . . 8
3.1. TLV Format . . . . . . . . . . . . . . . . . . . . . . . . 8
3.2. The Link State NLRI . . . . . . . . . . . . . . . . . . . 9
3.2.1. Identifier TLV . . . . . . . . . . . . . . . . . . . . 12
3.2.2. Node Descriptors . . . . . . . . . . . . . . . . . . . 14
3.2.3. Link Descriptors . . . . . . . . . . . . . . . . . . . 22
3.2.4. Prefix Descriptors . . . . . . . . . . . . . . . . . . 23
3.3. The LINK_STATE Attribute . . . . . . . . . . . . . . . . . 23
3.3.1. Link Attribute TLVs . . . . . . . . . . . . . . . . . 24
3.3.2. Node Attribute TLVs . . . . . . . . . . . . . . . . . 27
3.3.3. Prefix Attributes TLVs . . . . . . . . . . . . . . . . 29
3.4. BGP Next Hop Information . . . . . . . . . . . . . . . . . 33
3.5. Inter-AS Links . . . . . . . . . . . . . . . . . . . . . . 33
4. Link to Path Aggregation . . . . . . . . . . . . . . . . . . . 33
4.1. Example: No Link Aggregation . . . . . . . . . . . . . . . 34
4.2. Example: ASBR to ASBR Path Aggregation . . . . . . . . . . 34
4.3. Example: Multi-AS Path Aggregation . . . . . . . . . . . . 35
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 35
6. Manageability Considerations . . . . . . . . . . . . . . . . . 35
6.1. Operational Considerations . . . . . . . . . . . . . . . . 35
6.1.1. Operations . . . . . . . . . . . . . . . . . . . . . . 36
6.1.2. Installation and Initial Setup . . . . . . . . . . . . 36
6.1.3. Migration Path . . . . . . . . . . . . . . . . . . . . 36
6.1.4. Requirements on Other Protocols and Functional
Components . . . . . . . . . . . . . . . . . . . . . . 36
6.1.5. Impact on Network Operation . . . . . . . . . . . . . 36
6.1.6. Verifying Correct Operation . . . . . . . . . . . . . 37
6.2. Management Considerations . . . . . . . . . . . . . . . . 37
6.2.1. Management Information . . . . . . . . . . . . . . . . 37
6.2.2. Fault Management . . . . . . . . . . . . . . . . . . . 37
6.2.3. Configuration Management . . . . . . . . . . . . . . . 37
6.2.4. Accounting Management . . . . . . . . . . . . . . . . 37
6.2.5. Performance Management . . . . . . . . . . . . . . . . 37
6.2.6. Security Management . . . . . . . . . . . . . . . . . 38
7. TLV/SubTLV Code Points Summary . . . . . . . . . . . . . . . . 38
8. Security Considerations . . . . . . . . . . . . . . . . . . . 40
9. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 40
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 40
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 40
11.1. Normative References . . . . . . . . . . . . . . . . . . . 40
11.2. Informative References . . . . . . . . . . . . . . . . . . 42
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 43
Gredler, et al. Expires August 28, 2013 [Page 3]
Internet-Draft Link-State Info Distribution using BGP February 2013
1. Introduction
The contents of a Link State Database (LSDB) or a Traffic Engineering
Database (TED) has the scope of an IGP area. Some applications, such
as end-to-end Traffic Engineering (TE), would benefit from visibility
outside one area or Autonomous System (AS) in order to make better
decisions.
The IETF has defined the Path Computation Element (PCE) [RFC4655] as
a mechanism for achieving the computation of end-to-end TE paths that
cross the visibility of more than one TED or which require CPU-
intensive or coordinated computations. The IETF has also defined the
ALTO Server [RFC5693] as an entity that generates an abstracted
network topology and provides it to network-aware applications.
Both a PCE and an ALTO Server need to gather information about the
topologies and capabilities of the network in order to be able to
fulfill their function
This document describes a mechanism by which Link State and TE
information can be collected from networks and shared with external
components using the BGP routing protocol [RFC4271]. This is
achieved using a new BGP Network Layer Reachability Information
(NLRI) encoding format. The mechanism is applicable to physical and
virtual links. The mechanism described is subject to policy control.
A router maintains one or more databases for storing link-state
information about nodes and links in any given area. Link attributes
stored in these databases include: local/remote IP addresses, local/
remote interface identifiers, link metric and TE metric, link
bandwidth, reservable bandwidth, per CoS class reservation state,
preemption and Shared Risk Link Groups (SRLG). The router's BGP
process can retrieve topology from these LSDBs and distribute it to a
consumer, either directly or via a peer BGP Speaker (typically a
dedicated Route Reflector), using the encoding specified in this
document.
The collection of Link State and TE link state information and its
distribution to consumers is shown in the following figure.
Gredler, et al. Expires August 28, 2013 [Page 4]
Internet-Draft Link-State Info Distribution using BGP February 2013
+-----------+
| Consumer |
+-----------+
^
|
+-----------+
| BGP | +-----------+
| Speaker | | Consumer |
+-----------+ +-----------+
^ ^ ^ ^
| | | |
+---------------+ | +-------------------+ |
| | | |
+-----------+ +-----------+ +-----------+
| BGP | | BGP | | BGP |
| Speaker | | Speaker | . . . | Speaker |
+-----------+ +-----------+ +-----------+
^ ^ ^
| | |
IGP IGP IGP
Figure 1: TE Link State info collection
A BGP Speaker may apply configurable policy to the information that
it distributes. Thus, it may distribute the real physical topology
from the LSDB or the TED. Alternatively, it may create an abstracted
topology, where virtual, aggregated nodes are connected by virtual
paths. Aggregated nodes can be created, for example, out of multiple
routers in a POP. Abstracted topology can also be a mix of physical
and virtual nodes and physical and virtual links. Furthermore, the
BGP Speaker can apply policy to determine when information is updated
to the consumer so that there is reduction of information flow form
the network to the consumers. Mechanisms through which topologies
can be aggregated or virtualized are outside the scope of this
document
2. Motivation and Applicability
This section describes uses cases from which the requirements can be
derived.
2.1. MPLS-TE with PCE
As described in [RFC4655] a PCE can be used to compute MPLS-TE paths
within a "domain" (such as an IGP area) or across multiple domains
(such as a multi-area AS, or multiple ASes).
Gredler, et al. Expires August 28, 2013 [Page 5]
Internet-Draft Link-State Info Distribution using BGP February 2013
o Within a single area, the PCE offers enhanced computational power
that may not be available on individual routers, sophisticated
policy control and algorithms, and coordination of computation
across the whole area.
o If a router wants to compute a MPLS-TE path across IGP areas its
own TED lacks visibility of the complete topology. That means
that the router cannot determine the end-to-end path, and cannot
even select the right exit router (Area Border Router - ABR) for
an optimal path. This is an issue for large-scale networks that
need to segment their core networks into distinct areas, but which
still want to take advantage of MPLS-TE.
Previous solutions used per-domain path computation [RFC5152]. The
source router could only compute the path for the first area because
the router only has full topological visibility for the first area
along the path, but not for subsequent areas. Per-domain path
computation uses a technique called "loose-hop-expansion" [RFC3209],
and selects the exit ABR and other ABRs or AS Border Routers (ASBRs)
using the IGP computed shortest path topology for the remainder of
the path. This may lead to sub-optimal paths, makes alternate/
back-up path computation hard, and might result in no TE path being
found when one really does exist.
The PCE presents a computation server that may have visibility into
more than one IGP area or AS, or may cooperate with other PCEs to
perform distributed path computation. The PCE obviously needs access
to the TED for the area(s) it serves, but [RFC4655] does not describe
how this is achieved. Many implementations make the PCE a passive
participant in the IGP so that it can learn the latest state of the
network, but this may be sub-optimal when the network is subject to a
high degree of churn, or when the PCE is responsible for multiple
areas.
The following figure shows how a PCE can get its TED information
using the mechanism described in this document.
Gredler, et al. Expires August 28, 2013 [Page 6]
Internet-Draft Link-State Info Distribution using BGP February 2013
+----------+ +---------+
| ----- | | BGP |
| | TED |<-+-------------------------->| Speaker |
| ----- | TED synchronization | |
| | | mechanism: +---------+
| | | BGP with Link-State NLRI
| v |
| ----- |
| | PCE | |
| ----- |
+----------+
^
| Request/
| Response
v
Service +----------+ Signaling +----------+
Request | Head-End | Protocol | Adjacent |
-------->| Node |<------------>| Node |
+----------+ +----------+
Figure 2: External PCE node using a TED synchronization mechanism
The mechanism in this document allows the necessary TED information
to be collected from the IGP within the network, filtered according
to configurable policy, and distributed to the PCE as necessary.
2.2. ALTO Server Network API
An ALTO Server [RFC5693] is an entity that generates an abstracted
network topology and provides it to network-aware applications over a
web service based API. Example applications are p2p clients or
trackers, or CDNs. The abstracted network topology comes in the form
of two maps: a Network Map that specifies allocation of prefixes to
Partition Identifiers (PIDs), and a Cost Map that specifies the cost
between PIDs listed in the Network Map. For more details, see
[I-D.ietf-alto-protocol].
ALTO abstract network topologies can be auto-generated from the
physical topology of the underlying network. The generation would
typically be based on policies and rules set by the operator. Both
prefix and TE data are required: prefix data is required to generate
ALTO Network Maps, TE (topology) data is required to generate ALTO
Cost Maps. Prefix data is carried and originated in BGP, TE data is
originated and carried in an IGP. The mechanism defined in this
document provides a single interface through which an ALTO Server can
retrieve all the necessary prefix and network topology data from the
underlying network. Note an ALTO Server can use other mechanisms to
get network data, for example, peering with multiple IGP and BGP
Gredler, et al. Expires August 28, 2013 [Page 7]
Internet-Draft Link-State Info Distribution using BGP February 2013
Speakers.
The following figure shows how an ALTO Server can get network
topology information from the underlying network using the mechanism
described in this document.
+--------+
| Client |<--+
+--------+ |
| ALTO +--------+ BGP with +---------+
+--------+ | Protocol | ALTO | Link-State NLRI | BGP |
| Client |<--+------------| Server |<----------------| Speaker |
+--------+ | | | | |
| +--------+ +---------+
+--------+ |
| Client |<--+
+--------+
Figure 3: ALTO Server using network topology information
3. Carrying Link State Information in BGP
This specification contains two parts: definition of a new BGP NLRI
that describes links, nodes and prefixes comprising IGP link state
information, and definition of a new BGP path attribute that carries
link, node and prefix properties and attributes, such as the link and
prefix metric or node properties.
3.1. TLV Format
Information in the new link state NLRIs and attributes is encoded in
Type/Length/Value triplets. The TLV format is shown in Figure 4.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Value (variable) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: TLV format
The Length field defines the length of the value portion in octets
(thus a TLV with no value portion would have a length of zero). The
Gredler, et al. Expires August 28, 2013 [Page 8]
Internet-Draft Link-State Info Distribution using BGP February 2013
TLV is not padded to four-octet alignment. Unrecognized types are
ignored.
3.2. The Link State NLRI
The MP_REACH and MP_UNREACH attributes are BGP's containers for
carrying opaque information. Each Link State NLRI describes either a
node, a link or a prefix.
All link, node and prefix information SHALL be encoded using a TBD
AFI / TBD SAFI header into those attributes.
In order for two BGP speakers to exchange Link-State NLRI, they MUST
use BGP Capabilities Advertisement to ensure that they both are
capable of properly processing such NLRI. This is done as specified
in [RFC4760], by using capability code 1 (multi-protocol BGP), with
an AFI/SAFI TBD.
The format of the Link State NLRI is shown in the following figure.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NLRI Type | Total NLRI Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Link-State NLRI (variable) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: Link State SAFI (TBD) NLRI Format
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NLRI Type | Total NLRI Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ Route Distinguisher +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Link-State NLRI (variable) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: Link State SAFI 128 NLRI Format
Gredler, et al. Expires August 28, 2013 [Page 9]
Internet-Draft Link-State Info Distribution using BGP February 2013
The 'Total NLRI Length' field contains the cumulative length of rest
of the NLRI not including the NLRI Type field or itself. For VPN
applications it also includes the length of the Route Distinguisher.
The 'NLRI Type' field can contain one of the following values:
Type = 1: Link NLRI, contains link descriptors and link attributes
Type = 2: Node NLRI, contains node attributes
Type = 3: IPv4 Topology Prefix NLRI
Type = 4: IPv6 Topology Prefix NLRI
The Link NLRI (NLRI Type = 1) is shown in the following figure.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Protocol-ID | Reserved | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| Identifier (variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local Node Descriptors (variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote Node Descriptors (variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link Descriptors (variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 7: The Link NLRI format
The Node NLRI (NLRI Type = 2) is shown in the following figure.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Protocol-ID | Reserved | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| Identifier (variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local Node Descriptors (variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 8: The Node NLRI format
The IPv4 and IPv6 Prefix NLRIs (NLRI Type = 3 and Type = 4) use the
same format as shown in the following figure.
Gredler, et al. Expires August 28, 2013 [Page 10]
Internet-Draft Link-State Info Distribution using BGP February 2013
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Protocol-ID | Reserved | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| Identifier (variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local Node Descriptor (variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reachability information (variable; one or more prefixes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 9: The IPv4/IPv6 Topology Prefix NLRI format
The 'Protocol-ID' field can contain one of the following values:
Protocol-ID = 0: Unknown, The source of NLRI information could not
be determined
Protocol-ID = 1: IS-IS Level 1, The NLRI information has been
sourced by IS-IS Level 1
Protocol-ID = 2: IS-IS Level 2, The NLRI information has been
sourced by IS-IS Level 2
Protocol-ID = 3: OSPF, The NLRI information has been sourced by
OSPF
Protocol-ID = 4: Direct, The NLRI information has been sourced
from local interface state
Protocol-ID = 5: Static, The NLRI information has been sourced by
static configuration
Both OSPF and IS-IS may run multiple routing protocol instances over
the same link. See [RFC6822] and [RFC6549].
Identifier TLV is a mandatory TLV containing identifiers of the NLRI
and used to associate the NLRI to an instance, a domain, an area or a
prefix.
Each Node Descriptor and Link Descriptor consists of one or more TLVs
described in the following sections. The sender of an UPDATE message
MUST order the TLVs within a Node Descriptor or a Link Descriptor in
ascending order of TLV type.
Gredler, et al. Expires August 28, 2013 [Page 11]
Internet-Draft Link-State Info Distribution using BGP February 2013
3.2.1. Identifier TLV
Identifier TLV (Type 256) is a mandatory TLV that appear in Node,
Link and Prefix NLRIs. Identifier TLV carries all identifiers
associated with the NLRI in a SubTLV format. Possible Sub TLVs are
Instance Identifier, Domain Identifier, Area Identifier, OSPF Route
Type and Multi-Topology ID.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Identifier Sub-TLVs (variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Where:
Type: 256
Length: variable
Identifier Sub-TLVs: Identifiers
Figure 10: Identifier TLV Format
An Identifier may be used to distinguish a Node, a Link or a Prefix
with different types of identifiers. Therefore different SubTLVs are
defined here below in order to address the different requirements.
3.2.1.1. Instance Identifier SubTLV
Instance Identifier is a mandatory SubTLV that MUST be present in all
NLRIs. It is used to identify the topology instance the content of
the NLRI and attributes refers to.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Instance Identifier (variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Where:
Type: 1
Length: variable
Figure 11: Instance Identifier Sub-TLV Format
Gredler, et al. Expires August 28, 2013 [Page 12]
Internet-Draft Link-State Info Distribution using BGP February 2013
3.2.1.2. Domain Identifier SubTLV
Domain Identifier is an optional SubTLV that MAY be present in all
NLRIs. It is used to identify the domain (or sub-domain) to which
the NLRI belongs.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Domain Identifier (variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Where:
Type: 2
Length: variable
Figure 12: Domain Identifier Sub-TLV Format
3.2.1.3. Area Identifier SubTLV
Area Identifier is an optional SubTLV that MAY be present in all
NLRIs. It is used to identify the area to which the NLRI belongs.
Example: an OSPF ABR router advertises itself multiple time (one for
each area it participates into). Area Identifier allows the
different NLRIs of the same router to be discriminated.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Area Identifier (variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Where:
Type: 3
Length:variable
Figure 13: Area Identifier Sub-TLV Format
3.2.1.4. OSPF Route Type SubTLV
Route Type is an optional SubTLV that MAY be present in the Prefix
NLRIs. It is used to identify the OSPF route-type of the prefix. It
is used when an OSPF prefix is advertised in the OSPF domain with
multiple different route-types. The Route Type Identifier allows to
Gredler, et al. Expires August 28, 2013 [Page 13]
Internet-Draft Link-State Info Distribution using BGP February 2013
discriminate these advertisements.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Route Type |
+-+-+-+-+-+-+-+-+
Where:
Type: 4
Length: 1
Figure 14: OSPF Route Type Sub-TLV Format
OSPF Route Type can be either: Intra-Area (0x1), Inter-Area (0x2),
External 1 (0x3), External 2 (0x4), NSSA (0x5) and is encoded in a 3
bits number. For prefixes learned from IS-IS, this field MUST to be
set to 0x0 on transmission.
3.2.1.5. Multi Topology ID SubTLV
The Multi Topology ID SubTLV (type: 5) carries the Multi Topology ID
for the link, node or prefix. The semantics of the Multi Topology ID
are defined in RFC5120, Section 7.2 [RFC5120], and the OSPF Multi
Topology ID), defined in RFC4915, Section 3.7 [RFC4915]. If the
value in the Multi Topology ID TLV is derived from OSPF, then the
upper 9 bits of the Multi Topology ID are set to 0.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|R R R R| Multi Topology ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 15: Multi Topology ID SubTLV format
The Multi Topology Identifier SubTLV is present in any NLRI Type.
3.2.2. Node Descriptors
Each link gets anchored by at least a pair of router-IDs. Since
there are many Router-IDs formats (32 Bit IPv4 router-ID, 56 Bit ISO
Node-ID and 128 Bit IPv6 router-ID) a link may be anchored by more
than one Router-ID pair. The set of Local and Remote Node
Gredler, et al. Expires August 28, 2013 [Page 14]
Internet-Draft Link-State Info Distribution using BGP February 2013
Descriptors describe which Protocols Router-IDs will be following to
"anchor" the link described by the "Link attribute TLVs". There must
be at least one "like" router-ID pair of a Local Node Descriptors and
a Remote Node Descriptors per-protocol. If a peer sends an illegal
combination in this respect, then this is handled as an NLRI error,
described in [RFC4760].
It is desirable that the Router-ID assignments inside the Node anchor
are globally unique. However there may be router-ID spaces (e.g.
ISO) where not even a global registry exists, or worse, Router-IDs
have been allocated following private-IP RFC 1918 [RFC1918]
allocation. We use AS Number (or Confederation ID) and BGP
Identifier in order to disambiguate the Router-IDs, as described in
Section 3.2.2.4.
3.2.2.1. Local Node Descriptors
The Local Node Descriptors TLV (Type 257) contains Node Descriptors
for the node anchoring the local end of the link. The length of this
TLV is variable. The value contains one or more Node Descriptor Sub-
TLVs defined in Section 3.2.2.3.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Node Descriptor Sub-TLVs (variable) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 16: Local Node Descriptors TLV format
3.2.2.2. Remote Node Descriptors
The Remote Node Descriptors TLV (Type 258) contains Node Descriptors
for the node anchoring the remote end of the link. The length of
this TLV is variable. The value contains one or more Node Descriptor
Sub-TLVs defined in Section 3.2.2.3.
Gredler, et al. Expires August 28, 2013 [Page 15]
Internet-Draft Link-State Info Distribution using BGP February 2013
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Node Descriptor Sub-TLVs (variable) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 17: Remote Node Descriptors TLV format
3.2.2.3. Node Descriptor Sub-TLVs
The Node Descriptor Sub-TLV type codepoints and lengths are listed in
the following table:
+------------+-------------------+----------+
| TLV/SubTLV | Description | Length |
+------------+-------------------+----------+
| 259 | Autonomous System | 4 |
| 260 | BGP Identifier | 4 |
| 261 | ISO Node-ID | 7 |
| 262 | IPv4 Router-ID | variable |
| 263 | IPv6 Router-ID | 16 |
+------------+-------------------+----------+
Table 1: Node Descriptor Sub-TLVs
The TLV values in Node Descriptor Sub-TLVs are defined as follows:
Autonomous System: opaque value (32 Bit AS Number)
BGP-Identifier: opaque value (32 Bit AS ID); uniquely identifying
the BGP-LS speaker within an AS.
IPv4 Router ID: opaque value (can be an IPv4 address or an 32 Bit
router ID). When encoding an OSPF Designated Router ID, the
length is 8 (first 4 bytes is the Router-ID originating the Type-2
LSA and next 4 bytes are taken from the Type-2 LSA ID). In other
cases, the length is 4.
IPv6 Router ID: opaque value (can be an IPv6 address or 128 Bit
router ID).
Gredler, et al. Expires August 28, 2013 [Page 16]
Internet-Draft Link-State Info Distribution using BGP February 2013
ISO Node ID: ISO node-ID (6 octets ISO system-ID) followed by a PSN
octet in case LAN "Pseudonode" information gets advertised. The
PSN octet must be zero for non-LAN "Pseudonodes".
There can be at most one instance of each TLV type present in any
Node Descriptor. The TLV ordering within a Node descriptor MUST
be kept in order of increasing numeric value of type. TLVs 259
and 260 specify administrative context in which TLVs 261-263 are
to be evaluated. The first TLV from range 261-263 is to be
interpreted as the primary node identifier by which the node can
be referenced within its administrative contexts. Any further
TLVs are to be treated as secondary identifiers, which may be used
for cross-reference, but are to be treated as if they are object
attributes.
3.2.2.4. Globally Unique BGP-LS Identifiers
One problem that needs to be addressed is the ability to identify an
IGP node globally (by "global", we mean within the BGP-LS database
collected by all BGP-LS speakers that talk to each other). This can
be expressed through the following two requirements:
(A) The same node must not be represented by two keys (otherwise one
node will look like two nodes).
(B) Two different nodes must not be represented by the same key
(otherwise, two nodes will look like one node).
We define an "IGP domain" to be the set of nodes (and links), within
which, each node has a unique IGP representation by using the
combination of area-id, IGP router-id, Level, instance ID, etc. The
problem is that BGP brings nodes from multiple independent "IGP
domains" and we need to distinguish between them. Moreover, we can't
assume there is always one and only one IGP domain per Autonomous
System (or Autonomous System confederation member). Following cases
illustrate scenario's where IGP domain and ASs boundaries do not
match.
(i) Stub ASs or non-contiguous AS: One can have an AS that has
disjoint parts, each running an independent IGP domain.
Gredler, et al. Expires August 28, 2013 [Page 17]
Internet-Draft Link-State Info Distribution using BGP February 2013
IGP domain 1 IGP domain 2
AS 1 AS 1
+---+ +---+
| | | |
+---+ +---+
\ /
+---------+
| |
+---------+
Transit AS
Figure 18: Stub-ASs or non-contiguous AS
Using ASN to globally identify IGP node may break requirement (B).
(ii) It is possible to run the same IGP domain across multiple AS.
+----------------------+
| +------+ +------+ |
| | AS 1 | | AS 2 | |
| +------+ +------+ |
+----------------------+
IGP domain
Figure 19: IGP Domain
Using ASN to globally identify IGP node will break requirement (A).
(iii) It is possible to run IGP across member-ASs in a confederation.
+-------------------------------+
| +--------------------------+ |
| | +--------+ +--------+ | |
| | | member | | member | | |
| | | AS 1 | | AS 2 | | |
| | +--------+ +--------+ | |
| +--------------------------+ |
| IGP domain |
+-------------------------------+
Confederation (confed-id 1)
Figure 20: Confederation
Using a Confederation/MemberAS identifier to globally identify IGP
node will break requirement (A).
(iv) It is possible to run more than one IGP domain within an AS by
setting up "transit BGP speakers".
Gredler, et al. Expires August 28, 2013 [Page 18]
Internet-Draft Link-State Info Distribution using BGP February 2013
+---------------------------------+
| +----------+ +----------+ |
| | IGP | +---+ | IGP | |
| | domain 1 +-+ +-+ domain 2 | |
| +----------+ +---+ +----------+ |
| ^ |
| | |
| Transit BGP node |
+---------------------------------+
AS 1
Figure 21: Transit BGP Node
Using ASN to globally identify IGP node may break requirement (A).
In summary, there is no strict relation between BGP AS division and
IGP domains. Therefore, the following mechanism is proposed to
address the requirements. We assume that a BGP-LS speaker is
collocated with one and only one IGP node. The BGP-LS speaker
originates BGP-LS NLRIs that correspond to the objects in the LSDB of
that IGP node.
We embed a "string" (identifier) in the node descriptor to globally
identify the node. The question is how we construct such a string,
and what should be the scope of such a string so that the
construction of the string can be simple. Let the set of IGP nodes
within which LSA/LSP flooding is limited to be the "flooding set".
Consider a given "flooding set". We have the following three
possibilities:
Case a) There is no BGP LS speaker running on any node in the
flooding set.
Case b) There is one BGP LS speaker running on one node in the
flooding set.
Case c) There is more than one BGP LS speakers running on the nodes
in the flooding set.
For Case a), the nodes in that flooding set do not appear in BGP LS
database. So we can ignore that case for this discussion. To
satisfy requirement (B), the string we use in different IGP domains
must be different. One possible approach is as follows:
Approach 1) The user configures a unique "string" on all BGP LS
speakers within one IGP domain.
Now we make an observation that simplifies the task: it is sufficient
Gredler, et al. Expires August 28, 2013 [Page 19]
Internet-Draft Link-State Info Distribution using BGP February 2013
to have a unique "string" per flooding set.
When we have a unique string per flooding set, then two nodes in
different IGP domains, which by definition belong to different
flooding sets, would have different "strings". So requirement B) is
satisfied. On the other hand, a given node appears only in the LSDB
of the nodes in the same flooding set. So a given node will always
have only one "string" and we satisfy requirement A). Given this, we
have:
Approach 2) Each BGP LS speaker uses the <Autonomous System Number,
BGP Identifier> as the string.
The combination of <Autonomous System, BGP Identifier> is globally
unique, as per [RFC6286].
For Case b), which is the simplest BGP-LS deployment scenario, this
approach requires no additional configuration from the user.
For Case c), however, if each BGP-LS speaker in the given flooding
set attaches its own <Autonomous System, BGP Identifier>, then we
will violate requirement A). So that case, the user needs to choose
one of the BGP-LS speakers in the flooding set as the "chosen
speaker" and configure the rest of the BGP-LS speakers in that
flooding set to use the <Autonomous System, BGP Identifier>
combination of the "chosen speaker".
When an IGP node belongs to two or more flooding sets, it views
itself as a collocation of one node per flooding set and accordingly
encodes the NLRIs. Consider the following example:
Level-1 level-1-2 level-1
N1 N0 N2
+---+ link1 +---+ link 2 +---+
| +-------+ +---------+ |
+---+ +---+ +---+
|<- Level 1 ->| |<- level 2 ->|
L11 L12
"str1" "str2"
Figure 22: IGP Node in multiple flooding sets
The node N0 is a level 1-2 node. Link1 belongs to level 1 area L11,
which has string "str1". Link2 belongs to level 1 area L12 which has
string "str2". N0 has both link1 and link2 in its LSDB. If BGP LS
speaker is running on N0, then N0 views itself as a collocation of
two nodes: N0(L11) and N0(L12) and originate <str1, N1, N0> and
<str2, N0, N2>.
Gredler, et al. Expires August 28, 2013 [Page 20]
Internet-Draft Link-State Info Distribution using BGP February 2013
To sum up, the mechanism works as follows:
1. We use <Autonomous System, BGP Identifier> as the
disambiguating string.
2. By default, a BGP-LS speaker uses its own ASN, BGP identifier
(router-id) for these fields for the NLRIs it originates.
3. Operator has the ability to configure other <ASN, BGP ID> per
flooding set the IGP node underneath belongs to. In that case,
the node descriptor(s) for a given NLRI uses the string
corresponding to the flooding set where the node belongs.
The operator needs to provide the configuration if there are multiple
BGP-LS speakers running in the same flooding set.
3.2.2.5. Router-ID Anchoring Example: ISO Pseudonode
IS-IS Pseudonodes are a good example for the variable Router-ID
anchoring. Consider Figure 23. This represents a Broadcast LAN
between a pair of routers. The "real" (=non pseudonode) routers have
both an IPv4 Router-ID and IS-IS Node-ID. The pseudonode does not
have an IPv4 Router-ID. Two unidirectional links (Node1, Pseudonode
1) and (Pseudonode 1, Node 2) are being generated.
The NRLI for (Node1, Pseudonode1) encodes local IPv4 router-ID, local
ISO node-ID and remote ISO node-id)
The NLRI for (Pseudonode1, Node2) encodes a local ISO node-ID and
remote ISO node-id.
+-----------------+ +-----------------+ +-----------------+
| Node1 | | Pseudonode 1 | | Node2 |
|1920.0000.2001.00|--->|1920.0000.2001.02|--->|1920.0000.2002.00|
| 192.0.2.1 | | | | 192.0.2.2 |
+-----------------+ +-----------------+ +-----------------+
Figure 23: IS-IS Pseudonodes
3.2.2.6. Router-ID Anchoring Example: OSPFv2 to IS-IS Migration
Migrating gracefully from one IGP to another requires congruent
operation of both routing protocols during the migration period. The
target protocol (IS-IS) supports more router-ID spaces than the
source (OSPFv2) protocol. When advertising a point-to-point link
between an OSPFv2-only router and an OSPFv2 and IS-IS enabled router
the following link information may be generated. Note that the IS-IS
router also supports the IPv6 traffic engineering extensions RFC 6119
Gredler, et al. Expires August 28, 2013 [Page 21]
Internet-Draft Link-State Info Distribution using BGP February 2013
[RFC6119] for IS-IS.
The NRLI encodes local IPv4 router-id, remote IPv4 router-id, remote
ISO node-id and remote IPv6 node-id.
3.2.3. Link Descriptors
The 'Link Descriptor' field is a set of Type/Length/Value (TLV)
triplets. The format of each TLV is shown in Section 3.1. The 'Link
descriptor' TLVs uniquely identify a link between a pair of anchor
Routers. A link described by the Link descriptor TLVs actually is a
"half-link", a unidirectional representation of a logical link. In
order to fully describe a single logical link two originating routers
need to advertise a half-link each, i.e. two link NLRIs will be
advertised.
The format and semantics of the 'value' fields in most 'Link
Descriptor' TLVs correspond to the format and semantics of value
fields in IS-IS Extended IS Reachability sub-TLVs, defined in
[RFC5305], [RFC5307] and [RFC6119]. Although the encodings for 'Link
Descriptor' TLVs were originally defined for IS-IS, the TLVs can
carry data sourced either by IS-IS or OSPF.
The following link descriptor TLVs are valid in the Link NLRI:
+------------+--------------------+---------------+-----------------+
| TLV/SubTLV | Description | IS-IS | Value defined |
| | | TLV/Sub-TLV | in: |
+------------+--------------------+---------------+-----------------+
| 264 | Link Local/Remote | 22/4 | [RFC5307]/1.1 |
| | Identifiers | | |
| 265 | IPv4 interface | 22/6 | [RFC5305]/3.2 |
| | address | | |
| 266 | IPv4 neighbor | 22/8 | [RFC5305]/3.3 |
| | address | | |
| 267 | IPv6 interface | 22/12 | [RFC6119]/4.2 |
| | address | | |
| 268 | IPv6 neighbor | 22/13 | [RFC6119]/4.3 |
| | address | | |
| 256/5 | Multi Topology ID | --- | Section 3.2.1.5 |
+------------+--------------------+---------------+-----------------+
Table 2: Link Descriptor TLVs
Gredler, et al. Expires August 28, 2013 [Page 22]
Internet-Draft Link-State Info Distribution using BGP February 2013
3.2.4. Prefix Descriptors
The 'Prefix descriptor' TLVs uniquely identify a Prefix (IPv4 or
IPv6) originated by a Node.
The following Prefix descriptor TLVs are valid in the IPv4/IPv6
Prefix NLRI:
+------------+-----------------+-----------------+------------------+
| TLV/SubTLV | Description | IS-IS | Value defined |
| | | TLV/Sub-TLV | in: |
+------------+-----------------+-----------------+------------------+
| 256/5 | Multi Topology | --- | Section 3.2.1.5 |
| | ID | | |
+------------+-----------------+-----------------+------------------+
Table 3: Prefix Descriptor TLVs
3.2.4.1. The Prefix NLRI
The Prefix NLRI is a variable length field that contains one or more
IP address prefixes (IPv4 or IPv6) originally advertised in the IGP
topology. The NLRI Type determines the address-family. Reachability
information is encoded as one or more 2-tuples of the form <length,
prefix>, whose fields are described below:
+---------------------------+
| Length (1 octet) |
+---------------------------+
| Prefix (variable) |
+---------------------------+
Figure 24: Prefix NLRI format
The 'Length' field contains the length of the prefix in bits. Only
the most significant octets of the prefix are encoded. I.e. 1 octet
for prefix length 1 up to 8, 2 octets for prefix length 9 to 16, 3
octets for prefix length 17 up to 24 and 4 octets for prefix length
25 up to 32, etc.
3.3. The LINK_STATE Attribute
This is an optional, non-transitive BGP attribute that is used to
carry link, node and prefix parameters and attributes. It is defined
as a set of Type/Length/Value (TLV) triplets, described in the
following section. This attribute SHOULD only be included with Link
State NLRIs. This attribute MUST be ignored for all other NLRIs.
Gredler, et al. Expires August 28, 2013 [Page 23]
Internet-Draft Link-State Info Distribution using BGP February 2013
3.3.1. Link Attribute TLVs
Each 'Link Attribute' is a Type/Length/Value (TLV) triplet formatted
as defined in Section 3.1. The format and semantics of the 'value'
fields in some 'Link Attribute' TLVs correspond to the format and
semantics of value fields in IS-IS Extended IS Reachability sub-TLVs,
defined in [RFC5305] and [RFC5307]. Other 'Link Attribute' TLVs are
defined in this document. Although the encodings for 'Link
Attribute' TLVs were originally defined for IS-IS, the TLVs can carry
data sourced either by IS-IS or OSPF.
The following 'Link Attribute' TLVs are are valid in the LINK_STATE
attribute:
+------------+---------------------+--------------+-----------------+
| TLV/SubTLV | Description | IS-IS | Defined in: |
| | | TLV/Sub-TLV | |
+------------+---------------------+--------------+-----------------+
| 256/3 | Area Identifier | --- | Section 3.2.1.3 |
| 269 | Administrative | 22/3 | [RFC5305]/3.1 |
| | group (color) | | |
| 270 | Maximum link | 22/9 | [RFC5305]/3.3 |
| | bandwidth | | |
| 271 | Max. reservable | 22/10 | [RFC5305]/3.5 |
| | link bandwidth | | |
| 272 | Unreserved | 22/11 | [RFC5305]/3.6 |
| | bandwidth | | |
| 273 | TE Default Metric | 22/18 | [RFC5305]/3.7 |
| 274 | Link Protection | 22/20 | [RFC5307]/1.2 |
| | Type | | |
| 275 | MPLS Protocol Mask | --- | Section 3.3.1.1 |
| 276 | Metric | --- | Section 3.3.1.2 |
| 277 | Shared Risk Link | --- | Section 3.3.1.3 |
| | Group | | |
| 278 | OSPF specific link | --- | Section 3.3.1.4 |
| | attribute | | |
| 279 | IS-IS Specific Link | --- | Section 3.3.1.5 |
| | Attribute | | |
+------------+---------------------+--------------+-----------------+
Table 4: Link Attribute TLVs
3.3.1.1. MPLS Protocol Mask TLV
The MPLS Protocol TLV (Type 275) carries a bit mask describing which
MPLS signaling protocols are enabled. The length of this TLV is 1.
The value is a bit array of 8 flags, where each bit represents an
MPLS Protocol capability.
Gredler, et al. Expires August 28, 2013 [Page 24]
Internet-Draft Link-State Info Distribution using BGP February 2013
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|L R |
+-+-+-+-+-+-+-+-+
Figure 25: MPLS Protocol TLV
The following bits are defined:
+-----+---------------------------------------------+-----------+
| Bit | Description | Reference |
+-----+---------------------------------------------+-----------+
| 0 | Label Distribution Protocol (LDP) | [RFC5036] |
| 1 | Extension to RSVP for LSP Tunnels (RSVP-TE) | [RFC3209] |
| 2-7 | Reserved for future use | |
+-----+---------------------------------------------+-----------+
Table 5: MPLS Protocol Mask TLV Codes
3.3.1.2. Metric TLV
The IGP Metric TLV (Type 276) carries the metric for this link. The
length of this TLV is 3. If the length of the metric from which the
IGP Metric value is derived is less than 3 (e.g. for OSPF link
metrics or non-wide IS-IS metric), then the upper bits of the TLV are
set to 0.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IGP Link Metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 26: Metric TLV format
3.3.1.3. Shared Risk Link Group TLV
The Shared Risk Link Group (SRLG) TLV (Type 277) carries the Shared
Risk Link Group information (see Section 2.3, "Shared Risk Link Group
Information", of [RFC4202]). It contains a data structure consisting
of a (variable) list of SRLG values, where each element in the list
has 4 octets, as shown in Figure 27. The length of this TLV is 4 *
(number of SRLG values).
Gredler, et al. Expires August 28, 2013 [Page 25]
Internet-Draft Link-State Info Distribution using BGP February 2013
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Shared Risk Link Group Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ............ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Shared Risk Link Group Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 27: Shared Risk Link Group TLV format
Note that there is no SRLG TLV in OSPF-TE. In IS-IS the SRLG
information is carried in two different TLVs: the IPv4 (SRLG) TLV
(Type 138) defined in [RFC5307], and the IPv6 SRLG TLV (Type 139)
defined in [RFC6119]. Since the Link State NLRI uses variable
Router-ID anchoring, both IPv4 and IPv6 SRLG information can be
carried in a single TLV.
3.3.1.4. OSPF Specific Link Attribute TLV
The OSPF specific link attribute TLV (Type 278) is an envelope that
transparently carries optional link properties TLVs advertised by an
OSPF router. The value field contains one or more optional OSPF link
attribute TLVs. An originating router shall use this TLV for
encoding information specific to the OSPF protocol or new OSPF
extensions for which there is no protocol neutral representation in
the BGP link-state NLRI.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| OSPF specific link attributes (variable) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 28: OSPF specific link attribute format
3.3.1.5. IS-IS specific link attribute TLV
The IS-IS specific link attribute TLV (Type 279) is an envelope that
transparently carries optional link properties TLVs advertised by an
IS-IS router. The value field contains one or more optional IS-IS
Gredler, et al. Expires August 28, 2013 [Page 26]
Internet-Draft Link-State Info Distribution using BGP February 2013
link attribute TLVs. An originating router shall use this TLV for
encoding information specific to the IS-IS protocol or new IS-IS
extensions for which there is no protocol neutral representation in
the BGP link-state NLRI.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| IS-IS specific link attributes (variable) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 29: IS-IS specific link attribute format
3.3.1.6. IS-IS Area Address attribute TLV
The area address is carried in the Area Identifier SubTLV of the
Identifier TLV and consists of the Area Address which is assigned to
the link. If more than one Area Addresses are present, only the
lower address is encoded. Note that the Area Identifier SubTLV may
appear in all NLRI types (Link, Node and Prefix) and is defined in
Section 3.2.1.3.
3.3.2. Node Attribute TLVs
The following node attribute TLVs are defined:
+------------+--------------------------------------+----------+
| TLV/SubTLV | Description | Length |
+------------+--------------------------------------+----------+
| 256/5 | Multi Topology | 2 |
| 280 | Node Flag Bits | 1 |
| 281 | OSPF Specific Node Properties | variable |
| 282 | IS-IS Specific Node Properties | variable |
| 256 | IS-IS Area Address/Domain Identifier | variable |
+------------+--------------------------------------+----------+
Table 6: Node Attribute TLVs
3.3.2.1. Node Multi Topology ID
The Node Multi Topology ID is carried in the Multi Topolofy ID SubTLV
(type 5) of Identifier ID TLV TLV (Type 256) and carries the Multi
Topology ID and topology specific flags for this node. The format
and semantics of the 'value' field in the Multi Topology TLV is
Gredler, et al. Expires August 28, 2013 [Page 27]
Internet-Draft Link-State Info Distribution using BGP February 2013
defined in Section 3.2.1.5. If the value in the Multi Topology TLV
is derived from OSPF, then the upper 9 bits of the Multi Topology ID
and the 'O' and 'A' bits are set to 0.
3.3.2.2. Node Flag Bits TLV
The Node Flag Bits TLV (Type 280) carries a bit mask describing node
attributes. The value is a variable length bit array of flags, where
each bit represents a node capability.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags (variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 30: Node Flag Bits TLV format
The bits are defined as follows:
+-----+--------------+-----------+
| Bit | Description | Reference |
+-----+--------------+-----------+
| 0 | Overload Bit | [RFC1195] |
| 1 | Attached Bit | [RFC1195] |
| 2 | External Bit | [RFC2328] |
| 3 | ABR Bit | [RFC2328] |
+-----+--------------+-----------+
Table 7: Node Flag Bits Definitions
3.3.2.3. OSPF Specific Node Properties TLV
The OSPF Specific Node Properties TLV (Type 281) is an envelope that
transparently carries optional node properties TLVs advertised by an
OSPF router. The value field contains one or more optional OSPF node
property TLVs, such as the OSPF Router Informational Capabilities TLV
defined in [RFC4970], or the OSPF TE Node Capability Descriptor TLV
described in [RFC5073]. An originating router shall use this TLV for
encoding information specific to the OSPF protocol or new OSPF
extensions for which there is no protocol neutral representation in
the BGP link-state NLRI.
Gredler, et al. Expires August 28, 2013 [Page 28]
Internet-Draft Link-State Info Distribution using BGP February 2013
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| OSPF specific node properties (variable) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 31: OSPF specific Node property format
3.3.2.4. IS-IS Specific Node Properties TLV
The IS-IS Router Specific Node Properties TLV (Type 282) is an
envelope that transparently carries optional node specific TLVs
advertised by an IS-IS router. The value field contains one or more
optional IS-IS node property TLVs, such as the IS-IS TE Node
Capability Descriptor TLV described in [RFC5073]. An originating
router shall use this TLV for encoding information specific to the
IS-IS protocol or new IS-IS extensions for which there is no protocol
neutral representation in the BGP link-state NLRI.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| IS-IS specific node properties (variable) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 32: IS-IS specific Node property format
3.3.2.5. ISIS Area Address TLV
The area address is carried in the Area Identifier SubTLV of the
Identifier TLV and consists of the Area Address which is assigned to
the node. If more than one Area Addresses are present, only the
lower address is encoded. Note that the Area Identifier SubTLV may
appear in all NLRI types (Link, Node and Prefix) and is defined in
Section 3.2.1.3.
3.3.3. Prefix Attributes TLVs
Prefixes are learned from the IGP topology (ISIS or OSPF) with a set
of IGP attributes (such as metric, route tags, etc.) that MUST be
Gredler, et al. Expires August 28, 2013 [Page 29]
Internet-Draft Link-State Info Distribution using BGP February 2013
reflected into the LINK_STATE attribute. This section describes the
different attributes related to the IPv4/IPv6 prefixes. Prefix
Attributes TLVs SHOULD be used when advertising NLRI types 3 and 4
only. The following attributes TLVs are defined:
+-------------------------+-------------+-----------+-----------+
| TLV/SubTLV | Description | Length | Reference |
+-------------------------+-------------+-----------+-----------+
| 283 | IGP Flags | 4 | 284 |
| Route Tag | 4*n | [RFC5130] | 285 |
| Extended Tag | 8*n | [RFC5130] | 286 |
| Prefix Metric | 4 | [RFC5305] | 287 |
| OSPF Forwarding Address | 4 | [RFC2328] | |
+-------------------------+-------------+-----------+-----------+
Table 8: Prefix Attribute TLVs
3.3.3.1. IGP Flags TLV
IGP Flags TLV contains ISIS and OSPF flags and bits originally
assigned to the prefix. The IGP Flags TLV is encoded as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IGP Flags (variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 33: IGP Flag TLV format
where:
Type is 283
Length is variable
The following bits are defined according to the table here below:
+------+------------------+-----------+
| Bit | Description | Reference |
+------+------------------+-----------+
| 0 | ISIS Up/Down Bit | [RFC5305] |
| 1-3 | OSPF Route Type | [RFC2328] |
| 4-15 | RESERVED | |
+------+------------------+-----------+
Gredler, et al. Expires August 28, 2013 [Page 30]
Internet-Draft Link-State Info Distribution using BGP February 2013
Table 9: IGP Flag Bits Definitions
OSPF Route Type can be either: Intra-Area (0x1), Inter-Area (0x2),
External 1 (0x3), External 2 (0x4), NSSA (0x5) and is encoded in a 3
bits number. For prefixes learned from IS-IS, this field MUST to be
set to 0x0 on transmission.
3.3.3.2. Route Tag
Route Tag TLV carries the original IGP TAG (ISIS or OSPF) of the
prefix and is encoded as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Route Tags (one or more) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 34: IGP Route TAG TLV format
where:
Type is 284
Length is a multiple of 4
One or more Route Tags as learned in the IGP topology.
3.3.3.3. Extended Route Tag
Extended Route Tag TLV carries the ISIS Extended Route TAG of the
prefix and is encoded as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Extended Route Tag (one or more) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 35: Extended IGP Route TAG TLV format
where:
Gredler, et al. Expires August 28, 2013 [Page 31]
Internet-Draft Link-State Info Distribution using BGP February 2013
Type is 285
Length is a multiple of 8
Extended Route Tag contains one or more Extended Route Tags as
learned in the IGP topology.
3.3.3.4. Prefix Metric TLV
Prefix Metric TLV carries the metric of the prefix as known in the
IGP topology. The attribute is mandatory and can only appear once.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 36: Prefix Metric TLV Format
where:
Type is 286
Length is 4
3.3.3.5. OSPF Forwarding Address TLV
OSPF Forwarding Address TLV carries the OSPF forwarding address as
known in the original OSPF advertisement. Forwarding address can be
either IPv4 or IPv6.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Forwarding Address (variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 37: OSPF Forwarding Address TLV Format
where:
Type is 287
Gredler, et al. Expires August 28, 2013 [Page 32]
Internet-Draft Link-State Info Distribution using BGP February 2013
Length is 4 for an IPv4 forwarding address an 16 for an IPv6
forwarding address
3.4. BGP Next Hop Information
BGP link-state information for both IPv4 and IPv6 networks can be
carried over either an IPv4 BGP session, or an IPv6 BGP session. If
IPv4 BGP session is used, then the next hop in the MP_REACH_NLRI
SHOULD be an IPv4 address. Similarly, if IPv6 BGP session is used,
then the next hop in the MP_REACH_NLRI SHOULD be an IPv6 address.
Usually the next hop will be set to the local end-point address of
the BGP session. The next hop address MUST be encoded as described
in [RFC4760]. The length field of the next hop address will specify
the next hop address-family. If the next hop length is 4, then the
next hop is an IPv4 address; if the next hop length is 16, then it is
a global IPv6 address and if the next hop length is 32, then there is
one global IPv6 address followed by a link-local IPv6 address. The
link-local IPv6 address should be used as described in [RFC2545].
The BGP Next Hop attribute is used by each BGP-LS spaker to validate
the NLRI it receives. However, this specification doesn't mandate
any rule regarding the re-write of the BGP Next Hop attribute.
3.5. Inter-AS Links
The main source of TE information is the IGP, which is not active on
inter-AS links. In order to inject a non-IGP enabled link into the
BGP link-state RIB an implementation must support configuration of
static links.
4. Link to Path Aggregation
Distribution of all links available in the global Internet is
certainly possible, however not desirable from a scaling and privacy
point of view. Therefore an implementation may support link to path
aggregation. Rather than advertising all specific links of a domain,
an ASBR may advertise an "aggregate link" between a non-adjacent pair
of nodes. The "aggregate link" represents the aggregated set of link
properties between a pair of non-adjacent nodes. The actual methods
to compute the path properties (of bandwidth, metric) are outside the
scope of this document. The decision whether to advertise all
specific links or aggregated links is an operator's policy choice.
To highlight the varying levels of exposure, the following deployment
examples shall be discussed.
Gredler, et al. Expires August 28, 2013 [Page 33]
Internet-Draft Link-State Info Distribution using BGP February 2013
4.1. Example: No Link Aggregation
Consider Figure 38. Both AS1 and AS2 operators want to protect their
inter-AS {R1,R3}, {R2, R4} links using RSVP-FRR LSPs. If R1 wants to
compute its link-protection LSP to R3 it needs to "see" an alternate
path to R3. Therefore the AS2 operator exposes its topology. All
BGP TE enabled routers in AS1 "see" the full topology of AS and
therefore can compute a backup path. Note that the decision if the
direct link between {R3, R4} or the {R4, R5, R3) path is used is made
by the computing router.
AS1 : AS2
:
R1-------R3
| : | \
| : | R5
| : | /
R2-------R4
:
:
Figure 38: no-link-aggregation
4.2. Example: ASBR to ASBR Path Aggregation
The brief difference between the "no-link aggregation" example and
this example is that no specific link gets exposed. Consider
Figure 39. The only link which gets advertised by AS2 is an
"aggregate" link between R3 and R4. This is enough to tell AS1 that
there is a backup path. However the actual links being used are
hidden from the topology.
AS1 : AS2
:
R1-------R3
| : |
| : |
| : |
R2-------R4
:
:
Figure 39: asbr-link-aggregation
Gredler, et al. Expires August 28, 2013 [Page 34]
Internet-Draft Link-State Info Distribution using BGP February 2013
4.3. Example: Multi-AS Path Aggregation
Service providers in control of multiple ASes may even decide to not
expose their internal inter-AS links. Consider Figure 40. AS3 is
modeled as a single node which connects to the border routers of the
aggregated domain.
AS1 : AS2 : AS3
: :
R1-------R3-----
| : : \
| : : vR0
| : : /
R2-------R4-----
: :
: :
Figure 40: multi-as-aggregation
5. IANA Considerations
This document requests a code point from the registry of Address
Family Numbers.
This document requests a code point from the BGP Path Attributes
registry.
This document requests creation of a new registry for node anchor,
link descriptor and link attribute TLVs. Values 0-255 are reserved.
Values 256-65535 will be used for Codepoints. The registry will be
initialized as shown in Table 2 and Table 4. Allocations within the
registry will require documentation of the proposed use of the
allocated value and approval by the Designated Expert assigned by the
IESG (see [RFC5226]).
Note to RFC Editor: this section may be removed on publication as an
RFC.
6. Manageability Considerations
This section is structured as recommended in [RFC5706].
6.1. Operational Considerations
Gredler, et al. Expires August 28, 2013 [Page 35]
Internet-Draft Link-State Info Distribution using BGP February 2013
6.1.1. Operations
Existing BGP operation procedures apply. No new operation procedures
are defined in this document. It shall be noted that the NLRI
information present in this document purely carries application level
data that have no immediate corresponding forwarding state impact.
As such, any churn in reachability information has different impact
than regular BGP update which needs to change forwarding state for an
entire router. Furthermore it is anticipated that distribution of
this NLRI will be handled by dedicated route-reflectors providing a
level of isolation and fault-containment between different NLRI
types.
6.1.2. Installation and Initial Setup
Configuration parameters defined in Section 6.2.3 SHOULD be
initialized to the following default values:
o The Link-State NLRI capability is turned off for all neighbors.
o The maximum rate at which Link State NLRIs will be advertised/
withdrawn from neighbors is set to 200 updates per second.
6.1.3. Migration Path
The proposed extension is only activated between BGP peers after
capability negotiation. Moreover, the extensions can be turned on/
off an individual peer basis (see Section 6.2.3), so the extension
can be gradually rolled out in the network.
6.1.4. Requirements on Other Protocols and Functional Components
The protocol extension defined in this document does not put new
requirements on other protocols or functional components.
6.1.5. Impact on Network Operation
Frequency of Link-State NLRI updates could interfere with regular BGP
prefix distribution. A network operator MAY use a dedicated Route-
Reflector infrastructure to distribute Link-State NLRIs.
Distribution of Link-State NLRIs SHOULD be limited to a single admin
domain, which can consist of multiple areas within an AS or multiple
ASes.
Gredler, et al. Expires August 28, 2013 [Page 36]
Internet-Draft Link-State Info Distribution using BGP February 2013
6.1.6. Verifying Correct Operation
Existing BGP procedures apply. In addition, an implementation SHOULD
allow an operator to:
o List neighbors with whom the Speaker is exchanging Link-State
NLRIs
6.2. Management Considerations
6.2.1. Management Information
6.2.2. Fault Management
TBD.
6.2.3. Configuration Management
An implementation SHOULD allow the operator to specify neighbors to
which Link-State NLRIs will be advertised and from which Link-State
NLRIs will be accepted.
An implementation SHOULD allow the operator to specify the maximum
rate at which Link State NLRIs will be advertised/withdrawn from
neighbors
An implementation SHOULD allow the operator to specify the maximum
number of Link State NLRIs stored in router's RIB.
An implementation SHOULD allow the operator to create abstracted
topologies that are advertised to neighbors; Create different
abstractions for different neighbors.
An implementation SHOULD allow the operator to configure a pair of
ASN and BGP identifier per flooding set the node participates in.
6.2.4. Accounting Management
Not Applicable.
6.2.5. Performance Management
An implementation SHOULD provide the following statistics:
o Total number of Link-State NLRI updates sent/received
o Number of Link-State NLRI updates sent/received, per neighbor
Gredler, et al. Expires August 28, 2013 [Page 37]
Internet-Draft Link-State Info Distribution using BGP February 2013
o Number of errored received Link-State NLRI updates, per neighbor
o Total number of locally originated Link-State NLRIs
6.2.6. Security Management
An operator SHOULD define ACLs to limit inbound updates as follows:
o Drop all updates from Consumer peers
7. TLV/SubTLV Code Points Summary
This section contains the global table of all TLVs/SubTLVs defined in
this document.
Gredler, et al. Expires August 28, 2013 [Page 38]
Internet-Draft Link-State Info Distribution using BGP February 2013
+------------+--------------------+---------------+-----------------+
| TLV/SubTLV | Description | IS-IS | Value defined |
| | | TLV/Sub-TLV | in: |
+------------+--------------------+---------------+-----------------+
| 256 | Identifier | -- | Section 3.2.1 |
| 257 | Local Node | -- | Section 3.2.2.1 |
| | Descriptors | | |
| 258 | Remote Node | -- | Section 3.2.2.2 |
| | Descriptors | | |
| 259 | Autonomous System | -- | Section 3.2.2.3 |
| 260 | BGP Identifier | -- | Section 3.2.2.3 |
| 261 | ISO Node-ID | -- | Section 3.2.2.3 |
| 262 | IPv4 Router-ID | -- | Section 3.2.2.3 |
| 263 | IPv6 Router-ID | -- | Section 3.2.2.3 |
| 264 | Link Local/Remote | 22/4 | [RFC5307]/1.1 |
| | Identifiers | | |
| 265 | IPv4 interface | 22/6 | [RFC5305]/3.2 |
| | address | | |
| 266 | IPv4 neighbor | 22/8 | [RFC5305]/3.3 |
| | address | | |
| 267 | IPv6 interface | 22/12 | [RFC6119]/4.2 |
| | address | | |
| 268 | IPv6 neighbor | 22/13 | [RFC6119]/4.3 |
| | address | | |
| 256/5 | Multi Topology ID | -- | Section 3.2.1.5 |
| 269 | Administrative | 22/3 | [RFC5305]/3.1 |
| | group (color) | | |
| 270 | Maximum link | 22/9 | [RFC5305]/3.3 |
| | bandwidth | | |
| 271 | Max. reservable | 22/10 | [RFC5305]/3.5 |
| | link bandwidth | | |
| 272 | Unreserved | 22/11 | [RFC5305]/3.6 |
| | bandwidth | | |
| 273 | TE Default Metric | 22/18 | [RFC5305]/3.7 |
| 274 | Link Protection | 22/20 | [RFC5307]/1.2 |
| | Type | | |
| 275 | MPLS Protocol Mask | -- | Section 3.3.1.1 |
| 276 | Metric | -- | Section 3.3.1.2 |
| 277 | Shared Risk Link | -- | Section 3.3.1.3 |
| | Group | | |
| 278 | OSPF specific link | -- | Section 3.3.1.4 |
| | attribute | | |
| 279 | IS-IS Specific | -- | Section 3.3.1.5 |
| | Link Attribute | | |
| 280 | Node Flag Bits | -- | Section 3.3.2.2 |
| 281 | OSPF Specific Node | -- | Section 3.3.2.3 |
| | Properties | | |
Gredler, et al. Expires August 28, 2013 [Page 39]
Internet-Draft Link-State Info Distribution using BGP February 2013
| 282 | IS-IS Specific | -- | Section 3.3.2.4 |
| | Node Properties | | |
| 283 | IGP Flags | -- | Section 3.3.3.1 |
| 284 | Route Tag | -- | [RFC5130] |
| 285 | Extended Tag | -- | [RFC5130] |
| 286 | Prefix Metric | -- | [RFC5305] |
| 287 | OSPF Forwarding | -- | [RFC2328] |
| | Address | | |
+------------+--------------------+---------------+-----------------+
Table 10: Summary Table of TLV/SubTLV Codepoints
8. Security Considerations
Procedures and protocol extensions defined in this document do not
affect the BGP security model.
A BGP Speaker SHOULD NOT accept updates from a Consumer peer.
An operator SHOULD employ a mechanism to protect a BGP Speaker
against DDOS attacks from Consumers.
9. Contributors
We would like to thank Robert Varga for the significant contribution
he gave to this document.
10. Acknowledgements
We would like to thank Nischal Sheth, Alia Atlas, David Ward, Derek
Yeung, Murtuza Lightwala, John Scudder, Kaliraj Vairavakkalai, Les
Ginsberg, Liem Nguyen, Manish Bhardwaj, Mike Shand, Peter Psenak, Rex
Fernando, Richard Woundy, Steven Luong, Tamas Mondal, Waqas Alam,
Vipin Kumar, Naiming Shen and Yakov Rekhter for their comments.
11. References
11.1. Normative References
[RFC1195] Callon, R., "Use of OSI IS-IS for routing in TCP/IP and
dual environments", RFC 1195, December 1990.
[RFC1918] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and
E. Lear, "Address Allocation for Private Internets",
Gredler, et al. Expires August 28, 2013 [Page 40]
Internet-Draft Link-State Info Distribution using BGP February 2013
BCP 5, RFC 1918, February 1996.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998.
[RFC2545] Marques, P. and F. Dupont, "Use of BGP-4 Multiprotocol
Extensions for IPv6 Inter-Domain Routing", RFC 2545,
March 1999.
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, December 2001.
[RFC4202] Kompella, K. and Y. Rekhter, "Routing Extensions in
Support of Generalized Multi-Protocol Label Switching
(GMPLS)", RFC 4202, October 2005.
[RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway
Protocol 4 (BGP-4)", RFC 4271, January 2006.
[RFC4760] Bates, T., Chandra, R., Katz, D., and Y. Rekhter,
"Multiprotocol Extensions for BGP-4", RFC 4760,
January 2007.
[RFC4915] Psenak, P., Mirtorabi, S., Roy, A., Nguyen, L., and P.
Pillay-Esnault, "Multi-Topology (MT) Routing in OSPF",
RFC 4915, June 2007.
[RFC5036] Andersson, L., Minei, I., and B. Thomas, "LDP
Specification", RFC 5036, October 2007.
[RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi
Topology (MT) Routing in Intermediate System to
Intermediate Systems (IS-ISs)", RFC 5120, February 2008.
[RFC5130] Previdi, S., Shand, M., and C. Martin, "A Policy Control
Mechanism in IS-IS Using Administrative Tags", RFC 5130,
February 2008.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008.
[RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic
Engineering", RFC 5305, October 2008.
Gredler, et al. Expires August 28, 2013 [Page 41]
Internet-Draft Link-State Info Distribution using BGP February 2013
[RFC5307] Kompella, K. and Y. Rekhter, "IS-IS Extensions in Support
of Generalized Multi-Protocol Label Switching (GMPLS)",
RFC 5307, October 2008.
[RFC6119] Harrison, J., Berger, J., and M. Bartlett, "IPv6 Traffic
Engineering in IS-IS", RFC 6119, February 2011.
[RFC6822] Previdi, S., Ginsberg, L., Shand, M., Roy, A., and D.
Ward, "IS-IS Multi-Instance", RFC 6822, December 2012.
11.2. Informative References
[I-D.ietf-alto-protocol]
Alimi, R., Penno, R., and Y. Yang, "ALTO Protocol",
draft-ietf-alto-protocol-13 (work in progress),
September 2012.
[RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation
Element (PCE)-Based Architecture", RFC 4655, August 2006.
[RFC4970] Lindem, A., Shen, N., Vasseur, JP., Aggarwal, R., and S.
Shaffer, "Extensions to OSPF for Advertising Optional
Router Capabilities", RFC 4970, July 2007.
[RFC5073] Vasseur, J. and J. Le Roux, "IGP Routing Protocol
Extensions for Discovery of Traffic Engineering Node
Capabilities", RFC 5073, December 2007.
[RFC5152] Vasseur, JP., Ayyangar, A., and R. Zhang, "A Per-Domain
Path Computation Method for Establishing Inter-Domain
Traffic Engineering (TE) Label Switched Paths (LSPs)",
RFC 5152, February 2008.
[RFC5693] Seedorf, J. and E. Burger, "Application-Layer Traffic
Optimization (ALTO) Problem Statement", RFC 5693,
October 2009.
[RFC5706] Harrington, D., "Guidelines for Considering Operations and
Management of New Protocols and Protocol Extensions",
RFC 5706, November 2009.
[RFC6286] Chen, E. and J. Yuan, "Autonomous-System-Wide Unique BGP
Identifier for BGP-4", RFC 6286, June 2011.
[RFC6549] Lindem, A., Roy, A., and S. Mirtorabi, "OSPFv2 Multi-
Instance Extensions", RFC 6549, March 2012.
Gredler, et al. Expires August 28, 2013 [Page 42]
Internet-Draft Link-State Info Distribution using BGP February 2013
Authors' Addresses
Hannes Gredler
Juniper Networks, Inc.
1194 N. Mathilda Ave.
Sunnyvale, CA 94089
US
Email: hannes@juniper.net
Jan Medved
Cisco Systems, Inc.
170, West Tasman Drive
San Jose, CA 95134
US
Email: jmedved@cisco.com
Stefano Previdi
Cisco Systems, Inc.
Via Del Serafico, 200
Rome 00142
Italy
Email: sprevidi@cisco.com
Adrian Farrel
Juniper Networks, Inc.
1194 N. Mathilda Ave.
Sunnyvale, CA 94089
US
Email: afarrel@juniper.net
Saikat Ray
Cisco Systems, Inc.
170, West Tasman Drive
San Jose, CA 95134
US
Email: sairay@cisco.com
Gredler, et al. Expires August 28, 2013 [Page 43]