draft-ietf-ccamp-isis-interas-te-extension-04.txt   rfc5316.txt 
Network working group M. Chen
Internet Draft Renhai Zhang
Category: Standards Track Huawei Technologies Co.,Ltd
Created: September 4, 2008 Xiaodong Duan
Expires: March 4, 2009 China Mobile
ISIS Extensions in Support of Inter-AS Multiprotocol Label Switching
(MPLS) and Generalized MPLS (GMPLS) Traffic Engineering
draft-ietf-ccamp-isis-interas-te-extension-04.txt
Status of this Memo Network Working Group M. Chen
Request for Comments: 5316 R. Zhang
Category: Standards Track Huawei Technologies Co., Ltd
X. Duan
China Mobile
December 2008
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any applicable patent or other IPR claims of which he or she is MPLS and GMPLS Traffic Engineering
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Abstract Abstract
This document describes extensions to the ISIS (ISIS) protocol to This document describes extensions to the ISIS (ISIS) protocol to
support Multiprotocol Label Switching (MPLS) and Generalized MPLS support Multiprotocol Label Switching (MPLS) and Generalized MPLS
(GMPLS) Traffic Engineering (TE) for multiple Autonomous Systems (GMPLS) Traffic Engineering (TE) for multiple Autonomous Systems
(ASes). It defines ISIS-TE extensions for the flooding of TE (ASes). It defines ISIS-TE extensions for the flooding of TE
information about inter-AS links which can be used to perform inter- information about inter-AS links, which can be used to perform inter-
AS TE path computation. AS TE path computation.
No support for flooding information from within one AS to another AS No support for flooding information from within one AS to another AS
is proposed or defined in this document. is proposed or defined in this document.
Conventions used in this document
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].
Table of Contents Table of Contents
1. Introduction................................................ 2 1. Introduction ....................................................2
2. Problem Statement .......................................... 3 1.1. Conventions Used in This Document ..........................3
2.1. A Note on Non-Objectives............................... 4 2. Problem Statement ...............................................3
2.2. Per-Domain Path Determination.......................... 4 2.1. A Note on Non-Objectives ...................................4
2.3. Backward Recursive Path Computation.................... 6 2.2. Per-Domain Path Determination ..............................4
3. Extensions to ISIS-TE....................................... 7 2.3. Backward Recursive Path Computation ........................6
3.1. Inter-AS Reachability TLV.............................. 8 3. Extensions to ISIS-TE ...........................................7
3.2. TE Router ID .......................................... 9 3.1. Inter-AS Reachability TLV ..................................7
3.3. Sub-TLV Detail........................................ 10 3.2. TE Router ID ...............................................9
3.3.1. Remote AS Number Sub-TLV......................... 10 3.3. Sub-TLV Detail .............................................9
3.3.2. IPv4 Remote ASBR ID Sub-TLV...................... 11 3.3.1. Remote AS Number Sub-TLV ............................9
3.3.3. IPv6 Remote ASBR ID Sub-TLV...................... 11 3.3.2. IPv4 Remote ASBR ID Sub-TLV ........................10
3.3.4. IPv4 TE Router ID sub-TLV........................ 12 3.3.3. IPv6 Remote ASBR ID Sub-TLV ........................11
3.3.5. IPv6 TE Router ID sub-TLV........................ 13 3.3.4. IPv4 TE Router ID sub-TLV ..........................11
4. Procedure for Inter-AS TE Links............................ 13 3.3.5. IPv6 TE Router ID sub-TLV ..........................12
4.1. Origin of Proxied TE Information...................... 15 4. Procedure for Inter-AS TE Links ................................12
5. Security Considerations.................................... 15 4.1. Origin of Proxied TE Information ..........................14
6. IANA Considerations........................................ 16 5. Security Considerations ........................................14
6.1. Inter-AS Reachability TLV............................. 16 6. IANA Considerations ............................................15
6.2. Sub-TLVs for the Inter-AS Reachability TLV............ 16 6.1. Inter-AS Reachability TLV .................................15
6.3. Sub-TLVs for the IS-IS Router Capability TLV.......... 17 6.2. Sub-TLVs for the Inter-AS Reachability TLV ................15
7. Acknowledgments............................................ 17 6.3. Sub-TLVs for the IS-IS Router Capability TLV ..............17
8. References................................................. 17 7. Acknowledgments ................................................17
8.1. Normative References.................................. 17 8. References .....................................................17
8.2. Informative References................................ 18 8.1. Normative References ......................................17
Authors' Addresses............................................ 19 8.2. Informative References ....................................17
Intellectual Property Statement .............................. 19
Disclaimer of Validity........................................ 20
Copyright Statement........................................... 20
1. Introduction 1. Introduction
[ISIS-TE] defines extensions to the ISIS protocol [ISIS] to support [ISIS-TE] defines extensions to the ISIS protocol [ISIS] to support
intra-area Traffic Engineering (TE). The extensions provide a way of intra-area Traffic Engineering (TE). The extensions provide a way of
encoding the TE information for TE-enabled links within the network encoding the TE information for TE-enabled links within the network
(TE links) and flooding this information within an area. The (TE links) and flooding this information within an area. The
Extended IS Reachability TLV and Traffic Engineering Router ID TLV, extended IS reachability TLV and traffic engineering router ID TLV,
which are defined in [ISIS-TE], are used to carry such TE which are defined in [ISIS-TE], are used to carry such TE
information. The Extended IS Reachability TLV has several nested information. The extended IS reachability TLV has several nested
sub-TLVs which describe the TE attributes for a TE link. sub-TLVs that describe the TE attributes for a TE link.
[ISIS-TE-V3] and [GMPLS-TE] define similar extensions to ISIS [ISIS] [ISIS-TE-V3] and [GMPLS-TE] define similar extensions to ISIS [ISIS]
in support of IPv6 and GMPLS traffic engineering respectively. in support of IPv6 and GMPLS traffic engineering, respectively.
Requirements for establishing Multiprotocol Label Switching (MPLS) Requirements for establishing Multiprotocol Label Switching (MPLS) TE
TE Label Switched Paths (LSPs) that cross multiple Autonomous Label Switched Paths (LSPs) that cross multiple Autonomous Systems
Systems (ASes) are described in [INTER-AS-TE-REQ]. As described in (ASes) are described in [INTER-AS-TE-REQ]. As described in [INTER-
[INTER-AS-TE-REQ], a method SHOULD provide the ability to compute a AS-TE-REQ], a method SHOULD provide the ability to compute a path
path spanning multiple ASes. So a path computation entity that may spanning multiple ASes. So a path computation entity that may be the
be the head-end Label Switching Router (LSR), an AS Border Router head-end Label Switching Router (LSR), an AS Border Router (ASBR), or
(ASBR), or a Path Computation Element (PCE [PCE]) needs to know the a Path Computation Element (PCE [PCE]) needs to know the TE
TE information not only of the links within an AS, but also of the information not only of the links within an AS, but also of the links
links that connect to other ASes. that connect to other ASes.
In this document, a new TLV, which is referred to as the Inter-AS In this document, a new TLV, which is referred to as the inter-AS
Reachability TLV, is defined to advertise inter-AS TE information, reachability TLV, is defined to advertise inter-AS TE information,
three new sub-TLVs are defined for inclusion in the Inter-AS and three new sub-TLVs are defined for inclusion in the inter-AS
Reachability TLV to carry the information about the remote AS number reachability TLV to carry the information about the remote AS number
and remote ASBR ID. The sub-TLVs defined in [ISIS-TE], [ISIS-TE-V3] and remote ASBR ID. The sub-TLVs defined in [ISIS-TE], [ISIS-TE-V3],
and other documents for inclusion in the Extended IS Reachability and other documents for inclusion in the extended IS reachability TLV
TLV for describing the TE properties of a TE link are applicable to for describing the TE properties of a TE link are applicable to be
be included in the Inter-AS Reachability TLV for describing the TE included in the inter-AS reachability TLV for describing the TE
properties of an inter-AS TE link as well. And two more new sub-TLVs properties of an inter-AS TE link as well. Also, two more new sub-
are defined for inclusion in the IS-IS Router Capability TLV to TLVs are defined for inclusion in the IS-IS router capability TLV to
carry the TE Router ID when TE Router ID needs to reach all routers carry the TE Router ID when the TE Router ID needs to reach all
within an entire ISIS routing domain. The extensions are equally routers within an entire ISIS routing domain. The extensions are
applicable to IPv4 and IPv6 as identical extensions to [ISIS-TE] and equally applicable to IPv4 and IPv6 as identical extensions to
[ISIS-TE-V3]. The detailed definitions and procedures are discussed [ISIS-TE] and [ISIS-TE-V3]. Detailed definitions and procedures are
in the following sections. discussed in the following sections.
This document does not propose or define any mechanisms to advertise This document does not propose or define any mechanisms to advertise
any other extra-AS TE information within ISIS. See Section 2.1 for a any other extra-AS TE information within ISIS. See Section 2.1 for a
full list of non-objectives for this work. full list of non-objectives for this work.
1.1. Conventions Used in This Document
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].
2. Problem Statement 2. Problem Statement
As described in [INTER-AS-TE-REQ], in the case of establishing an As described in [INTER-AS-TE-REQ], in the case of establishing an
inter-AS TE LSP traversing multiple ASes, the Path message [RFC3209] inter-AS TE LSP that traverses multiple ASes, the Path message
may include the following elements in the Explicit Route Object (ERO) [RFC3209] may include the following elements in the Explicit Route
in order to describe the path of the LSP: Object (ERO) in order to describe the path of the LSP:
- a set of AS numbers as loose hops; and/or - a set of AS numbers as loose hops, and/or
- a set of LSRs including ASBRs as loose hops. - a set of LSRs including ASBRs as loose hops.
Two methods for determining inter-AS paths are currently being Two methods for determining inter-AS paths are currently being
discussed. The per-domain method [PD-PATH] determines the path one discussed. The per-domain method [PD-PATH] determines the path one
domain at a time. The backward recursive method [BRPC] uses domain at a time. The backward recursive method [BRPC] uses
cooperation between PCEs to determine an optimum inter-domain path. cooperation between PCEs to determine an optimum inter-domain path.
The sections that follow examine how inter-AS TE link information The sections that follow examine how inter-AS TE link information
could be useful in both cases. could be useful in both cases.
2.1. A Note on Non-Objectives 2.1. A Note on Non-Objectives
It is important to note that this document does not make any change It is important to note that this document does not make any change
to the confidentiality and scaling assumptions surrounding the use to the confidentiality and scaling assumptions surrounding the use of
of ASes in the Internet. In particular, this document is conformant ASes in the Internet. In particular, this document is conformant to
to the requirements set out in [INTER-AS-TE-REQ]. the requirements set out in [INTER-AS-TE-REQ].
The following features are explicitly excluded: The following features are explicitly excluded:
o There is no attempt to distribute TE information from within one o There is no attempt to distribute TE information from within one
AS to another AS. AS to another AS.
o There is no mechanism proposed to distribute any form of TE o There is no mechanism proposed to distribute any form of TE
reachability information for destinations outside the AS. reachability information for destinations outside the AS.
o There is no proposed change to the PCE architecture or usage. o There is no proposed change to the PCE architecture or usage.
skipping to change at page 4, line 45 skipping to change at page 4, line 34
o There is no exchange of private information between ASes. o There is no exchange of private information between ASes.
o No ISIS adjacencies are formed on the inter-AS link. o No ISIS adjacencies are formed on the inter-AS link.
2.2. Per-Domain Path Determination 2.2. Per-Domain Path Determination
In the per-domain method of determining an inter-AS path for an In the per-domain method of determining an inter-AS path for an
MPLS-TE LSP, when an LSR that is an entry-point to an AS receives a MPLS-TE LSP, when an LSR that is an entry-point to an AS receives a
Path message from an upstream AS with an ERO containing a next hop Path message from an upstream AS with an ERO containing a next hop
that is an AS number, it needs to find which LSRs (ASBRs) within the that is an AS number, it needs to find which LSRs (ASBRs) within the
local AS are connected to the downstream AS so that it can compute a local AS are connected to the downstream AS. That way, it can
TE LSP segment across the local AS to one of those LSRs and forward compute a TE LSP segment across the local AS to one of those LSRs and
the Path message to it and hence into the next AS. See Figure 1 for forward the Path message to that LSR and hence into the next AS. See
an example: Figure 1 for an example.
R1------R3----R5-----R7------R9-----R11 R1------R3----R5-----R7------R9-----R11
| | \ | / | | | \ | / |
| | \ | ---- | | | \ | ---- |
| | \ | / | | | \ | / |
R2------R4----R6 --R8------R10----R12 R2------R4----R6 --R8------R10----R12
: : : :
<-- AS1 -->:<---- AS2 --->:<--- AS3 ---> <-- AS1 -->:<---- AS2 --->:<--- AS3 --->
Figure 1: Inter-AS Reference Model Figure 1: Inter-AS Reference Model
The figure shows three ASes (AS1, AS2, and AS3) and twelve LSRs (R1 The figure shows three ASes (AS1, AS2, and AS3) and twelve LSRs (R1
through R12). R3 and R4 are ASBRs in AS1. R5, R6, R7, and R8 are through R12). R3 and R4 are ASBRs in AS1. R5, R6, R7, and R8 are
ASBRs in AS2. R9 and R10 are ASBRs in AS3. ASBRs in AS2. R9 and R10 are ASBRs in AS3.
If an inter-AS TE LSP is planned to be established from R1 to R12, If an inter-AS TE LSP is planned to be established from R1 to R12,
the AS sequence will be: AS1, AS2, AS3. the AS sequence will be: AS1, AS2, AS3.
Suppose that the Path message enters AS2 from R3. The next hop in Suppose that the Path message enters AS2 from R3. The next hop in
the ERO shows AS3, and R5 must determine a path segment across AS2 the ERO shows AS3, and R5 must determine a path segment across AS2 to
to reach AS3. It has a choice of three exit points from AS2 (R6, R7, reach AS3. It has a choice of three exit points from AS2 (R6, R7,
and R8) and it needs to know which of these provide TE connectivity and R8), and it needs to know which of these provide TE connectivity
to AS3, and whether the TE connectivity (for example, available to AS3, and whether the TE connectivity (for example, available
bandwidth) is adequate for the requested LSP. bandwidth) is adequate for the requested LSP.
Alternatively, if the next hop in the ERO is the entry ASBR for AS3 Alternatively, if the next hop in the ERO is the entry ASBR for AS3
(say R9), R5 needs to know which of its exit ASBRs has a TE link (say R9), R5 needs to know which of its exit ASBRs has a TE link that
that connects to R9. Since there may be multiple ASBRs that are connects to R9. Since there may be multiple ASBRs that are connected
connected to R9 (both R7 and R8 in this example), R5 also needs to to R9 (both R7 and R8 in this example), R5 also needs to know the TE
know the TE properties of the inter-AS TE links so that it can properties of the inter-AS TE links so that it can select the correct
select the correct exit ASBR. exit ASBR.
Once the path message reaches the exit ASBR, any choice of inter-AS Once the Path message reaches the exit ASBR, any choice of inter-AS
TE link can be made by the ASBR if not already made by entry ASBR TE link can be made by the ASBR if not already made by the entry ASBR
that computed the segment. that computed the segment.
More details can be found in the Section 4. of [PD-PATH], which More details can be found in Section 4 of [PD-PATH], which clearly
clearly points out why advertising of inter-AS links is desired. points out why advertising of inter-AS links is desired.
To enable R5 to make the correct choice of exit ASBR the following To enable R5 to make the correct choice of exit ASBR, the following
information is needed: information is needed:
o List of all inter-AS TE links for the local AS. o List of all inter-AS TE links for the local AS.
o TE properties of each inter-AS TE link. o TE properties of each inter-AS TE link.
o AS number of the neighboring AS connected to by each inter-AS TE o AS number of the neighboring AS connected to by each inter-AS TE
link. link.
o Identity (TE Router ID) of the neighboring ASBR connected to by o Identity (TE Router ID) of the neighboring ASBR connected to by
each inter-AS TE link. each inter-AS TE link.
In GMPLS networks further information may also be required to select In GMPLS networks, further information may also be required to select
the correct TE links as defined in [GMPLS-TE]. the correct TE links as defined in [GMPLS-TE].
The example above shows how this information is needed at the entry The example above shows how this information is needed at the entry-
point ASBRs for each AS (or the PCEs that provide computation point ASBRs for each AS (or the PCEs that provide computation
services for the ASBRs), but this information is also needed services for the ASBRs). However, this information is also needed
throughout the local AS if path computation function is fully throughout the local AS if path computation functionality is fully
distributed among LSRs in the local AS, for example to support LSPs distributed among LSRs in the local AS, for example to support LSPs
that have start points (ingress nodes) within the AS. that have start points (ingress nodes) within the AS.
2.3. Backward Recursive Path Computation 2.3. Backward Recursive Path Computation
Another scenario using PCE techniques has the same problem. [BRPC] Another scenario using PCE techniques has the same problem. [BRPC]
defines a PCE-based TE LSP computation method (called Backward defines a PCE-based TE LSP computation method (called Backward
Recursive Path Computation) to compute optimal inter-domain Recursive Path Computation) to compute optimal inter-domain
constrained MPLS-TE or GMPLS LSPs. In this path computation method, constrained MPLS-TE or GMPLS LSPs. In this path computation method,
a specific set of traversed domains (ASes) are assumed to be a specific set of traversed domains (ASes) are assumed to be selected
selected before computation starts. Each downstream PCE in domain(i) before computation starts. Each downstream PCE in domain(i) returns
returns to its upstream neighbor PCE in domain(i-1) a multipoint-to- to its upstream neighbor PCE in domain(i-1) a multipoint-to-point
point tree of potential paths. Each tree consists of the set of tree of potential paths. Each tree consists of the set of paths from
paths from all Boundary Nodes located in domain(i) to the all boundary nodes located in domain(i) to the destination where each
destination where each path satisfies the set of required path satisfies the set of required constraints for the TE LSP
constraints for the TE LSP (bandwidth, affinities, etc.). (bandwidth, affinities, etc.).
So a PCE needs to select Boundary Nodes (that is, ASBRs) that So a PCE needs to select boundary nodes (that is, ASBRs) that provide
provide connectivity from the upstream AS. In order that the tree of connectivity from the upstream AS. In order for the tree of paths
paths provided by one PCE to its neighbor can be correlated, the provided by one PCE to its neighbor to be correlated, the identities
identities of the ASBRs for each path need to be referenced, so the of the ASBRs for each path need to be referenced. Thus, the PCE must
PCE must know the identities of the ASBRs in the remote AS reached know the identities of the ASBRs in the remote AS that are reached by
by any inter-AS TE link, and, in order that it provides only any inter-AS TE link, and, in order to provide only suitable paths in
suitable paths in the tree, the PCE must know the TE properties of the tree, the PCE must know the TE properties of the inter-AS TE
the inter-AS TE links. See the following figure as an example: links. See the following figure as an example.
PCE1<------>PCE2<-------->PCE3 PCE1<------>PCE2<-------->PCE3
/ : : / : :
/ : : / : :
R1------R3----R5-----R7------R9-----R11 R1------R3----R5-----R7------R9-----R11
| | \ | / | | | \ | / |
| | \ | ---- | | | \ | ---- |
| | \ | / | | | \ | / |
R2------R4----R6 --R8------R10----R12 R2------R4----R6 --R8------R10----R12
: : : :
skipping to change at page 7, line 29 skipping to change at page 6, line 52
PCE2, and PCE3), and twelve LSRs (R1 through R12). R3 and R4 are PCE2, and PCE3), and twelve LSRs (R1 through R12). R3 and R4 are
ASBRs in AS1. R5, R6, R7, and R8 are ASBRs in AS2. R9 and R10 are ASBRs in AS1. R5, R6, R7, and R8 are ASBRs in AS2. R9 and R10 are
ASBRs in AS3. PCE1, PCE2, and PCE3 cooperate to perform inter-AS ASBRs in AS3. PCE1, PCE2, and PCE3 cooperate to perform inter-AS
path computation and are responsible for path segment computation path computation and are responsible for path segment computation
within their own domain(s). within their own domain(s).
If an inter-AS TE LSP is planned to be established from R1 to R12, If an inter-AS TE LSP is planned to be established from R1 to R12,
the traversed domains are assumed to be selected: AS1->AS2->AS3, and the traversed domains are assumed to be selected: AS1->AS2->AS3, and
the PCE chain is: PCE1->PCE2->PCE3. First, the path computation the PCE chain is: PCE1->PCE2->PCE3. First, the path computation
request originated from the PCC (R1) is relayed by PCE1 and PCE2 request originated from the PCC (R1) is relayed by PCE1 and PCE2
along the PCE chain to PCE3, then PCE3 begins to compute the path along the PCE chain to PCE3. Then, PCE3 begins to compute the path
segments from the entry boundary nodes that provide connection from segments from the entry boundary nodes that provide connection from
AS2 to the destination (R12). But, to provide suitable path segments, AS2 to the destination (R12). But, to provide suitable path
PCE3 must determine which entry boundary nodes provide connectivity segments, PCE3 must determine which entry boundary nodes provide
to its upstream neighbor AS (identified by its AS number), and must connectivity to its upstream neighbor AS (identified by its AS
know the TE properties of the inter-AS TE links. In the same way, number), and must know the TE properties of the inter-AS TE links.
PCE2 also needs to determine the entry boundary nodes according to In the same way, PCE2 also needs to determine the entry boundary
its upstream neighbor AS and the inter-AS TE link capabilities. nodes according to its upstream neighbor AS and the inter-AS TE link
capabilities.
Thus, to support Backward Recursive Path Computation the same Thus, to support Backward Recursive Path Computation, the same
information listed in Section 2.2 is required. The AS number of the information listed in Section 2.2 is required. The AS number of the
neighboring AS connected to by each inter-AS TE link is particularly neighboring AS connected to by each inter-AS TE link is particularly
important. important.
3. Extensions to ISIS-TE 3. Extensions to ISIS-TE
Note that this document does not define mechanisms for distribution Note that this document does not define mechanisms for distribution
of TE information from one AS to another, does not distribute any of TE information from one AS to another, does not distribute any
form of TE reachability information for destinations outside the AS, form of TE reachability information for destinations outside the AS,
does not change the PCE architecture or usage, does not suggest or does not change the PCE architecture or usage, does not suggest or
recommend any form of TE aggregation, and does not feed private recommend any form of TE aggregation, and does not feed private
information between ASes. See Section 2.1. information between ASes. See Section 2.1.
In this document, for the advertisement of inter-AS TE links, a new In this document, for the advertisement of inter-AS TE links, a new
TLV, which is referred to as the Inter-AS Reachability TLV, is TLV, which is referred to as the inter-AS reachability TLV, is
defined and three new sub-TLVs are defined for inclusion in the defined. Three new sub-TLVs are also defined for inclusion in the
Inter-AS Reachability TLV to carry the information about the inter-AS reachability TLV to carry the information about the
neighboring AS number and the remote ASBR ID of an inter-AS link. neighboring AS number and the remote ASBR ID of an inter-AS link.
The sub-TLVs defined in [ISIS-TE], [ISIS-TE-V3] and other documents The sub-TLVs defined in [ISIS-TE], [ISIS-TE-V3], and other documents
for inclusion in the Extended IS Reachability TLV are applicable to for inclusion in the extended IS reachability TLV are applicable to
be included in the Inter-AS Reachability TLV for inter-AS TE links be included in the inter-AS reachability TLV for inter-AS TE links
advertisement. And another two new sub-TLVs are defined for advertisement. Also, two other new sub-TLVs are defined for
inclusion in the IS-IS Router Capability TLV to carry the TE Router inclusion in the IS-IS router capability TLV to carry the TE Router
ID when the TE Router ID is needed to reach all routers within an ID when the TE Router ID is needed to reach all routers within an
entire ISIS routing domain. entire ISIS routing domain.
While some of the TE information of an inter-AS TE link may be While some of the TE information of an inter-AS TE link may be
available within the AS from other protocols, in order to avoid any available within the AS from other protocols, in order to avoid any
dependency on where such protocols are processed, this mechanism dependency on where such protocols are processed, this mechanism
carries all the information needed for the required TE operations. carries all the information needed for the required TE operations.
3.1. Inter-AS Reachability TLV 3.1. Inter-AS Reachability TLV
The Inter-AS Reachability TLV has type 141 (which needs to be The inter-AS reachability TLV has type 141 (see Section 6.1) and
confirmed by IANA see Section 6.1), it contains a data structure contains a data structure consisting of:
consisting of:
4 octets of Router ID o 4 octets of Router ID
3 octets of default metric o 3 octets of default metric
1 octet of control information, consisting of: o 1 octet of control information, consisting of:
1 bit of flooding-scope information (S bit) - 1 bit of flooding-scope information (S bit)
1 bit of up/down information (D bit) - 1 bit of up/down information (D bit)
6 bits reserved - 6 bits reserved
1 octet of length of sub-TLVs o 1 octet of length of sub-TLVs
0-246 octets of sub-TLVs o 0-246 octets of sub-TLVs, where each sub-TLV consists of a
where each sub-TLV consists of a sequence of: sequence of:
1 octet of sub-type - 1 octet of sub-type
1 octet of length of the value field of the sub-TLV - 1 octet of length of the value field of the sub-TLV
0-244 octets of value - 0-244 octets of value
Compare to the Extended Reachability TLV which is defined in [ISIS- Compared to the extended reachability TLV, which is defined in
TE], the Inter-AS Reachability TLV replaces the "7 octets of System [ISIS-TE], the inter-AS reachability TLV replaces the "7 octets of
ID and Pseudonode Number" field with a "4 octets of Router ID" field System ID and Pseudonode Number" field with a "4 octets of Router ID"
and introduces an extra "control information" field which is field and introduces an extra "control information" field, which
consisted of a flooding-scope bit (S bit), a up/down bit (D bit) and consists of a flooding-scope bit (S bit), an up/down bit (D bit), and
6 reserved bits. 6 reserved bits.
The Router ID field of the Inter-AS Reachability TLV is four octets The Router ID field of the inter-AS reachability TLV is 4 octets in
in length, which contains the Router ID of the router who generates length, which contains the Router ID of the router who generates the
the Inter-AS Reachability TLV. The Router ID MUST be unique within inter-AS reachability TLV. The Router ID MUST be unique within the
the ISIS area. If the router generates Inter-AS Reachability TLV ISIS area. If the router generates inter-AS reachability TLV with
with entire ISIS routing domain flooding scope, then the Router ID entire ISIS routing domain flooding scope, then the Router ID MUST
MUST also be unique within the entire ISIS routing domain. The also be unique within the entire ISIS routing domain. The Router ID
Router ID could be used to indicate the source of the Inter-AS could be used to indicate the source of the inter-AS reachability
Reachability TLV. TLV.
The flooding procedures for Inter-AS Reachability TLV are identical The flooding procedures for inter-AS reachability TLV are identical
to the flooding procedures for the GENINFO TLV which are defined in to the flooding procedures for the GENINFO TLV, which are defined in
the Section 4 of [GENINFO]. These procedures have been previously Section 4 of [GENINFO]. These procedures have been previously
discussed in [ISIS-CAP]. The flooding-scope bit (S bit) SHOULD be discussed in [ISIS-CAP]. The flooding-scope bit (S bit) SHOULD be
set to 0 if the flooding scope is to be limited to within the single set to 0 if the flooding scope is to be limited to within the single
IGP area to which the ASBR belongs, or MAY be set to 1 if the IGP area to which the ASBR belongs. It MAY be set to 1 if the
information is intended to reach all routers (including area border information is intended to reach all routers (including area border
routers, ASBRs, and PCEs) in the entire ISIS routing domain. The routers, ASBRs, and PCEs) in the entire ISIS routing domain. The
choice between the use of 0 or 1 is an AS-wide policy choice, and choice between the use of 0 or 1 is an AS-wide policy choice, and
configuration control SHOULD be provided in ASBR implementations configuration control SHOULD be provided in ASBR implementations that
that supports the advertisement of inter-AS TE links. support the advertisement of inter-AS TE links.
The sub-TLVs which are defined in [ISIS-TE], [ISIS-TE-V3] and other The sub-TLVs defined in [ISIS-TE], [ISIS-TE-V3], and other documents
documents for describing the TE properties of an TE link are also for describing the TE properties of a TE link are also applicable to
applicable to be carried in the Inter-AS Reachability TLV to the inter-AS reachability TLV for describing the TE properties of an
describe the TE properties of an Inter-AS TE link. Apart from these inter-AS TE link. Apart from these sub-TLVs, three new sub-TLVs are
sub-TLVs, three new sub-TLVs are defined for inclusion in the Inter- defined for inclusion in the inter-AS reachability TLV defined in
AS Reachability TLV in this document: this document:
Sub-TLV type Length Name Sub-TLV type Length Name
------------ ------ --------------------------- ------------ ------ ---------------------------
23 4 Remote AS number 24 4 remote AS number
24 4 IPv4 Remote ASBR Identifier 25 4 IPv4 remote ASBR identifier
25 16 IPv6 Remote ASBR Identifier 26 16 IPv6 remote ASBR identifier
The detailed definitions of the three new sub-TLVs are described in The detailed definitions of the three new sub-TLVs are described in
Section 3.3. Section 3.3.
3.2. TE Router ID 3.2. TE Router ID
The IPv4 TE Router ID TLV (type 134) and IPv6 TE Router ID TLV (type The IPv4 TE Router ID TLV and IPv6 TE Router ID TLV, which are
140), which are defined in [ISIS-TE] and [ISIS-TE-V3] respectively, defined in [ISIS-TE] and [ISIS-TE-V3] respectively, only have area
only have area flooding-scope, when performing inter-AS TE, the TE flooding-scope. When performing inter-AS TE, the TE Router ID MAY be
Router ID MAY be needed to reach all routers within an entire ISIS needed to reach all routers within an entire ISIS routing domain and
routing domain, and it MUST have the same flooding scope as the it MUST have the same flooding scope as the inter-AS reachability TLV
Inter-AS Reachability TLV does. does.
[ISIS-CAP] defines a generic advertisement mechanism for ISIS which [ISIS-CAP] defines a generic advertisement mechanism for ISIS, which
allows a router to advertise its capabilities within an ISIS area or allows a router to advertise its capabilities within an ISIS area or
an entire ISIS routing domain. And [ISIS-CAP] also points out that an entire ISIS routing domain. [ISIS-CAP] also points out that the
TE Router ID is candidate to be carried in the IS-IS Router TE Router ID is a candidate to be carried in the IS-IS router
Capability TLV when performing inter-area TE. capability TLV when performing inter-area TE.
This document uses such mechanism for TE Router ID advertisement This document uses such mechanism for TE Router ID advertisement when
when the TE Router ID is needed to reach all routers within an the TE Router ID is needed to reach all routers within an entire ISIS
entire ISIS Routing domain. Two new sub-TLVs are defined for Routing domain. Two new sub-TLVs are defined for inclusion in the
inclusion in the IS-IS Router Capability TLV to carry the IPv4 and IS-IS router capability TLV to carry the IPv4 and IPv6 TE Router IDs,
IPv6 TE Router ID respectively: respectively:
Sub-TLV type Length Name Sub-TLV type Length Name
------------ ------ ----------------- ------------ ------ -----------------
11 4 IPv4 TE Router ID 11 4 IPv4 TE Router ID
12 16 IPv6 TE Router ID 12 16 IPv6 TE Router ID
The Detailed definitions of the two new sub-TLVs are described in Detailed definitions of the two new sub-TLVs are described in Section
Section 3.3. 3.3.
3.3. Sub-TLV Detail 3.3. Sub-TLV Detail
3.3.1. Remote AS Number Sub-TLV 3.3.1. Remote AS Number Sub-TLV
A new sub-TLV, the Remote AS Number sub-TLV is defined for inclusion A new sub-TLV, the remote AS number sub-TLV, is defined for inclusion
in the Inter-AS Reachability TLV when advertising inter-AS links. in the inter-AS reachability TLV when advertising inter-AS links.
The Remote AS Number sub-TLV specifies the AS number of the The remote AS number sub-TLV specifies the AS number of the
neighboring AS to which the advertised link connects. neighboring AS to which the advertised link connects.
The Remote AS number sub-TLV is TLV type 23 (which needs to be The remote AS number sub-TLV is TLV type 24 (see Section 6.2) and is
confirmed by IANA see Section 6.2), and is four octets in length. 4 octets in length. The format is as follows:
The format is as follows:
0 1 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 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 | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote AS Number | | Remote AS Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The Remote AS number field has 4 octets. When only two octets are The Remote AS number field has 4 octets. When only 2 octets are used
used for the AS number, as in current deployments, the left (high- for the AS number, as in current deployments, the left (high-order) 2
order) two octets MUST be set to zero. The Remote AS Number Sub-TLV octets MUST be set to 0. The remote AS number sub-TLV MUST be
MUST be included when a router advertises an inter-AS TE link. included when a router advertises an inter-AS TE link.
3.3.2. IPv4 Remote ASBR ID Sub-TLV 3.3.2. IPv4 Remote ASBR ID Sub-TLV
A new sub-TLV, which is referred to as the IPv4 Remote ASBR ID sub- A new sub-TLV, which is referred to as the IPv4 remote ASBR ID sub-
TLV, is defined for inclusion in the Inter-AS Reachability TLV when TLV, is defined for inclusion in the inter-AS reachability TLV when
advertising inter-AS links. The IPv4 Remote ASBR ID sub-TLV advertising inter-AS links. The IPv4 remote ASBR ID sub-TLV
specifies the IPv4 identifier of the remote ASBR to which the specifies the IPv4 identifier of the remote ASBR to which the
advertised inter-AS link connects. This could be any stable and advertised inter-AS link connects. This could be any stable and
routable IPv4 address of the remote ASBR. Use of the TE Router ID as routable IPv4 address of the remote ASBR. Use of the TE Router ID as
specified in the Traffic Engineering Router ID TLV [ISIS-TE] is specified in the Traffic Engineering router ID TLV [ISIS-TE] is
RECOMMENDED. RECOMMENDED.
The IPv4 Remote ASBR ID sub-TLV is TLV type 24 (which needs to be The IPv4 remote ASBR ID sub-TLV is TLV type 25 (see Section 6.2) and
confirmed by IANA see Section 6.2), and is four octets in length. is 4 octets in length. The format of the IPv4 remote ASBR ID sub-TLV
The format of the IPv4 Remote ASBR ID sub-TLV is as follows: is as follows:
0 1 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 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 | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote ASBR ID | | Remote ASBR ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The IPv4 Remote ASBR ID sub-TLV MUST be included if the neighboring The IPv4 remote ASBR ID sub-TLV MUST be included if the neighboring
ASBR has an IPv4 address. If the neighboring ASBR does not have an ASBR has an IPv4 address. If the neighboring ASBR does not have an
IPv4 address (not even an IPv4 TE Router ID), the IPv6 Remote ASBR IPv4 address (not even an IPv4 TE Router ID), the IPv6 remote ASBR ID
ID sub-TLV MUST be included instead. An IPv4 Remote ASBR ID sub-TLV sub-TLV MUST be included instead. An IPv4 remote ASBR ID sub-TLV and
and IPv6 Remote ASBR ID sub-TLV MAY both be present in an Extended IPv6 remote ASBR ID sub-TLV MAY both be present in an extended IS
IS Reachability TLV. reachability TLV.
3.3.3. IPv6 Remote ASBR ID Sub-TLV 3.3.3. IPv6 Remote ASBR ID Sub-TLV
A new sub-TLV, which is referred to as the IPv6 Remote ASBR ID sub- A new sub-TLV, which is referred to as the IPv6 remote ASBR ID sub-
TLV, is defined for inclusion in the Inter-AS Reachability TLV when TLV, is defined for inclusion in the inter-AS reachability TLV when
advertising inter-AS links. The IPv6 Remote ASBR ID sub-TLV advertising inter-AS links. The IPv6 remote ASBR ID sub-TLV
specifies the IPv6 identifier of the remote ASBR to which the specifies the IPv6 identifier of the remote ASBR to which the
advertised inter-AS link connects. This could be any stable and advertised inter-AS link connects. This could be any stable and
routable IPv6 address of the remote ASBR. Use of the TE Router ID as routable IPv6 address of the remote ASBR. Use of the TE Router ID as
specified in the IPv6 Traffic Engineering Router ID TLV [ISIS-TE-V3] specified in the IPv6 Traffic Engineering router ID TLV [ISIS-TE-V3]
is RECOMMENDED. is RECOMMENDED.
The IPv6 Remote ASBR ID sub-TLV is TLV type 25 (which needs to be The IPv6 remote ASBR ID sub-TLV is TLV type 26 (see Section 6.2) and
confirmed by IANA see Section 6.2), and is sixteen octets in length. is 16 octets in length. The format of the IPv6 remote ASBR ID sub-
The format of the IPv6 Remote ASBR ID sub-TLV is as follows: TLV is as follows:
0 1 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 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 | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote ASBR ID | | Remote ASBR ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote ASBR ID (continued) | | Remote ASBR ID (continued) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote ASBR ID (continued) | | Remote ASBR ID (continued) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote ASBR ID (continued) | | Remote ASBR ID (continued) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The IPv6 Remote ASBR ID sub-TLV MUST be included if the neighboring The IPv6 remote ASBR ID sub-TLV MUST be included if the neighboring
ASBR has an IPv6 address. If the neighboring ASBR does not have an ASBR has an IPv6 address. If the neighboring ASBR does not have an
IPv6 address, the IPv4 Remote ASBR ID sub-TLV MUST be included IPv6 address, the IPv4 remote ASBR ID sub-TLV MUST be included
instead. An IPv4 Remote ASBR ID sub-TLV and IPv6 Remote ASBR ID sub- instead. An IPv4 remote ASBR ID sub-TLV and IPv6 remote ASBR ID
TLV MAY both be present in an Extended IS Reachability TLV. sub-TLV MAY both be present in an extended IS reachability TLV.
3.3.4. IPv4 TE Router ID sub-TLV 3.3.4. IPv4 TE Router ID sub-TLV
The IPv4 TE Router ID sub-TLV is TLV type 11 (which needs to be The IPv4 TE Router ID sub-TLV is TLV type 11 (see Section 6.3) and is
confirmed by IANA see Section 6.3), and is four octets in length. 4 octets in length. The format of the IPv4 TE Router ID sub-TLV is
The format of the IPv4 TE Router ID sub-TLV is as follows: as follows:
0 1 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 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 | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TE Router ID | | TE Router ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
When the TE Router ID is needed to reach all routers within an entire
When the TE Router ID is needed to reach all routers within an ISIS routing domain, the IS-IS Router capability TLV MUST be included
entire ISIS routing domain, the IS-IS Router Capability TLV MUST be in its LSP. If an ASBR supports Traffic Engineering for IPv4 and if
included in its LSP. And if an ASBR supports Traffic Engineering for the ASBR has an IPv4 TE Router ID, the IPv4 TE Router ID sub-TLV MUST
IPv4, the IPv4 TE Router ID sub-TLV MUST be included if the ASBR has be included. If the ASBR does not have an IPv4 TE Router ID, the
an IPv4 TE Router ID. If the ASBR does not have an IPv4 TE Router ID, IPv6 TE Router sub-TLV MUST be included instead. An IPv4 TE Router
the IPv6 TE Router sub-TLV MUST be included instead. An IPv4 TE ID sub-TLV and IPv6 TE Router ID sub-TLV MAY both be present in an
Router ID sub-TLV and IPv6 TE Router ID sub-TLV MAY both be present IS-IS router capability TLV.
in an IS-IS Router Capability TLV.
3.3.5. IPv6 TE Router ID sub-TLV 3.3.5. IPv6 TE Router ID sub-TLV
The IPv6 TE Router ID sub-TLV is TLV type 12 (which needs to be The IPv6 TE Router ID sub-TLV is TLV type 12 (see Section 6.3) and is
confirmed by IANA see Section 6.3), and is four octets in length. 4 octets in length. The format of the IPv6 TE Router ID sub-TLV is
The format of the IPv6 TE Router ID sub-TLV is as follows: as follows:
0 1 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 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 | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TE Router ID | | TE Router ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TE Router ID (continued) | | TE Router ID (continued) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TE Router ID (continued) | | TE Router ID (continued) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TE Router ID (continued) | | TE Router ID (continued) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
When the TE Router ID is needed to reach all routers within an When the TE Router ID is needed to reach all routers within an entire
entire ISIS routing domain, the IS-IS Router Capability TLV MUST be ISIS routing domain, the IS-IS router capability TLV MUST be included
included in its LSP. And if an ASBR supports Traffic Engineering for in its LSP. If an ASBR supports Traffic Engineering for IPv6 and if
IPv6, the IPv6 TE Router ID sub-TLV MUST be included if the ASBR has the ASBR has an IPv6 TE Router ID, the IPv6 TE Router ID sub-TLV MUST
an IPv6 TE Router ID. If the ASBR does not have an IPv6 TE Router ID, be included. If the ASBR does not have an IPv6 TE Router ID, the
the IPv4 TE Router sub-TLV MUST be included instead. An IPv4 TE IPv4 TE Router sub-TLV MUST be included instead. An IPv4 TE Router
Router ID sub-TLV and IPv6 TE Router ID sub-TLV MAY both be present ID sub-TLV and IPv6 TE Router ID sub-TLV MAY both be present in an
in an IS-IS Router Capability TLV. IS-IS router capability TLV.
4. Procedure for Inter-AS TE Links 4. Procedure for Inter-AS TE Links
When TE is enabled on an inter-AS link and the link is up, the ASBR When TE is enabled on an inter-AS link and the link is up, the ASBR
SHOULD advertise this link using the normal procedures for ISIS-TE SHOULD advertise this link using the normal procedures for ISIS-TE
[ISIS-TE]. When either the link is down or TE is disabled on the [ISIS-TE]. When either the link is down or TE is disabled on the
link, the ASBR SHOULD withdraw the advertisement. When there are link, the ASBR SHOULD withdraw the advertisement. When there are
changes to the TE parameters for the link (for example, when the changes to the TE parameters for the link (for example, when the
available bandwidth changes) the ASBR SHOULD re-advertise the link, available bandwidth changes), the ASBR SHOULD re-advertise the link
but the ASBR MUST take precautions against excessive re- but MUST take precautions against excessive re-advertisements.
advertisements.
Hellos MUST NOT be exchanged over the inter-AS link, and Hellos MUST NOT be exchanged over the inter-AS link, and
consequently, an ISIS adjacency MUST NOT be formed. consequently, an ISIS adjacency MUST NOT be formed.
The information advertised comes from the ASBR's knowledge of the TE The information advertised comes from the ASBR's knowledge of the TE
capabilities of the link, the ASBR's knowledge of the current status capabilities of the link, the ASBR's knowledge of the current status
and usage of the link, and configuration at the ASBR of the remote and usage of the link, and configuration at the ASBR of the remote AS
AS number and remote ASBR TE Router ID. number and remote ASBR TE Router ID.
Legacy routers receiving an advertisement for an inter-AS TE link Legacy routers receiving an advertisement for an inter-AS TE link are
are able to ignore it because they do not know the new TLV and sub- able to ignore it because they do not know the new TLV and sub-TLVs
TLVs that are defined in Section 3 in this document. They will that are defined in Section 3 of this document. They will continue
continue to flood the LSP, but will not attempt to use the to flood the LSP, but will not attempt to use the information
information received. received.
In the current operation of ISIS TE the LSRs at each end of a TE In the current operation of ISIS TE, the LSRs at each end of a TE
link emit LSAs describing the link. The databases in the LSRs then link emit LSAs describing the link. The databases in the LSRs then
have two entries (one locally generated, the other from the peer) have two entries (one locally generated, the other from the peer)
that describe the different 'directions' of the link. This enables that describe the different 'directions' of the link. This enables
CSPF to do a two-way check on the link when performing path Constrained Shortest Path First (CSPF) to do a two-way check on the
computation and eliminate it from consideration unless both link when performing path computation and eliminate it from
directions of the link satisfy the required constraints. consideration unless both directions of the link satisfy the required
constraints.
In the case we are considering here (i.e., of a TE link to another In the case we are considering here (i.e., of a TE link to another
AS) there is, by definition, no IGP peering and hence no bi- AS), there is, by definition, no IGP peering and hence no
directional TE link information. In order for the CSPF route bidirectional TE link information. In order for the CSPF route
computation entity to include the link as a candidate path, we have computation entity to include the link as a candidate path, we have
to find a way to get LSAs describing its (bidirectional) TE to find a way to get LSAs describing its (bidirectional) TE
properties into the TE database. properties into the TE database.
This is achieved by the ASBR advertising, internally to its AS, This is achieved by the ASBR advertising, internally to its AS,
information about both directions of the TE link to the next AS. The information about both directions of the TE link to the next AS. The
ASBR will normally generate a LSA describing its own side of a link; ASBR will normally generate an LSA describing its own side of a link;
here we have it 'proxy' for the ASBR at the edge of the other AS and here we have it 'proxy' for the ASBR at the edge of the other AS and
generate an additional LSA that describes that devices 'view' of the generate an additional LSA that describes that device's 'view' of the
link. link.
Only some essential TE information for the link needs to be Only some essential TE information for the link needs to be
advertised; i.e., the Interface Address, the Remote AS number and advertised; i.e., the Interface Address, the remote AS number, and
the Remote ASBR ID of an inter-AS TE link. the remote ASBR ID of an inter-AS TE link.
Routers or PCEs that are capable of processing advertisements of Routers or PCEs that are capable of processing advertisements of
inter-AS TE links SHOULD NOT use such links to compute paths that inter-AS TE links SHOULD NOT use such links to compute paths that
exit an AS to a remote ASBR and then immediately re-enter the AS exit an AS to a remote ASBR and then immediately re-enter the AS
through another TE link. Such paths would constitute extremely rare through another TE link. Such paths would constitute extremely rare
occurrences and SHOULD NOT be allowed except as the result of occurrences and SHOULD NOT be allowed except as the result of
specific policy configurations at the router or PCE computing the specific policy configurations at the router or PCE computing the
path. path.
4.1. Origin of Proxied TE Information 4.1. Origin of Proxied TE Information
Section 4 describes how to an ASBR advertises TE link information as Section 4 describes how an ASBR advertises TE link information as a
a proxy for its neighbor ASBR, but does not describe where this proxy for its neighbor ASBR, but does not describe where this
information comes from. information comes from.
Although the source of this information is outside the scope of this Although the source of this information is outside the scope of this
document, it is possible that it will be a configuration requirement document, it is possible that it will be a configuration requirement
at the ASBR, as are other, local, properties of the TE link. Further, at the ASBR, as are other local properties of the TE link. Further,
where BGP is used to exchange IP routing information between the where BGP is used to exchange IP routing information between the
ASBRs, a certain amount of additional local configuration about the ASBRs, a certain amount of additional local configuration about the
link and the remote ASBR is likely to be available. link and the remote ASBR is likely to be available.
We note further that it is possible, and may be operationally We note further that it is possible, and may be operationally
advantageous, to obtain some of the required configuration advantageous, to obtain some of the required configuration
information from BGP. Whether and how to utilize these possibilities information from BGP. Whether and how to utilize these possibilities
is an implementation matter. is an implementation matter.
5. Security Considerations 5. Security Considerations
The protocol extensions defined in this document are relatively The protocol extensions defined in this document are relatively minor
minor and can be secured within the AS in which they are used by the and can be secured within the AS in which they are used by the
existing ISIS security mechanisms. existing ISIS security mechanisms (e.g., using the cleartext
passwords or Hashed Message Authentication Codes - Message Digest 5
(HMAC-MD5) algorithm, which are defined in [ISIS] and [RFC5304],
respectively).
There is no exchange of information between ASes, and no change to There is no exchange of information between ASes, and no change to
the ISIS security relationship between the ASes. In particular, the ISIS security relationship between the ASes. In particular,
since no ISIS adjacency is formed on the inter-AS links, there is no since no ISIS adjacency is formed on the inter-AS links, there is no
requirement for ISIS security between the ASes. requirement for ISIS security between the ASes.
Some of the information included in these new advertisements (e.g., Some of the information included in these new advertisements (e.g.,
the remote AS number and the remote ASBR ID) is obtained manually the remote AS number and the remote ASBR ID) is obtained manually
from a neighboring administration as part of commercial relationship. from a neighboring administration as part of a commercial
The source and content of this information should be carefully relationship. The source and content of this information should be
checked before it is entered as configuration information at the carefully checked before it is entered as configuration information
ASBR responsible for advertising the inter-AS TE links. at the ASBR responsible for advertising the inter-AS TE links.
It is worth noting that in the scenario we are considering a Border It is worth noting that in the scenario we are considering, a Border
Gateway Protocol (BGP) peering may exist between the two ASBRs and Gateway Protocol (BGP) peering may exist between the two ASBRs and
this could be used to detect inconsistencies in configuration (e.g., that this could be used to detect inconsistencies in configuration
the administration that originally supplied the information may be (e.g., the administration that originally supplied the information
lying, or some manual mis-configurations or mistakes are made by the may be lying, or some manual mis-configurations or mistakes may be
operators). For example, if a different remote AS number is received made by the operators). For example, if a different remote AS number
in a BGP OPEN [BGP] from that locally configured into ISIS-TE, as we is received in a BGP OPEN [BGP] from that locally configured to
describe here, then local policy SHOULD be applied to determine ISIS-TE, as we describe here, then local policy SHOULD be applied to
whether to alert the operator to a potential mis-configuration or to determine whether to alert the operator to a potential mis-
suppress the ISIS advertisement of the inter-AS TE link. Note, configuration or to suppress the ISIS advertisement of the inter-AS
further, that if BGP is used to exchange TE information as described TE link. Note further that if BGP is used to exchange TE information
in Section 4.1, the inter-AS BGP session SHOULD be secured using as described in Section 4.1, the inter-AS BGP session SHOULD be
mechanisms as described in [BGP] to provide authentication and secured using mechanisms as described in [BGP] to provide
integrity checks. authentication and integrity checks.
For a discussion of general security considerations for IS-IS, see
[RFC5304].
6. IANA Considerations 6. IANA Considerations
IANA is requested to make the following allocations from registries IANA has made the following allocations from registries under its
under its control. control.
6.1. Inter-AS Reachability TLV 6.1. Inter-AS Reachability TLV
This document defines the following new ISIS TLV type, described in This document defines the following new ISIS TLV type, described in
Section 3.4, that needs to be registered in the ISIS TLV code-point Section 3.1, which has been registered in the ISIS TLV codepoint
registry: registry:
Type Description IIH LSP SNP Type Description IIH LSP SNP
---- ---------------------- --- --- --- ---- ---------------------- --- --- ---
141 Inter-AS reachability n y n 141 inter-AS reachability n y n
information information
6.2. Sub-TLVs for the Inter-AS Reachability TLV 6.2. Sub-TLVs for the Inter-AS Reachability TLV
This document defines the following new sub-TLV types, described in This document defines the following new sub-TLV types (described in
Sections 3.3.1, 3.3.2 and 3.3.3, of top-level TLV 141 (see section Sections 3.3.1, 3.3.2, and 3.3.3) of top-level TLV 141 (see Section
6.1 above) that need to be registered in the ISIS sub-TLV registry 6.1 above), which have been registered in the ISIS sub-TLV registry
for TLV 141, note that these three new sub-TLVs SHOULD NOT appear in for TLV 141. Note that these three new sub-TLVs SHOULD NOT appear in
TLV 22 (or TLV 222) and MUST be ignored in TLV 22 (or TLV 222): TLV 22 (or TLV 222) and MUST be ignored in TLV 22 (or TLV 222).
Type Description Length Type Description
---- ------------------------------ -------- ---- ------------------------------
23 Remote AS number 4 24 remote AS number
24 IPv4 Remote ASBR Identifier 4 25 IPv4 remote ASBR Identifier
25 IPv6 Remote ASBR Identifier 16 26 IPv6 remote ASBR Identifier
As described above in Section 3.1, the sub-TLVs which are defined in As described above in Section 3.1, the sub-TLVs defined in [ISIS-TE],
[ISIS-TE], [ISIS-TE-V3] and other documents for describing the TE [ISIS-TE-V3], and other documents for describing the TE properties of
properties of an TE link are applicable to describe an inter-AS TE a TE link are applicable to describe an inter-AS TE link and MAY be
link and MAY be included in the Inter-AS Reachability TLV when included in the inter-AS reachability TLV when adverting inter-AS TE
adverting inter-AS TE links. And it's possible that some sub-TLVs links.
may be defined for inclusion in both TLV 22 and TLV 141 in the
future. It's better if these sub-TLVs have the same registry value IANA has updated the registry that was specified as "Sub-TLVs for TLV
no matter where they are included in TLV 22 or TLV 141. The same 22" to be named "Sub-TLVs for TLVs 22, 141, and 222". Three new
condition will occur when these sub-TLVs need to be included in TLV columns have been added to the registry to show in which TLVs the
222. So, in order to simplify the registration and reduce the sub-TLVs may be present. All sub-TLVs currently defined may be
potential code point conflict, this document suggests that TLV 22, present in all three TLVs, hence the registry (with the definition of
TLV 141 and TLV 222 share the same sub-TLV registry. The proposal is the new sub-TLVs defined here) should read as follows.
that change the current Registry Name from "Sub-TLVs for TLV 22" to
"Sub-TLVs for TLV 22, 141 and 222" and add three columns ("May be TLV TLV TLV
present on TLV 22","May be present on TLV 141" and "May be present Type Description 22 141 222 Reference
on TLV 222") to the registry for indicating whether a specific sub- ------- ------------------------------------ --- --- --- ---------
TLV may be present on the TLV. 0 Unassigned y y y
1 Unassigned y y y
2 Unassigned y y y
3 Administrative group (color) y y y [RFC5305]
4 Link Local/Remote Identifiers y y y
[RFC4205][RFC5307]
5 Unassigned y y y
6 IPv4 interface address y y y [RFC5305]
7 Unassigned y y y
8 IPv4 neighbor address y y y [RFC5305]
9 Maximum link bandwidth y y y [RFC5305]
10 Maximum reservable link bandwidth y y y [RFC5305]
11 Unreserved bandwidth y y y [RFC5305]
12 Unassigned y y y
13 Unassigned y y y
14 Unassigned y y y
15 Unassigned y y y
16 Unassigned y y y
17 Unassigned y y y
18 TE Default metric y y y [RFC5305]
19 Link-attributes y y y [RFC5029]
20 Link Protection Type y y y
[RFC4205][RFC5307]
21 Interface Switching Capability Desc y y y
[RFC4205][RFC5307]
22 Bandwidth Constraints y y y [RFC4124]
23 Unconstrained TE LSP Count (sub-)TLV y y y [RFC5330]
24 remote AS number n y n [RFC5316]
25 IPv4 remote ASBR identifier n y n [RFC5316]
26 IPv6 remote ASBR identifier n y n [RFC5316]
27-249 Unassigned
250-254 Reserved for Cisco-specific exts
255 Reserved for future expansion
Further sub-TLVs may be defined in the future for inclusion in any of
the TLVs 22, 141, or 222. The re-naming of the registry as above
ensures that there is no accidental overlap of sub-TLV codepoints.
The introduction of the columns within the registry clarify the use
of the sub-TLVs.
6.3. Sub-TLVs for the IS-IS Router Capability TLV 6.3. Sub-TLVs for the IS-IS Router Capability TLV
This document defines the following new sub-TLV types, described in This document defines the following new sub-TLV types, described in
Sections 3.3.4 and 3.3.5, of top-level TLV 242 (which is defined in Sections 3.3.4 and 3.3.5, of top-level TLV 242 (which is defined in
[ISIS-CAP]) that need to be registered in the ISIS sub-TLV registry [ISIS-CAP]) that have been registered in the ISIS sub-TLV registry
for TLV 242: for TLV 242:
Type Description Length Type Description Length
---- ------------------------------ -------- ---- ------------------------------ --------
11 IPv4 TE Router ID 4 11 IPv4 TE Router ID 4
12 IPv6 TE Router ID 16 12 IPv6 TE Router ID 16
7. Acknowledgments 7. Acknowledgments
The authors would like to thank Adrian Farrel, Jean-Louis Le Roux, The authors would like to thank Adrian Farrel, Jean-Louis Le Roux,
Christian Hopps, Les Ginsberg, and Hannes Gredler for their review Christian Hopps, Les Ginsberg, and Hannes Gredler for their review
and comments on this document. and comments on this document.
8. References 8. References
8.1. Normative References 8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T.,
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP Srinivasan, V., and G. Swallow, "RSVP-TE:
Tunnels", RFC 3209, December 2001. Extensions to RSVP for LSP Tunnels", RFC 3209,
December 2001.
[ISIS] Callon, R., "Use of OSI IS-IS for routing in TCP/IP and [RFC5304] Li, T. and R. Atkinson, "IS-IS Cryptographic
dual environments", RFC 1195, December 1990. Authentication", RFC 5304, October 2008.
[ISIS-CAP] Vasseur, J.P. et al., "IS-IS extensions for advertising [ISIS] Callon, R., "Use of OSI IS-IS for routing in TCP/IP
router information", RFC 4971, July 2007. and dual environments", RFC 1195, December 1990.
[ISIS-CAP] Vasseur, JP., Ed., Shen, N., Ed., and R. Aggarwal,
Ed., "Intermediate System to Intermediate System
(IS-IS) Extensions for Advertising Router
Information", RFC 4971, July 2007.
8.2. Informative References 8.2. Informative References
[INTER-AS-TE-REQ] Zhang and Vasseur, "MPLS Inter-AS Traffic [INTER-AS-TE-REQ] Zhang, R., Ed., and J.-P. Vasseur, Ed., "MPLS
Engineering Requirements", RFC4216, November 2005. Inter-Autonomous System (AS) Traffic Engineering
(TE) Requirements", RFC 4216, November 2005.
[PD-PATH] Ayyangar, A., Vasseur, JP., and Zhang, R., "A Per-domain [PD-PATH] Vasseur, JP., Ed., Ayyangar, A., Ed., and R. Zhang,
path computation method for establishing Inter-domain", "A Per-Domain Path Computation Method for
RFC 5152, February 2008. Establishing Inter-Domain Traffic Engineering (TE)
Label Switched Paths (LSPs)", RFC 5152, February
2008.
[BRPC] JP. Vasseur, Ed., R. Zhang, N. Bitar, JL. Le Roux, "A [BRPC] Vasseur, JP., Ed., Zhang, R., Bitar, N., JL. Le
Backward Recursive PCE-based Computation (BRPC) procedure Roux, "A Backward Recursive PCE-Based Computation
to compute shortest inter-domain Traffic Engineering Label (BRPC) Procedure to Compute Shortest Inter-Domain
Switched Paths", draft-ietf-pce-brpc, (work in progress) Traffic Engineering Label Switched Paths", Work in
Progress, April 2008.
[PCE] Farrel, A., Vasseur, JP., and Ash, J., "A Path Computation [PCE] Farrel, A., Vasseur, J.-P., and J. Ash, "A Path
Element (PCE)-Based Architecture", RFC4655, August 2006. Computation Element (PCE)-Based Architecture", RFC
4655, August 2006.
[ISIS-TE] Smit, H. and T. Li, "Intermediate System to Intermediate [ISIS-TE] Li, T. and H. Smit, "IS-IS Extensions for Traffic
System (IS-IS) Extensions for Traffic Engineering (TE)", Engineering", RFC 5305, October 2008.
RFC 3784, June 2004.
[ISIS-TE-V3] Harrison, J., Berger, J., and Bartlett, M., "IPv6 [ISIS-TE-V3] Harrison, J., Berger, J., and Bartlett, M., "IPv6
Traffic Engineering in IS-IS", draft-ietf-isis-ipv6-te, Traffic Engineering in IS-IS", Work in Progress,
{work in progress}. June 2008.
[GMPLS-TE] K.Kompella and Y.Rekhter, "IS-IS Extensions in Support of [GMPLS-TE] Kompella, K., Ed., and Y. Rekhter, Ed., "IS-IS
Generalized Multi-Protocol Label Switching", RFC 4205, Extensions in Support of Generalized Multi-Protocol
October 2005. Label Switching (GMPLS)", RFC 5307, October 2008.
[BGP] Rekhter, Li, Hares, "A Border Gateway Protocol 4 (BGP-4)", [BGP] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed.,
RFC4271, January 2006. "A Border Gateway Protocol 4 (BGP-4)", RFC 4271,
January 2006.
[GENINFO] L. Ginsberg., S. Previdi., and M. Shand., "Advertising [GENINFO] L. Ginsberg., Previdi, S., and M. Shand,
Generic Information in IS-IS", draft-ietf-isis-genapp, "Advertising Generic Information in IS-IS", Work in
(work in progress). Progress, June 2008.
Authors' Addresses Authors' Addresses
Mach(Guoyi) Chen Mach(Guoyi) Chen
Huawei Technologies Co.,Ltd Huawei Technologies Co.,Ltd
KuiKe Building, No.9 Xinxi Rd., KuiKe Building, No.9 Xinxi Rd.
Hai-Dian District Hai-Dian District
Beijing, 100085 Beijing, 100085
P.R. China P.R. China
Email: mach@huawei.com EMail: mach@huawei.com
Renhai Zhang Renhai Zhang
Huawei Technologies Co.,Ltd Huawei Technologies Co.,Ltd
KuiKe Building, No.9 Xinxi Rd., KuiKe Building, No.9 Xinxi Rd.
Hai-Dian District Hai-Dian District
Beijing, 100085 Beijing, 100085
P.R. China P.R. China
Email: zhangrenhai@huawei.com EMail: zhangrenhai@huawei.com
Xiaodong Duan Xiaodong Duan
China Mobile China Mobile
53A,Xibianmennei Ave,Xunwu District 53A, Xibianmennei Ave.
Xunwu District
Beijing, China Beijing, China
Email: duanxiaodong@chinamobile.com EMail: duanxiaodong@chinamobile.com
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