draft-ietf-ccamp-isis-interas-te-extension-02.txt   draft-ietf-ccamp-isis-interas-te-extension-03.txt 
Network working group M. Chen Network working group M. Chen
Internet Draft Renhai Zhang Internet Draft Renhai Zhang
Category: Standards Track Huawei Technologies Co.,Ltd Category: Standards Track Huawei Technologies Co.,Ltd
Created: April 14, 2008 Xiaodong Duan Created: August 25, 2008 Xiaodong Duan
Expires: October 14, 2008 China Mobile Expires: February 25, 2009 China Mobile
ISIS Extensions in Support of Inter-AS Multiprotocol Label Switching ISIS Extensions in Support of Inter-AS Multiprotocol Label Switching
(MPLS) and Generalized MPLS (GMPLS) Traffic Engineering (MPLS) and Generalized MPLS (GMPLS) Traffic Engineering
draft-ietf-ccamp-isis-interas-te-extension-02.txt draft-ietf-ccamp-isis-interas-te-extension-03.txt
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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 TE information from outside the AS is No support for flooding information from within one AS to another AS
proposed or defined in this document. is proposed or defined in this document.
Conventions used in this document Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC-2119 [RFC2119]. document are to be interpreted as described in RFC-2119 [RFC2119].
Table of Contents Table of Contents
1. Introduction.................................................3 1. Introduction.................................................2
2. Problem Statement............................................4 2. Problem Statement............................................3
2.1. A Note on Non-Objectives................................4 2.1. A Note on Non-Objectives................................4
2.2. Per-Domain Path Determination...........................5 2.2. Per-Domain Path Determination...........................4
2.3. Backward Recursive Path Computation.....................6 2.3. Backward Recursive Path Computation.....................6
3. Extensions to ISIS-TE........................................7 3. Extensions to ISIS-TE........................................7
3.1. Inter-AS Reachability TLV...............................8 3.1. Inter-AS Reachability TLV...............................8
3.2. TE Router ID............................................9 3.2. TE Router ID............................................9
3.3. Sub-TLV Detail.........................................10 3.3. Sub-TLV Detail.........................................10
3.3.1. Remote AS Number Sub-TLV..........................10 3.3.1. Remote AS Number Sub-TLV..........................10
3.3.2. IPv4 Remote ASBR ID Sub-TLV.......................10 3.3.2. IPv4 Remote ASBR ID Sub-TLV.......................11
3.3.3. IPv6 Remote ASBR ID Sub-TLV.......................11 3.3.3. IPv6 Remote ASBR ID Sub-TLV.......................11
3.3.4. IPv4 TE Router ID sub-TLV.........................12 3.3.4. IPv4 TE Router ID sub-TLV.........................12
3.3.5. IPv6 TE Router ID sub-TLV.........................12 3.3.5. IPv6 TE Router ID sub-TLV.........................13
4. Procedure for Inter-AS TE Links.............................13 4. Procedure for Inter-AS TE Links.............................13
4.1. Origin of Proxied TE Information.......................14 4.1. Origin of Proxied TE Information.......................15
5. Security Considerations.....................................14 5. Security Considerations.....................................15
6. IANA Considerations.........................................15 6. IANA Considerations.........................................16
6.1. Inter-AS Reachability TLV..............................15 6.1. Inter-AS Reachability TLV..............................16
6.2. Sub-TLVs for the Inter-AS Reachability TLV.............15 6.2. Sub-TLVs for the Inter-AS Reachability TLV.............16
6.3. Sub-TLVs for the IS-IS Router Capability TLV...........16 6.3. Sub-TLVs for the IS-IS Router Capability TLV...........17
7. Acknowledgments.............................................16 7. Acknowledgments.............................................17
8. References..................................................16 8. References..................................................17
8.1. Normative References...................................16 8.1. Normative References...................................17
8.2. Informative References.................................16 8.2. Informative References.................................18
Authors' Addresses.............................................17 Authors' Addresses.............................................19
Intellectual Property Statement................................18 Intellectual Property Statement................................19
Disclaimer of Validity.........................................18 Disclaimer of Validity.........................................20
Copyright Statement............................................18 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 Extended (TE links) and flooding this information within an area. The
IS Reachability TLV and Traffic Engineering Router ID TLV, which are Extended IS Reachability TLV and Traffic Engineering Router ID TLV,
defined in [ISIS-TE], are used to carry such TE information. The which are defined in [ISIS-TE], are used to carry such TE
Extended IS Reachability TLV has several nested sub-TLVs which information. The Extended IS Reachability TLV has several nested
describe the TE attributes for a TE link. sub-TLVs which 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) TE Requirements for establishing Multiprotocol Label Switching (MPLS)
Label Switched Paths (LSPs) that cross multiple Autonomous Systems TE Label Switched Paths (LSPs) that cross multiple Autonomous
(ASes) are described in [INTER-AS-TE-REQ]. As described in [INTER-AS- Systems (ASes) are described in [INTER-AS-TE-REQ]. As described in
TE-REQ], a method SHOULD provide the ability to compute a path [INTER-AS-TE-REQ], a method SHOULD provide the ability to compute a
spanning multiple ASes. So a path computation entity that may be the path spanning multiple ASes. So a path computation entity that may
head-end Label Switching Router (LSR), an AS Border Router (ASBR), or be the head-end Label Switching Router (LSR), an AS Border Router
a Path Computation Element (PCE [PCE]) needs to know the TE (ASBR), or a Path Computation Element (PCE [PCE]) needs to know the
information not only of the links within an AS, but also of the links TE information not only of the links within an AS, but also of the
that connect to other ASes. links 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 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 TLV and other documents for inclusion in the Extended IS Reachability
for describing the TE properties of a TE link are applicable to be TLV for describing the TE properties of a TE link are applicable to
included in the Inter-AS Reachability TLV for describing the TE be 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. And two more new sub-TLVs
are defined for inclusion in the IS-IS Router Capability TLV to carry are defined for inclusion in the IS-IS Router Capability TLV to
the TE Router ID when TE Router ID needs to reach all routers within carry the TE Router ID when TE Router ID needs to reach all routers
an entire ISIS routing domain. The extensions are equally applicable within an entire ISIS routing domain. The extensions are equally
to IPv4 and IPv6 as identical extensions to [ISIS-TE] and [ISIS-TE- applicable to IPv4 and IPv6 as identical extensions to [ISIS-TE] and
V3]. The detailed definitions and procedures are discussed in the [ISIS-TE-V3]. The detailed definitions and procedures are discussed
following sections. 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.
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 traversing multiple ASes, the Path message [RFC3209]
may include the following elements in the Explicit Route Object (ERO) may include the following elements in the Explicit Route Object (ERO)
skipping to change at page 4, line 26 skipping to change at page 4, line 19
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 of to the confidentiality and scaling assumptions surrounding the use
ASes in the Internet. In particular, this document is conformant to of ASes in the Internet. In particular, this document is conformant
the requirements set out in [INTER-AS-TE-REQ]. to 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.
o TE aggregation is not supported or recommended. o TE aggregation is not supported or recommended.
o There is no exchange of private information between ASes. o There is no exchange of private information between ASes.
o No OSPF adjacencies are formed on the inter-AS link. o No ISIS adjacencies are formed on the inter-AS link.
Note also that the extensions proposed in this document are used only
to advertise information about inter-AS TE links. As such these
extensions address an entirely different problem from L1VPN Auto-
Discovery [L1VPN-OSPF-AD] which defines how TE information about
links between Customer Edge (CE) equipment and Provider Edge (PE)
equipment can be advertised in OSPF-TE alongside the auto-discovery
information for the CE-PE links. There is no overlap between this
document and [L1VPN-OSPF-AD].
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 MPLS- In the per-domain method of determining an inter-AS path for an
TE LSP, when an LSR that is an entry-point to an AS receives a Path MPLS-TE LSP, when an LSR that is an entry-point to an AS receives a
message from an upstream AS with an ERO containing a next hop that is Path message from an upstream AS with an ERO containing a next hop
an AS number, it needs to find which LSRs (ASBRs) within the local AS that is an AS number, it needs to find which LSRs (ASBRs) within the
are connected to the downstream AS so that it can compute a TE LSP local AS are connected to the downstream AS so that it can compute a
segment across the local AS to one of those LSRs and forward the PATH TE LSP segment across the local AS to one of those LSRs and forward
message to it and hence into the next AS. See Figure 1 for an the Path message to it and hence into the next AS. See Figure 1 for
example: 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 the Suppose that the Path message enters AS2 from R3. The next hop in
ERO shows AS3, and R5 must determine a path segment across AS2 to the ERO shows AS3, and R5 must determine a path segment across AS2
reach AS3. It has a choice of three exit points from AS2 (R6, R7, and to reach AS3. It has a choice of three exit points from AS2 (R6, R7,
R8) and it needs to know which of these provide TE connectivity to and R8) and it needs to know which of these provide TE connectivity
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 that (say R9), R5 needs to know which of its exit ASBRs has a TE link
connects to R9. Since there may be multiple ASBRs that are connected that connects to R9. Since there may be multiple ASBRs that are
to R9 (both R7 and R8 in this example), R5 also needs to know the TE connected to R9 (both R7 and R8 in this example), R5 also needs to
properties of the inter-AS TE links so that it can select the correct know the TE properties of the inter-AS TE links so that it can
exit ASBR. select the correct 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 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 the Section 4. of [PD-PATH], which
clearly points out why advertising of inter-AS links is desired. clearly 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:
skipping to change at page 6, line 33 skipping to change at page 6, line 26
services for the ASBRs), but this information is also needed services for the ASBRs), but this information is also needed
throughout the local AS if path computation function is fully throughout the local AS if path computation function 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, a constrained MPLS-TE or GMPLS LSPs. In this path computation method,
specific set of traversed domains (ASes) are assumed to be selected a specific set of traversed domains (ASes) are assumed to be
before computation starts. Each downstream PCE in domain(i) returns selected before computation starts. Each downstream PCE in domain(i)
to its upstream neighbor PCE in domain(i-1) a multipoint-to-point returns to its upstream neighbor PCE in domain(i-1) a multipoint-to-
tree of potential paths. Each tree consists of the set of paths from point tree of potential paths. Each tree consists of the set of
all Boundary Nodes located in domain(i) to the destination where each paths from all Boundary Nodes located in domain(i) to the
path satisfies the set of required constraints for the TE LSP destination where each path satisfies the set of required
(bandwidth, affinities, etc.). constraints for the TE LSP (bandwidth, affinities, etc.).
So a PCE needs to select Boundary Nodes (that is, ASBRs) that provide So a PCE needs to select Boundary Nodes (that is, ASBRs) that
connectivity from the upstream AS. In order that the tree of paths provide connectivity from the upstream AS. In order that the tree of
provided by one PCE to its neighbor can be correlated, the identities paths provided by one PCE to its neighbor can be correlated, the
of the ASBRs for each path need to be referenced, so the PCE must identities of the ASBRs for each path need to be referenced, so the
know the identities of the ASBRs in the remote AS reached by any PCE must know the identities of the ASBRs in the remote AS reached
inter-AS TE link, and, in order that it provides only suitable paths by any inter-AS TE link, and, in order that it provides only
in the tree, the PCE must know the TE properties of the inter-AS TE suitable paths in the tree, the PCE must know the TE properties of
links. See the following figure as an example: the inter-AS TE 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
: : : :
<-- AS1 -->:<---- AS2 --->:<--- AS3 ---> <-- AS1 -->:<---- AS2 --->:<--- AS3 --->
Figure 2: BRPC for Inter-AS Reference Model Figure 2: BRPC for Inter-AS Reference Model
The figure shows three ASes (AS1, AS2, and AS3), three PCEs (PCE1, The figure shows three ASes (AS1, AS2, and AS3), three PCEs (PCE1,
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 path ASBRs in AS3. PCE1, PCE2, and PCE3 cooperate to perform inter-AS
computation and are responsible for path segment computation within path computation and are responsible for path segment computation
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 segments,
PCE3 must determine which entry boundary nodes provide connectivity PCE3 must determine which entry boundary nodes provide connectivity
to its upstream neighbor AS (identified by its AS number), and must to its upstream neighbor AS (identified by its AS number), and must
skipping to change at page 8, line 9 skipping to change at page 8, line 9
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 and three new sub-TLVs are 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. The neighboring AS number and the remote ASBR ID of an inter-AS link.
sub-TLVs defined in [ISIS-TE], [ISIS-TE-V3] and other documents for The sub-TLVs defined in [ISIS-TE], [ISIS-TE-V3] and other documents
inclusion in the Extended IS Reachability TLV are applicable to be for inclusion in the Extended IS Reachability TLV are applicable to
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 inclusion advertisement. And another two new sub-TLVs are defined for
in the IS-IS Router Capability TLV to carry the TE Router ID when the inclusion in the IS-IS Router Capability TLV to carry the TE Router
TE Router ID is needed to reach all routers within an entire ISIS ID when the TE Router ID is needed to reach all routers within an
routing domain. entire ISIS routing domain.
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
dependency on where such protocols are processed, this mechanism
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 (which needs to be
confirmed by IANA see Section 6.1), it contains a data structure confirmed by IANA see Section 6.1), it contains a data structure
consisting of: consisting of:
7 octets of System ID and Pseudonode Number 4 octets of Router ID
3 octets of default metric 3 octets of default metric
1 octet of control information, consisting of: 1 octet of control information, consisting of:
1 bit of flooding-scope information 1 bit of flooding-scope information (S bit)
1 bit of up/down information 1 bit of up/down information (D bit)
6 bits reserved 6 bits reserved
1 octet of length of sub-TLVs 1 octet of length of sub-TLVs
0-243 octets of sub-TLVs 0-246 octets of sub-TLVs
where each sub-TLV consists of a sequence of: where each sub-TLV consists of a 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
0-241 octets of value 0-244 octets of value
Compare to the Extended Reachability TLV which is defined in [ISIS- Compare to the Extended Reachability TLV which is defined in [ISIS-
TE], the Inter-AS Reachability TLV introduces an extra "control TE], the Inter-AS Reachability TLV replaces the "7 octets of System
information" field which is consisted of a flooding-scope bit, a ID and Pseudonode Number" field with a "4 octets of Router ID" field
up/down bit and 6 reserved bits. and introduces an extra "control information" field which is
consisted of a flooding-scope bit (S bit), a up/down bit (D bit) and
6 reserved bits.
As the S bit defined in [ISIS-CAP], the flooding-scope bit is used to The Router ID field of the Inter-AS Reachability TLV is four octets
control the flooding scope of the Inter-AS Reachability TLV. When the in length, which contains the Router ID of the router who generates
flooding-scope bit is set to 1, the Inter-AS Reachability TLV MUST be the Inter-AS Reachability TLV. The Router ID MUST be unique within
flooded into the entire ISIS routing domain. If the flooding-scope the ISIS area. If the router generates Inter-AS Reachability TLV
bit is set to 0, the Inter-AS Reachability TLV MUST NOT be leaked with entire ISIS routing domain flooding scope, then the Router ID
between different levels. And this flooding-scope bit MUST NOT be MUST also be unique within the entire ISIS routing domain. The
modified during the TLV leaking. The choice between the use of 0 or 1 Router ID could be used to indicate the source of the Inter-AS
is a AS-wide policy choice, and configuration control SHOULD be Reachability TLV.
provided in ASBR implementations that supports the advertisement of
inter-AS TE links.
The semantics of the up/down bit in the Inter-AS Reachability TLV are The flooding procedures for Inter-AS Reachability TLV are identical
identical to the semantics of the up/down bit defined in [ISIS-TE]. to the flooding procedures for the GNINFO TLV which are defined in
It can be used to facilitate the redistribution of inter-AS TE the Section 4 of [GENINFO]. These procedures have been previously
information freely between level 1 and level 2. And the up/down bit discussed in [ISIS-CAP]. The flooding-scope bit (S bit) SHOULD be
MUST be set to 0 when the Inter-AS TE information first injected into set to 0 if the flooding scope is to be limited to within the single
ISIS [ISIS], and the up/dawn bit MUST be set to 1 if the Inter-AS TE IGP area to which the ASBR belongs, or MAY be set to 1 if the
information needs to be advertised from high level to low level. information is intended to reach all routers (including area border
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
configuration control SHOULD be provided in ASBR implementations
that supports the advertisement of inter-AS TE links.
The sub-TLVs which are defined in [ISIS-TE], [ISIS-TE-V3] and other The sub-TLVs which are defined in [ISIS-TE], [ISIS-TE-V3] and other
documents for describing the TE properties of an TE link are also documents for describing the TE properties of an TE link are also
applicable to be carried in the Inter-AS Reachability TLV to describe applicable to be carried in the Inter-AS Reachability TLV to
the TE properties of an Inter-AS TE link. Apart from these sub-TLVs, describe the TE properties of an Inter-AS TE link. Apart from these
three new sub-TLVs are defined for inclusion in the Inter-AS sub-TLVs, three new sub-TLVs are defined for inclusion in the Inter-
Reachability TLV in this document: AS Reachability TLV in this document:
Sub-TLV type Length Name Sub-TLV type Length Name
------------ ------ --------------------------- ------------ ------ ---------------------------
23 4 Remote AS number 23 4 Remote AS number
24 4 IPv4 Remote ASBR Identifier 24 4 IPv4 Remote ASBR Identifier
25 16 IPv6 Remote ASBR Identifier 25 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.
skipping to change at page 9, line 40 skipping to change at page 10, line 4
The IPv4 TE Router ID TLV (type 134) and IPv6 TE Router ID TLV (type The IPv4 TE Router ID TLV (type 134) and IPv6 TE Router ID TLV (type
140), which are defined in [ISIS-TE] and [ISIS-TE-V3] respectively, 140), which are defined in [ISIS-TE] and [ISIS-TE-V3] respectively,
only have area flooding-scope, when performing inter-AS TE, the TE only have area flooding-scope, when performing inter-AS TE, the TE
Router ID MAY be needed to reach all routers within an entire ISIS Router ID MAY be needed to reach all routers within an entire ISIS
routing domain, and it MUST have the same flooding scope as the routing domain, and it MUST have the same flooding scope as the
Inter-AS Reachability TLV does. Inter-AS Reachability TLV 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 TE an entire ISIS routing domain. And [ISIS-CAP] also points out that
Router ID is candidate to be carried in the IS-IS Router Capability TE Router ID is candidate to be carried in the IS-IS Router
TLV when performing inter-area TE. Capability TLV when performing inter-area TE.
This document uses such mechanism for TE Router ID advertisement when This document uses such mechanism for TE Router ID advertisement
the TE Router ID is needed to reach all routers within an entire ISIS when the TE Router ID is needed to reach all routers within an
Routing domain. Two new sub-TLVs are defined for inclusion in the IS- entire ISIS Routing domain. Two new sub-TLVs are defined for
IS Router Capability TLV to carry the IPv4 and IPv6 TE Router ID inclusion in the IS-IS Router Capability TLV to carry the IPv4 and
respectively: IPv6 TE Router ID 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 The Detailed definitions of the two new sub-TLVs are described in
Section 3.3. Section 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. The in the Inter-AS Reachability TLV when advertising inter-AS links.
Remote AS Number sub-TLV specifies the AS number of the neighboring The Remote AS Number sub-TLV specifies the AS number of the
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 23 (which needs to be
confirmed by IANA see Section 6.2), and is four octets in length. The confirmed by IANA see Section 6.2), and is four octets in length.
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 two octets are
used for the AS number, as in current deployments, the left (high- used for the AS number, as in current deployments, the left (high-
order) two octets MUST be set to zero. The Remote AS Number Sub-TLV order) two octets MUST be set to zero. The Remote AS Number Sub-TLV
MUST be included when a router advertises an inter-AS TE link. MUST be 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 specifies advertising inter-AS links. The IPv4 Remote ASBR ID sub-TLV
the IPv4 identifier of the remote ASBR to which the advertised inter- specifies the IPv4 identifier of the remote ASBR to which the
AS link connects. This could be any stable and routable IPv4 address advertised inter-AS link connects. This could be any stable and
of the remote ASBR. Use of the TE Router ID as specified in the routable IPv4 address of the remote ASBR. Use of the TE Router ID as
Traffic Engineering Router ID TLV [ISIS-TE] is RECOMMENDED. specified in the Traffic Engineering Router ID TLV [ISIS-TE] is
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 24 (which needs to be
confirmed by IANA see Section 6.2), and is four octets in length. The confirmed by IANA see Section 6.2), and is four octets in length.
format of the IPv4 Remote ASBR ID sub-TLV is as follows: The format of the IPv4 Remote ASBR ID sub-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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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 ID IPv4 address (not even an IPv4 TE Router ID), the IPv6 Remote ASBR
sub-TLV MUST be included instead. An IPv4 Remote ASBR ID sub-TLV and ID sub-TLV MUST be included instead. An IPv4 Remote ASBR ID sub-TLV
IPv6 Remote ASBR ID sub-TLV MAY both be present in an Extended IS and IPv6 Remote ASBR ID sub-TLV MAY both be present in an Extended
Reachability TLV. IS 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 specifies advertising inter-AS links. The IPv6 Remote ASBR ID sub-TLV
the IPv6 identifier of the remote ASBR to which the advertised inter- specifies the IPv6 identifier of the remote ASBR to which the
AS link connects. This could be any stable and routable IPv6 address advertised inter-AS link connects. This could be any stable and
of the remote ASBR. Use of the TE Router ID as specified in the IPv6 routable IPv6 address of the remote ASBR. Use of the TE Router ID as
Traffic Engineering Router ID TLV [ISIS-TE-V3] is RECOMMENDED. specified in the IPv6 Traffic Engineering Router ID TLV [ISIS-TE-V3]
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 25 (which needs to be
confirmed by IANA see Section 6.2), and is sixteen octets in length. confirmed by IANA see Section 6.2), and is sixteen octets in length.
The format of the IPv6 Remote ASBR ID sub-TLV is as follows: The format of the IPv6 Remote ASBR ID sub-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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
skipping to change at page 12, line 8 skipping to change at page 12, line 28
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 sub-
TLV MAY both be present in an Extended IS Reachability TLV. 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 (which needs to be
confirmed by IANA see Section 6.3), and is four octets in length. The confirmed by IANA see Section 6.3), and is four octets in length.
format of the IPv4 TE Router ID sub-TLV is as follows: The format of the IPv4 TE Router ID sub-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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 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. And if an ASBR supports Traffic Engineering for IPv4, the included in its LSP. And if an ASBR supports Traffic Engineering for
IPv4 TE Router ID sub-TLV MUST be included if the ASBR has an IPv4 TE IPv4, the IPv4 TE Router ID sub-TLV MUST be included if the ASBR has
Router ID. If the ASBR does not have an IPv4 TE Router ID, the IPv6 an IPv4 TE Router ID. If the ASBR does not have an IPv4 TE Router ID,
TE Router sub-TLV MUST be included instead. An IPv4 TE Router ID sub- the IPv6 TE Router sub-TLV MUST be included instead. An IPv4 TE
TLV and IPv6 TE Router ID sub-TLV MAY both be present in an IS-IS Router ID sub-TLV and IPv6 TE Router ID sub-TLV MAY both be present
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 (which needs to be
confirmed by IANA see Section 6.3), and is four octets in length. The confirmed by IANA see Section 6.3), and is four octets in length.
format of the IPv6 TE Router ID sub-TLV is as follows: The format of the IPv6 TE Router ID sub-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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 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 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. And if an ASBR supports Traffic Engineering for IPv6, the included in its LSP. And if an ASBR supports Traffic Engineering for
IPv6 TE Router ID sub-TLV MUST be included if the ASBR has an IPv6 TE IPv6, the IPv6 TE Router ID sub-TLV MUST be included if the ASBR has
Router ID. If the ASBR does not have an IPv6 TE Router ID, the IPv4 an IPv6 TE Router ID. If the ASBR does not have an IPv6 TE Router ID,
TE Router sub-TLV MUST be included instead. An IPv4 TE Router ID sub- the IPv4 TE Router sub-TLV MUST be included instead. An IPv4 TE
TLV and IPv6 TE Router ID sub-TLV MAY both be present in an IS-IS Router ID sub-TLV and IPv6 TE Router ID sub-TLV MAY both be present
Router Capability TLV. in an 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 but the ASBR MUST take precautions against excessive re-
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 AS and usage of the link, and configuration at the ASBR of the remote
number and remote ASBR TE Router ID. AS number and remote ASBR TE Router ID.
Legacy routers receiving an advertisement for an inter-AS TE link are Legacy routers receiving an advertisement for an inter-AS TE link
able to ignore it because they do not know the new TLV and sub-TLVs are able to ignore it because they do not know the new TLV and sub-
that are defined in Section 3 in this document. They will continue to TLVs that are defined in Section 3 in this document. They will
flood the LSP, but will not attempt to use the information received. continue to flood the LSP, but will not attempt to use the
information received.
In the current operation of ISIS TE the LSRs at each end of a TE link In the current operation of ISIS TE the LSRs at each end of a TE
emit LSAs describing the link. The databases in the LSRs then have link emit LSAs describing the link. The databases in the LSRs then
two entries (one locally generated, the other from the peer) that have two entries (one locally generated, the other from the peer)
describe the different 'directions' of the link. This enables CSPF that describe the different 'directions' of the link. This enables
to do a two-way check on the link when performing path computation CSPF to do a two-way check on the link when performing path
and eliminate it from consideration unless both directions of the computation and eliminate it from consideration unless both
link satisfy the required constraints. 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 AS) there is, by definition, no IGP peering and hence no bi-
bi-directional TE link information. In order for the CSPF route directional 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 a 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 devices '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 the advertised; i.e., the Interface Address, the Remote AS number and
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
skipping to change at page 14, line 38 skipping to change at page 15, line 25
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 minor The protocol extensions defined in this document are relatively
and can be secured within the AS in which they are used by the minor and can be secured within the AS in which they are used by the
existing ISIS security mechanisms. existing ISIS security mechanisms.
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, since the ISIS security relationship between the ASes. In particular,
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 commercial relationship.
The source and content of this information should be carefully The source and content of this information should be carefully
checked before it is entered as configuration information at the ASBR checked before it is entered as configuration information at the
responsible for advertising the inter-AS TE links. 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. For this could be used to detect inconsistencies in configuration (e.g.,
example, if a different remote AS number is received in a BGP OPEN the administration that originally supplied the information may be
[BGP] from that locally configured into ISIS-TE, as we describe here, lying, or some manual mis-configurations or mistakes are made by the
then something is amiss. Note, further, that if BGP is used to operators). For example, if a different remote AS number is received
exchange TE information as described in Section 4.1, the inter-AS BGP in a BGP OPEN [BGP] from that locally configured into ISIS-TE, as we
session will need to be fully secured. describe here, then local policy SHOULD be applied to determine
whether to alert the operator to a potential mis-configuration or to
suppress the ISIS advertisement of the inter-AS TE link. Note,
further, that if BGP is used to exchange TE information as described
in Section 4.1, the inter-AS BGP session SHOULD be secured using
mechanisms as described in [BGP] to provide authentication and
integrity checks.
6. IANA Considerations 6. IANA Considerations
IANA is requested to make the following allocations from registries IANA is requested to make the following allocations from registries
under its control. under its 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 3.4, that needs to be registered in the ISIS TLV code-point
skipping to change at page 15, line 35 skipping to change at page 16, line 30
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) that need to be registered in the ISIS sub-TLV registry
for TLV 141: 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):
Type Description Length Type Description Length
---- ------------------------------ -------- ---- ------------------------------ --------
23 Remote AS number 4 23 Remote AS number 4
24 IPv4 Remote ASBR Identifier 4 24 IPv4 Remote ASBR Identifier 4
25 IPv6 Remote ASBR Identifier 16 25 IPv6 Remote ASBR Identifier 16
As described above in Section 3.1, the sub-TLVs which are defined in As described above in Section 3.1, the sub-TLVs which are defined in
[ISIS-TE], [ISIS-TE-V3] and other documents for describing the TE [ISIS-TE], [ISIS-TE-V3] and other documents for describing the TE
properties of an TE link are applicable to describe an inter-AS TE properties of an TE link are applicable to describe an inter-AS TE
link and MAY be included in the Inter-AS Reachability TLV when link and MAY be included in the Inter-AS Reachability TLV when
adverting inter-AS TE links. So, these sub-TLVs need to be registered adverting inter-AS TE links. So, these sub-TLVs need to be
in the ISIS sub-TLV registry for TLV 141. And in order to simplify registered in the ISIS sub-TLV registry for TLV 141. And in order to
the registration, we suggest using the same registry value as they simplify the registration, we suggest using the same registry value
are registered in the ISIS sub-TLV registry for TLV 22. as they are registered in the ISIS sub-TLV registry for TLV 22.
Type Description
---- ------------------------------
3 Administrative group (color) [ISIS-TE]
4 Link Local/Remote Identifiers [GMPLS-TE]
6 IPv4 interface address [ISIS-TE]
9 Maximum link bandwidth [ISIS-TE]
10 Reservable link bandwidth [ISIS-TE]
11 Unreserved bandwidth [ISIS-TE]
12 IPv6 Interface Address [ISIS-TE-V3]
18 TE Default metric [ISIS-TE]
19 Link-attributes [RFC5029]
20 Link Protection Type [GMPLS-TE]
21 Interface Switching Capability Descriptor [GMPLS-TE]
22 Bandwidth Constraints [RFC4124]
Because sub-TLVs defined for TLV 22 can be advertised in the Inter-
AS Reachability TLV, the new sub-TLVs defined in this document
SHOULD NOT conflict with existing and/or future sub-TLV definitions
for TLV 22. Therefore the new sub-TLVs MUST be defined from a sub-
TLV registry which is shared by these two 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 need to be registered in the ISIS sub-TLV registry
for TLV 242: for TLV 242:
Type Description Length Type Description Length
---- ------------------------------ -------- ---- ------------------------------ --------
skipping to change at page 16, line 46 skipping to change at page 18, line 21
[ISIS-CAP] Vasseur, J.P. et al., "IS-IS extensions for advertising [ISIS-CAP] Vasseur, J.P. et al., "IS-IS extensions for advertising
router information", RFC 4971, July 2007. 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 and Vasseur, "MPLS Inter-AS Traffic
Engineering Requirements", RFC4216, November 2005. Engineering Requirements", RFC4216, November 2005.
[PD-PATH] Ayyangar, A., Vasseur, JP., and Zhang, R., "A Per-domain [PD-PATH] Ayyangar, A., Vasseur, JP., and Zhang, R., "A Per-domain
path computation method for establishing Inter-domain", RFC path computation method for establishing Inter-domain",
5152, February 2008. RFC 5152, February 2008.
[BRPC] JP. Vasseur, Ed., R. Zhang, N. Bitar, JL. Le Roux, "A [BRPC] JP. Vasseur, Ed., R. Zhang, N. Bitar, JL. Le Roux, "A
Backward Recursive PCE-based Computation (BRPC) procedure Backward Recursive PCE-based Computation (BRPC) procedure
to compute shortest inter-domain Traffic Engineering Label to compute shortest inter-domain Traffic Engineering Label
Switched Paths", draft-ietf-pce-brpc, (work in progress). Switched Paths", draft-ietf-pce-brpc, (work in progress)
[PCE] Farrel, A., Vasseur, JP., and Ash, J., "A Path Computation [PCE] Farrel, A., Vasseur, JP., and Ash, J., "A Path Computation
Element (PCE)-Based Architecture", RFC4655, August 2006. Element (PCE)-Based Architecture", RFC4655, August 2006.
[ISIS-TE] Smit, H. and T. Li, "Intermediate System to Intermediate [ISIS-TE] Smit, H. and T. Li, "Intermediate System to Intermediate
System (IS-IS) Extensions for Traffic Engineering (TE)", System (IS-IS) Extensions for Traffic Engineering (TE)",
RFC 3784, June 2004. 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", draft-ietf-isis-ipv6-te,
(work in progress). {work in progress}.
[GMPLS-TE] K.Kompella and Y.Rekhter, "IS-IS Extensions in Support of [GMPLS-TE] K.Kompella and Y.Rekhter, "IS-IS Extensions in Support of
Generalized Multi-Protocol Label Switching", RFC 4205, Generalized Multi-Protocol Label Switching", RFC 4205,
October 2005. October 2005.
[L1VPN-OSPF-AD] Bryskin, I., and Berger, L., "OSPF Based L1VPN Auto-
Discovery", draft-ietf-l1vpn-ospf-auto-discovery, (work in
progress).
[BGP] Rekhter, Li, Hares, "A Border Gateway Protocol 4 (BGP-4)", [BGP] Rekhter, Li, Hares, "A Border Gateway Protocol 4 (BGP-4)",
RFC4271, January 2006 RFC4271, January 2006.
[RFC5029] Vasseur, JP., and Previdi, S., "Definition of an IS-IS
Link Attribute Sub-TLV", RFC5029, September 2007.
[RFC4124] Le Faucheur, F. "Protocol Extensions for Support of
Diffserv-aware MPLS Traffic Engineering", RFC 4124, June
2005.
[GENINFO] L. Ginsberg., S. Previdi., and M. Shand., "Advertising
Generic Information in IS-IS", draft-ietf-isis-genapp,
(work in progress).
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
skipping to change at page 18, line 14 skipping to change at page 19, line 43
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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