Networking Working Group JP. Vasseur, Ed.
Internet-Draft Cisco Systems, Inc
Intended status: Standards Track R. Zhang
Expires: October 16, 2008 BT Infonet
N. Bitar
Verizon
JL. Le Roux
France Telecom
April 14, 2008
A Backward Recursive PCE-based Computation (BRPC) Procedure To Compute
Shortest Constrained Inter-domain Traffic Engineering Label Switched
Paths
draft-ietf-pce-brpc-09.txt
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Abstract
The ability to compute shortest constrained Traffic Engineering Label
Switched Paths (TE LSPs) in Multiprotocol Label Switching (MPLS) and
Generalized MPLS (GMPLS) networks across multiple domains (where a
domain is a collection of network elements within a common sphere of
address management or path computational responsibility such as an
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IGP area or an Autonomous Systems) has been identified as a key
requirement. This document specifies a procedure relying on the use
of multiple Path Computation Elements (PCEs) to compute such inter-
domain shortest constrained paths across a predetermined sequence of
domains, using a backward recursive path computation technique. This
technique preserves confidentiality across domains, which is
sometimes required when domains are managed by different Service
Providers.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. General Assumptions . . . . . . . . . . . . . . . . . . . . . 5
4. BRPC Procedure . . . . . . . . . . . . . . . . . . . . . . . . 6
4.1. Domain Path Selection . . . . . . . . . . . . . . . . . . 7
4.2. Mode of Operation . . . . . . . . . . . . . . . . . . . . 7
5. PCEP Protocol Extensions . . . . . . . . . . . . . . . . . . . 9
6. VSPT Encoding . . . . . . . . . . . . . . . . . . . . . . . . 10
7. Inter-AS TE Links . . . . . . . . . . . . . . . . . . . . . . 10
8. Usage In Conjunction With Per-domain Path Computation . . . . 11
9. BRPC Procedure Completion Failure . . . . . . . . . . . . . . 11
10. Applicability . . . . . . . . . . . . . . . . . . . . . . . . 12
10.1. Diverse end-to-end path computation . . . . . . . . . . . 12
10.2. Path Optimality . . . . . . . . . . . . . . . . . . . . . 12
11. Reoptimization Of An Inter-domain TE LSP . . . . . . . . . . . 13
12. Path Computation Failure . . . . . . . . . . . . . . . . . . . 13
13. Metric Normalization . . . . . . . . . . . . . . . . . . . . . 13
14. Manageability Considerations . . . . . . . . . . . . . . . . . 14
14.1. Control of Function And Policy . . . . . . . . . . . . . . 14
14.2. Information And Data Models . . . . . . . . . . . . . . . 14
14.3. Liveness Detection and Monitoring . . . . . . . . . . . . 14
14.4. Verifying Correct Operation . . . . . . . . . . . . . . . 14
14.5. Requirements on Other Protocols and Functional
Components . . . . . . . . . . . . . . . . . . . . . . . . 15
14.6. Impact on Network Operation . . . . . . . . . . . . . . . 15
14.7. Path Computation Chain Monitoring . . . . . . . . . . . . 15
15. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
15.1. New Flag Of The RP Object . . . . . . . . . . . . . . . . 15
15.2. New Error-Type And Error-Value . . . . . . . . . . . . . . 15
15.3. New Flag Of The NO-PATH-VECTOR TLV . . . . . . . . . . . . 16
16. Security Considerations . . . . . . . . . . . . . . . . . . . 16
17. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 16
18. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16
18.1. Normative References . . . . . . . . . . . . . . . . . . . 16
18.2. Informative References . . . . . . . . . . . . . . . . . . 17
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 18
Intellectual Property and Copyright Statements . . . . . . . . . . 20
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1. Introduction
The requirements for inter-area and inter-AS MPLS Traffic Engineering
(TE) have been developed by the Traffic Engineering Working Group (TE
WG) and have been stated in [RFC4105] and [RFC4216], respectively.
The framework for inter-domain Multiprotocol Label Switching (MPLS)
Traffic Engineering (TE) has been provided in [RFC4726].
[RFC5152] defines a technique for establishing an inter-domain
Generalized MPLS (GMPLS) TE Label Switched Path (LSP) whereby the
path is computed during the signalling process on a per-domain basis
by the entry boundary node of each domain (each node responsible for
triggering the computation of a section of an inter-domain TE LSP
path is always along the path of such TE LSP). This path computation
technique fulfills some of the requirements stated in [RFC4105] and
[RFC4216] but not all of them. In particular, it cannot guarantee to
find an optimal (shortest) inter-domain constrained path.
Furthermore, it cannot be efficiently used to compute a set of inter-
domain diversely routed TE LSPs.
The Path Computation Element (PCE) architecture is defined in
[RFC4655]. The aim of this document is to describe a PCE-based path
computation procedure to compute optimal inter-domain constrained
(G)MPLS TE LSPs.
Qualifying a path as optimal requires some clarification. Indeed, a
globally optimal TE LSP placement usually refers to a set of TE LSPs
whose placements optimize the network resources with regards to a
specified objective function (e.g., a placement that reduces the
maximum or average network load while satisfying the TE LSP
constraints). In this document, an optimal inter-domain constrained
TE LSP is defined as the shortest path satisfying the set of required
constraints that would be obtained in the absence of multiple domains
(in other words, in a totally flat IGP network between the source and
destination of the TE LSP). Note that this requires to use
consistent metric schemes in each domain (see section Section 13).
2. Terminology
ABR: Area Border Routers. Routers used to connect two IGP areas
(areas in OSPF or levels in IS-IS).
ASBR: Autonomous System Border Routers. Routers used to connect
together ASes of the same or different Service Providers via one or
more Inter-AS links.
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Boundary Node (BN): a boundary node is either an ABR in the context
of inter-area Traffic Engineering or an ASBR in the context of
inter-AS Traffic Engineering.
Entry BN of domain(n): a BN connecting domain(n-1) to domain(n) along
a determined sequence of domains.
Exit BN of domain(n): a BN connecting domain(n) to domain(n+1) along
a determined sequence of domains.
Inter-AS TE LSP: A TE LSP that crosses an AS boundary.
Inter-area TE LSP: A TE LSP that crosses an IGP area boundary.
LSR: Label Switching Router.
LSP: Label Switched Path.
PCC: Path Computation Client. Any client application requesting a
path computation to be performed by the Path Computation Element.
PCE (Path Computation Element): an entity (component, application or
network node) that is capable of computing a network path or route
based on a network graph and applying computational constraints.
PCE(i) is a PCE with the scope of domain(i).
TED: Traffic Engineering Database.
VSPT: Virtual Shortest Path Tree.
The notion of contiguous, stitched and nested TE LSPs is defined in
[RFC4726] and will not be repeated here.
3. General Assumptions
In the rest of this document, we make the following set of
assumptions common to inter-area and inter-AS MPLS TE:
o Each IGP area or Autonomous System (AS) is assumed to be Traffic
Engineering enabled.
o No topology or resource information is distributed between domains
(as mandated per [RFC4105] and [RFC4216]), which is critical to
preserve IGP/BGP scalability and confidentiality.
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o While certain constraints like bandwidth can be used across
different domains, other TE constraints like resource affinity,
color, metric, etc. as listed in [RFC2702] could be translated at
domain boundaries. If required, it is assumed that, at the domain
boundary nodes, there will exist some sort of local mapping based
on policy agreement, in order to translate such constraints across
domain boundaries during the inter-PCE communication process.
o Each AS can be made of several IGP areas. The path computation
procedure described in this document applies to the case of a
single AS made of multiple IGP areas, multiple ASes made of a
single IGP area or any combination of the above. For the sake of
simplicity, each AS will be considered to be made of a single area
in this document. The case of an Inter-AS TE LSP spanning
multiple ASes where some of those ASes are themselves made of
multiple IGP areas can be easily derived from this case by
applying the BRPC procedure described in this document,
recursively.
o The domain path (set of domains traversed to reach the destination
domain) is either administratively pre-determined or discovered by
some means that is outside of the scope of this document.
4. BRPC Procedure
The BRPC procedure is a Multiple-PCE path computation technique as
described in [RFC4655]. A possible model consists of hosting the PCE
function on boundary nodes (e.g., ABR or ASBR) but this is not
mandated by the BRPC procedure.
The BRPC procedure relies on communication between cooperating PCEs.
In particular, the PCC sends a PCReq to a PCE in its domain. The
request is forwarded between PCEs, domain-by-domain until the PCE
responsible for the domain containing the LSP destination is reached.
The PCE in the destination domain creates a tree of potential paths
to the destination (the Virtual Shortest Path Tree - VSPT) and passes
this back to the previous PCE in a PCRep. Each PCE in turn adds to
the VSPT and passes it back until the PCE in the source domain uses
the VSPT to select an end-to-end path that it sends to the PCC.
The BRPC procedure does not make any assumption with regards to the
nature of the inter-domain TE LSP that could be contiguous, nested or
stitched.
Furthermore, no assumption is made on the actual path computation
algorithm in use by a PCE (e.g., it can be any variant of CSPF or an
algorithm based on linear-programming to solve multi-constraint
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optimization problems).
4.1. Domain Path Selection
The PCE-based BRPC procedure applies to the computation of an optimal
constrained inter-domain TE LSP. The sequence of domains to be
traversed is either administratively pre-determined or discovered by
some means that is outside of the scope of this document. The PCC
MAY indicate the sequence of domains to be traversed using the IRO
defined in [I-D.ietf-pce-pcep] so that it is available to all PCEs.
Note also that a sequence of PCEs MAY be enforced by policy on the
PCC and this constraint can be carried in the PCEP path computation
request (as defined in [I-D.ietf-pce-monitoring]).
The BRPC procedure guarantees to compute the optimal path across a
specific sequence of traversed domains (which constitutes an
additional constraint). In the case of an arbitrary set of meshed
domains, the BRPC procedure can be used to compute the optimal path
across each domain set in order to get the optimal constrained path
between the source and the destination of the TE LSP. The BRPC
procedure can also be used across a subset of all domain sequences,
and the best path among these sequences can then be selected.
4.2. Mode of Operation
Definition of VSPT(i)
In each domain i:
o There is a set of X-en(i) entry BNs noted BN-en(k,i) where BN-
en(k,i) is the kth entry BN of domain(i).
o There is a set of X-ex(i) exit BNs noted BN-ex(k,i) where BN-
ex(k,i) is the kth exit BN of domain(i).
VSPT(i): MP2P (MultiPoint To Point) tree returned by PCE(i) to
PCE(i-1):
Root (TE LSP destination)
/ I \
BN-en(1,i) BN-en(2,i) ... BN-en(j,i).
Where [X-en(i)] is the number of entry BNs in domain i
and j<= [X-en(i)]
Figure 1 - MP2P Tree
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Each link of tree VSPT(i) represents the shortest constrained path
between BN-en(j,i) and the TE LSP destination that satisfies the set
of required constraints for the TE LSP (bandwidth, affinities, ...).
These are path segments to reach the TE LSP destination from BN-
en(j,i).
Note that PCE(i) only considers the entry BNs of domain(i). That is
only the BNs that provide connectivity from domain(i-1). That is,
the set BN-en(k,i) is only made of those BNs that provide
connectivity from domain (i-1) to domain(i). Furthermore, some BNs
may be excluded according to policy constraints (either due to local
policy or policies signaled in the path computation request).
Step 1: the PCC needs to first determine the PCE capable of serving
its path computation request (this can be done thanks to local
configuration or via IGP discovery (see [RFC5088] and [RFC5089])).
The path computation request is then relayed until reaching a PCE(n)
such that the TE LSP destination resides in the domain(n). At each
step of the process, the next PCE can either be statically configured
or dynamically discovered via IGP/BGP extensions. If no next PCE can
be found or the next hop PCE of choice is unavailable, the procedure
stops and a path computation error is returned (see Section 9). If
PCE(i-1) discovers multiple PCEs for the adjacent domain(i), PCE(i)
may select a subset of these PCEs based on some local policies or
heuristics. The PCE selection process is outside of the scope of
this document.
Step 2: PCE(n) computes VSPT(n) made of the list of shortest
constrained paths between every BN-en(j,n) and the TE LSP destination
using a suitable path computation algorithm (e.g. CSPF) and returns
the computed VSPT(n) to PCE(n-1).
Step i:
- For i=n-1 to 2: PCE(i) computes VSPT(i), the tree made of the
shortest constrained paths between each BN-en(j,i) and the TE LSP
destination. It does this by considering its own TED and the
information in VSPT(i+1).
In the case of Inter-AS TE LSP computation, this requires to also add
the inter-AS TE links connecting the domain(i) to the domain(i+1).
Step n
Finally PCE(1) computes the end-to-end shortest constrained path from
the source to the destination and returns the corresponding path to
the requesting PCC in the form of a PCRep message as defined in
[I-D.ietf-pce-pcep].
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Each branch of the VSPT tree (path) may be returned in the form of an
explicit path (in which case all the hops along the path segment are
listed) or a loose path (in which case only the BN is specified) so
as to preserve confidentiality along with the respective cost. In
the later case, various techniques can be used in order to retrieve
the computed explicit paths on a per domain basis during the
signaling process thanks to the use of path keys as described in
[I-D.ietf-pce-path-key].
A PCE that can compute the requested path for more than one
consecutive domain on the path SHOULD perform this computation for
all such domains before passing the PCRep to the previous PCE in the
sequence.
BRPC guarantees to find the optimal (shortest) constrained inter-
domain TE LSP according to a set of defined domains to be traversed.
Note that other variants of the BRPC procedure relying on the same
principles are also possible.
Note also that in case of ECMP paths, more than one path could be
returned to the requesting LSR.
5. PCEP Protocol Extensions
The BRPC procedure requires the specification of a new flag of the RP
object carried within the PCReq message (defined in
[I-D.ietf-pce-pcep]) to specify that the shortest paths satisfying
the constraints from the destination to the set of entry boundary
nodes are requested (such set of paths forms the downstream VSPT as
specified in Section 4.2).
The following new flag of the RP object is defined:
VSPT Flag
Bit Number Name Flag
7 VSPT
When set, the VSPT Flag indicates that the PCC requests the
computation of an inter-domain TE LSP using the BRPC procedure
defined in this document.
Because path segments computed by a downstream PCE in the context of
the BRPC procedure MUST be provided along with their respective path
costs, the C flag of the METRIC object carried within the PCReq
message MUST be set. It is the choice of the requester to
appropriately set the O bit of the RP object.
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6. VSPT Encoding
The VSPT is returned within a PCRep message. The encoding consists
of a non-ordered lists of EROs where each ERO represents a path
segment from a BN to the destination specified in the END-POINT
object of the corresponding PCReq message.
Example:
<---- area 1 ----><---- area 0 -----><------ area 2 ------>
ABR1-A-B-+
| |
ABR2-----D
| |
ABR3--C--+
Figure 2 - An Example of VPST Encoding Using a Set of EROs
In the simple example shown in figure 2, if we make the assumption
that a constrained path exists between each ABR and the destination
D, the VSPT computed by a PCE serving area 2 consists of the
following non-ordered set of EROs:
o ERO1: ABR1(TE Router ID)-A(Interface IP address)-B(Interface IP
address)-D(TE Router ID)
o ERO2: ABR2(TE Router ID)-D(TE Router ID)
o ERO3: ABR3(TE Router ID)-C(interface IP adress)-D(TE Router ID)
The PCReq message, PCRep message, PCEP END-POINT and ERO objects are
defined in [I-D.ietf-pce-pcep]
7. Inter-AS TE Links
In the case of Inter-AS TE LSP path computation, the BRPC procedure
requires the knowledge of the traffic engineering attributes of the
Inter-AS TE links: the process by which the PCE acquires this
information is out of the scope of the BRPC procedure, which is
compliant with the PCE architecture defined in [RFC4655].
That said, a straightforward solution consists of allowing the ASBRs
to flood the TE information related to the inter-ASBR links although
no IGP TE is enabled over those links (there is no IGP adjacency over
the inter-ASBR links). This allows the PCE of a domain to get entire
TE visibility up to the set of entry ASBRs in the downstream domain
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(see the IGP extensions defined in
[I-D.ietf-ccamp-isis-interas-te-extension] and
[I-D.ietf-ccamp-ospf-interas-te-extension]).
8. Usage In Conjunction With Per-domain Path Computation
The BRPC procedure may be used to compute path segments in
conjunction with other path computation techniques (such as the per-
domain path computation technique defined in [RFC5152]) to compute
the end-to-end path. In this case end-to-end path optimality can no
longer be guaranteed.
9. BRPC Procedure Completion Failure
If the BRPC procedure cannot be completed because a PCE along the
domain does not recognize the procedure (VSPT flag of the RP object),
as stated in [I-D.ietf-pce-pcep], the PCE sends a PCErr message to
the upstream PCE with an Error-Type=4 (not supported object), Error-
value-4 (Unsupported paramater). The PCE may include the parent
object (RP object) up to and including (but no further than) the
unknown or unsupported parameter. In this case where the unknown or
unsupported parameter is a bit flag (VSPT flag), the included RP
object should contain the whole bit flag field with all bits after
the parameter at issue set to zero. The corresponding path
computation request is then cancelled by the PCE without further
notification.
If the BRPC procedure cannot be completed because a PCE along the
domain path recognises but does not support the procedure, it MUST
return a PCErr message to the upstream PCE with an Error-Type "BRPC
procedure completion failure".
The PCErr message MUST be relayed to the requesting PCC.
PCEP-ERROR objects are used to report a PCEP protocol error and are
characterized by an Error-Type which specifies the type of error and
an Error-value that provides additional information about the error
type. Both the Error-Type and the Error-Value are managed by IANA.
A new Error-Type is defined that relates to the BRPC procedure.
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Error-type Meaning
13 BRPC procedure completion failure
Error-value
1: BRPC procedure not supported by one or more PCEs
along the domain path
10. Applicability
As discussed in Section 3, the requirements for inter-area and
inter-AS MPLS Traffic Engineering have been developed by the Traffic
Engineering Working Group (TE WG) and have been stated in [RFC4105]
and [RFC4216], respectively. Among the set of requirements, both
documents indicate the need for some solution providing the ability
to compute an optimal (shortest) constrained inter-domain TE LSP and
to compute a set of diverse inter-domain TE LSPs.
10.1. Diverse end-to-end path computation
PCEP (see [I-D.ietf-pce-pcep]) allows a PCC to request the
computation of a set of diverse TE LSPs thanks to the SVEC object by
setting the flags L, N or S to request link, node or SRLG diversity
respectively. Such requests MUST be taken into account by each PCE
along the path computation chain during the VSPT computation. In the
context of the BRPC procedure, a set of diversely routed TE LSPs
between two LSRs can be computed since the paths segments of the VSPT
are simultaneously computed by a given PCE. The BRPC procedure
allows for the computation of diverse paths under various objective
functions (such as minimizing the sum of the costs of the N diverse
paths, etc).
By constrast, with a 2-step approach consisting of computing the
first path followed by the computation of the second path after
having removed the set of network elements traversed by the first
path (if that does not violate confidentiality preservation), one
cannot guarantee that a solution will be found even if such solution
exists. Furthermore, even if a solution is found, it may not be the
most optimal one with respect to an objective function such as
minimizing the sum of the paths costs, bounding the path delays of
both paths and so on. Finally, it must be noted that such a 2-step
path computation approach is usually less efficient in term of
signalling delays since it requires two serialized TE LSP set up.
10.2. Path Optimality
BRPC guarantees that the optimal (shortest) constrained inter-domain
path will always be found subject to policy constraints. When
combined with other local path computation techniques (e.g. in the
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case of stitched/nested TE LSP) and in the case where a domain has
more than one BN-en or more than one BN-ex, optimality after some
network change within the domain can only be guaranteed by re-
executing the BRPC procedure.
11. Reoptimization Of An Inter-domain TE LSP
The ability to reoptimize an existing inter-domain TE LSP path has
been explicitly listed as a requirement in [RFC4105] and [RFC4216].
In the case of a TE LSP reoptimization request, the reoptimization
procedure defined in [I-D.ietf-pce-pcep] applies where the path in
use (if available on the head-end) is provided as part of the path
computation request in order for the PCEs involved in the
reoptimization request to avoid double bandwidth accounting.
12. Path Computation Failure
If a PCE requires to relay a path computation request according to
the BRPC procedure defined in this document to a downstream PCE and
no such PCE is available, the PCE MUST send a negative path
computation reply to the requester using a PCReq message as specified
in [I-D.ietf-pce-pcep] that contains a NO-PATH object. In such case,
the NO-PATH object MUST carry a NO-PATH-VECTOR TLV (defined in
[I-D.ietf-pce-pcep]) with the newly defined bit named "BRPC Path
Computation chain unavailable" set.
Bit number Name Flag
4 BRPC Path computation chain unavailable
13. Metric Normalization
In the case of inter-area TE, the same IGP/TE metric scheme is
usually adopted for all the IGP areas (e.g., based on the link-speed,
propagation delay or some other combination of link attributes).
Hence, the proposed set of mechanisms always computes the shortest
path across multiple areas obeying the required set of constraints
with respect to a specified objective function. Conversely, in the
case of Inter-AS TE, in order for this path computation to be
meaningful, metric normalization between ASes may be required. One
solution to avoid IGP metric modification would be for the Service
Providers to agree on a TE metric normalization scheme and use the TE
metric for TE LSP path computation (in that case, this must be
requested in the PCEP Path computation request) using the METRIC
object (defined in [I-D.ietf-pce-pcep]).
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14. Manageability Considerations
This section follows the guidance of
[I-D.ietf-pce-manageability-requirements].
14.1. Control of Function And Policy
The only configurable item is the support of the BRPC procedure on a
PCE. The support of the BRPC procedure by the PCE MAY be controlled
by a policy module governing the conditions under which a PCE should
participate to the BRPC procedure (origin of the requests, number of
requests per second, ...). If the BRPC is not supported/allowed on a
PCE, it MUST send a PCErr message as specified in Section 9.
14.2. Information And Data Models
A BRPC MIB module will be specified in a separate document.
14.3. Liveness Detection and Monitoring
The BRPC procedure is a Multiple-PCE path computation technique and
as such a set of PCEs are involved in the path computation chain. If
the path computation chain is not operational either because at least
one PCE does not support the BRPC procedure or because one of the
PCEs that must be involved in the path computation chain is not
available, procedures are defined to report such failures in
Section 9 and Section 12 respectively. Furthermore, a built-in
diagnostic tool to check the availability and performances of a PCE
chain is defined in [I-D.ietf-pce-monitoring].
14.4. Verifying Correct Operation
Verifying the correct operation of BRPC can be performed by
monitoring a set of parameters. A BRPC implementation SHOULD provide
the following parameters:
o Number of successful BRPC Procedure completions on a per PCE peer
basis,
o Number of BRPC procedure completion failures because the VSPT flag
was not recognized (on a per PCE peer basis),
o Number of BRPC procedure completetion failures because the BRPC
procedure was not supported (on a per PCE peer basis),
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14.5. Requirements on Other Protocols and Functional Components
The BRPC procedure does not put any new requirements on other
protocol. That said, since the BRPC procedure relies on the PCEP
protocol, there is a dependency between BRPC and PCEP; consequently
the BRPC procedure inherently makes use of the management functions
developed for PCEP.
14.6. Impact on Network Operation
The BRPC procedure does not have any significant impact on network
operation: indeed, BRPC is a Multiple-PCE path computation scheme as
defined in [RFC4655] and does not differ from any other path
computation request.
14.7. Path Computation Chain Monitoring
[I-D.ietf-pce-monitoring] specifies a set of mechanisms that can be
used to gather PCE state metrics. Because BRPC is a Multiple-PCE
path computation techniques, such mechanism could be advantageously
used in the context of the BRPC procedure to check the liveness of
the path computation chain, locate a faulty component, monitor the
overall performance and so on.
15. IANA Considerations
15.1. New Flag Of The RP Object
A new flag of the RP object (specified in [I-D.ietf-pce-pcep]) is
defined in this document.
VSPT Flag
Bit Number Name Flag Reference
7 VSPT This document
15.2. New Error-Type And Error-Value
A new Error-Type is defined in this document (Error-Type and Error-
value to be assigned by IANA).
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Error-type Meaning Reference
13 BRPC procedure completion failure This document
Error-value
1: BRPC procedure not supported by
one a PCE along the domain path
15.3. New Flag Of The NO-PATH-VECTOR TLV
A new flag of the NO-PATH-VECTOR TLV defined in [I-D.ietf-pce-pcep])
is specified in this document.
Bit number Meaning Reference
4 BRPC Path computation This document
chain unavailable
16. Security Considerations
The BRPC procedure relies on the use of the PCEP protocol and as such
is subjected to the potential attacks listed in section 11 of
[I-D.ietf-pce-pcep]. In addition to the security mechanisms
described in [I-D.ietf-pce-pcep] with regards to spoofing, snooping,
falsification and Denial of Service, an implementation MAY support a
policy module governing the conditions under which a PCE should
participate to the BRPC procedure.
The BRPC procedure does not increase the information exchanged
between ASes and preserves topology confidentiality, in compliance
with [RFC4105] and [RFC4216].
17. Acknowledgements
The authors would like to thank Arthi Ayyangar, Dimitri
Papadimitriou, Siva Sivabalan, Meral Shirazipour and Mach Chen for
their useful comments. A special thank to Adrian Farrel for his
useful comments and suggestions.
18. References
18.1. Normative References
[I-D.ietf-pce-pcep]
Ayyangar, A., Oki, E., Atlas, A., Dolganow, A., Ikejiri,
Y., Kumaki, K., Vasseur, J., and J. Roux, "Path
Computation Element (PCE) Communication Protocol (PCEP)",
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draft-ietf-pce-pcep-12 (work in progress), March 2008.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
18.2. Informative References
[I-D.ietf-ccamp-isis-interas-te-extension]
Chen, M., Zhang, R., and X. Duan, "ISIS Extensions in
Support of Inter-AS Multiprotocol Label Switching (MPLS)
and Generalized MPLS (GMPLS) Traffic Engineering",
draft-ietf-ccamp-isis-interas-te-extension-02 (work in
progress), April 2008.
[I-D.ietf-ccamp-ospf-interas-te-extension]
Chen, M., Zhang, R., and X. Duan, "OSPF Extensions in
Support of Inter-AS Multiprotocol Label Switching (MPLS)
and Generalized MPLS (GMPLS) Traffic Engineering",
draft-ietf-ccamp-ospf-interas-te-extension-05 (work in
progress), April 2008.
[I-D.ietf-pce-manageability-requirements]
Farrel, A., "Inclusion of Manageability Sections in PCE
Working Group Drafts",
draft-ietf-pce-manageability-requirements-03 (work in
progress), February 2008.
[I-D.ietf-pce-monitoring]
Vasseur, J., Roux, J., and Y. Ikejiri, "A set of
monitoring tools for Path Computation Element based
Architecture", draft-ietf-pce-monitoring-01 (work in
progress), February 2008.
[I-D.ietf-pce-path-key]
Bradford, R. and J. Vasseur, "Preserving Topology
Confidentiality in Inter-Domain Path Computation Using a
Key-Based Mechanism", draft-ietf-pce-path-key-02 (work in
progress), February 2008.
[RFC2702] Awduche, D., Malcolm, J., Agogbua, J., O'Dell, M., and J.
McManus, "Requirements for Traffic Engineering Over MPLS",
RFC 2702, September 1999.
[RFC4105] Le Roux, J., Vasseur, J., and J. Boyle, "Requirements for
Inter-Area MPLS Traffic Engineering", RFC 4105, June 2005.
[RFC4216] Zhang, R. and J. Vasseur, "MPLS Inter-Autonomous System
(AS) Traffic Engineering (TE) Requirements", RFC 4216,
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November 2005.
[RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation
Element (PCE)-Based Architecture", RFC 4655, August 2006.
[RFC4726] Farrel, A., Vasseur, J., and A. Ayyangar, "A Framework for
Inter-Domain Multiprotocol Label Switching Traffic
Engineering", RFC 4726, November 2006.
[RFC5088] Le Roux, JL., Vasseur, JP., Ikejiri, Y., and R. Zhang,
"OSPF Protocol Extensions for Path Computation Element
(PCE) Discovery", RFC 5088, January 2008.
[RFC5089] Le Roux, JL., Vasseur, JP., Ikejiri, Y., and R. Zhang,
"IS-IS Protocol Extensions for Path Computation Element
(PCE) Discovery", RFC 5089, January 2008.
[RFC5152] Vasseur, JP., Ayyangar, A., and R. Zhang, "A Per-Domain
Path Computation Method for Establishing Inter-Domain
Traffic Engineering (TE) Label Switched Paths (LSPs)",
RFC 5152, February 2008.
Authors' Addresses
JP Vasseur (editor)
Cisco Systems, Inc
1414 Massachusetts Avenue
Boxborough, MA 01719
USA
Email: jpv@cisco.com
Raymond Zhang
BT Infonet
2160 E. Grand Ave.
El Segundo, CA 90025
USA
Email: raymond_zhang@bt.infonet.com
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Nabil Bitar
Verizon
40 Sylvan Road
Waltham, MA 02145
USA
Email: nabil.bitar@verizon.com
JL Le Roux
France Telecom
2, Avenue Pierre-Marzin
Lannion, 22307
FRANCE
Email: jeanlouis.leroux@orange-ft.com
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