Network Working Group Quintin Zhao
Internet-Draft Huawei Technology
Category: Standards Track Daniel King (Editor)
Expires: August 20, 2008 Aria Networks
Tomonori Takeda
NTT
Fabien Verhaeghe
Marben Products
February 17, 2008
Extensions to the Path Computation Element Communication Protocol
(PCEP) for Point-to-Multipoint Traffic Engineering Label Switched
Paths
draft-zhao-pce-pcep-extension-p2mp-00.txt
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Abstract
Point-to-point Multiprotocol Label Switching (MPLS) and Generalized
MPLS (GMPLS) Traffic Engineering Label Switched Paths (TE LSPs)
may be established using signaling techniques, but their paths may
first be determined. The Path Computation Element (PCE) has been
identified as an appropriate technology for the determination of the
paths of P2MP TE LSPs.
This document describes extensions to the PCE Communication Protocol
PCEP) to handle requests and responses for the computation of paths
for P2MP TE LSPs.
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Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
Table of Contents
1. Introduction .................................................. 2
2. Requirements .................................................. 3
3. Protocol Procedures and Extensions............................. 4
3.1 PCEP Message Common Header Extension for Large Message
Support......................................................... 4
3.2 Open Message Extension for P2MP Capability Advertisement.... 5
3.2.1 Capability TLV......................................... 5
3.3 RP Object Definitions for P2MP Capability................... 6
3.3.1 Extend the Existing P2P RP Object......................... 6
3.4 END-POINT Object extension.................................. 7
3.4.1 Extending existing END-POINT object.................... 7
3.4.2 Defining a new END-POINT object type for P2MP.......... 9
3.5 P2MP Trees Efficient Presentation........................... 9
3.5.1 P2MP Tree Presentation.(using S2L)..................... 9
3.5.2 P2MP Tree Presentation (using BRANCH object)........... 9
3.6 UNREACH_DESTINATION object................................. 12
3.7 P2MP PCEP Error Object..................................... 13
3.8 PCEP NO-PATH Indicator..................................... 14
4. IANA considerations........................................... 14
5. Manageability Considerations.................................. 14
5.1 Control of Function and Policy............................. 15
5.2 Information and Data Models................................ 15
5.3 Liveness Detection and Monitoring.......................... 15
5.4 Verifying Correct Operation................................ 15
5.5 Requirements on Other Protocols and Functional Components.. 15
5.6 Impact on Network Operation................................ 15
6. Security Considerations........................................ 16
7. References..................................................... 16
7.1. Normative Reference........................................ 16
7.2. Informative Reference...................................... 16
8. Acknowledgements............................................... 17
9. Authors' Addresses............................................. 17
10. Intellectual Property Statement............................... 17
1. Introduction
The Path Computation Element (PCE) defined in [RFC4655] is an entity
that is capable of computing a network path or route based on a
network graph, and applying computational constraints. A Path
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Computation Client (PCC) may make requests to a PCE for paths to be
computed.
[RFC4875] describes how to set up point-to-multipoint (P2MP) Traffic
Engineering Label Switched Paths (TE LSPs) for use in Multiprotocol
Label Switching (MPLS) and Generalized MPLS (GMPLS) networks.
The PCE is identified as a suitable application for the computation
of paths for P2MP TE LSPs [PCEP-P2MP].
The PCE communication protocol (PCEP) is designed as a communication
protocol between PCCs and PCEs for point-to-point (P2P) path
computations and is defined in [PCEP]. However, that specification
does not provide a mechanism to request path computation of P2MP TE
LSPs
This document presents extensions to PCEP to support P2MP path
computation satisfying the set of requirements described in Sections
2.1.1 to 2.1.13 of [PCEP-P2MP].
This document relies on the semantics of PCEP for requesting path
computation for P2MP TE LSPs. A P2MP LSP is comprised of multiple
source-to-leaf (S2L) sub-LSPs. These S2L sub-LSPs are set up between
ingress and egress LSRs and are appropriately combined by the branch
LSRs using computation result from PCE to result in a P2MP TE LSP.
One request message from a PCC may signal one or more S2L sub-LSP
path computation requests to the PCE for a single P2MP LSP with
certain constraints. Hence the S2L sub-LSPs belonging to a P2MP LSP
can use one path computation request message or be split across
multiple path computation messages.
This document uses the terminology defined in [RFC4655],
[RFC4875], and [PCEP].
In some places in this draft, multiple options are presented for
consideration. After each of these options has been fully evaluated
by the PCE working group, the ones which satisfy the corresponding
requirements and are most practical from the point view of
implementation will be chosen. [EDITORS NOTE: We will remove this
paragraph before publication as an RFC.]
2. Requirements
This section summarizes the PCEP requirements specific to Point to
Multi point as described in [PCEP-P2MP].
R1: Indication of P2MP Path Computation Request.
R2: Indication of P2MP Objective Functions.
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R3: Non-Support of P2MP Path Computation.
R4: Non-Support by Back-Level PCE Implementations.
R5: Specification of Destinations.
R6: Indication of P2MP Paths.
R7: Multi-Message Requests and Responses.
R8: Non-Specification of Per-Destination Constraints and Parameters.
R9: Path Modification and Path Diversity.
R10: Reoptimization of P2MP TE LSPs.
R11: Addition and Removal of Destinations from Existing Paths.
R12: Specification of Applicable Branch Nodes.
R13: Capabilities Exchange.
3. Protocol Procedures and Extensions
The following two sections describe the procedures adopted by
a PCE handling a request from a PCC for P2MP path computation, and
define how those requests and their responses are encoded.
3.1 PCEP Message Header Extension for PCEP Large Message Support
As specified in Common Header Section of [PCEP], the message length
is encoded in a 16 bit field, and each object in the message also
has its length encoded in a 16 bit field as specified in the Object
Format Section of [PCEP].
P2MP path computation may require the transfer of larger amounts of
data between PCC and PCE than is required for P2P path computation.
This may mean that in some circumstances a single PCEP message is
unable to contain all of the necessary data. This possibility is
exacerbated by the potential use of IPv6 addresses. In this case, we
need to use multiple messages to represent the P2MP paths and there
is a need to correlate this sequence of fragmented messages into a
single computation request or response.
In this draft, we propose to extend the PCEP message header by using
one of the Flags bits as the F (fragmentation) bit.
We will extend the PCEP message header as below:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Ver | Flags |F| Message Type | Message Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Extended PCEP Message Common Header
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In this extended format, one of the Flags bits is used as the F bit:
F: 0 This means that the message is the last of a sequence
of correlated messages.
F: 1 This means that the message is one of a sequence of
messages, but not the last in the sequence.
In the case of F set to zero, it will be the last of a sequence of
correlated messages if the previous message has the F bit set to 1 or
there is no previous message at all and it is single non-fragmented
message.
In the case of F set to 1, then the receiver of the message needs to
wait until it receives the message which has the F bit set to 0 and
treat all the previous messages which have F bit set 1 and this last
message which has the F bit set to 0 as a single complete message.
The duration to wait is specified by the SyncTimerdefined in
[PCEP] for the handling of the SVEC Object, it is recommended for
the PCE to implement a local timer, activated upon the receipt of
the first PCReq message.
This F bit can be used implicitly to signal the receiver of the
message if the P2MP tree data is sent by using a single message or it
is sent by using a sequence of messages. It is assumed that in-order
delivery of the fragments is assumed from the use of TCP.
3.2 Open Message Extension for P2MP Capability Advertisement
Based on the Capabilities Exchange requirement described in
[PCEP-P2MP], if a PCE does not advertise its P2MP capability
through discovery and the capability is not configured to the PCC,
we need to use PCEP to allow a PCC to discover which PCEs with
which it communicates support P2MP path computation. To satisfy
this requirement, we extend the OPEN object format as described in
the following section.
3.2.1 Capability TLV
The capability TLV allows the PCE to advertise its path computation
capabilities. Inside the open object, we suggest to add the P2MP
capability TLV in the optional field.
The TLV type number will be assigned by IANA, the LENGTH value is 2
bytes. The value field is set to default value 0.
Note that the capability TLV is meaningful only for a PCE so it will
typically appear only in one of the two Open messages during PCE
session establishment. However, in case of PCE cooperation (e.g.,
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inter-domain), when a PCE behaving as a PCC initiates a PCE session
it SHOULD also indicate its Path Computation capability.
3.3 RP Object Definitions for P2MP Capability
3.3.1 Extend the Existing P2P RP Object
In this option, the PCE path computation request message adds an
explicit parameter to allow a receiving PCE to identify that the
request is for a P2MP path. The M bit is added in the flag bits
field of the RP object to signal the receiver of the message that
the request is for P2P or it is for P2MP.
When the M bit is set to 1, we also propose to include a TLV for the
P2MP Tree ID. [EDITORS NOTE: The authors wish to highlight the need
for a P2MP Tree ID in case the PCE needs to store the P2MP tree data
for PCCs to reference it instead of passing the whole P2MP tree
again. This function requires further discussion before text is
included for the next draft.]
The extended format of the RP object body, to include the M bit, is
as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Flags |M|O|B|R| Pri |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Request-ID-number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TYPE (Tree ID) | LENGTH = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tree ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| |
// Optional TLV(s) //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: RP Object Body Format
The following flags are added in this draft:
M ( P2MP bit - 1 bit):
0: This indicates that this is not PCReq for P2MP.
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1: This indicates that this is PCReq or PCRep message for P2MP.
3.4 P2MP END-POINT Object Extensions
There are two options to represent the end points for a P2MP path.
One is that we extend the existing END-POINT object and the second
option is that we define a new type of end-point object of P2MP
path.
The PCE path computation request message is expanded in a way such
that it allows a single request message to list multiple
destinations.
Further discussion and working group feedback is required for this
section.
[EDITORS NOTE: We will remove multiple options as the draft
progresses and working group feedback is gained.]
3.4.1 Extending the existing END-POINT object
With the existing END-POINTS object, the same source with multiple
destinations need use multiple END-POINTS object in the request
message. It works fine except that it is not efficient in the case
that one source have many destinations, since we need repeat the
same source in each END-POINTS object.
We propose to extend the END-POINTS object such that it has one
single source address and it can have one or more than one
destination address. With this extension, the request message size
for the multiple destinations can be reduced almost 50% for a P2MP
path where a single source address has many destinations.
The format of the END-POINTS object body for IPv4 (Object-Type is as
same as defined in [PCEP]) is as follows:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source IPv4 address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination IPv4 address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination IPv4 address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: Extended END-POINTS Object Body Format for IPv4
The format of the END-POINTS object body for IPv6 (the Object-Type is
as same as defined in [PCEP]) is as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Source IPv6 address (16 bytes) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Destination IPv6 address (16 bytes) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| ... |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| ... |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| ... |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Destination IPv6 address (16 bytes) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: Extended END-POINTS Object Body Format for IPv6
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The END-POINTS object body has a variable length of multiple of 4
bytes for IPv4 and multiple of 16 bytes for IPv6.
3.4.2 Defining a new END-POINT object type for P2MP
The format for the END-POINT object is the same as what we have
described in the previous section, except that it has a new object
type which is different from the END-POINT object type defined for
the P2P. The new type will be assigned by IANA.
3.5 P2MP LSPs Efficient Presentation
For supporting the optimization of P2MP TE LSPs as specified in
section 2.1.10 of [PCEP-P2MP], we need to pass an existing P2MP LSP
from the PCC to PCE. In this case, we need a new object for
efficiently passing the existing P2MP LSP from PCE to PCC.
There are two options provided here for passing an existing P2MP LSP.
In option 1, we use a separate instance of the ERO which represents
each individual S2L.
In option 2, we treat the P2MP LSP as a normal tree structure which
is represented by tree nodes. Each tree node is a LSR which can be
root node, a branch node or a leaf node.
3.5.1 P2MP LSP Presentation (using S2L)
In this option, the P2MP LSP uses Explicit Route Object which is
specified in the Explicit Route Object section in [PCEP] to present
each S2L in the P2MP.
3.5.2 P2MP LSP Presentation (using BRANCH object)
In this option, the P2MP LSP is presented using the BRANCH object we
define here.
The format of the BRANCH object body for IPv4 is as follows:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Current IPv4 address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Parent IPv4 address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Child IPv4 address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Child IPv4 address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: The New BRANCH Object Body Format for IPv4
The format of the END-POINTS object for IPv6 is as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Current IPv6 address (16 bytes) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Parent IPv6 address (16 bytes) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Child IPv6 address (16 bytes) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| ... |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Child IPv6 address (16 bytes) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: The New BRANCH Object Body Format for IPv6
BRANCH Object-Class is to be assigned by IANA.
BRANCH Object-Type is to be assigned by IANA.
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The BRANCH object is used in a PCReq message to specify a branch for
a P2MP LSP. For the case that the IP address for the parent field is
not set to 0, it means that this is the branch which starts from the
source node of the P2MP LSP to a leaf node of the P2MP LSP. For
the case that the IP address for the parent field is set to 0, it
means that this is the branch which starts from a none-source node
of the P2MP LSP to a leaf node of the P2MP LSP.
The BRANCH object body has a variable length of multiple of 8 bytes
required and the parent is optional (if it is the root node, it is
set to 0) and there should be 1 child node or more children nodes.
The advantage of this option is that in the case of one parent
with many children nodes, it can be efficiently represented.
The disadvantage is that in the existing RSVP-TE extension for P2MP,
the P2MP LSP is presented using the S2L structure already, which
requires the conversion if we use a different coding scheme.
The efficiency of this option can be seen through the following
example of P2MP LSP:
A
|
|
B
/ / / \ \ \
| | | | | |
C D E F G H
Using the option 1 specified in section 3.5.1, we have the following
6 objects to represent the P2MP LSP:
S2L sub-LSP-C: ERO = {A, B, C}, <S2L_SUB_LSP> object-C
S2L sub-LSP-D: SERO= {B, D}, <S2L_SUB_LSP> object-D
S2L sub-LSP-E: SERO= {B, E}, <S2L_SUB_LSP> object-E
S2L sub-LSP-F: SERO= {B, F}, <S2L_SUB_LSP> object-F
S2L sub-LSP-G: SERO= {B, G}, <S2L_SUB_LSP> object-G
S2L sub-LSP-H: SERO= {B, H}, <S2L_SUB_LSP> object-H
Using the option 2 specified in the section 3.5.2, we have the
following 2 branch objects to represents the P2MP LSP:
Branch Object: Current(A), Parent(Null), Child(B)
Branch Object: Current(B), Parent(A), Child(C, D, E, F, G, H )
From the above example, we can see that using the option 1, the B
node is repeated 6 times in the request message and using the
option2, the B node is only repeated 2 times in the request message.
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3.6. UNREACH_DESTINATION object
The PCE path computation request may fail because all or a subset of
the destinations are unreachable.
In such a case, the UNREACH-DESTINATION object allows the PCE to
optionally specify the list of unreachable destinations.
This object can be present in PCRep messages. There can be up to one
such object per RP.
UNREACH_DESTINATION Object-Class is to be assigned by IANA.
UNREACH_DESTINATION Object-Type for IPv4 is to be assigned by IANA
UNREACH_DESTINATION Object-Type for IPv6 is to be assigned by IANA.
The format of the UNREACH_DESTINATION object body for IPv4
(Object-Type=1) is as follows:
0 1 2 3
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination IPv4 address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ... ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination IPv4 address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 7: The New UNREACH-DESTINATION Object Body Format for IPv4
The format of the UNREACH_DESTINATION object body for IPv6
(Object-Type=2) is as follows:
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0 1 2 3
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Destination IPv6 address (16 bytes) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ... ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Destination IPv6 address (16 bytes) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 8: The New UNREACH_DESTINATION Object Body Format for IPv6
3.7 P2MP PCEP Error Object
To indicate errors associated with the P2MP path optimization request,
a new Error-Type (16) and subsequent error-values are defined as
follows for inclusion in the PCEP-ERROR object:
A new Error-Type (16) and subsequent error-values are defined as
follows:
Error-Type=16 and Error-Value=1: if a PCE receives a P2MP path
request and the PCE is not capable of the request due to
insufficient memory, the PCE MUST send a PCErr message with a PCEP
ERROR object (Error-Type=16) and an Error-Value(Error-Value=1). The
corresponding P2MP path computation request MUST be cancelled.
Error-Type=16; Error-Value=2: if a PCE receives a P2MP path requesrt
request and the PCE is not capable of P2MP computation, the PCE
MUST send a PCErr message with a PCEP-ERROR Object (Error-Type=16)
and an Error-Value (Error-Value=2). The corresponding P2MP path
computation request MUST be cancelled.
To indicate an error associated with policy violation, a new error
value "P2MP Path computation not allowed" should be added to an
existing error code for policy violation (Error-Type=5) as defined
in [PCEP].
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Error-Type=5; Error-Value=4: if a PCE receives a P2MP path
computation request which is not compliant with administrative
privileges (i.e., the PCE policy does not support P2MP path
computation), the PCE sends a PCErr message with a PCEP-ERROR Object
(Error-Type=5) and an Error-Value (Error-Value=4). The corresponding
P2MP path computation request MUST be cancelled.
3.8 PCEP NO-PATH Indicator
To communicate the reason(s) for not being able to find P2MP
path computation, the NO-PATH object can be used in the PCRep
message. The format of the NO-PATH object body is as follows:
0 1 2 3
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|C| Flags | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// Optional TLV(s) //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 9: Flags (16 bits). The C flag is defined in [PCEP].
One new bit flags are defined in the NO-PATH-VECTOR TLV carried in
the NO-PATH Object:
0x20: when set, the PCE indicates that there is a reachability
problem with all or a subset of the P2MP destinations. Optionally
the PCE can specify the list of destination(s) that are not
reachable using the new UNREACH_DESTINATION object defined in
section 3.6.
4. IANA Considerations
A number of IANA considerations have been highlighted in the
relevent sections of this document. Further clarifications of these
requests will be made in a future version of this document
5. Manageability Considerations
[PCEP-P2MP] describes various manageability requirements in support
of P2MP path computation when applying PCEP. This section
describes how manageability requirements mentioned in [PCEP-P2MP]
are supported in the context of PCEP extensions specified in this
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document.
Note that [PCEP] describes various manageability considerations in
PCEP, and most of manageability requirements mentioned in [PCEP-P2MP
P2MP] are already covered there.
5.1 Control of Function and Policy
In addition to configuration parameters listed in [PCEP], the
following parameters MAY be required.
o P2MP path computations enabled or disabled
o Advertisement of P2MP path computation capability enabled or
disabled (discovery protocol, capability exchange)
5.2 Information and Data Models
As described in [PCEP-P2MP], MIB objects MUST be supported for PCEP
extensions specified in this document.
5.3 Liveness Detection and Monitoring
There are no additional considerations beyond those expressed in
[PCEP], since [PCEP-P2MP] does not address any additional
requirements.
5.4 Verifying Correct Operation
There are no additional considerations beyond those expressed in
[PCEP], since [PCEP-P2MP] does not address any additional
requirements.
5.5 Requirements on Other Protocols and Functional Components
As described in [PCEP-P2MP], the PCE MUST obtain information about
the P2MP signaling and branching capabilities of each LSR in the
network.
Protocol extensions specified in this document does not provide such
capability. Other mechanisms MUST be present.
5.6 Impact on Network Operation
It is expected that use of PCEP extensions specified in this document
does not have significant impact on network operations.
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6. Security Considerations
As described in [PCEP-P2MP], P2MP path computation requests are more
CPU-intensive and also use more link bandwidth. Therefore, it may
be more vulnerable to denial of service attacks.
[PCEP] describes various mechanisms for denial of service attacks,
and these tools MAY be advantageously used.
7. References
7.1 Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[PCEP] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
Element (PCE) communication Protocol (PCEP) - Version 8",
draft-ietf-pce-pcep, work in progress.
[RFC4875] R. Aggarwal, D. Papadimitriou, S. Yasukawa,"Extensions
to Resource Reservation Protocol - Traffic Engineering
(RSVP-TE)for Point-to-Multipoint TE Label Switching
Paths (LSPs)
[PCEP-P2MP] S. Yasukawa, A. Farrel," PCC-PCE Communication
Requirements for Point to Multipoint Multiprotocol Label
Switching Traffic Engineering (MPLS-TE)"
7.2 Informative References
[RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation
Element (PCE)-Based Architecture", RFC 4655, August 2006.
8. Acknowledgements
The authors would like to thank Adrian Farrel, Young Lee, Dan Tappan,
Autumn Liu and Huaimo Chen, and Eiji Oki for their valuable comments
on this draft.
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9. Authors' Addresses
Daniel King
Aria Networks Ltd.
44-45 Market Place
Chippenham, SN153HU UK
Email: daniel.king@aria-networks.com
Tomonori Takeda
NTT Network Service Systems Laboratories, NTT Corporation
3-9-11, Midori-Cho
Musashino-Shi, Tokyo 180-8585 Japan
Email : takeda.tomonori@lab.ntt.co.jp
Fabien Verhaeghe
Marben Products
176 avenue Jean Jaures
92800 Puteaux
France
Email: fabien.verhaeghe@marben-products.com
Quintin Zhao
Huawei Technology
125 Nagog Technology Park
Acton, MA 01719
USA
Email: qzhao@huawei.com
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