PCE Working Group D. Dhody
Internet-Draft U. Palle
Intended status: Experimental V. Kondreddy
Expires: April 14, 2013 Huawei Technologies India Pvt
Ltd
October 11, 2012
Supporting explicit inclusion or exclusion of abstract nodes for a
subset of P2MP destinations in Path Computation Element Communication
Protocol (PCEP).
draft-dhody-pce-pcep-p2mp-per-destination-03
Abstract
The ability to determine paths of point-to-multipoint (P2MP)
Multiprotocol Label Switching (MPLS) and Generalized MPLS (GMPLS)
Traffic Engineering Label Switched Paths (TE LSPs) is one the key
requirements for Path Computation Element (PCE). [RFC6006] and
[PCE-P2MP-PROCEDURES] describes these mechanisms for intra and inter
domain path computation via PCE.
This document describes the need for explicitly specifying abstract
nodes for inclusion or exclusion for a subset of destinations during
the Point to Multipoint (P2MP) path computation via PCE. Further an
extension to the PCE communication Protocol (PCEP) for P2MP is
suggested to support this.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on April 14, 2013.
Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
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document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.1. Domain Sequence Tree in Inter Domain P2MP Path
Computation . . . . . . . . . . . . . . . . . . . . . . . 4
3.2. Explicit inclusion or exclusion of abstract nodes . . . . 6
4. Detailed Description . . . . . . . . . . . . . . . . . . . . . 7
4.1. Objective . . . . . . . . . . . . . . . . . . . . . . . . 7
4.2. Request Message Format . . . . . . . . . . . . . . . . . . 7
4.3. Backward Compatibility . . . . . . . . . . . . . . . . . . 8
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
6. Security Considerations . . . . . . . . . . . . . . . . . . . 9
7. Manageability Considerations . . . . . . . . . . . . . . . . . 9
7.1. Control of Function and Policy . . . . . . . . . . . . . . 9
7.2. Information and Data Models . . . . . . . . . . . . . . . 9
7.3. Liveness Detection and Monitoring . . . . . . . . . . . . 9
7.4. Verify Correct Operations . . . . . . . . . . . . . . . . 9
7.5. Requirements On Other Protocols . . . . . . . . . . . . . 9
7.6. Impact On Network Operations . . . . . . . . . . . . . . . 10
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 10
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
9.1. Normative References . . . . . . . . . . . . . . . . . . . 10
9.2. Informative References . . . . . . . . . . . . . . . . . . 10
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1. Introduction
The Path Computation Element (PCE) architecture is defined in
[RFC4655]. [RFC5862] lay out the requirements for Path Computation
Client (PCC) and Path Computation Element (PCE) to support Point-to-
Multipoint (P2MP) path computation. [RFC6006] describe an extension
to PCEP to compute optimal constrained intra-domain (G)MPLS P2MP TE
LSPs. [PCE-P2MP-PROCEDURES] describes the mechanism for inter-domain
P2MP path computation.
[PCE-P2MP-PROCEDURES] describes the core-tree procedure for computing
inter-domain P2MP tree. It assumes that, due to deployment and
commercial limitations, the sequence of domains for a path (the path
domain tree) will be known in advance. For a group of destination
which belong to a destination domain, the domain-sequence needs to be
encoded seperately as described in [DOMAIN-SEQ]. The mechanism of
explicitly specifying abstract nodes for inclusion or exclusion for a
subset of destinations can be used for this purpose, where abstract
nodes are domains.
[RFC6006] describe a PCE-based path computation procedure to compute
optimal constrained (G)MPLS P2MP TE LSPs. It describes mechanism to
specify branch nodes that can or cannot be used via Branch Node
Capability (BNC) object (which only supports IPv4 and IPv6 prefix
sub-objects). This document adds the capability to explicitly
specify any abstract nodes for inclusion or exclusion for a subset of
destinations.
1.1. 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 [RFC2119].
2. Terminology
The following terminology is used in this document.
IRO: Include Route Object.
PCC: Path Computation Client: any client application requesting a
path computation to be performed by a 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.
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P2MP: Point-to-Multipoint
P2P: Point-to-Point
RRO: Record Route Object
RSVP: Resource Reservation Protocol
TE LSP: Traffic Engineering Label Switched Path.
XRO: Exclude Route Object.
3. Motivation
3.1. Domain Sequence Tree in Inter Domain P2MP Path Computation
[PCE-P2MP-PROCEDURES] describes the core-tree procedure for inter-
domain path computation. The procedure assumes that the sequence of
domains for a path (the path domain tree) will be known in advance
due to deployment and commercial limitations (e.g., inter-AS peering
agreements).
In the Figure 1 below, D1 is the root domain; D5 and D6 are the
destination domains. The ingress is A in domain D1; egresses are X,
Y in Domain D6 and Z in Domain D5.
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|
| +-------------+ +----------------+
| |D 3 | |D 6 |
| | +--+| | +--+ |
| | |J || | |X | |
| | +--+ +--+| | +--+ +--+ |
| | |F | | | |U | |
| | *--+ | | +--+ |
| | / +--+ | | +--+ |
| |/ |K | | | |Y | |
| / +--+ | | +--+ +--+ |
| /| +--+ |+--------------+| |V | |
|/ | |G | ++-+ +-++ +--+ |
+-------------+/ | +--+ ||N| |S|| |
| /| | ++-+ +-++ |
| +--*|| +-------------+| |+----------------+
| |D ||| | +--+ |
| +--+|| | |P | |
| +--+ || | +--+ |
| |B | || | |
| +--+ || | |
| || | +--+ |
|+--+ || | |Q | |
||A | || | +--+ |
|+--+ || | |
| || | +--+ |
| +--+ || +------------+ | |R | |+----------------+
| |C | || |D 2 +-++ +--+ +-++ D 5 |
| +--+ || | |O|| |T|| |
| || | +-++ +-++ |
| +--+|| | +--+ | | D 4 || +--+ |
| |E ||| | |L | | +--------------+| |W | |
| +--*|| | +--+ | | +--+ |
| \| | | | +--+ |
|D 1 |\ | +--+ | | |Z | |
+-------------+|\ | |H | | | +--+ |
| \| +--+ +--+ | |
| \ |M | | |
| |\ +--+ | |
| | \ +--+ | | |
| | \|I | | | |
| | *--+ | | |
| | | | |
| +------------+ +----------------+
|
|
As 100 | AS 200
|
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Figure 1: Domain Topology Example
In the Figure 2 below, the P2MP tree spans 5 domains. Destination in
D6 (X & Y) would use the domain-sequence: D1-D3-D4-D6; and
destination in D5 (Z) would use the domain-sequence: D1-D3-D4-D5.
D3 D6
/ \ /
D1 D4
\
D5
Figure 2: Domain Sequence Tree
Since destinations in different destination domain will have
different domain sequence within the domain tree, it requires
following encoding-
o Destination X and Y: D1-D3-D4-D6
o Destination Z : D1-D3-D4-D5
An extension in P2MP Path Compuatation request is needed to support
this. (Refer Section 4.2)
The abstract nodes MAY include (but not limited to) domain subobjects
AS number and IGP Area as described in [DOMAIN-SEQ].
3.2. Explicit inclusion or exclusion of abstract nodes
[RFC6006] describes four possible types of leaves in a P2MP request
encoded in P2MP END-POINTS object.
o New leaves to add
o Old leaves to remove
o Old leaves whose path can be modified/reoptimized
o Old leaves whose path must be left unchanged
Currently [RFC6006] only allows a list of nodes that can be used as
branch nodes or a list of nodes that cannot be used as branch nodes
by using the Branch Node Capability (BNC) Object, which applies to
all leaves (old and new) in the P2MP tree.
For an existing P2MP tree which may already have a branch node
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through which most of the leaves are connected, but when adding a set
of new leaves, administrator may want to exclude that branch node (as
it may soon be overloaded) and would like to balance the final P2MP
tree. This could be done explicitly by excluding a particular branch
node or including a different branch node only for a set of new
leaves encoded in the one P2MP END-POINTS object.
Administrator at the source can exert stronger control by providing
explicit inclusion or exclusion of any abstract nodes (not limited to
branch nodes) for a group (subset) of destinations.
4. Detailed Description
4.1. Objective
[RFC6006] defines Request Message Format and Objects, along with
<end-point-rro-pair-list>. This section introduce the use of <IRO>
and <XRO> which are added to the <end-point-rro-pair-list>.
To allow abstract nodes to be explicitly included or excluded for a
subset of destinations (encoded in one <END-POINTS> object), changes
are made as shown below.
The abstract node (encoded as subobject in <IRO> and <XRO>) MAY be an
absolute hop, IP-Prefix, Autonomous system or IGP Area. The
subobjects are described in [RFC3209], [RFC3477], [RFC4874] and
[DOMAIN-SEQ].
Note that one P2MP Path request can have multiple <END-POINTS>
objects and each P2MP <END-POINTS> object may have multiple
destinations, the <IRO> and <XRO> is applied for all destinations in
one such P2MP <END-POINTS> object.
4.2. Request Message Format
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The format of PCReq message is modified as follows:
<PCReq Message>::= <Common Header>
<request>
where:
<request>::= <RP>
<end-point-iro-xro-rro-pair-list>
[<OF>]
[<LSPA>]
[<BANDWIDTH>]
[<metric-list>]
[<IRO>]
[<LOAD-BALANCING>]
where:
<end-point-iro-xro-rro-pair-list>::=
<END-POINTS>
[<IRO>]
[<XRO>]
[<RRO-List>][<BANDWIDTH>]
[<end-point-iro-xro-rro-pair-list>]
<RRO-List>::=<RRO>[<BANDWIDTH>][<RRO-List>]
<metric-list>::=<METRIC>[<metric-list>]
From [RFC6006] usage of <end-point-rro-pair-list> is changed to <end-
point-iro-xro-rro-pair-list> in this document.
[RFC6006] describes Branch Node Capability (BNC) Object which is
different from the use of <IRO> and <XRO> to specify inclusion/
exclusion of abstract nodes for a subset of destinations as described
here.
4.3. Backward Compatibility
A legacy implementation that does not support explicit inclusion or
exclusion of abstract nodes for a subset of P2MP destinations will
act according to the procedures set out in [RFC5440], that is it will
find the P2MP Path Request message out of order with respect to the
format specified in [RFC6006].
5. IANA Considerations
There are no new IANA allocation in this document.
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6. Security Considerations
PCEP security mechanisms as described in [RFC5440], [RFC6006] and
[PCE-P2MP-PROCEDURES] are applicable for this document.
The new explicit inclusion or exclusion of abstract nodes for a
subset of P2MP destination defined in this document allow finer and
more specific control of the path computed by a PCE. Such control
increases the risk if a PCEP message is intercepted, modified, or
spoofed because it allows the attacker to exert control over the path
that the PCE will compute or to make the path computation impossible.
Therefore, the security techniques described in [RFC5440], [RFC6006]
and [PCE-P2MP-PROCEDURES] are considered more important.
Note, however, that the route exclusion mechanisms also provide the
operator with the ability to route around vulnerable parts of the
network and may be used to increase overall network security.
7. Manageability Considerations
7.1. Control of Function and Policy
Mechanisms defined in this document do not add any new control
function/policy requirements in addition to those already listed in
[RFC6006].
7.2. Information and Data Models
Mechanisms defined in this document do not imply any new MIB
requirements in addition to those already listed in [PCE-P2MP-MIB].
7.3. Liveness Detection and Monitoring
Mechanisms defined in this document do not imply any new liveness
detection and monitoring requirements in addition to those already
listed in [RFC6006].
7.4. Verify Correct Operations
Mechanisms defined in this document do not imply any new operation
verification requirements in addition to those already listed in
[RFC6006].
7.5. Requirements On Other Protocols
Mechanisms defined in this document do not imply any requirements on
other protocols in addition to those already listed in [RFC6006].
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7.6. Impact On Network Operations
Mechanisms defined in this document do not have any impact on network
operations in addition to those already listed in [RFC6006].
8. Acknowledgments
We would like to thank Pradeep Shastry, Suresh babu, Quintin Zhao,
Daniel King and Chen Huaimo for their useful comments and
suggestions.
9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to
Indicate Requirement Levels", BCP 14,
RFC 2119, March 1997.
9.2. Informative References
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T.,
Srinivasan, V., and G. Swallow, "RSVP-TE:
Extensions to RSVP for LSP Tunnels", RFC 3209,
December 2001.
[RFC3477] Kompella, K. and Y. Rekhter, "Signalling
Unnumbered Links in Resource ReSerVation
Protocol - Traffic Engineering (RSVP-TE)",
RFC 3477, January 2003.
[RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path
Computation Element (PCE)-Based Architecture",
RFC 4655, August 2006.
[RFC4874] Lee, CY., Farrel, A., and S. De Cnodder,
"Exclude Routes - Extension to Resource
ReserVation Protocol-Traffic Engineering
(RSVP-TE)", RFC 4874, April 2007.
[RFC5440] Vasseur, JP. and JL. Le Roux, "Path
Computation Element (PCE) Communication
Protocol (PCEP)", RFC 5440, March 2009.
[RFC5862] Yasukawa, S. and A. Farrel, "Path Computation
Clients (PCC) - Path Computation Element (PCE)
Requirements for Point-to-Multipoint MPLS-TE",
RFC 5862, June 2010.
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[RFC6006] Zhao, Q., King, D., Verhaeghe, F., Takeda, T.,
Ali, Z., and J. Meuric, "Extensions to the
Path Computation Element Communication
Protocol (PCEP) for Point-to-Multipoint
Traffic Engineering Label Switched Paths",
RFC 6006, September 2010.
[PCE-P2MP-PROCEDURES] Zhao, Q., Dhody, D., Ali, Z., Saad,, T.,
Sivabalan,, S., and R. Casellas, "PCE-based
Computation Procedure To Compute Shortest
Constrained P2MP Inter-domain Traffic
Engineering Label Switched Paths (draft-ietf-
pce-pcep-inter-domain-p2mp-procedures-02)",
May 2012.
[PCE-P2MP-MIB] Zhao, Q., Dhody, D., Palle, U., and D. King,
"Management Information Base for the PCE
Communications Protocol (PCEP) When Requesting
Point-to-Multipoint Services
(draft-zhao-pce-pcep-p2mp-mib-05)",
August 2012.
[DOMAIN-SEQ] Dhody, D., Palle, U., and R. Casellas,
"Standard Representation Of Domain Sequence
(draft-ietf-pce-pcep-domain-sequence-01)",
July 2012.
Authors' Addresses
Dhruv Dhody
Huawei Technologies India Pvt Ltd
Leela Palace
Bangalore, Karnataka 560008
INDIA
EMail: dhruv.dhody@huawei.com
Udayasree Palle
Huawei Technologies India Pvt Ltd
Leela Palace
Bangalore, Karnataka 560008
INDIA
EMail: udayasree.palle@huawei.com
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Venugopal Reddy Kondreddy
Huawei Technologies India Pvt Ltd
Leela Palace
Bangalore, Karnataka 560008
INDIA
EMail: venugopalreddyk@huawei.com
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