draft-ietf-mpls-p2mp-requirement-03.txt   draft-ietf-mpls-p2mp-requirement-04.txt 
Network Working Group Seisho Yasukawa (NTT) Network Working Group Seisho Yasukawa (NTT)
Internet Draft Editor Internet Draft Editor
Category: Informational Category: Informational
Expiration Date: December 2004 July 2004 Expiration Date: February 2005 September 2004
Requirements for Point to Multipoint Traffic Engineered MPLS LSPs Requirements for Point to Multipoint Traffic Engineered MPLS LSPs
<draft-ietf-mpls-p2mp-requirement-03.txt> <draft-ietf-mpls-p2mp-requirement-04.txt>
Status of this Memo Status of this Memo
By submitting this Internet-Draft, I certify that any applicable By submitting this Internet-Draft, I certify that any applicable
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or will be disclosed, and any of which I become aware will be or will be disclosed, and any of which I become aware will be
disclosed, in accordance with RFC 3668. disclosed, in accordance with RFC 3668.
This document is an Internet-Draft and is in full conformance with
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Abstract Abstract
This document presents a set of requirements for This document presents a set of requirements for
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This document presents a set of requirements for This document presents a set of requirements for
Point-to-Multipoint(P2MP) Traffic Engineered (TE) Multiprotocol Point-to-Multipoint(P2MP) Traffic Engineered (TE) Multiprotocol
Label Switching (MPLS) Label Switched Paths (LSPs). It specifies Label Switching (MPLS) Label Switched Paths (LSPs). It specifies
functional requirements for solutions in order to deliver P2MP functional requirements for solutions in order to deliver P2MP
applications over a MPLS TE infrastructure. It is intended that applications over a MPLS TE infrastructure. It is intended that
solutions that specify procedures for P2MP TE LSP setup satisfy solutions that specify procedures for P2MP TE LSP setup satisfy
these requirements. these requirements.
There is no intent to either specify solution specific details in There is no intent to either specify solution specific details in
this document or application specific requirements. this document or application specific requirements.
It is intended that the requirements presented in this document are It is intended that the requirements presented in this document are
not limited to the requirements of packet switched networks, but not limited to the requirements of packet switched networks, but also
also encompass the requirements of L2SC, TDM, lambda and port encompass the requirements of L2SC, TDM, lambda and port switching
switching networks managed by Generalized MPLS (GMPLS) protocols. networks managed by Generalized MPLS (GMPLS) protocols. Protocol
Protocol solutions developed to meet the requirements set out in solutions developed to meet the requirements set out in this document
this document must attempt to be equally applicable to MPLS and must attempt to be equally applicable to MPLS and GMPLS.
GMPLS.
Table of Contents Table of Contents
1. Introduction ................................................. 04
2. Definitions .................................................. 05 1. Introduction .................................................. 04
2.1 Acronyms ................................................. 05 2. Definitions ................................................... 07
2.2 Terminology .............................................. 06 2.1 Acronyms .................................................. 07
2.3 Conventions .............................................. 07 2.2 Terminology ............................................... 07
3. Problem Statement ............................................ 07 2.3 Conventions ............................................... 09
3.1 Motivation ............................................... 07 3. Problem Statement ............................................. 09
3.2 Requirements Overview .................................... 08 3.1 Motivation ................................................ 09
4. Examples of candidate applications that may require 3.2. Requirements Overview .................................... 10
P2MP TE LSP ...................................................10 4. Examples of candidate applications that may require P2MP TE LSP 12
4.1 P2MP TE LSP for IP multicast data ....................... 10 4.1 P2MP TE LSP for IP multicast data ......................... 13
4.2 P2MP TE backbone network for IP multicast network ....... 11 4.2 P2MP TE backbone network for IP multicast network ........ 13
4.3 Layer 2 Multicast Over MPLS ............................. 13 4.3 Layer 2 Multicast Over MPLS .............................. 14
4.4 VPN multicast network ................................... 13 4.4 VPN multicast network ..................................... 15
4.5 GMPLS Networks .......................................... 14 4.5 GMPLS Networks ............................................ 16
5. Detailed requirements for P2MP TE extensions ................. 15 5. Detailed requirements for P2MP TE extensions .................. 16
5.1 P2MP LSP tunnels ........................................ 15 5.1 P2MP LSP tunnels .......................................... 16
5.2 P2MP explicit routing ................................... 15 5.2 P2MP explicit routing ..................................... 17
5.3 Explicit Path Loose Hops and Widely Scoped Abstract Nodes.17 5.3 Explicit Path Loose Hops and Widely Scoped Abstract Nodes . 18
5.4 P2MP TE LSP establishment, teardown, and modification 5.4 P2MP TE LSP establishment, teardown, and modification mecha 19
mechanisms .............................................. 17 5.5 Fragmentation ............................................. 19
5.5 Fragmentation ........................................... 18 5.6 Failure Reporting and Error Recovery ...................... 20
5.6 Failure Reporting and Error Recovery .................... 18 5.7 Record route of P2MP TE LSP tunnels ....................... 21
5.7 Record route of P2MP TE LSP tunnels ..................... 19 5.8 Call Admission Control (CAC) and QoS Control mechanism .... 21
5.8 Call Admission Control (CAC) and QoS Control mechanism .. 19 5.9 Variation of LSP Parameters ............................... 22
5.9 Reoptimization of P2MP TE LSP ........................... 20 5.10 Re-optimization of P2MP TE LSPs .......................... 22
5.10 IPv4/IPv6 support ....................................... 20 5.11 Tree Remerge ............................................. 23
5.11 P2MP MPLS Label ......................................... 21 5.12 Data Duplication ......................................... 24
5.12 Routing advertisement of P2MP capability ................ 21 5.13 IPv4/IPv6 support ........................................ 24
5.13 Multi-Area/AS LSP ....................................... 21 5.14 P2MP MPLS Label .......................................... 24
5.14 P2MP MPLS OAM ........................................... 21 5.15 Routing advertisement of P2MP capability ................. 24
5.15 Scalability ............................................. 22 5.16 Multi-Area/AS LSP ........................................ 25
5.16 Backwards Compatibility ................................. 22 5.17 Multi-access LANs ........................................ 25
5.17 GMPLS ................................................... 23 5.18 P2MP MPLS OAM ............................................ 25
5.18 Requirements for Hierarchical P2MP TE LSPs .............. 24 5.19 Scalability .............................................. 26
5.19 P2MP Crankback routing .................................. 24 5.20 Backwards Compatibility .................................. 28
6. Security Considerations ...................................... 24 5.21 GMPLS .................................................... 28
7. Acknowledgements ............................................. 25 5.22 Requirements for Hierarchical P2MP TE LSPs ............... 29
8. References ................................................... 25 5.23 P2MP Crankback routing ................................... 29
8.1 Normative References ..................................... 25 6. Security Considerations ....................................... 29
8.2 Informational References ................................. 26 7. Acknowledgements .............................................. 30
9. Editor's Address ............................................. 27 8. References .................................................... 30
10. Authors' Addresses .......................................... 27 8.1 Normative References ...................................... 30
11. Intellectual Property Consideration ......................... 29 8.2 Informational References .................................. 31
11.1 IPR Disclosure Acknowledgement .......................... 29 9. Editor's Address .............................................. 32
12. Full Copyright Statement .................................... 29 10. Authors' Addresses ........................................... 32
11. Intellectual Property Consideration .......................... 34
12. Full Copyright Statement ..................................... 34
1. Introduction 1. Introduction
Existing MPLS Traffic Engineering (MPLS-TE) allows for strict QoS Existing MPLS Traffic Engineering (MPLS-TE) allows for strict QoS
guarantees, resources optimization, and fast failure recovery, but guarantees, resources optimization, and fast failure recovery, but is
is limited to P2P applications. There are P2MP applications like limited to P2P applications. There are P2MP applications like Content
Content Distribution, Interactive Multimedia and VPN multicast that Distribution, Interactive Multimedia and VPN multicast that would
would also benefit from these TE capabilities. This clearly also benefit from these TE capabilities. This clearly motivates
motivates enhancements of the base MPLS-TE tool box in order to enhancements of the base MPLS-TE tool box in order to support P2MP
support P2MP applications. applications.
[RFC2702] specifies requirements for traffic engineering over MPLS.
It describes traffic engineering in some detail, and those
definitions and objectives are equally applicable to traffic
engineering in a point-to-multipoint service environment. They are
not repeated here, but it is assumed that the reader is fully
familiar with them.
[RFC2702] also explains how MPLS is particularly suited to traffic
engineering, and presents the following eight reason.
1. Explicit label switched paths which are not constrained by
the destination based forwarding paradigm can be easily created
through manual administrative action or through automated
action by the underlying protocols.
2. LSPs can potentially be efficiently maintained.
3. Traffic trunks can be instantiated and mapped onto LSPs.
4. A set of attributes can be associated with traffic trunks
which modulate their behavioral characteristics.
5. A set of attributes can be associated with resources which
constrain the placement of LSPs and traffic trunks across
them.
6. MPLS allows for both traffic aggregation and disaggregation
whereas classical destination only based IP forwarding
permits only aggregation.
7. It is relatively easy to integrate a "constraint-based routing"
framework with MPLS.
8. A good implementation of MPLS can offer significantly lower
overhead than competing alternatives for Traffic Engineering.
These points are equally applicable to point-to-multipoint
traffic engineering. Points 1. and 7. are particularly important.
That is, the traffic flow for a point-to-multipoint LSP is not
constrained to the path or paths that it would follow during
multicast routing or shortest path destination-based routing, but
can be explicitly controlled through manual or automated action.
Further, the explicit paths that are used may be computed using
algorithms based on a variety of constraints to produce all manner of
tree shapes. For example, an explicit path may be cost-based
[STEINER], shortest path, QoS-based, or may use some fair-cost QoS
algorithm. Such computations are potentially bound to be more complex
and varied than anything available in the multicast forwarding
paradigm.
[RFC2702] also describes the functional capabilities required to
fully support Traffic Engineering over MPLS in large networks.
1. A set of attributes associated with traffic trunks which
collectively specify their behavioral characteristics.
2. A set of attributes associated with resources which constrain
the placement of traffic trunks through them. These can also be
viewed as topology attribute constraints.
3. A "constraint-based routing" framework which is used to select
paths for traffic trunks subject to constraints imposed by
items 1) and 2) above. The constraint-based routing framework
does not have to be part of MPLS. However, the two need to be
tightly integrated together.
These basic requirements also should be supported by
point-to-multipoint traffic engineering.
This document presents a set of requirements for This document presents a set of requirements for
Point-to-Multipoint(P2MP) Traffic Engineering (TE) extensions to Point-to-Multipoint(P2MP) Traffic Engineering (TE) extensions to
Multiprotocol Label Switching (MPLS). It specifies functional Multiprotocol Label Switching (MPLS). It specifies functional
requirements for solutions to deliver P2MP TE LSPs. For the sake of requirements for solutions to deliver P2MP TE LSPs. For the sake of
illustration, RSVP-TE [RFC3209] is one possible candidate to provide illustration, RSVP-TE [RFC3209] is one possible candidate to provide
such a solution so as to deliver P2MP TE LSPs. such a solution so as to deliver P2MP TE LSPs.
It is intended that solutions that specify procedures for It is intended that solutions that specify procedures for P2MP TE LSP
P2MP TE LSP setup satisfy these requirements. There is no intent to setup satisfy these requirements. There is no intent to either
either specify solution specific details in this document or specify solution specific details in this document or application
application specific requirements. specific requirements.
It is intended that the requirements presented in this document are It is intended that the requirements presented in this document are
not limited to the requirements of packet switched networks, but not limited to the requirements of packet switched networks, but
also encompass the requirements of TDM, lambda and port switching also encompass the requirements of TDM, lambda and port switching
networks managed by Generalized MPLS (GMPLS) protocols. Protocol networks managed by Generalized MPLS (GMPLS) protocols. Protocol
solutions developed to meet the requirements set out in this solutions developed to meet the requirements set out in this
document must attempt to be equally applicable to MPLS and GMPLS. document must attempt to be equally applicable to MPLS and GMPLS.
Content Distribution (CD), Interactive multi-media (IMM), and VPN Content Distribution (CD), Interactive multi-media (IMM), and VPN
multicast are applications that are best supported with multicast multicast are applications that are best supported with multicast
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traffic cannot currently benefit from P2P TE LSPs. Hence, Call traffic cannot currently benefit from P2P TE LSPs. Hence, Call
Admission Control for P2P TE LSP cannot take into account the Admission Control for P2P TE LSP cannot take into account the
bandwidth used for multicast traffic. P2MP TE will allow the bandwidth used for multicast traffic. P2MP TE will allow the
bandwidth used by both the unicast and multicast traffics to be bandwidth used by both the unicast and multicast traffics to be
counted by means of CAC. counted by means of CAC.
This document is organized as follows: Section 2 provides a set of This document is organized as follows: Section 2 provides a set of
definitions used throughout the document. The problem statement is definitions used throughout the document. The problem statement is
then discussed in Section 3. for the sake of illustration, this then discussed in Section 3. for the sake of illustration, this
document lists various applications that could make use P2MP TE document lists various applications that could make use P2MP TE
LSP. Detailed application-specific requirements as far as LSP. Detailed application-specific requirements as far as P2MP TE LSP
P2MP TE LSP is concerned are out of the scope of this document. is concerned are out of the scope of this document.
Detailed requirements for the support of applications that require Detailed requirements for the support of applications that require
P2MP MPLS TE LSPs are described in section 4. P2MP MPLS TE LSPs are described in section 4.
The requirement for Multipoint-to-Point and Multipoint-to-Multipoint The requirement for Multipoint-to-Point and Multipoint-to-Multipoint
TE LSPs are outside of the scope of this document. TE LSPs are outside of the scope of this document.
2. Definitions 2. Definitions
2.1 Acronyms 2.1 Acronyms
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A traffic engineered label switched path that has one unique A traffic engineered label switched path that has one unique
ingress LSR (also referred to as the root) and one or more ingress LSR (also referred to as the root) and one or more
egress LSRs (also referred to as the leaf). egress LSRs (also referred to as the leaf).
P2MP tree: P2MP tree:
The ordered set of LSRs and links that comprise the path of a The ordered set of LSRs and links that comprise the path of a
P2MP TE LSP from its ingress LSR to all of its egress LSRs. P2MP TE LSP from its ingress LSR to all of its egress LSRs.
sub-P2MP tree:
A sub-P2MP tree is a portion of a P2MP tree starting at
a particular LSR that is a member of the P2MP tree and includes
ALL downstream LSRs that are also members of the P2MP tree.
P2P sub-LSP:
The path from the ingress LSR to a particular egress LSR.
ingress LSR: ingress LSR:
The LSR that is responsible for initiating the signaling The LSR that is responsible for initiating the signaling
messages that set up the P2MP TE LSP. messages that set up the P2MP TE LSP.
egress LSR: egress LSR:
One of potentially many destinations of the P2MP TE LSP. One of potentially many destinations of the P2MP TE LSP.
Egress LSRs may also be referred to as leaf nodes or leaves. Egress LSRs may also be referred to as leaf nodes or leaves.
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An LSR that is already a member of the P2MP tree and is in An LSR that is already a member of the P2MP tree and is in
process of signaling a new sub-P2MP tree. process of signaling a new sub-P2MP tree.
prune LSR: prune LSR:
An LSR that is a member of the P2MP tree and is in An LSR that is a member of the P2MP tree and is in
process of tearing down an existing sub-P2MP tree. process of tearing down an existing sub-P2MP tree.
P2MP-ID (Pid): P2MP-ID (Pid):
The ID that can be used to map a set of P2P sub-LSPs to a A unique identifier of a P2MP TE LSP, that is constant for the
particular P2MP LSP. whole LSP regardless of the number of branches and/or leaves.
2.2.1 Terminology for Partial LSPs
It is convenient to sub-divide P2MP trees for functional and
representational reasons. a tree may be divided in two dimensions:
- A division may be made along the length of the tree. For example,
the tree may be split into two components each running from the
ingress LSR to a discrete set of egress LSRs
- A tree may be divided at a branch LSR (or any transit LSR) to
produce a component of the tree that runs from the branch (or
transit) LSR to all downsetram egress LSRs.
These two methods of splitting the P2MP tree can be combined, so it
is useful to introduce some terminology to allow the partitioned
trees to be clearly described.
Use the following designations:
Source (ingress) LSR - S
Leaf (egress) LSR - L
Branch LSR - B
Transit LSR - X
Define three terms:
Sub-LSP
A component of the P2MP LSP that runs from one LSR to another
without (or ignoring) any branches.
Sub-tree
A component of the P2MP LSP that runs from one LSR to more than
one other LSR by branching.
Tree
A component of the P2MP LSP that runs from one LSR to all
downstream LSRs.
Using these new concepts we can define any combination or split of
the P2MP tree. For example:
S2L sub-LSP
The path from the source to one specific leaf.
S2L sub-tree
The path from the source to a set of leaves.
B2L tree
The path from a branch LSR to all downstream leaves.
X2X sub-LSP
A component of the P2MP LSP that is a simple path with
no branches.
2.3 Conventions 2.3 Conventions
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 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in
this document are to be interpreted as described in [RFC2119]. this document are to be interpreted as described in [RFC2119].
3. Problem Statement 3. Problem Statement
3.1 Motivation 3.1 Motivation
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multicast are applications that are best supported with multicast multicast are applications that are best supported with multicast
capabilities. capabilities.
IP Multicast provides P2MP communication. However, there are no IP Multicast provides P2MP communication. However, there are no
Traffic Engineering (TE) capabilities or QoS guarantees with Traffic Engineering (TE) capabilities or QoS guarantees with
existing IP multicast protocols. Note that Diff-serv existing IP multicast protocols. Note that Diff-serv
(see [RFC2475],[RFC2597] and [RFC3246]) combined with IP multicast (see [RFC2475],[RFC2597] and [RFC3246]) combined with IP multicast
routing may not be sufficient for P2MP applications for many of the routing may not be sufficient for P2MP applications for many of the
same reasons that it is not sufficient for unicast applications. same reasons that it is not sufficient for unicast applications.
Note also that multicast trees provided by existing IP multicast Note also that multicast trees provided by existing IP multicast
routing protocols are not optimal from a bandwidth usage routing protocols are not optimal from a bandwidth usage perspective,
perspective, which may lead to significant bandwidth wasting. which may lead to significant bandwidth wasting.
TE and Constraint Based Routing, including Call Admission TE and Constraint Based Routing, including Call Admission
Control(CAC), explicit source routing and bandwidth reservation, is Control(CAC), explicit source routing and bandwidth reservation, is
required to enable efficient resource usage and strict QoS required to enable efficient resource usage and strict QoS
guarantees. guarantees.
Furthermore there are no existing P2MP mechanisms for carrying layer Furthermore there are no existing P2MP mechanisms for carrying layer
2 or SONET/SDH multicast traffic over MPLS. TE capabilities are 2 or SONET/SDH multicast traffic over MPLS. TE capabilities are
desirable for both these applications; the related set of application desirable for both these applications; the related set of application
requirements are outside of the scope of this document and might requirements are outside of the scope of this document and might
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Hence, to provide MPLS TE [RFC2702] for a P2MP application in an Hence, to provide MPLS TE [RFC2702] for a P2MP application in an
efficient manner (that is, with scalable impact on signaling and efficient manner (that is, with scalable impact on signaling and
protocol state) in a large scale environment, P2MP TE mechanisms protocol state) in a large scale environment, P2MP TE mechanisms
are required. Existing MPLS P2P TE mechanisms have to be enhanced are required. Existing MPLS P2P TE mechanisms have to be enhanced
to support P2MP TE LSP. to support P2MP TE LSP.
3.2. Requirements Overview 3.2. Requirements Overview
This document states basic requirements for the setup of P2MP TE This document states basic requirements for the setup of P2MP TE
LSPs and a solution SHOULD satisfy them without requiring that a LSPs and a solution SHOULD satisfy them without requiring that a
multicast routing protocol is used, although such a protocol multicast routing protocol is used, although such a protocol MUST NOT
MUST NOT be prohibited. It is desirable to maximize the re-use of be prohibited. The mechanism used to construct the TED from which
existing MPLS TE techniques and protocols. Note that the use of the paths of P2MP trees are computed is out of scope of this document
MPLS forwarding to carry the multicast traffic may also be useful although it is desirable to maximize the re-use of existing MPLS TE
in the context of some network designs where it might be desired to techniques and protocols. Note that the use of MPLS forwarding to
avoid running some multicast routing protocol like PIM [PIM-SM] or carry the multicast traffic may also be useful in the context of some
BGP (which might be required for the use of PIM). network designs where it might be desired to avoid running some
multicast routing protocol like PIM [PIM-SM] or BGP (which might be
required for the use of PIM).
A P2MP TE LSP path will be computed taking into account various A P2MP TE LSP path will be computed taking into account various
constraints such as bandwidth, affinities, required level of constraints such as bandwidth, affinities, required level of
protection and so on. The solution MUST allow for the computation protection and so on. The solution MUST allow for the computation
of P2MP TE LSP paths satisfying constraints with the objective of of P2MP TE LSP paths satisfying constraints with the objective of
supporting various optimization criteria such as delays, bandwidth supporting various optimization criteria such as delays, bandwidth
consumption in the network, or any other combinations. consumption in the network, or any other combinations.
This document does not restrict the choice of signaling protocol This document does not restrict the choice of signaling protocol
used to set up a P2MP TE LSP, but it should be noted that [RFC3468] used to set up a P2MP TE LSP, but it should be noted that [RFC3468]
states states
... the consensus reached by the Multiprotocol Label Switching ... the consensus reached by the Multiprotocol Label Switching
(MPLS) Working Group within the IETF to focus its (MPLS) Working Group within the IETF to focus its efforts on
efforts on "Resource Reservation Protocol (RSVP)-TE: Extensions to "Resource Reservation Protocol (RSVP)-TE: Extensions to RSVP for
RSVP for Label-Switched Paths (LSP) Tunnels" (RFC 3209) as the MPLS Label-Switched Paths (LSP) Tunnels" (RFC 3209) as the MPLS signaling
signaling protocol for traffic engineering applications... protocol for traffic engineering applications...
The P2MP TE LSP setup mechanism MUST include the ability to The P2MP TE LSP setup mechanism MUST include the ability to
add/remove egress LSRs to/from an existing P2MP TE LSP and MUST allow add/remove egress LSRs to/from an existing P2MP TE LSP and MUST
for the support of all the TE LSP management procedures already allow for the support of all the TE LSP management procedures
defined for P2P TE LSP such as the non disruptive rerouting (the so already defined for P2P TE LSP such as the non disruptive rerouting
called "Make before break" procedure). (the so called "Make before break" procedure).
The computation of P2MP TE trees is implementation dependent and is The computation of P2MP TE trees is implementation dependent and is
beyond the scope of the solutions that are built with this document beyond the scope of the solutions that are built with this document
as a guideline. as a guideline.
A separate document(s) will specify how to build P2MP TE LSPs. A separate document(s) will specify how to build P2MP TE LSPs.
The usage of those solutions will be application dependent and is The usage of those solutions will be application dependent and is
out of the scope of this document. However, it is a requirement that out of the scope of this document. However, it is a requirement that
those solutions attempt to be applicable to GMPLS as well as to MPLS those solutions attempt to be applicable to GMPLS as well as to MPLS
so that only a single set of solutions are developed. so that only a single set of solutions are developed.
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E-LSR3, E-LSR4 and E-LSR5). I-LSR1 is attached to a traffic source E-LSR3, E-LSR4 and E-LSR5). I-LSR1 is attached to a traffic source
that is generating traffic for a P2MP application. that is generating traffic for a P2MP application.
Receivers R1, R2, R3 and R4 are attached to E-LSR2, E-LSR3 and Receivers R1, R2, R3 and R4 are attached to E-LSR2, E-LSR3 and
E-LSR4. E-LSR4.
The following are the objectives of P2MP LSP establishment and use. The following are the objectives of P2MP LSP establishment and use.
a) A P2MP TE LSP tree which satisfies various constraints is a) A P2MP TE LSP tree which satisfies various constraints is
pre-determined and supplied to ingress I-LSR1. pre-determined and supplied to ingress I-LSR1.
Note that no assumption is made on whether the tree is provided Note that no assumption is made on whether the tree is
to I-LSR1 or computed by I-LSR1. Note that the solution SHOULD provided to I-LSR1 or computed by I-LSR1. Note that the
also allow for the support of partial path by means of loose solution SHOULD also allow for the support of partial path by
routing. means of loose routing.
Typical constraints are bandwidth requirements, resource class Typical constraints are bandwidth requirements, resource class
affinities, fast rerouting, preemption, to mention a few of affinities, fast rerouting, preemption, to mention a few of
them. There should not be any restriction on the possibility them. There should not be any restriction on the possibility
to support the set of constraints already defined for point to to support the set of constraints already defined for point to
point TE LSPs. A new constraint may specify which LSRs should point TE LSPs. A new constraint may specify which LSRs should
be used as branch points for the P2MP LSR in order to take be used as branch points for the P2MP LSR in order to take
into account some LSR capabilities or network constraints. into account some LSR capabilities or network constraints.
b) A P2MP TE LSP is set up from I-LSR1 to E-LSR2, E-LSR3 and b) A P2MP TE LSP is set up from I-LSR1 to E-LSR2, E-LSR3 and
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4.2 P2MP TE backbone network for IP multicast network 4.2 P2MP TE backbone network for IP multicast network
P2MP TE LSPs are applicable in a backbone network to construct or P2MP TE LSPs are applicable in a backbone network to construct or
support a multicast network(e.g. IPmcast network). support a multicast network(e.g. IPmcast network).
The IP multicast access networks are interconnected by P2MP TE LSPs. The IP multicast access networks are interconnected by P2MP TE LSPs.
A P2MP TE LSP is established from an ingress LSR which accommodates A P2MP TE LSP is established from an ingress LSR which accommodates
an IP multicast network that has a multicast source to multiple an IP multicast network that has a multicast source to multiple
egress LSRs which each accommodate an IP multicast network. egress LSRs which each accommodate an IP multicast network.
In this scenario, ingress/egress LSRs placed at the edge of In this scenario, ingress/egress LSRs placed at the edge of multicast
multicast network handle an IP multicast routing protocol. network handle an IP multicast routing protocol.
This means that the ingress/egress LSRs exchange IP multicast This means that the ingress/egress LSRs exchange IP multicast
routing messages as neighbor routers. Figure 3 shows a network routing messages as neighbor routers. Figure 3 shows a network
example of this scenario. example of this scenario.
A P2MP TE LSP is established from a I-LSR1 to E-LSR2, E-LSR3, E-LSR4 A P2MP TE LSP is established from a I-LSR1 to E-LSR2, E-LSR3, E-LSR4
and the ingress/egress LSR exchanges the multicast routing messages and the ingress/egress LSR exchanges the multicast routing messages
with each other. with each other.
As specified in the section related to the problem statement it
should be possible for a solution to add/remove egress LSRs to/from
the P2MP MPLS TE LSP. IP multicast group membership distribution
between the egress LSRs may change frequently. This in turn may
require a potential P2MP MPLS TE solution, that is suitable for IP
multicast, to handle additions/deletions of egress LSRs with an
appropriate reactiveness.
It is recommended to support a message exchange mechanism on top of
P2MP LSP setup mechanism to support multicast (S, G) Join/Leave.
Though several schemes exist to handle this scenario, these are out Though several schemes exist to handle this scenario, these are out
of scope of this document. This document only describes requirements of scope of this document. This document only describes requirements
to setup a P2MP TE LSP. to setup a P2MP TE LSP.
Mcast Source Mcast Source
| |
+-----MR-----+ +-----MR-----+
| | | | | |
| MR | | MR |
+------|-----+ +------|-----+
skipping to change at page 13, line 38 skipping to change at page 15, line 28
to be added to the P2MP TE LSP carrying this channel using a P2MP TE to be added to the P2MP TE LSP carrying this channel using a P2MP TE
grafting procedure, if it is not already egress LSR for that LSP. grafting procedure, if it is not already egress LSR for that LSP.
Pruning procedure has to be used to remove a DSLAM from the P2MP TE Pruning procedure has to be used to remove a DSLAM from the P2MP TE
LSP when there is no longer any client behind the DSLAM, watching LSP when there is no longer any client behind the DSLAM, watching
the channel. the channel.
4.4 VPN multicast network 4.4 VPN multicast network
In this scenario, P2MP TE LSPs could be utilized to construct a In this scenario, P2MP TE LSPs could be utilized to construct a
provider network which can deliver VPN multicast service(s) to its provider network which can deliver VPN multicast service(s) to its
customers. customers. It is, however, not a requirement that VPN multicast
services be delivered using P2MP TE LSPs.
A P2MP TE LSP is established between all the PE routers which A P2MP TE LSP is established between all the PE routers which
accommodate the customer private network(s) that handle the IP accommodate the customer private network(s) that handle the IP
multicast packets. Each PE router must handle a VPN instance. multicast packets. Each PE router must handle a VPN instance.
For example, in Layer3 VPNs like BGP/MPLS based IP VPNs For example, in Layer3 VPNs like BGP/MPLS based IP VPNs
[BGPMPLS-VPN], this means that each PE router must handle both [BGPMPLS-VPN], this means that each PE router must handle both
private multicast VRF tables and common multicast routing and private multicast VRF tables and common multicast routing and
forwarding table. And each PE router exchanges private multicast forwarding table. And each PE router exchanges private multicast
routing information between the corresponding PE routers. In case routing information between the corresponding PE routers. In case
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GMPLS currently supports only P2P TE-LSPs just like MPLS. GMPLS GMPLS currently supports only P2P TE-LSPs just like MPLS. GMPLS
enhances MPLS to support four new classes of interfaces: Layer-2 enhances MPLS to support four new classes of interfaces: Layer-2
Switch Capable (L2SC), Time-Division Multiplex (TDM), Lambda Switch Switch Capable (L2SC), Time-Division Multiplex (TDM), Lambda Switch
Capable (LSC) and Fiber-Switch Capable (FSC) in addition to Packet Capable (LSC) and Fiber-Switch Capable (FSC) in addition to Packet
Switch Capable (PSC) already supported by MPLS. All of these Switch Capable (PSC) already supported by MPLS. All of these
interface classes have so far been limited to P2P TE LSPs interface classes have so far been limited to P2P TE LSPs
(see [RFC3473] and [RFC 3471]). (see [RFC3473] and [RFC 3471]).
The requirement for P2MP services for non-packet switch interfaces The requirement for P2MP services for non-packet switch interfaces
is similar to that for PSC interfaces. In particular, cable is similar to that for PSC interfaces. In particular, cable
distribution services such as video distribution are prime distribution services such as video distribution are prime candidates
candidates to use P2MP features. Therefore, it is a requirement that to use P2MP features. Therefore, it is a requirement that reasonable
reasonable attempts must be made to make all the features/mechanisms attempts must be made to make all the features/mechanisms
(and protocol extensions) that will be defined to provide MPLS P2MP (and protocol extensions) that will be defined to provide MPLS P2MP
TE LSPs equally applicable to P2MP PSC and non-PSC TE-LSPs. If the TE LSPs equally applicable to P2MP PSC and non-PSC TE-LSPs. If the
requirements of non-PSC networks over-complicate the PSC solution a requirements of non-PSC networks over-complicate the PSC solution a
decision may be taken to separate the solutions. This decision must decision may be taken to separate the solutions. This decision must
be taken in full consultation with the MPLS and CCAMP working be taken in full consultation with the MPLS and CCAMP working groups.
groups.
5. Detailed requirements for P2MP TE extensions 5. Detailed requirements for P2MP TE extensions
5.1 P2MP LSP tunnels 5.1 P2MP LSP tunnels
The P2MP TE extensions MUST be applicable to the signaling of LSPs The P2MP TE extensions MUST be applicable to the signaling of LSPs
of different traffic types. For example, it MUST be possible to of different traffic types. For example, it MUST be possible to
signal a P2MP TE LSP to carry any kind of payload being packet or signal a P2MP TE LSP to carry any kind of payload being packet or
non-packet based (including frame, cell, TDM un/structured, etc.) non-packet based (including frame, cell, TDM un/structured, etc.)
Carrying IP multicast or Ethernet traffic within a P2MP tunnel are Carrying IP multicast or Ethernet traffic within a P2MP tunnel are
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and/or leaves. Therefore, the identification of the P2MP session by and/or leaves. Therefore, the identification of the P2MP session by
its destination addresses is not adequate. its destination addresses is not adequate.
5.2 P2MP explicit routing 5.2 P2MP explicit routing
Various optimizations in P2MP tree formation need to be applied to Various optimizations in P2MP tree formation need to be applied to
meet various QoS requirements and operational constraints. meet various QoS requirements and operational constraints.
Some P2MP applications may request a bandwidth guaranteed P2MP tree Some P2MP applications may request a bandwidth guaranteed P2MP tree
which satisfies end-to-end delay requirements. And some operators which satisfies end-to-end delay requirements. And some operators
may want to set up a cost minimum P2MP tree by specifying branch LSRs may want to set up a cost minimum P2MP tree by specifying branch
explicitly. LSRs explicitly.
The P2MP TE solution therefore MUST provide a means of establishing The P2MP TE solution therefore MUST provide a means of establishing
arbitrary P2MP trees under the control of an external tree arbitrary P2MP trees under the control of an external tree
computation process or path configuration process or dynamic tree computation process or path configuration process or dynamic tree
computation process located on the ingress LSR. Figure 4 shows two computation process located on the ingress LSR. Figure 4 shows two
typical examples. typical examples.
A A A A
| / \ | / \
B B C B B C
skipping to change at page 16, line 22 skipping to change at page 18, line 8
Steiner P2MP tree SPF P2MP tree Steiner P2MP tree SPF P2MP tree
Figure 4 Examples of P2MP TE LSP topology Figure 4 Examples of P2MP TE LSP topology
One example is the Steiner P2MP tree (Cost minimum P2MP tree) One example is the Steiner P2MP tree (Cost minimum P2MP tree)
[STEINER]. This P2MP tree is suitable for constructing a cost [STEINER]. This P2MP tree is suitable for constructing a cost
minimum P2MP tree so as to minimize the bandwidth consumption in minimum P2MP tree so as to minimize the bandwidth consumption in
the core. To realize this P2MP tree, several intermediate LSRs must the core. To realize this P2MP tree, several intermediate LSRs must
be both MPLS data terminating LSRs and transit LSRs (LSRs E, F, G, be both MPLS data terminating LSRs and transit LSRs (LSRs E, F, G,
H, I, J and K in the figure 4). This means that the LSRs must H, I, J and K in the figure 4). This means that the LSRs must perform
perform both label swapping and popping at the same time. Therefore, both label swapping and popping at the same time. Therefore, the P2MP
the P2MP TE solution MUST support a mechanism that can setup this TE solution MUST support a mechanism that can setup this kind of bud
kind of bud LSR between an ingress LSR and egress LSRs. Note that LSR between an ingress LSR and egress LSRs. Note that this includes
this includes constrained Steiner trees that allow for the constrained Steiner trees that allow for the computation of a minimal
computation of a minimal cost trees with some other constraints such cost trees with some other constraints such as a bounded delay
as a bounded delay between the source and every receiver. between the source and every receiver.
Another example is a CSPF (Constraint Shortest Path First) P2MP Another example is a CSPF (Constraint Shortest Path First) P2MP
tree. By some metric (which can be set upon any specific criteria tree. By some metric (which can be set upon any specific criteria
like the delay, bandwidth, a combination of those), one can like the delay, bandwidth, a combination of those), one can
calculate a shortest path P2MP tree. This P2MP tree is suitable for calculate a shortest path P2MP tree. This P2MP tree is suitable for
carrying real time traffic. carrying real time traffic.
The solution MUST allow the operator to make use of any tree The solution MUST allow the operator to make use of any tree
computation technique. In the former case an efficient/optimal tree computation technique. In the former case an efficient/optimal tree
is defined as a minimal cost tree (Steiner tree) whereas in the is defined as a minimal cost tree (Steiner tree) whereas in the
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This situation may arrise in either of the following circumstances. This situation may arrise in either of the following circumstances.
a. The ingress LSR cannot signal the whole tree in a single a. The ingress LSR cannot signal the whole tree in a single
message. message.
b. The information in a message expands to be too large (or is b. The information in a message expands to be too large (or is
discovered to be too large) at some transit node. This may discovered to be too large) at some transit node. This may
occur because of some increase in the information that needs occur because of some increase in the information that needs
to be signaled or because of a reduction in the size of to be signaled or because of a reduction in the size of
signaling message that is supported. signaling message that is supported.
The solution to these problems SHOULD NOT rely on IP fragmentation,
it is RECOMMENDED to rely on some protocol procedures specific to
the signaling solution.
It is NOT RECOMMENDED that fragmented protocol messages are
re-combined at any downstream LSR.
5.6 Failure Reporting and Error Recovery 5.6 Failure Reporting and Error Recovery
Failure events may cause egress nodes or sub-P2MP LSPs to become Failure events may cause egress nodes or sub-P2MP LSPs to become
detached from the P2MP TE LSP. These events MUST be reported detached from the P2MP TE LSP. These events MUST be reported
upstream as for a P2P LSP. upstream as for a P2P LSP.
The solution SHOULD provide recovery techniques such as protection The solution SHOULD provide recovery techniques such as protection
and restoration allowing recovery of any impacted sub-P2MP TE and restoration allowing recovery of any impacted sub-P2MP TE
LSPs. In particular, a solution MUST provide fast protection LSPs. In particular, a solution MUST provide fast protection
mechanisms applicable to P2MP TE LSP similar to the solutions mechanisms applicable to P2MP TE LSP similar to the solutions
specified in [FRR] for P2P TE LSPs. Note also that no assumption is specified in [FRR] for P2P TE LSPs. Note also that no assumption is
made on whether backup paths for P2MP TE LSPs should or should not made on whether backup paths for P2MP TE LSPs should or should not
be shared with P2P TE LSPs backup paths. be shared with P2P TE LSPs backup paths.
Note that the functions specified in [FRR] are currently specific to
packet environments and do not apply to non-packet environments.
Thus, while solutions MUST provide fast protection mechanisms
similar to those specified in [FRR], this requirement is limited to
the subset of the solution space that applies to packet switched
networks only.
Note that other application-specific requirement documents may Note that other application-specific requirement documents may
introduce even more stringent requirement such as non packet loss, introduce even more stringent requirement such as non packet loss,
at the cost of some increased bandwidth consumption. at the cost of some increased bandwidth consumption.
The solution SHOULD also support the ability to meet other network The solution SHOULD also support the ability to meet other network
recovery requirements such as bandwidth protection and bounded recovery requirements such as bandwidth protection and bounded
propagation delay increase along the backup path during failure. propagation delay increase along the backup path during failure.
A P2MP TE solution MUST support P2MP fast protection mechanism to A P2MP TE solution MUST support P2MP fast protection mechanism to
handle P2MP applications sensitive to traffic disruption. handle P2MP applications sensitive to traffic disruption.
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P2MP tree may be disparate, the branch node MUST report all such P2MP tree may be disparate, the branch node MUST report all such
errors to its upstream neighbor. The ingress node can then decide errors to its upstream neighbor. The ingress node can then decide
to re-compute the path to those particular egress nodes, around the to re-compute the path to those particular egress nodes, around the
failure point. failure point.
Solutions MAY include the facility for transit LSRs and particularly Solutions MAY include the facility for transit LSRs and particularly
branch nodes to recompute sub-P2MP trees to restore them after branch nodes to recompute sub-P2MP trees to restore them after
failures. In the event of successful repair, error notifications failures. In the event of successful repair, error notifications
SHOULD NOT be reported to upstream nodes, but the new paths are SHOULD NOT be reported to upstream nodes, but the new paths are
reported if route recording is in use. Crankback requirements are reported if route recording is in use. Crankback requirements are
discussed in Section 5.18. discussed in Section 5.23.
5.7 Record route of P2MP TE LSP tunnels 5.7 Record route of P2MP TE LSP tunnels
Being able to identify the established topology of P2MP TE LSP is Being able to identify the established topology of P2MP TE LSP is
very important for various purposes such as management and operation very important for various purposes such as management and operation
of some local recovery mechanisms like Fast Reroute [FRR]. A network of some local recovery mechanisms like Fast Reroute [FRR]. A network
operator uses this information to manage P2MP TE LSPs. Therefore, operator uses this information to manage P2MP TE LSPs. Therefore,
topology information MUST be collected and updated after P2MP TE LSP topology information MUST be collected and updated after P2MP TE LSP
establishment and modification process. establishment and modification process.
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that can provide consistent QoS control in P2MP LSP traffic. that can provide consistent QoS control in P2MP LSP traffic.
Any solution SHOULD also satisfy the DS-TE requirements [RFC3564] Any solution SHOULD also satisfy the DS-TE requirements [RFC3564]
and interoperate smoothly with current P2P DS-TE protocol and interoperate smoothly with current P2P DS-TE protocol
specifications. specifications.
Note that this requirement document does not make any assumption on Note that this requirement document does not make any assumption on
the type of bandwidth pool used for P2MP TE LSPs which can either be the type of bandwidth pool used for P2MP TE LSPs which can either be
shared with P2P TE LSP or be dedicated for P2MP use. shared with P2P TE LSP or be dedicated for P2MP use.
5.9 Reoptimization of P2MP TE LSP 5.9 Variation of LSP Parameters
Various parameters to an LSP (such as priority, bandwidth, etc.) are
signaled along each branch of the LSP.
Any solution MUST NOT allow for variance of these parameters. That
is,
- no attributes set and signaled by the ingress of a P2MP LSP may be
varied by downstream LSRs
- there MUST be homogenous QoS from the root to all leaves.
THIS IS A PROVISIONAL REQUIREMENT STILL OPEN FOR DISCUSSION.
5.10 Re-optimization of P2MP TE LSPs
The detection of a more optimal path (for example, one with a lower The detection of a more optimal path (for example, one with a lower
overall cost) is an example of a situation where P2MP TE LSP overall cost) is an example of a situation where P2MP TE LSP
re-routing may be required. While re-routing is in progress, an re-routing may be required. While re-routing is in progress, an
important requirement is avoiding double bandwidth reservation important requirement is avoiding double bandwidth reservation
(over the common parts between the old and new LSP) thorough the use (over the common parts between the old and new LSP) thorough the use
of resource sharing. of resource sharing.
Make-before-break MUST be supported for a P2MP TE LSP to ensure that Make-before-break MUST be supported for a P2MP TE LSP to ensure that
there is no traffic disruption when the P2MP TE LSP is re-routed. there is minimal traffic disruption when the P2MP TE LSP is
For example, the P2P MPLS TE make-before-break mechanism could be re-routed.
extended and used if RSVP-TE was used as the P2MP signaling protocol.
It is possible to achieve make-before-break that only applies to a It is possible to achieve make-before-break that only applies to a
sub-P2MP tree without impacting the data on all of the other parts sub-P2MP tree without impacting the data on all of the other parts
of the P2MP tree. of the P2MP tree.
The solution SHOULD allow for make-before-break reoptimization of a The solution SHOULD allow for make-before-break re-optimization of
sub-tree with no impact on the rest of the tree (no label any subdivision of the P2MP LSP (S2L sub-tree, S2X sub-LSP, S2L
reallocation, no change in identifiers, etc.). sub-LSP, X2L sub-tree, B2L sub-tree, X2L tree, or B2L tree) with no
impact on the rest of the P2MP LSP (no label reallocation, no change
in identifiers, etc.).
The solution SHOULD also provide the ability for the ingress LSR to The solution SHOULD also provide the ability for the ingress LSR to
have a strict control on the reoptimization process. have a strict control on the re-optimization process.
Such reoptimization MAY be initiated by the sub-tree root branch Such re-optimization MAY be initiated by the sub-tree root branch
node (that is, the branch node MAY setup a new sub-tree, then splice node (that is, the branch node MAY setup a new sub-tree, then splice
traffic on the new subtree and delete the former sub-tree). traffic on the new subtree and delete the former sub-tree).
5.10 IPv4/IPv6 support THE REQUIREMENT FOR RE-OPTIMIZATION BY SUB-TREE ROOT BRANCH IS
STILL OPEN FOR DISCUSSION
5.11 Tree Remerge
It is possible for a single transit LSR to receive multiple
signaling messages for the same P2MP LSP but for different
sets of desinations. These messages may be received from the
same or different upstream nodes and may need to be passed on
to the same or different downstream nodes.
This situation may arise as the result of the signaling solution
definition or implementation options within the signaling
solution. Further, it may happen during make-before-break
reoptimization (section 5.9), or as a result of signaling
message fragmentation (section 5.5).
It is even possible that it is necessary to construct distinct
upstream branches in order to achieve the correct label choices
in certain switching technologies managed by GMPLS (for example,
photonic cross-connects where the selection of a particular
lambda for the downstream branches is only available on differnt
upstream switches).
The solution MUST handle the case where multiple signaling
messages for the same P2MP LSP are received at a single transit
LSR with the end result of all receivers being added to the
P2MP LSP.
THIS REQUIREMENT IS STILL UNDER DISCUSSION
5.12 Data Duplication
Data duplication refers to the receipt by any recipient of duplicate
instances of the data. In a packet environment this means the
receipt of duplicate packets - although this should be a benign (if
inefficient) situation, it may be catastrophic in certain existing
and deployed applications. In a non-packet environment this means
the duplication in time of some part of the signal that may lead to
the replication of data or to the scrambling of data.
Data duplication may legitimately arrise in various scenarios
including re-optimization of active LSPs as described in the
previous section, and protection of LSPs. Thus, it is impractical to
regulate against data duplication in this document.
Instead, the solution MUST provide a mechanism to resolve, limit or
avoid data duplication at either or both of:
- the point at which the data path diverges
- the point at which the data paths converge.
THE EXTENT TO WHICH DATA DUPLICATION MAY BE TOLERATED (in time or in
a count of bits or packets) IS FOR FURTHER STUDY.
5.13 IPv4/IPv6 support
Any P2MP TE solution MUST be equally applicable to IPv4 and IPv6. Any P2MP TE solution MUST be equally applicable to IPv4 and IPv6.
5.11 P2MP MPLS Label 5.14 P2MP MPLS Label
A P2MP TE solution MUST support establishment of both P2P and P2MP A P2MP TE solution MUST support establishment of both P2P and P2MP
TE LSPs and MUST NOT impede the operation of P2P TE LSPs within the TE LSPs and MUST NOT impede the operation of P2P TE LSPs within the
same network. A P2MP TE solution MUST be specified in such a way same network. A P2MP TE solution MUST be specified in such a way
that it allows P2MP and P2P TE LSPs to be signaled on the same that it allows P2MP and P2P TE LSPs to be signaled on the same
interface. Labels for P2MP TE LSPs and P2P TE LSPs MAY be assigned interface. Labels for P2MP TE LSPs and P2P TE LSPs MAY be assigned
from shared or dedicated label space(s). Label space shareability is from shared or dedicated label space(s). Label space shareability is
implementation specific. implementation specific.
5.12 Routing advertisement of P2MP capability 5.15 Routing advertisement of P2MP capability
Several high-level requirements have been identified to determine Several high-level requirements have been identified to determine
the capabilities of LSRs within a P2MP network. The aim of such the capabilities of LSRs within a P2MP network. The aim of such
information is to facilitate the computation of P2MP trees using TE information is to facilitate the computation of P2MP trees using TE
constraints within a network that contains LSRs that do not all have constraints within a network that contains LSRs that do not all have
the same capabilities levels with respect to P2MP signaling and data the same capabilities levels with respect to P2MP signaling and data
forwarding. forwarding.
These capabilities include, but are not limited to: These capabilities include, but are not limited to:
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- the ability of an LSR to act as an egress and a branch for the - the ability of an LSR to act as an egress and a branch for the
same LSP. same LSP.
- the ability of an LSR to support P2MP MPLS-TE signalling. - the ability of an LSR to support P2MP MPLS-TE signalling.
It is expected that it may be appropriate to gather this information It is expected that it may be appropriate to gather this information
through extensions to TE IGPs (see [RFC3630] and [IS-IS-TE]), but through extensions to TE IGPs (see [RFC3630] and [IS-IS-TE]), but
the precise requirements and mechanisms are out of the scope of this the precise requirements and mechanisms are out of the scope of this
document. It is expected that a separate document will cover this document. It is expected that a separate document will cover this
requirement. requirement.
5.13 Multi-Area/AS LSP 5.16 Multi-Area/AS LSP
P2MP TE solutions SHOULD support multi-area/AS P2MP TE LSPs. P2MP TE solutions SHOULD support multi-area/AS P2MP TE LSPs.
The precise requirements in support of multi-area/AS P2MP TE LSPs is The precise requirements in support of multi-area/AS P2MP TE LSPs is
out of the scope of this document. It is expected that a separate out of the scope of this document. It is expected that a separate
document will cover this requirement. document will cover this requirement.
5.14 P2MP MPLS OAM 5.17 Multi-access LANs
P2MP MPLS TE may be used to traverse network segments that are
provided by multi-access media such as Ethernet. In these cases, it
is also possible that the entry point to the network segment is a
branch point of the P2MP LSP.
Two options clearly exist:
- the branch point replicates the data and transmits multiple
copies onto the segment
- the branch point sends a single copy of the data to the segment
and relies on the exit points to discriminate the reception of
the data.
The first option has a significant scaling issue since all
replicated data must be sent through the same port and carried on
the same segment. Thus, a solution SHOULD provide a mechanism for a
branch node to send a single copy of the data onto a multi-access
network and reach multiple (adjacent) downstrem nodes.
5.18 P2MP MPLS OAM
Management of P2MP LSPs is as important as the management of P2P Management of P2MP LSPs is as important as the management of P2P
LSPs. LSPs.
The MPLS and GMPLS MIB modules MUST be enhanced to provide P2MP TE The MPLS and GMPLS MIB modules MUST be enhanced to provide P2MP TE
LSP management. LSP management.
In order to facilitate correct management, P2MP TE LSPs MUST have In order to facilitate correct management, P2MP TE LSPs MUST have
unique identifiers. unique identifiers.
OAM facilities will have special demands in P2MP environments OAM facilities will have special demands in P2MP environments
especially within the context of tracing the paths and connectivity especially within the context of tracing the paths and connectivity
of P2MP TE LSPs. The precise requirements and mechanisms for OAM are of P2MP TE LSPs. The precise requirements and mechanisms for OAM are
out of the scope of this document. It is expected that a separate out of the scope of this document. It is expected that a separate
document will cover these requirements. document will cover these requirements.
5.15 Scalability 5.19 Scalability
Scalability is a key requirement in P2MP MPLS systems. Solutions Scalability is a key requirement in P2MP MPLS systems. Solutions
MUST be designed to scale well with an increase in the number of any MUST be designed to scale well with an increase in the number of any
of the following: of the following:
- the number of recipients - the number of recipients
- the number of branch points - the number of branch points
- the number of branches. - the number of branches.
Both scalability of performance and operation MUST be considered. Both scalability of performance and operation MUST be considered.
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- the amount of protocol information transmitted to manage - the amount of protocol information transmitted to manage
a P2MP TE LSP (i.e. the message size). a P2MP TE LSP (i.e. the message size).
- the amount of potential routing extensions. - the amount of potential routing extensions.
- the amount of control plane processing required by the ingress, - the amount of control plane processing required by the ingress,
transit and egress LSRs to add/delete a branch LSP to/from an transit and egress LSRs to add/delete a branch LSP to/from an
existing P2MP LSP. existing P2MP LSP.
It is expected that the applicability of each solution will be It is expected that the applicability of each solution will be
evaluated with regards to the aforementioned scalability criteria. evaluated with regards to the aforementioned scalability criteria.
5.16 Backwards Compatibility 5.19.1 Absolute Limits
THIS IS SECTION DESCRIBES PROVISIONAL REQUIREMENTS STILL OPEN FOR
DISCUSSION.
In order to achieve the best solution for the problem space it is
helpful to clarify the boundaries for P2MP TE LSPs.
- Number of recipients.
A P2MP TE LSP MUST reduce to similar scaling properties as a P2P
LSP when the number of recipients reduces to one.
It is important to classify the problem as a Traffic Engineering
problem. It is anticipated that the initial deployments of P2MP TE
LSPs may be limited to only several hundred recipients, but also
that future deployments may require significantly larger numbers.
An acceptable solution, therefore, is one that scales linearly
with the number of recipients.
Solutions that scale worse than linear (that is, exponential or
polynomial) are not acceptable whatever the number of recipients
they could support
- Number of branch points.
Solutions MUST support all possiblities from one extreme of a
single branch point that forks to all leaves on a separate branch,
to the greatest number of branch points which is (n-1) for n
recipients. Assumptions MUST NOT be made in the solution regarding
which topology is more common, and the solution MUST be designed
to ensure scalability in all topologies.
- Dynamics of P2MP tree.
Recall that the mechanisms for determining which recipients should
be added to an LSP, and for adding and removing recipients from
that group are out of the scope of this document. Nevertheless, it
is useful to understand the expected rates of arrival and
departure of recipients since this can impact the selection of
solution techniques.
Again, it must be recall that this document is limited to Traffic
Engineering, and in this model the rate of change of recipients
may be expected to be lower than in an IP multicast group.
Although the absolute number of recipients coming and going is the
important element for determining the scalability of a solution,
it may be noted that a percentage may be a more comprehensible
measure but that this is not as significant for LSPs with a small
number of recipients.
A working figure for an established P2MP TE LSP is less than 10%
churn per day. That is, a relatively slow rate of churn.
We could say that a P2MP LSP would be shared by multiple multicast
groups and dynamics of P2MP LSP would be relatively small.
Considering applicability that P2MP LSP to use L2 multi-access
path technology, we can consider stable P2MP L2 path even when we
transfer IP multicast traffic over the path.
Solutions MUST optimize around such relatively low rates of change
and are NOT REQUIRED to optimize for significantly higher rates
of change.
- Rate of change within the network.
It is also important to understand the scaling with regard to
changes within the network. That is, one of the features of a
P2MP TE LSP is that it can be robust or protected against network
failures, and can be re-optimized to take advantage of newly
available network resources.
It is more important that a solution be optimized for scaling with
respect to recovery and re-optimization of the LSP, than for change
in the recipients, because P2MP is used as a TE tool.
The solution MUST follow this distinction.
5.20 Backwards Compatibility
It SHOULD be an aim of any P2MP solution to offer as much backward It SHOULD be an aim of any P2MP solution to offer as much backward
compatibility as possible. An ideal which is probably impossible to compatibility as possible. An ideal which is probably impossible to
achieve would be to offer P2MP services across legacy MPLS networks achieve would be to offer P2MP services across legacy MPLS networks
without any change to any LSR in the network. without any change to any LSR in the network.
If this ideal cannot be achieved, the aim SHOULD be to use legacy If this ideal cannot be achieved, the aim SHOULD be to use legacy
nodes as both transit non-branch LSRs and egress LSRs. nodes as both transit non-branch LSRs and egress LSRs.
It is a further requirement for the solution that any LSR that It is a further requirement for the solution that any LSR that
implements the solution SHALL NOT be prohibited by that act from implements the solution SHALL NOT be prohibited by that act from
supporting P2P TE LSPs using existing signaling mechanisms. That is, supporting P2P TE LSPs using existing signaling mechanisms. That is,
unless administratively prohibited, P2P TE LSPs MUST be supported unless administratively prohibited, P2P TE LSPs MUST be supported
through a P2MP network. through a P2MP network.
Also, it is a requirement that P2MP TE LSPs MUST be able to co-exist Also, it is a requirement that P2MP TE LSPs MUST be able to co-exist
with IP unicast and IP multicast networks. with IP unicast and IP multicast networks.
5.17 GMPLS 5.21 GMPLS
Solutions for MPLS P2MP TE-LSPs when applied to GMPLS P2MP PSC or Solutions for MPLS P2MP TE-LSPs when applied to GMPLS P2MP PSC or
non-PSC TE-LSPs MUST be backward and forward compatible with the non-PSC TE-LSPs MUST be backward and forward compatible with the
other features of GMPLS including: other features of GMPLS including:
- control and data plane separation (IF_ID RSVP_HOP and IF_ID - control and data plane separation (IF_ID RSVP_HOP and IF_ID
ERROR_SPEC), ERROR_SPEC),
- full support of numbered and unnumbered TE links (see [RFC 3477] - full support of numbered and unnumbered TE links (see [RFC 3477]
and [GMPLS-ROUTE]), and [GMPLS-ROUTE]),
- use of the GENERALIZED_LABEL_REQUEST, the GENERALIZED_LABEL - use of the GENERALIZED_LABEL_REQUEST, the GENERALIZED_LABEL
(C-Type 2 and 3), the SUGGESTED_LABEL and the RECOVERY_LABEL, (C-Type 2 and 3), the SUGGESTED_LABEL and the RECOVERY_LABEL,
in conjunction with the LABEL_SET and the ACCEPTABLE_LABEL_SET in conjunction with the LABEL_SET and the ACCEPTABLE_LABEL_SET
object, object,
- processing of the ADMIN_STATUS object, - processing of the ADMIN_STATUS object,
- processing of the PROTECTION object, - processing of the PROTECTION object,
- support of Explicit Label Control, - support of Explicit Label Control,
- processing of the Path_State_Removed Flag, - processing of the Path_State_Removed Flag,
- handling of Graceful Deletion procedures. - handling of Graceful Deletion procedures.
- E2E and Segment Recovery procedures. - E2E and Segment Recovery procedures.
- support of Graceful Restart
In addition, since non-PSC TE-LSPs may have to be processed in In addition, since non-PSC TE-LSPs may have to be processed in
environments where the "P2MP capability" could be limited, specific environments where the "P2MP capability" could be limited, specific
constraints may also apply during the P2MP TE Path computation. constraints may also apply during the P2MP TE Path computation.
Being technology specific, these constraints are outside the scope Being technology specific, these constraints are outside the scope
of this document. However, technology independent constraints of this document. However, technology independent constraints
(i.e. constraints that are applicable independently of the LSP (i.e. constraints that are applicable independently of the LSP
class) SHOULD be allowed during P2MP TE LSP message processing. class) SHOULD be allowed during P2MP TE LSP message processing.
It has to be emphasized that path computation and management It has to be emphasized that path computation and management
techniques shall be as close as possible to those being used for techniques shall be as close as possible to those being used for
PSC P2P TE LSPs and P2MP TE LSPs. PSC P2P TE LSPs and P2MP TE LSPs.
5.18 Requirements for Hierarchical P2MP TE LSPs 5.22 Requirements for Hierarchical P2MP TE LSPs
[LSP-HIER] defines concepts and procedures for P2P LSP hierarchy. [LSP-HIER] defines concepts and procedures for P2P LSP hierarchy.
These procedures SHOULD be extended to support P2MP LSP hierarchy. These procedures SHOULD be extended to support P2MP LSP hierarchy.
The P2MP MPLS-TE solution SHOULD support the concept of region and The P2MP MPLS-TE solution SHOULD support the concept of region and
region hierarchy (PSC1<PSC2<PSC3<PSC4<L2SC<TDM<LSC<FSC). region hierarchy (PSC1<PSC2<PSC3<PSC4<L2SC<TDM<LSC<FSC).
Particularly it SHOULD allow a Region i P2MP TE LSP to be nested Particularly it SHOULD allow a Region i P2MP TE LSP to be nested
into a region j P2MP TE LSP or multiple region j P2P TE LSPs, into a region j P2MP TE LSP or multiple region j P2P TE LSPs,
providing that i<j. providing that i<j.
The precise requirements and mechanisms for this function are out of The precise requirements and mechanisms for this function are out of
the scope of this document. It is expected that a separate document the scope of this document. It is expected that a separate document
will cover these requirements. will cover these requirements.
5.19 P2MP Crankback routing 5.23 P2MP Crankback routing
P2MP solutions SHOULD support crankback requirements as defined in P2MP solutions SHOULD support crankback requirements as defined in
[CRANKBACK]. In particular, they SHOULD provide sufficient [CRANKBACK]. In particular, they SHOULD provide sufficient
information to a branch LSR from downstream LSRs to allow the branch information to a branch LSR from downstream LSRs to allow the branch
LSR to re-route a sub-tree around any failures or problems in the LSR to re-route a sub-tree around any failures or problems in the
network. network.
6. Security Considerations 6. Security Considerations
This requirements document does not define any protocol extensions This requirements document does not define any protocol extensions
and does not, therefore, make any changes to any security models. and does not, therefore, make any changes to any security models.
It should be noted that P2MP signaling mechanisms built on P2P It should be noted that P2MP signaling mechanisms built on P2P
RSVP-TE signaling are likely to inherit all of the security RSVP-TE signaling are likely to inherit all of the security
techniques and problems associated with RSVP-TE. These problems may techniques and problems associated with RSVP-TE. These problems may
be exacerbated in P2MP situations where security relationships may be exacerbated in P2MP situations where security relationships may
need to maintained between an ingress and multiple egresses. Such need to maintained between an ingress and multiple egresses. Such
issues are similar to security issues for IP multicast. issues are similar to security issues for IP multicast.
skipping to change at page 25, line 8 skipping to change at page 30, line 20
be exacerbated in P2MP situations where security relationships may be exacerbated in P2MP situations where security relationships may
need to maintained between an ingress and multiple egresses. Such need to maintained between an ingress and multiple egresses. Such
issues are similar to security issues for IP multicast. issues are similar to security issues for IP multicast.
It is a requirement that documents offering solutions for P2MP LSPs It is a requirement that documents offering solutions for P2MP LSPs
MUST have detailed security sections. MUST have detailed security sections.
7. Acknowledgements 7. Acknowledgements
The authors would like to thank George Swallow, Ichiro Inoue, Dean The authors would like to thank George Swallow, Ichiro Inoue, Dean
Cheng, and Eric Rosen for their review and suggestions. Cheng, Lou Berger and Eric Rosen for their review and suggestions.
8. References 8. References
8.1 Normative References 8.1 Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2475] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z. [RFC2475] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z.
and W. Weiss, "An Architecture for Differentiated and W. Weiss, "An Architecture for Differentiated
skipping to change at page 26, line 31 skipping to change at page 31, line 39
Differentiated Services-aware MPLS Traffic Differentiated Services-aware MPLS Traffic
Engineering", RFC 3564, July 2003. Engineering", RFC 3564, July 2003.
[RFC3630] D. Katz, D. Yeung, K. Kompella, "Traffic Engineering [RFC3630] D. Katz, D. Yeung, K. Kompella, "Traffic Engineering
Extensions to OSPF Version 2", RFC 3630, September Extensions to OSPF Version 2", RFC 3630, September
2003. 2003.
[PIM-SM] B. Fenner, M. Hadley, H. Holbrook, I. Kouvelas, [PIM-SM] B. Fenner, M. Hadley, H. Holbrook, I. Kouvelas,
"Protocol Independent Multicast - Sparse Mode (PIM-SM): "Protocol Independent Multicast - Sparse Mode (PIM-SM):
Protocol Specification (Revised)", draft-ietf-pim-sm- Protocol Specification (Revised)", draft-ietf-pim-sm-
v2-new-08.txt, October 2003. v2-new-10.txt, July 2004.
[BGPMPLS-VPN] E. Rosen, Y.Rekhter, Editor, "BGP/MPLS IP VPNs", [BGPMPLS-VPN] E. Rosen, Y.Rekhter, Editor, "BGP/MPLS IP VPNs",
draft-ietf-l3vpn-rfc2547bis-01.txt, September 2003. draft-ietf-l3vpn-rfc2547bis-02.txt, September 2004.
[GMPLS-ROUTE] K. Kompella, Y. Rekhter, Editor, "Routing Extensions [GMPLS-ROUTE] K. Kompella, Y. Rekhter, Editor, "Routing Extensions
in Support of Generalized Multi-Protocol Label in Support of Generalized Multi-Protocol Label
Switching", draft-ietf-ccamp-gmpls-routing-08.txt, Switching", draft-ietf-ccamp-gmpls-routing-08.txt,
October 2003. October 2003.
[STEINER] H. Salama, et al., "Evaluation of Multicast Routing [STEINER] H. Salama, et al., "Evaluation of Multicast Routing
Algorithm for Real-Time Communication on High-Speed Algorithm for Real-Time Communication on High-Speed
Networks," IEEE Journal on Selected Area in Networks," IEEE Journal on Selected Area in
Communications, pp.332-345, 1997. Communications, pp.332-345, 1997.
[FRR] P. Pan, D. Gan, G. Swallow, J. P. Vasseur, D. Cooper, [FRR] P. Pan, G. Swallow, A. Atlas, "Fast Reroute Extensions
A. Atlas, M. Jork,"Fast Reroute Extensions to RSVP-TE to RSVP-TE for LSP Tunnels", draft-ietf-mpls-rsvp-lsp-
for LSP Tunnels", fastreroute-07.txt, August 2004.
draft-ietf-mpls-rsvp-lsp-fastreroute-03.txt, July
2003.
[IS-IS-TE] Henk Smit, Tony Li, "IS-IS extensions for Traffic [IS-IS-TE] Henk Smit, Tony Li, "Intermediate System to
Engineering", draft-ietf-isis-traffic-04.txt, December Intermediate System (IS-IS) Extensions for Traffic
2002. Engineering (TE)", RFC 3784, June 2004.
[CRANKBACK] A. Farrel, A. Satyanarayana, A. Iwata, N. Fujita, G. [CRANKBACK] A. Farrel, A. Satyanarayana, A. Iwata, N. Fujita, G.
Ash, S. Marshall, "Crankback Signaling Extensions for Ash, S. Marshall, "Crankback Signaling Extensions for
MPLS Signaling", draft-ietf-ccamp-crankback-01.txt, MPLS Signaling", draft-ietf-ccamp-crankback-02.txt,
January 2004. July 2004.
[LSP-HIER] K. Kompella, Y. Rekhter, "LSP Hierarchy with [LSP-HIER] K. Kompella, Y. Rekhter, "LSP Hierarchy with
Generalized MPLS TE", draft-ietf-mpls-lsp-hierarchy- Generalized MPLS TE", draft-ietf-mpls-lsp-hierarchy-
08.txt, September 2002. 08.txt, September 2002.
[NODE-ID] Vasseur, Ali and Sivabalan, "Definition of an RRO node- [NODE-ID] Vasseur, Ali and Sivabalan, "Definition of an RRO node-
id subobject", draft-ietf-mpls-nodeid-subobject-01.txt, id subobject", draft-ietf-mpls-nodeid-subobject-01.txt,
June 2003. June 2003.
9. Editor's Address 9. Editor's Address
skipping to change at page 29, line 28 skipping to change at page 34, line 34
attempt made to obtain a general license or permission for the use attempt made to obtain a general license or permission for the use
of such proprietary rights by implementers or users of this of such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository specification can be obtained from the IETF on-line IPR repository
at http://www.ietf.org/ipr. at http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention The IETF invites any interested party to bring to its attention
any copyrights, patents or patent applications, or other any copyrights, patents or patent applications, or other
proprietary rights that may cover technology that may be required proprietary rights that may cover technology that may be required
to implement this standard. Please address the information to the to implement this standard. Please address the information to the
IETF at ietf-ipr@ietf.org. IETF at ietf-ipr@ietf.org.
11.1 IPR Disclosure Acknowledgement
By submitting this Internet-Draft, I certify that any applicable
patent or other IPR claims of which I am aware have been disclosed,
and any of which I become aware will be disclosed, in accordance
with RFC 3668.
12. Full Copyright Statement 12. Full Copyright Statement
Copyright (C) The Internet Society (2004). This document is Copyright (C) The Internet Society (2004). This document is
subject to the rights, licenses and restrictions contained in BCP subject to the rights, licenses and restrictions contained in BCP
78, and except as set forth therein, the authors retain all their 78, and except as set forth therein, the authors retain all their
rights. rights.
This document and the information contained herein are provided This document and the information contained herein are provided
on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE
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