draft-ietf-mpls-p2mp-requirement-00.txt   draft-ietf-mpls-p2mp-requirement-01.txt 
Network Working Group Seisho Yasukawa (NTT) Network Working Group Seisho Yasukawa (NTT)
Internet Draft Dimitri Papadimitriou (Alcatel) Internet Draft Editor
Jean Philippe Vasseur (Cisco)
Adrian Farrel (Old Dog) Yuji Kamite (NTT Communications)
Markus Jork (Avici) Rahul Aggarwal (Juniper)
Andrew G. Malis(Tellabs) Alan Kullberg (Motorola)
Expiration Date: March 2004 October 2003 Expiration Date: June 2004 January 2004
Requirements for Point to Multipoint extension to RSVP-TE Requirements for Point to Multipoint extension to RSVP-TE
<draft-ietf-mpls-p2mp-requirement-00.txt> <draft-ietf-mpls-p2mp-requirement-01.txt>
Status of this Memo Status of this Memo
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet- other groups may also distribute working documents as Internet-
Drafts. Drafts.
skipping to change at page 2, line 7 skipping to change at page 1, line 44
This document presents a set of requirements for Point-to-Multipoint This document presents a set of requirements for Point-to-Multipoint
(P2MP) Traffic Engineering (TE) extensions to Multiprotocol Label (P2MP) Traffic Engineering (TE) extensions to Multiprotocol Label
Switching (MPLS). It specifies functional requirements for RSVP-TE in Switching (MPLS). It specifies functional requirements for RSVP-TE in
order to deliver P2MP applications over a MPLS TE infrastructure. It order to deliver P2MP applications over a MPLS TE infrastructure. It
is intended that potential solutions, that specify RSVP-TE procedures is intended that potential solutions, that specify RSVP-TE procedures
for P2MP TE LSP setup, use these requirements as a guideline. It is for P2MP TE LSP setup, use these requirements as a guideline. It is
not intended to specify solution specific details in this document. not intended to specify solution specific details in this document.
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 also not limited to the requirements of packet switched networks, but also
encompass the requirements of TDM, lambda and port switching networks encompass the requirements of L2SC, TDM, lambda and port switching
managed by Generalized MPLS (GMPLS) protocols. Protocol solutions networks managed by Generalized MPLS (GMPLS) protocols. Protocol
developed to meet the requirements set out in this document must be solutions developed to meet the requirements set out in this document
equally applicable to MPLS and GMPLS. must be equally applicable to MPLS and GMPLS.
Table of Contents Table of Contents
1. Introduction .................................................. 3 1. Introduction .................................................. 4
2. Definitions ................................................... 4 2. Definitions ................................................... 5
2.1 Acronyms .................................................. 4 2.1 Acronyms .................................................. 5
2.2 Terminology ............................................... 4 2.2 Terminology ............................................... 5
2.3 Conventions ............................................... 5 2.3 Conventions ............................................... 6
3. Problem statements ............................................ 5 3. Problem statements ............................................ 7
3.1 Motivation ................................................ 5 3.1 Motivation ................................................ 7
3.2 Requirements overview ..................................... 6 3.2 Requirements overview ..................................... 7
4. Application Specific Requirements ............................. 8 4. Application Specific Requirements ............................. 9
4.1 P2MP tunnel for IP multicast data ......................... 8 4.1 P2MP tunnel for IP multicast data ......................... 9
4.2 P2MP backbone network for IP multicast network ............ 9 4.2 P2MP TE backbone network for IP multicast network .........10
4.3 Layer 2 Multicast Over MPLS ...............................10 4.3 Layer 2 Multicast Over MPLS ...............................11
4.4 VPN multicast network .....................................10 4.4 VPN multicast network .....................................12
4.5 GMPLS network .............................................11 4.5 GMPLS network .............................................13
5. Requirements for P2MP capability exptension ...................12 5. Detailed requirements for P2MP TE extensions ..................13
5.1 P2MP LSP tunnels ..........................................12 5.1 P2MP LSP tunnels ..........................................13
5.2 P2MP explicit routing .....................................12 5.2 P2MP explicit routing .....................................14
5.3 Explicit Path Loose Hops and Widely Scoped Abstract Nodes .13 5.3 Explicit Path Loose Hops and Widely Scoped Abstract Nodes .15
5.4 P2MP LSP establishment, teardown, and modification 5.4 P2MP TE LSP establishment, teardown, and modification
mechanisms ................................................14 mechanisms ................................................16
5.5 Failure Reporting and Error Recovery ......................14 5.5 Failure Reporting and Error Recovery ......................16
5.6 Record route of P2MP TE LSP tunnels .......................15 5.6 Record route of P2MP TE LSP tunnels .......................17
5.7 Call Admission Control (CAC) and QoS control mechanism 5.7 Call Admission Control (CAC) and QoS control mechanism
of P2MP LSP tunnels .......................................15 of P2MP TE LSP tunnels ....................................18
5.8 Rerouting of P2MP TE LSP ..................................16 5.8 Reoptimization of P2MP TE LSP .............................18
5.9 IPv4/IPv6 support .........................................16 5.9 IPv4/IPv6 support .........................................19
5.10 P2MP MPLS Label ..........................................16 5.10 P2MP MPLS Label ..........................................19
5.11 Routing advertisement of P2MP capability .................17 5.11 Routing advertisement of P2MP capability .................19
5.12 Multi-Area/AS LSP ........................................17 5.12 Multi-Area/AS LSP ........................................19
5.13 P2MP MPLS management .....................................17 5.13 P2MP MPLS management .....................................20
6. Security Considerations........................................17 5.14 Scalability ..............................................20
7. Acknowledgements ..............................................17 5.15 Backwards Compatibility ..................................20
8. References ....................................................18 5.16 GMPLS ....................................................21
9. Author's Addresses ............................................19 5.17 Requirements for Hierarchical P2MP TE LSPs ...............21
5.18 P2MP Crankback routing ...................................22
6. Security Considerations........................................22
7. Acknowledgements ..............................................22
8. References ....................................................22
8.1 Normative References ......................................22
8.2 Informational References ..................................23
9. Author's Addresses ............................................24
10. Intellectual Property Consideration ...........................26
11. Full Copyright Statement ......................................26
1. Introduction 1. Introduction
Existing MPLS Traffic Engineering (MPLS-TE) allows for strict QoS
guarantees, resources optimization, and fast failure recovery but is
limited to P2P applications. There are P2MP applications like Content
Distribution, Interactive Multimedia and VPN multicast that would
also benefit from these TE capabilities. This clearly motivates for
enhancement of base MPLS-TE tool box in order to support P2MP
applications.
This document presents a set of requirements for Point-to-Multipoint This document presents a set of requirements for Point-to-Multipoint
(P2MP) Traffic Engineering (TE) extensions to Multiprotocol Label (P2MP) Traffic Engineering (TE) extensions to Multiprotocol Label
Switching (MPLS). It specifies functional requirements for RSVP-TE Switching (MPLS). It specifies functional requirements for RSVP-TE
[RFC3209] in order to deliver P2MP applications over a MPLS TE [RFC3209] in order to deliver P2MP applications over a MPLS TE.
infrastructure.
It is intended that potential solutions, that specify RSVP-TE It is intended that potential solutions, that specify RSVP-TE
procedures for P2MP TE LSP setup, use these requirements as a procedures for P2MP TE LSP setup, use these requirements as a
guideline. It is not intended to specify solution specific details guideline. It is not intended to specify solution specific details
in this document. in this document.
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 also not limited to the requirements of packet switched networks, but also
encompass the requirements of TDM, lambda and port switching networks encompass the requirements of TDM, lambda and port switching networks
managed by Generalized MPLS (GMPLS) protocols. Protocol solutions managed by Generalized MPLS (GMPLS) protocols. Protocol solutions
developed to meet the requirements set out in this document must be developed to meet the requirements set out in this document must be
equally applicable to MPLS and GMPLS. 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
capabilities. capabilities. One possible way to map P2MP flows onto LSPs in a MPLS
network is to setup multiple P2P TE LSPs, one to each of the required
One possible solution would be to setup multiple P2P TE LSPs, one egress LSRs. This requires replicating incoming packets to all the
to each of the required egress LSRs. This requires replicating P2P LSPs at the ingress LSR to accommodate multipoint communication.
incoming packets to all the P2P LSPs at the ingress LSR to This is sub-optimal. It places the replication burden on the ingress
accommodate multipoint communication. This is sub-optimal. It LSR and hence has very poor scaling characteristics. It also wastes
places the replication burden on the ingress LSR and hence has bandwidth resources, memory and MPLS (e.g. label) resources in the
very poor scaling characteristics. It also wastes bandwidth network.
resources, memory and MPLS (e.g. label) resources in the network.
Hence, to provide TE for a P2MP application in an efficient manner Hence, to provide TE for a P2MP application in an efficient manner
in a large scale environemnt, P2MP TE mechanisms are required. in a large-scale environment, P2MP TE mechanisms are required
Existing MPLS P2P TE mechanisms have to be enhanced to support P2MP specifically to support P2MP TE LSPs. Existing MPLS TE mechanisms
TE LSP setup. [RFC3209] do not support P2MP TE LSPs so new mechanisms must be
developed.
This should be achieved without running a multicast routing protocol This should be achieved without running a multicast routing protocol
in the network core and with maximum re-use of the existing MPLS in the network core and with maximum re-use of the existing MPLS
protocols. A P2MP LSP will be setup with TE constraints and will protocols in particular MPLS Traffic Engineering.
allow efficient packet replication at various branching points in
the network. RSVP-TE will be used for setting up a P2MP LSP with A P2MP TE LSP will be set up with TE constraints and will allow
enhancements to existing P2P TE LSP procedures. The P2MP TE LSP efficient packet replication at various branching points in the
setup mechanism will include the ability to add/remove receivers network. RSVP-TE will be used for setting up a P2MP TE LSP with
to/from an existing P2MP LSP. enhancements to existing P2P TE LSP procedures. The P2MP TE LSP setup
mechanism will include the ability to add/remove receivers to/from an
existing P2MP TE LSP.
Moreover, multicast traffic cannot currently benefit from P2P TE LSP.
Hence, CAC for P2P TE LSP cannot take into account the bandwidth used
for multicast traffic. P2MP TE will allow to count the bandwidth used
by unicast and multicast traffic by means of CAC.
The problem statement is discussed in the following section. This The problem statement is discussed in the following section. This
document discusses various applications that can use P2MP MPLS TE. document discusses various applications that can use P2MP TE LSP.
Detailed requirements for the setup of a P2MP MPLS TE LSP using Detailed requirements for the setup of a P2MP MPLS TE LSP using
RSVP-TE are described. Application specific requirements are also RSVP-TE are described. Application specific requirements are also
described. described.
2. Definitions 2. Definitions
2.1 Acronyms 2.1 Acronyms
P2P: P2P:
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2.2 Terminology 2.2 Terminology
The reader is assumed to be familiar with the terminology in The reader is assumed to be familiar with the terminology in
[RFC3031] and [RFC3209]. [RFC3031] and [RFC3209].
P2MP TE LSP: P2MP TE LSP:
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 more than one ingress LSR (also referred to as the root) and more than one
egress LSR (referred to as the leaf). egress LSR (also referred to as the leaf).
P2MP path: P2MP path:
The ordered set of LSRs and links that comprise the P2MP LSP. 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.
This path may be viewed as a tree.
sub-P2MP path: sub-P2MP path:
A sub-P2MP path is a portion of a P2MP path starting at A sub-P2MP path is a portion of a P2MP path starting at
a particular LSR that is a member of the P2MP path and includes a particular LSR that is a member of the P2MP path and includes
ALL downstream LSRs that are also members of the P2MP path. ALL downstream LSRs that are also members of the P2MP path.
A sub-P2MP path may be viewed as a sub-tree.
P2P sub-LSP path:
The path from the ingress LSR to a particular egress LSR.
ingress LSR: ingress LSR:
It is responsible for initiating the signaling messages that set The LSR that is responsible for initiating the signaling messages
up, modify and teardown the LSP that set up the P2MP TE LSP.
egress LSR:
One of potentially many destinations of the P2MP TE LSP. Egress
LSRs may also be referred to as leaf nodes or leaves.
bud LSR:
An LSR that is an egress, but also has one or more directly
connected downstream LSRs.
branch LSR: branch LSR:
A LSR that has more than one downstream LSR. A branch LSR receives An LSR that has more than one directly connected downstream LSR.
a single MPLS frame, makes a duplicate of it, and sends each to
downstream interfaces.
graft LSR: graft LSR:
A LSR that is already a member of the P2MP path and is in An LSR that is already a member of the P2MP path and is in
process of signaling a new sub-P2MP path. process of signaling a new sub-P2MP path.
prune LSR: prune LSR:
A LSR that is already a member of the P2MP path and is in An LSR that is already a member of the P2MP path and is in
process of tearing down an existing sub-P2MP path. process of tearing down an existing sub-P2MP path.
egress LSR:
One of potentially many destinations of the P2MP LSP. Note
that in some P2MP paths, an egress LSR may also have one or more
downstream LSRs. Such an egress LSR may also be referred to
as a branch LSR.
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 this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC2119 [5]. document are to be interpreted as described in RFC2119 [5].
3. Problem Statement 3. Problem Statement
3.1 Motivation 3.1 Motivation
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
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 existing Traffic Engineering (TE) capabilities or QoS guarantees with existing
IP multicast protocols. Note that Diff-serv (see [RFC2475],[RFC2597] IP multicast protocols. Note that Diff-serv (see [RFC2475],[RFC2597]
and [RFC3246]) combined with IP multicast routing is not sufficient and [RFC3246]) combined with IP multicast routing may not be
for P2MP applications for many of the same reasons that it is not sufficient for P2MP applications for many of the same reasons that
sufficient for unicast applications TE and constraint based routing it is not sufficient for unicast applications. Note also that
are required to enable and scale the efficient management of network multicast tree provided by existing IP multicast routing protocols
resources, mechanism to prevent congestion (including Call Admission are not optimal, which may lead to significant bandwidth wasting.
Function combined with explicit source routing, Diffserv), and to TE and Constraint Based Routing, including Call Admission Control
enable sub-second rerouting around network failures. Furthermore (CAC), explicit source routing and bandwidth reservation, is required
there are no existing P2MP mechanisms for carrying layer 2 or to enable efficient resource optimization, strict QoS guarantees, and
SONET/SDH multicast traffic over MPLS. TE capabilities are desirable fast recovery around network failures.
for both these applications.
Furthermore there are no existing P2MP mechanisms for carrying
layer 2 or SONET/SDH multicast traffic over MPLS. TE capabilities are
desirable for both these applications.
One possible solution would be to setup multiple P2P TE LSPs, one to One possible solution would be to setup multiple P2P TE LSPs, one to
each of the required egress LSRs. This requires replicating incoming each of the required egress LSRs. This requires replicating incoming
traffic to all the P2P LSPs at the ingress LSR to accommodate traffic to all the P2P LSPs at the ingress LSR to accommodate
multipoint communication. This is clearly sub-optimal. It places the multipoint communication. This is clearly sub-optimal. It places the
replication burden on the ingress LSR and hence has very poor scaling replication burden on the ingress LSR and hence has very poor scaling
characteristics. It also wastes bandwidth resources, memory and MPLS characteristics. It also wastes bandwidth resources, memory and MPLS
(e.g. label) resources in the network. (e.g. label) resources in the network.
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 in a large scale environment, P2MP TE mechanisms are efficient manner in a large scale environment, P2MP TE mechanisms are
required. Existing MPLS P2P TE mechanisms have to be enhanced to required. Existing MPLS P2P TE mechanisms have to be enhanced to
support P2MP TE LSP setup. support P2MP TE LSP.
3.2. Requirements Overview 3.2. Requirements Overview
This document is proposing requirements for the setup of P2MP TE This document is proposing requirements for the setup of P2MP TE
LSPs. This should be achieved without running a multicast routing LSPs. This should be achieved without running a multicast routing
protocol in the network core and with maximum re-use of the existing protocol in the network core and with maximum re-use of the existing
MPLS protocols. Note that the use of MPLS forwarding to carry the MPLS protocols. Note that the use of MPLS forwarding to carry the
multicast traffic may also be useful in the context of some network multicast traffic may also be useful in the context of some network
design where it is being desired to avoid running some multicast design where it is being desired to avoid running some multicast
routing protocol like PIM [PIM-SM] or BGP (which might be required routing protocol like PIM [PIM-SM] or BGP (which might be required
for the use of PIM). for the use of PIM).
A P2MP LSP will be setup with TE constraints and will allow efficient
MPLS packet replication at various branching points in the network. A P2MP LSP will be set up with TE constraints and will allow
RSVP-TE will be used for setting up a P2MP LSP with enhancements to efficient MPLS packet replication at various branching points in the
existing P2P TE LSP procedures. network. RSVP-TE will be used for setting up a P2MP TE LSP with
enhancements to existing P2P TE LSP procedures.
The P2MP TE LSP setup mechanism will include the ability to The P2MP TE LSP setup mechanism will include the ability to
add/remove receivers to/from an existing P2MP LSP and should support add/remove egress LSRs to/from an existing P2MP TE LSP and should
all the TE LSP management procedures defined for P2P TE LSP support all the TE LSP management procedures defined for P2P TE LSP
(like the non disruptive rerouting (so called "Make before break" (like the non disruptive rerouting - the so called "Make before
procedure). break" procedure).
The computation of P2MP TE paths is implementation dependent and is The computation of P2MP TE paths 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.
The MPLS WG will specify how to build solutions for the setup a P2MP The MPLS WG will specify how to build P2MP TE LSPs. The usage of
TE LSP. The usage of those solutions will be application dependent those solutions will be application dependent and is out of the scope
and is out of the scope of this draft. of this draft. However, it is a requirement that those solutions be
applicable to GMPLS as well as MPLS so that only a single set of
solutions are developed.
Consider the following figure. Consider the following figure.
Source 1 (S1) Source 1 (S1)
| |
I-LSR1 I-LSR1
| | | |
| | | |
R2----E-LSR3--LSR1 LSR2---E-LSR2--Receiver 1 (R1) R2----E-LSR3--LSR1 LSR2---E-LSR2--Receiver 1 (R1)
| : | :
R3----E-LSR4 E-LSR5 R3----E-LSR4 E-LSR5
| : | :
| : | :
R4 R5 R4 R5
Figure 1. Figure 1
The above figure shows I(Ingress)-LSR1, E(Egress)-LSR2, E-LSR3 and The figure above shows a single ingress (I-LSR1), and four egresses
E-LSR4. I-LSR1 is attached to a traffic source that is generating (E-LSR2, E-LSR3, E-LSR4 and E-LSR5). I-LSR1 is attached to a traffic
traffic for a P2MP application. E-LSR2, E-LSR3 and E-LSR4 are source that is generating traffic for a P2MP application.
attached to receivers that are interested in receiving traffic for Receivers:R1, R2, R3 and R4 are attached to E-LSR2, E-LSR3 and
the application. The following are the objectives that we wish to E-LSR4.
achieve:
a) A P2MP TE LSP path information which satisfies various The following are the objectives that we wish to achieve:
a) A P2MP TE LSP path which satisfies various
constrains is pre-determined and supplied to ingress I-LSR1. constrains is pre-determined and supplied to ingress I-LSR1.
Note that no assumption is made on whether the path is provided
to I-LSR1 or computed by I-LSR1.
Typical constraints are bandwidth requirements, resource class Typical constraints are bandwidth requirements, resource class
affinities, fast rerouting, preemption, along with several affinities, fast rerouting, preemption. There should not be any
potential other constraints. There should not be any
restriction on the possibility to support the set of restriction on the possibility to support the set of
constraints already defined for point to point TE LSPs. constraints already defined for point to point TE LSPs.
b) Set up a P2MP TE LSP from I-LSR1 to E-LSR2, E-LSR3 and E-LSR4
using the path information which could have been computed by b) A P2MP TE LSP is set up by means of RSVP-TE from I-LSR1 to
some off-line or on-line algorithms. E-LSR2, E-LSR3 and E-LSR4 using the path information.
c) In this case, the branch LSR1 should replicate incoming packets c) In this case, the branch LSR1 should replicate incoming packets
and send them to E-LSR3 and E-LSR4. and send them to E-LSR3 and E-LSR4.
d) The P2MP TE LSP should be setup by enhancing existing RSVP-TE
P2P procedures and without any requirement for multicast d) If a new receiver (R5) expresses an interest in receiving
routing protocol in the network core. traffic, a new path is determined and a sub-P2MP path from
e) The solution should provide the ability to gracefully modify LSR2 to E-LSR5 is grafted onto the P2MP path. LSR2 becomes
P2MP TE LSP (i.e add/remove some part of the p2mp TE LSP a branch LSR.
without requiring to entirely tearing down or setting up a
completely new p2mp TE LSP). Such operations should be
performed in a non traffic disruptive fashion. In this case,
a sub-P2MP path LSR2->E-LSR5 is grafted and pruned based on
traffic destination change.
4. Application Specific Requirements 4. Application Specific Requirements
This section describes some of the applications that P2MP MPLS This section describes some of the applications that P2MP MPLS
TE is applicable to along with application specific requirements, TE is applicable to along with application specific requirements.
if any.
4.1 P2MP tunnel for IP multicast data The purpose of this section is not to mandate how P2MP TE LSPs must
be used in certain application scenarios. Rather it is to illustrate
some of the potential application scenarios so as to highlight
the features and functions that any P2MP solution must provide in
order to be of wide use and applicability. This section is not meant
to be exhaustive and not limited to the described applications.
One typical scenario is to use P2MP TE LSPs as P2MP tunnels of 4.1 P2MP TE LSP for IP multicast data
multicast data traffic (e.g. IP mcast). In this scenario, a P2MP LSP
tunnel is established between an ingress LSR which accomodates One typical scenario is to use P2MP TE LSPs as P2MP tunnels carrying
IP multicast source and several egress LSRs which accomodate several multicast data traffic (e.g. IP mcast). In this scenario, a P2MP TE
IP multicast receivers. Instead of using IP multicast routing LSP is established between an ingress LSR which supports
protocol in the network core, a P2MP LSP tunnel is established over IP multicast source and several egress LSRs which support several
the network and IP multicast data are tunnelled from an ingress LSR IP multicast receivers. Instead of using an IP multicast routing
node to multiple egress leaf LSRs with the data replication at the protocol in the network core, a P2MP TE LSP is established over
branch LSRs in the network core. Figure 2 shows this example. the network and IP multicast data are tunneled from an ingress LSR
Note that a P2MP TE LSP can be established over multiple AREAs/ASs. node to multiple egress leaf LSRs with data replication at the
branch LSRs in the network core. Figure 2 shows an example.
Note that a P2MP TE LSP can be established over multiple areas/ASs
and that the egress LSRs may deliver data into an IP multicast
network.
Mcast Source Mcast Source
| |
+---------------I-LSR0----------------+ +---------------I-LSR0----------------+
| | | | | |
| LSR0 +----E-LSR2---R2 | LSR0 +----E-LSR2---R2
| / \ / | | / \ / |
R1---E-LSR1---LSR2-----LSR1 LSR3----LSR4----E-LSR3---R3 R1---E-LSR1---LSR2-----LSR1 LSR3----LSR4----E-LSR3---R3
| / \ \ | | / \ \ |
| / \ +----E-LSR4---R4 | / \ +----E-LSR4---R4
skipping to change at page 9, line 5 skipping to change at page 10, line 30
+-------- / ------++------ \ ---------+ +-------- / ------++------ \ ---------+
| | || | | | || |
R5---E-LSR5--------LSR5 || IPmcast Network | R5---E-LSR5--------LSR5 || IPmcast Network |
| / \ || | | / \ || |
+-E-LSR6---E-LSR7-++----MR0--MR1------+ +-E-LSR6---E-LSR7-++----MR0--MR1------+
| | | | | | | |
R6 R7 R8 R9 R6 R7 R8 R9
Figure 2 Figure 2
4.2 P2MP backbone network for IP multicast network 4.2 P2MP TE backbone network for IP multicast network
In this scenario, P2MP TE LSPs are utilized to construct a P2MP P2MP TE LSPs are applicable in a backbone network to construct or
backbone network for multicast network (e.g. IPmcast network). Each support a multicast network(e.g. IPmcast network).
IP multicast access networks is interconnected by a P2MP TE LSP. The IP multicast access networks are interconnected by P2MP TE LSPs.
A P2MP LSP is established from an ingress LSR which accomodates IP A P2MP TE LSP is established from an ingress LSR which accommodates
multicast network that has a Mcast Source to multiple egress LSRs an IP multicast network that has a multicast source to multiple
which accomodate an IP multicast network. In this scenario, egress LSRs which each accommodate an IP multicast network.
ingress/egress LSRs placed at the edge of multicast network must
handle IP multicast routing protocol. This means that each In this scenario, ingress/egress LSRs placed at the edge of multicast
ingress/egress LSR exchanges IP multicast routing messages as network must handle an IP multicast routing protocol. This means that
neighbour router. Figure 3 shows a network example of this scenario. the ingress/egress LSRs exchange IP multicast routing messages as
A P2MP LSP is established from a I-LSR1 to E-LSR2, E-LSR3, E-LSR4 and neighbour routers. Figure 3 shows a network example of this scenario.
each ingress/egress LSR exchanges the multicast routing messages each
other. 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
with each other.
As specified in the section on the problem statement it should be As specified in the section on the problem statement it should be
possible for a solution to add/remove egress LSRs to/from the possible for a solution to add/remove egress LSRs to/from the
P2MP MPLS TE LSP. IP multicast group membership distribution between P2MP MPLS TE LSP. IP multicast group membership distribution between
the egress LSRs may change frequently. This in turn may require a the egress LSRs may change frequently. This in turn may require a
potential P2MP MPLS TE solution, that is suitable for IP multicast, potential P2MP MPLS TE solution, that is suitable for IP multicast,
to handle additions/deletions of egress LSRs at a rapid rate. to handle additions/deletions of egress LSRs with an appropriate
reactiveness.
It is recommended to support a message exchange mechanism on top of It is recommended to support a message exchange mechanism on top of
P2MP LSP setup mechanism to support multicast (S, G) Join/ Leave and P2MP LSP setup mechanism to support multicast (S, G) Join/Leave.
to allow the ingress LSR to hold sufficient information in order to
optimise multicast FEC on sender nodes.
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 10, line 31 skipping to change at page 11, line 46
R1---MR---MR || MR || MR__ | R1---MR---MR || MR || MR__ |
| / \ || / \ || / \ \MR---R8 | / \ || / \ || / \ \MR---R8
+--MR--MR--++----MR--MR---++--MR--MR--+ +--MR--MR--++----MR--MR---++--MR--MR--+
| | | | | | | | | | | |
R2 R3 R4 R5 R6 R7 R2 R3 R4 R5 R6 R7
Figure 3 Figure 3
4.3 Layer 2 Multicast Over MPLS 4.3 Layer 2 Multicast Over MPLS
Existing layer 2 networks offer multicast video services. These are Existing layer 2 networks offer multicast video services. These
typically carried using layer 2 NBMA technology such as ATM or are typically carried using layer 2 NBMA technology such as ATM
layer 2 BA technology such as Ethernet. It may be desirable to or layer 2 Broadcast Access technology such as Ethernet. It may be
deliver these layer 2 multicast services over a converged MPLS desirable to deliver these layer 2 multicast services over a
infrastructure where P2MP TE LSPs are used instead. converged MPLS infrastructure where P2MP TE LSPs are used instead.
For instance, several SPs provision P2MP ATM VCs for TV/ADSL
services. These P2MP VCs are setup between a video server and a set
of ATM DSLAMs. Each channel is carried in a distinct P2MP VC. These
VC maybe be routed independently, or may all be nested into a unique
PVC, connecting the video sever to all DSLAMs.
Such service could benefit from a P2MP MPLS-TE control plane. An
option is to setup a permanent P2MP TE LSP between the video server
and all DSLAMs, that would correspond to a PVC carrying all channel
VCs. In this case each DSLAM receives all channels, even if there are
no receivers that are registered for a given channel. This ensure
fast zapping, but lead to significant bandwidth wasting.
A second option is to setup a distinct P2MP TE LSP per channel. If a
client, behind a DSLAM, zaps to a new channel, then the DSLAM has
to be added to the P2MP TE LSP carrying this channel using a P2MP TE
grafting procedure. Pruning procedure has to be used to remove a
DSLAM from the P2MP TE LSP if it is not already egress LSR for that
LSP because all the clients, behind the DSLAM, stop watching the
channel.
4.4 VPN multicast network 4.4 VPN multicast network
In this scenario, P2MP TE LSPs are utilized to construct a provider In this scenario, P2MP TE LSPs are utilized to construct a provider
network which can deliver VPN multicast service(s) to its customers. network which can deliver VPN multicast service(s) to its customers.
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 VPN instance. multicast packets. Each PE router must handle a VPN instance.
For example, in Layer3 VPN like BGP/MPLS based IP VPN For example, in Layer3 VPNs like BGP/MPLS based IP VPNs
[BGP/MPLS IP VPNs], this means that each PE router must handle both [BGP/MPLS IP VPNs], 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. It is routing information between the corresponding PE routers. It is
desirable that P2MP MPLS TE can be used for Layer3 VPN's data desirable that P2MP MPLS TE can be used for Layer3 VPN data
transmission. transmission.
Another example is Layer2 VPN that supports multipoint Another example is a Layer2 VPN that supports multipoint
LAN connectivity service. In Ethernet network environment, IP LAN connectivity service. In an Ethernet network environment, IP
multicast data is flooded to the appropriate Ethernet port(s). In multicast data is flooded to the appropriate Ethernet port(s).
Ethernet multipoint L2 VPN service provided by MPLS, this function is
achieved by switching MPLS encapsulated frames towards the relevant
PE nodes. But if existing P2P TE LSPs are used as tunnels between
PEs, any ingress PE must duplicate the frames and the send them to
the corresponding PEs. This means data stream is flooded just from
ingress PE, which will waste provider's network resources.
So, for Layer 2 VPNs, it is desirable that P2MP MPLS TE LSPs are used
for data transmission instead of P2P MPLS TE LSPs, contributing in
turn to savings of network resources.
4.5 GMPLS Network An Ethernet multipoint Layer2 VPN service provided by MPLS, this
function is achieved by switching MPLS encapsulated frames towards
the relevant PE nodes. But if existing P2P TE LSPs are used as
tunnels between PEs, any ingress PE must duplicate the frames and
send them to the corresponding PEs. This means the data stream is
flooded just from the ingress PE, which will waste the provider's
network resources.
So, for Layer 2 VPNs that are required to support multicast traffic,
it is desirable that P2MP MPLS TE LSPs are used for data transmission
instead of P2P MPLS TE LSPs, contributing in turn to savings of
network resources.
This document does not set requirements for how multicast VPNs are
provided, but it does set requirements for the function that must be
available in P2MP MPLS solutions. Therefore, it is not a requirement
that multicast VPNs utilize P2MP MPLS, but it is a requirement that
P2MP MPLS solutions should be capable of supporting multicast VPNs.
4.5 GMPLS Networks
GMPLS supports only P2P TE-LSPs just like MPLS. GMPLS enhances MPLS GMPLS supports only P2P TE-LSPs just like MPLS. GMPLS enhances MPLS
to support four new classes of interfaces Layer-2 Switch Capable to support four new classes of interfaces: Layer-2 Switch Capable
(L2SC), Time-Division Multiplex (TDM), Lambda Switch Capable (LSC) (L2SC), Time-Division Multiplex (TDM), Lambda Switch Capable (LSC)
and Fiber-Switch Capable (FSC) in addition to Packet Switch Capable and Fiber-Switch Capable (FSC) in addition to Packet Switch Capable
(PSC) already supported by MPLS. All of these interface classes have (PSC) already supported by MPLS. All of these interface classes have
so far been limited to P2P TE LSPs (see [RFC 3473] and [RFC 3471]). so far been limited to P2P TE LSPs (see [RFC 3473] 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 candidates distribution services such as video distribution are prime candidates
to use P2MP features. Therefore, it is a requirement that all the to use P2MP features. Therefore, it is a requirement that all the
features/mechanisms (and protocol extensions) that will be defined to features/mechanisms (and protocol extensions) that will be defined to
provide MPLS P2MP TE LSPs will be equally applicable to P2MP PSC and provide MPLS P2MP TE LSPs will be equally applicable to P2MP PSC and
non-PSC TE-LSPs. non-PSC TE-LSPs.
This also means that solutions for MPLS P2MP TE-LSPs when applied 5. Detailed requirements for P2MP TE extensions
to GMPLS P2MP PSC and non-PSC TE-LSPs shall be backward and
forward compatible with the other features of GMPLS including:
o control and data plane separation (IF_ID RSVP_HOP and
IF_ID ERROR_SPEC),
o full support of numbered and unnumbered TE links (see [RFC 3477]
and [GMPLS-ROUTING]),
o use of the GENERALIZED_LABEL_REQUEST and the GENERALIZED_LABEL
(C-Type 2 and 3) in conjunction with the LABEL_SET and the
ACCEPTABLE_LABEL_SET object,
o processing of the ADMIN_STATUS object,
o processing of the PROTECTION object,
o support of Explicit Label Control,
o processing of the Path_State_Removed Flag,
o handling of Graceful Deletion procedures.
In addition, since non-PSC TE-LSPs may have to be processed in
environments where the "P2MP capability" could be limited, specific
constraints may also apply during the P2MP TE Path computation. Being
technology specific, these constraints are outside the scope of this
document. However, technology independent constraints (i.e.
constraints that are applicable independently of the LSP class)
should be allowed during P2MP TE LSP message processing. It has to be
emphasized that path computation and management techniques shall be
as close as possible than those being used for PSC P2P and P2MP TE
LSPs.
5. Requirements for P2MP capability extension
5.1 P2MP LSP tunnels 5.1 P2MP LSP tunnels
The P2MP RSVP-TE extensions MUST be applicable to signaling LSPs The P2MP RSVP-TE extensions MUST be applicable to signaling 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 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
typical examples. typical examples.
As with P2P MPLS technology[RFC3031], traffic is classified with As with P2P MPLS technology[RFC3031], traffic is classified with
FEC in this extension. All packets which belong to a particular FEC FEC in this extension. All packets which belong to a particular FEC
and which travel from a particular node MUST follow the same P2MP and which travel from a particular node MUST follow the same P2MP
path. path.
In order to scale to a large number of branches, P2MP TE LSPs should In order to scale to a large number of branches, P2MP TE LSPs should
be identified by unique identifier that is constant for the whole LSP be identified by unique identifier that is constant for the whole LSP
regardless of the number of branches and/or leaves. Therefore, the regardless of the number of branches and/or leaves. Therefore, the
identification of the P2MP session by its destination addresses is identification of the P2MP session by its destination addresses is
not adequate. not adequate.
5.2 P2MP explicit routing 5.2 P2MP explicit routing
Various optimizations in P2MP path formation need to be applied to Various optimizations in P2MP path formation need to be applied to
meet various needs such as bandwidth guarantees, delay requirements, meet various QoS requirements and operational constraints.
and minimization of the total P2MP path cost. Some P2MP applications may request a bandwidth guaranteed P2MP path
which satisfies end-to-end delay requirements. And some operators
may want to set up a cost minimum P2MP path by specifying branch 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 paths. Figure 4 shows two typical examples. arbitrary P2MP paths under the control of an external path
computation process or path configuration process or dynamic path
computation process located on the ingress LSR. Figure 4 shows two
typical examples.
A A A A
| / \ | / \
B B C B B C
| / \ / \ | / \ / \
C D E F G C D E F G
| / \ / \/ \ / \ | / \ / \/ \ / \
D--E*-F*-G*-H*-I*-J*-K*--L H I J KL M N O D--E*-F*-G*-H*-I*-J*-K*--L H I J KL M N O
Steiner P2MP path SPF P2MP path Steiner P2MP path SPF P2MP path
Figure 4 Examples of P2MP LSP topology Figure 4 Examples of P2MP TE LSP topology
One example is Steiner[STEINER] P2MP path (Cost minimum P2MP path). One example is Steiner[STEINER] P2MP path (Cost minimum P2MP path).
This P2MP path is suitable for constructing cost minimum P2MP path. This P2MP path is suitable for constructing cost minimum P2MP path.
To realize this P2MP path, several intermediate LSRs must be both To realize this P2MP path, several intermediate LSRs must be both
MPLS data terminating LSR and transit LSR (LSR E, F, G, H, I, J, K, MPLS data terminating LSR and transit LSR (LSR E, F, G, H, I, J, K,
in the figure). This means that the LSR must perform both label in the figure 4). This means that the LSR must perform both label
swapping and popping at the same time. Therefore, the P2MP TE swapping and popping at the same time. Therefore, the P2MP TE
solution MUST support a mechanism that can setup this kind of solution MUST support a mechanism that can setup this kind of
terminate LSR between a ingress LSR and egress LSRs. bud LSR between an ingress LSR and egress LSRs.
Another example is CSPF (Constraint Shortest Path Fast) P2MP path. By Another example is CSPF (Constraint Shortest Path Fast) P2MP path. By
some metric (which can be set upon any specific criteria like the some metric (which can be set upon any specific criteria like the
delay, bandwidth, a combination of those), one can calculate a cost delay, bandwidth, a combination of those), one can calculate a cost
minimum P2MP path. This P2MP path is suitable for carrying real time minimum P2MP path. This P2MP path is suitable for carrying real time
traffic. traffic.
To support explicit setup of any reasonable P2MP path shape, a P2MP To support explicit setup of any reasonable P2MP path shape, a P2MP
TE solution must support some form of explicit source-based control TE solution MUST support some form of explicit source-based control
of the P2MP path. This can be used by the ingress LSR to setup the of the P2MP path which can explicitly include particular LSRs as
P2MP LSP. Being implementation specific (more precisely dependent of branch nodes. This can be used by the ingress LSR to setup the P2MP
TE LSP. Being implementation specific (more precisely dependent of
the data structure specific representation and its processing), the the data structure specific representation and its processing), the
detailed method for controlling the P2MP TE LSP topology depends on detailed method for controlling the P2MP TE LSP topology depends on
how the control plane represents the P2MP TE LSP data plane entity. how the control plane represents the P2MP TE LSP data plane entity.
For instance, a P2MP TE LSP can be simply represented by its
individual branches or as a whole. Here also, effectiveness of the For instance, a P2MP TE LSP can be simply represented as a
potential solutions is left outside the scope of this document. whole tree or by its individual branches.
In any case, it is expected that this control must be driven by the
ingress LSR. Here also, effectiveness of the potential solutions is left outside
the scope of this document. In any case, it is expected that this
control must be driven by the ingress LSR.
5.3 Explicit Path Loose Hops and Widely Scoped Abstract Nodes 5.3 Explicit Path Loose Hops and Widely Scoped Abstract Nodes
A P2MP path is completely specified if all of the required A P2MP path is completely specified if all of the required
branches and hops between a sender and leaf LSR are indicated. branches and hops between a sender and leaf LSR are indicated.
A P2MP path is partially specified if only a subset of intermediate A P2MP path is partially specified if only a subset of intermediate
branches and hops are indicated. This may be achieved using branches and hops are indicated. This may be achieved using
loose hops in the explicit path, or using widely scoped abstract loose hops in the explicit path, or using widely scoped abstract
nodes such as IPv4 prefixes shorter than 32 bits or AS numbers. nodes such as IPv4 prefixes shorter than 32 bits or AS numbers.
skipping to change at page 14, line 25 skipping to change at page 16, line 5
based control of the P2MP path as defined in the previous based control of the P2MP path as defined in the previous
section. Where this support is provided, protocol solutions section. Where this support is provided, protocol solutions
MUST allow downstream LSRs to apply further explicit MUST allow downstream LSRs to apply further explicit
control to the P2MP path to resolve a partially specified path control to the P2MP path to resolve a partially specified path
into a (more) completely specified path. into a (more) completely specified path.
Protocol solutions MUST allow the P2MP path to be completely Protocol solutions MUST allow the P2MP path to be completely
specified at the ingress where sufficient information exists to allow specified at the ingress where sufficient information exists to allow
the full path to be computed. the full path to be computed.
In all cases, the egress nodes of the P2MP LSP must be fully In all cases, the egress nodes of the P2MP TE LSP must be fully
specified. specified.
5.4 P2MP LSP establishment, teardown, and modification mechanisms In case of path being computed by some downstream LSRs (e.g. case of
hops specified as loose hops), the solution SHOULD provide the
ability for the ingress LSR of the P2MP TE LSP to learn the full
P2MP path. Note that this requirement may be relaxed in some
environment (e.g. Inter-AS) where confidentiality must be preserved.
5.4 P2MP TE LSP establishment, teardown, and modification mechanisms
The P2MP TE solution must support large scale P2MP TE LSPs The P2MP TE solution must support large scale P2MP TE LSPs
establishment and teardown in a scalable manner. establishment and teardown in a scalable manner.
In addition to whole P2MP TE LSP establishment and teardown In addition to P2MP TE LSP establishment and teardown mechanism,
mechanism, it SHOULD implement partial P2MP path modification it SHOULD implement partial P2MP path modification mechanism.
mechanism.
For the purpose of adding sub-P2MP TE LSPs for existing P2MP TE LSP, For the purpose of adding sub-P2MP TE LSPs for existing P2MP TE LSP,
the extension SHOULD support grafting mechanism. For the purpose of the extension SHOULD support grafting mechanism. For the purpose of
deleting a sub-P2MP TE LSPs from existing P2MP TE LSP, the extension deleting a sub-P2MP TE LSPs from existing P2MP TE LSP, the extension
SHOULD support pruning mechanism. SHOULD support pruning mechanism.
It is RECOMMENDED that these grafting and pruning operations do not It is RECOMMENDED that these grafting and pruning operations do not
cause any additional processing in nodes except along the path to the cause any additional processing in nodes except along the path to the
grafting and pruning node and its downstream nodes. grafting and pruning node and its downstream nodes. Moreover, both
grafting and pruning operations MUST not be traffic disruptive for
the traffic currently forwarded along the P2MP path.
5.5 Failure Reporting and Error Recovery 5.5 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 LSP. These events must be reported upstream as detached from the P2MP TE LSP. These events must be reported upstream
for a P2P LSP. as for a P2P LSP.
Protection and recovery techniques SHOULD be applied to the LSP to The solution SHOULD provide recovery techniques such as protection
build new sub-P2MP LSPs or use backup sub-P2MP LSPs to restore the and restoration allowing to recover any impacted sub-P2MP TE LSPs.
data to the severed egress nodes. In particular, it is required to provide fast protection mechanisms
applicable to P2MP TE LSP similar to the solutions specified in [FRR]
for P2P TE LSPs. Note also that no assumption is made on whether
backup paths for P2MP TE LSPs should or not be shared with P2P TE
LSPs backup paths.
A P2MP TE solution MUST support P2MP fast protection mechanism
to handle P2MP applications sensitive to traffic disruption.
The report of the failure of delivery to fewer than all of the egress The report of the failure of delivery to fewer than all of the egress
nodes SHOULD NOT cause automatic teardown of the P2MP LSP. That is, nodes SHOULD NOT cause automatic teardown of the P2MP TE LSP.
while some egress nodes remain connected to the P2MP path it should That is, while some egress nodes remain connected to the P2MP path it
be a matter of local policy at the ingress whether the P2MP LSP is should be a matter of local policy at the ingress whether the P2MP
retained. LSP is retained.
When all egress node downstreams of a branch node have become When all egress node downstreams of a branch node have become
disconnected from the P2MP path, and the branch node is unable to disconnected from the P2MP path, and the some branch node is unable
restore connectivity to any of them through recovery or protection to restore connectivity to any of them through recovery or protection
mechanisms, the branch node MAY remove itself from the P2MP path. mechanisms, the branch node MAY remove itself from the P2MP path.
Since the faults that severed the various downstream egress nodes Since the faults that severed the various downstream egress nodes
from the P2MP path may be disperate, the branch node MUST report all from the P2MP path may be disparate, the branch node MUST report all
such errors to its upstream neighbor. such errors to its upstream neighbor. The ingress node can then
decide to re-compute the path to that particular egress node, around
the failure point.
Solutions MAY include the facility for transit LSRs and particularly
branch nodes to recompute sub-P2MP paths to restore them after
failures. In the event of successful repair, no error notification is
reported to upstream nodes, but the new paths are reported if route
recording is in use. Crankback requirements are discussed in
[CRANKBACK].
5.6 Record route of P2MP TE LSP tunnels 5.6 Record route of P2MP TE LSP tunnels
Being able to identify the established topology of P2MP LSP is very Being able to identify the established topology of P2MP TE LSP is
important for various purpose:Management, operation of some local very important for various purpose:Management, operation of some
recovery mechanism like Fast Reroute [FRR]. A network operator uses local recovery mechanism like Fast Reroute [FRR]. A network operator
this information to manage P2MP LSP. Therefore, topology information uses this information to manage P2MP TE LSP. Therefore, topology
MUST be collected and updated after P2MP LSP establishment and information MUST be collected and updated after P2MP TE LSP
modification process. establishment and modification process.
For this purpose, conventional Record Route mechanism is useful. For this purpose, conventional Record Route mechanism is useful.
As with other conventional mechanism, this information should be As with other conventional mechanism, this information should be
forwarded upstream towards the sender node. The P2MP TE solution MUST forwarded upstream towards the sender node. The P2MP TE solution MUST
support a mechanism which can collect and update P2MP path topology support a mechanism which can collect and update P2MP path topology
information after P2MP LSP establishment and modification process. information after P2MP LSP establishment and modification process.
It is RECOMMENDED that those information are collected in a data It is RECOMMENDED that those information are collected in a data
format by which the sendor node can recognize the P2MP path topology format by which the sender node can recognize the P2MP path topology
without involving some complicated data calculation process. without involving some complicated data calculation process.
The solution MUST support the recording of both outgoing interfaces
or node-id [NODE-ID].
5.7 Call Admission Control (CAC) and QoS Control mechanism 5.7 Call Admission Control (CAC) and QoS Control mechanism
of P2MP LSP tunnels of P2MP TE LSP tunnels
P2MP LSP share network resource with P2P LSP. Therefore it is P2MP TE LSP share network resource with P2P TE LSP. Therefore it is
important to use CAC and QoS as P2P LSP for easy and scalable important to use CAC and QoS as P2P TE LSP for easy and scalable
operation. operation.
In particular, it should be highlighted that because In particular, it should be highlighted that because
mutliacst traffic cannot make use of point to point TE LSP, multicast Multicast traffic cannot make use of point to point TE LSP, multicast
traffic cannot be easily taken into account by point to point in traffic cannot be easily taken into account by point to point in
order to perform CAC. The use of P2MP TE LSP will now allow for an order to perform CAC. The use of P2MP TE LSP will now allow for an
accounting of the unicast and multicast traffic for bandwidth accounting of the unicast and multicast traffic for bandwidth
reservation. reservation.
P2MP TE solution MUST both supports FF and SE reservation style. P2MP TE solution MUST both supports FF and SE reservation style.
P2MP TE solution MUST be applicable to Diffserv-enabled network P2MP TE solution MUST be applicable to Diffserv-enabled network
that can provide consistent QoS control in P2MP LSP traffic. that can provide consistent QoS control in P2MP LSP traffic.
This solution SHOULD also satisfy DS-TE requirement [RFC3564] and This solution SHOULD also satisfy DS-TE requirement [RFC3564] and
interoprable smoothly with current P2P DS-TE protocol specification. interoperable smoothly with current P2P DS-TE protocol specification.
5.8 Rerouting of P2MP TE LSP Note that this requirement document does not make any assumption on
the type of bandwidth pool used for P2MP TE LSP which can either be
shared with P2P TE LSP or be dedicated.
The detection of a more optical path and network resource failure(s) 5.8 Reoptimization of P2MP TE LSP
(such as link(s) and node(s)) are examples of situation where P2MP TE
LSP re-routing is needed. While re-routing is in progress, an
important requirement is avoiding traffic disruption. An additional
requirement is avoiding double bandwidth reservation (over the common
parts between the old and new LSP) through the use of resource
sharing. Make-before-break (see [RFC 3209]) delivers simultaneously a
solution to these requirements.
Make-Before-Break MUST be supported for a P2MP TE LSP to ensure The detection of a more optimal path is an example of situation where
that there is no traffic disruption when the P2MP TE LSP is rerouted. P2MP TE LSP re-routing is may be required. While re-routing is in
progress, an important requirement is avoiding double bandwidth
reservation (over the common parts between the old and new LSP)
thorough the use of resource sharing. Make-before-break
(see [RFC3209]) delivers simultaneously a solution to these
requirements.
And a P2MP TE solution MUST support P2MP fast rerouting mechanism Make-before-break MUST be supported for a P2MP TE LSP to ensure that
to handle P2MP applications sensitive to traffic disruption. there is no traffic disruption when the P2MP TE LSP is rerouted.
There is a possibility to achieve make-before-break that only
applies to a sub-P2MP path without impacting the data on the all of
the other parts of the P2MP path.
The solution SHOULD allow for make-before-break reoptimization of
a sub-tree with no impact on the rest of the tree (no label
reallocation, no change in identifiers...).
Such reoptimization MAY be initiated by the sub-tree root branch
node. (e.g. the branch node setup a new sub-tree, then splices
traffic on the new subtree and delete the former sub-tree).
5.9 IPv4/IPv6 support 5.9 IPv4/IPv6 support
A P2MP TE solution MUST be applicable to IPv4/IPv6. A P2MP TE solution MUST be applicable to IPv4/IPv6.
5.10 P2MP MPLS Label 5.10 P2MP MPLS Label
A P2MP TE solution MUST support establishment of both P2P and A P2MP TE solution MUST support establishment of both P2P and
P2MP TE LSP and MUST NOT impede the operation of P2P LSPs within P2MP TE LSP and MUST NOT impede the operation of P2P TE LSPs within
the same network. A P2MP TE solution MUST be specified in such the same network. A P2MP TE solution MUST be specified in such
a way that it allows P2MP and P2P LSPs to be signaled on the a way 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 same interface. Labels for P2MP TE LSPs and P2P TE LSPs MAY be
assigned from shared or dedicated label space(s). Label space assigned from shared or dedicated label space(s). Label space
shareability is implementation specific. shareability is implementation specific.
5.11 Routing advertisement of P2MP capability 5.11 Routing advertisement of P2MP capability
This document has identified several high-level requirements for This document has identified several high-level requirements for
enhancements to routing protocols to support P2MP MPLS. enhancements to routing and signalling protocols to support
These are needed to facilitate the computation of P2MP paths using TE P2MP MPLS. These are needed to facilitate the computation of P2MP
constraints so that explicit source-control may be applied to the LSP paths using TE constraints so that explicit source-control may be
paths as they are signaled through the network. applied to the LSP paths as they are signaled through the network.
These requirements include but not restricted to: These requirements include but not restricted to:
- the ability of an LSR to support branching - the ability of an LSR to support branching.
- 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 applicability of these requirements is for further study. The applicability of these requirements is for further study.
These requirements are developed in a separate document. These requirements are developed in a separate document.
5.12 Multi-Area/AS LSP 5.12 Multi-Area/AS LSP
P2MP TE solution SHOULD support multi-Area/AS LSP. P2MP TE solution SHOULD support multi-Area/AS LSP.
A separate document may deal with the specifics of inter-area
and inter-AS P2MP TE LSPs.
5.13 P2MP MPLS management 5.13 P2MP MPLS management
The MPLS MIB should be enhanced to provide P2MP TE LSP management. The MPLS MIB should be enhanced to provide P2MP TE LSP management.
P2MP TE LSPs MUST have a unique identifier whose definition MAY be P2MP TE LSPs MUST have a unique identifier whose definition MAY be
partially or entirely shared with P2P TE LSP identifiers used for partially or entirely shared with P2P TE LSP identifiers used for
management purposes. management purposes.
5.14 Scalability
Scalability is a key requirement in P2MP MPLS systems. Solutions
should be designed to scale well with an increase in the number of
any of the following: the number of recipients, the number of branch
points and the number of branches. Both scalability of performance
and operation must be considered.
Key considerations may include:
- the amount of refresh processing associated with maintaining a
P2MP TE LSP.
- the amount of protocol state that must be maintained by transit
LSRs along a P2MP path.
- the number of protocol messages required to set up or tear down
a P2MP LSP as a function of the number of egress LSRs.
- the number of protocol messages required to repair a P2MP LSP
after failure or perform make-before-break.
- the amount of protocol information transmitted to manage a P2MP
TE LSP (i.e. the message size).
- the amount of potential routing extensions.
- the amount of control plane processing required by the ingress,
transit and egress LSRs to add/delete a branch LSP to/from an
existing P2MP LSP.
5.15 Backwards Compatibility
It should be an aim of any P2MP solution to offer as much backward
compatibility as possible. An ideal would be to offer P2MP services
across legacy MPLS networks without any change to any LSR in the
network.
If this ideal cannot be achieved, the aim should be to use legacy
nodes as both transit non-branch LSRs and egress LSRs.
It is a further requirement of all protocol solutions that any LSR
that implements the solution shall not be prohibited by that act from
supporting P2P TE LSPs using existing signaling mechanisms. That is,
unless administratively prohibited, P2P TE LSPs must be supported
through a P2MP network.
5.16 GMPLS
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 other features of GMPLS including:
o control and data plane separation (IF_ID RSVP_HOP and
IF_ID ERROR_SPEC),
o full support of numbered and unnumbered TE links (see [RFC 3477]
and [GMPLS-ROUTING]),
o use of the GENERALIZED_LABEL_REQUEST and the GENERALIZED_LABEL
(C-Type 2 and 3) in conjunction with the LABEL_SET and the
ACCEPTABLE_LABEL_SET object,
o processing of the ADMIN_STATUS object,
o processing of the PROTECTION object,
o support of Explicit Label Control,
o processing of the Path_State_Removed Flag,
o handling of Graceful Deletion procedures.
In addition, since non-PSC TE-LSPs may have to be processed in
environments where the "P2MP capability" could be limited, specific
constraints may also apply during the P2MP TE Path computation.
Being technology specific, these constraints are outside the scope
of this document. However, technology independent constraints (i.e.
constraints that are applicable independently of the LSP class)
should be allowed during P2MP TE LSP message processing. It has to
be emphasized that path computation and management techniques shall
be as close as possible than those being used for PSC P2P TE LSPs
and P2MP TE LSPs.
Finally, note that bi-directional TE LSPs are not applicable to
multicast traffic. Although many leaf nodes may be considered as
senders in a multicast group, a P2MP TE LSP models a single
distribution tree from a sender to multiple recipients. If such
a tree were made bi-directional it would be a multipoint-to-point
tree in the reverse direction.
5.17 Requirements for Hierarchical P2MP TE LSPs
[LSP-HIER] define concepts and procedures for P2P LSP hierarchy. They
should be extended to support P2MP LSP hierarchy.
The P2MP MPLS-TE solution SHOULD support the concept of region and
region hierarchy (PSC1<PSC2<PSC3<PSC4<L2SC<TDM<LSC<FSC).
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,
providing that i<j.
5.18 P2MP Crankback routing
P2MP solution SHOULD support cranckback requirements as defined in
[CRANKBACK]. In particular, it SHOULD provide sufficient 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 network.
6. Security Considerations 6. Security Considerations
Security considerations will be addressed in a future revision of This requirements draft does not define any protocol extensions and
this document. does not, therefore, make any changes to any security models.
It should be noted that P2MP signaling mechanisms built on P2P
signaling are likely to inherit all of the security techniques and
problems associated with RSVP-TE. These problems may be exacerbated
in P2MP situations where security relationships may need to
maintained between an ingress and multiple egresses. Such issues are
similar to security issues for IP multicast.
It is a requirement that documents offering solutions for P2MP LSPs
have detailed security sections.
7. Acknowledgements 7. Acknowledgements
The authors would like to thank George Swallow, Ichiro Inoue and The authors would like to thank George Swallow, Ichiro Inoue and
Dean Cheng for his review and suggestion of an earlier draft of this Dean Cheng for their review and suggestions on an earlier draft of
document. this document.
8. References 8. References
8.1 Normative References
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan,
V. and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP Tunnels", V. and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP Tunnels",
RFC 3209, December 2001. RFC 3209, December 2001.
[RFC3031] Rosen, E., Viswanathan, A. and R. Callon, "Multiprotocol [RFC3031] Rosen, E., Viswanathan, A. and R. Callon, "Multiprotocol
Label Switching Architecture", RFC 3031, January 2001. Label Switching Architecture", RFC 3031, January 2001.
[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 Services", RFC and W. Weiss, "An Architecture for Differentiated Services", RFC
2475, December 1998. 2475, December 1998.
skipping to change at page 18, line 33 skipping to change at page 23, line 24
"An Expedited Forwarding PHB (Per-Hop Behavior)", RFC 3246, "An Expedited Forwarding PHB (Per-Hop Behavior)", RFC 3246,
March 2002. March 2002.
[RFC2362] D. Estrin, D. Farinacci, A. Helmy, D. Thaler, S. Deering, [RFC2362] D. Estrin, D. Farinacci, A. Helmy, D. Thaler, S. Deering,
M. Handley, V. Jacobson, C. Liu, P. Sharma, L. Wei, "Protocol M. Handley, V. Jacobson, C. Liu, P. Sharma, L. Wei, "Protocol
Independent Multicast-Sparse Mode (PIM-SM): Protocol Specification.", Independent Multicast-Sparse Mode (PIM-SM): Protocol Specification.",
RFC 2362, June 1998. RFC 2362, June 1998.
[RFC2702] D. Awduche, J. Malcolm, J. Agogbua, M. O'Dell, J. McManus, [RFC2702] D. Awduche, J. Malcolm, J. Agogbua, M. O'Dell, J. McManus,
"Requirements for Traffic Engineering Over MPLS", RFC2702, "Requirements for Traffic Engineering Over MPLS", RFC2702,
September 1999 September 1999.
8.2 Informational References
[PIM-SM] B. Fenner, M. Hadley, H. Holbrook, I. Kouvelas, "Protocol [PIM-SM] B. Fenner, M. Hadley, H. Holbrook, I. Kouvelas, "Protocol
Independent Multicast - Sparse Mode (PIM-SM):Protocol Specification Independent Multicast - Sparse Mode (PIM-SM):Protocol Specification
(Revised)", draft-ietf-pim-sm-v2-new-08.txt, October 2003. (Revised)", draft-ietf-pim-sm-v2-new-08.txt, October 2003.
[BGP/MPLS IP VPNs] E. Rosen, Y.Rekhter, Editor, "BGP/MPLS IP VPNs", [BGP/MPLS IP VPNs] E. Rosen, Y.Rekhter, Editor, "BGP/MPLS IP VPNs",
draft-ietf-l3vpn-rfc2547bis-01.txt, September 2003 draft-ietf-l3vpn-rfc2547bis-01.txt, September 2003.
[RFC3471] Berger, L., Editor, "Generalized Multi-Protocol Label [RFC3471] Berger, L., Editor, "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Functional Description", RFC 3471, Switching (GMPLS) Signaling Functional Description", RFC 3471,
January 2003. January 2003.
[RFC3473] Berger, L., Editor, "Generalized Multi-Protocol Label [RFC3473] Berger, L., Editor, "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling - Resource ReserVation Protocol-Traffic Switching (GMPLS) Signaling - Resource ReserVation Protocol-Traffic
Engineering (RSVP-TE) Extensions", RFC 3473, January 2003. Engineering (RSVP-TE) Extensions", RFC 3473, January 2003.
[RFC3477] K. Kompella, Y. Rekhter, "Signalling Unnumbered Links in [RFC3477] K. Kompella, Y. Rekhter, "Signalling Unnumbered Links in
Resource ReSerVation Protocol -Traffic Engineering (RSVP-TE)", Resource ReSerVation Protocol -Traffic Engineering (RSVP-TE)",
RFC3477, January 2003. RFC3477, January 2003.
[GMPLS-ROUTING] K. Kompella, Y. Rekhter, Editor, "Routing [GMPLS-ROUTING] K. Kompella, Y. Rekhter, Editor, "Routing
Extensions in Support of Generalized Multi-Protocol Label Switching", Extensions in Support of Generalized Multi-Protocol Label Switching",
draft-ietf-ccamp-gmpls-routing-08.txt, October 2003. draft-ietf-ccamp-gmpls-routing-08.txt, 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 Networks," Algorithm for Real-Time Communication on High-Speed Networks,"
IEEE Journal on Selected Area in Communications, pp.332-345, 1997 IEEE Journal on Selected Area in Communications, pp.332-345, 1997.
[DJIKSTRA] E. W. Djikstra, "A note on two problem in connection with [DJIKSTRA] E. W. Djikstra, "A note on two problem in connection with
graphs," Numerische Mathematik, vol.1, pp.269-271, 1959 graphs," Numerische Mathematik, vol.1, pp.269-271, 1959.
[IPMCAST-MPLS] D. Ooms, B. Sales, W. Livens, A. Acharya, F. Griffoul [IPMCAST-MPLS] D. Ooms, B. Sales, W. Livens, A. Acharya, F. Griffoul
and F. Ansari, "Overview of IP Multicast in a Multi-Protocol Label and F. Ansari, "Overview of IP Multicast in a Multi-Protocol Label
Switching (MPLS) Environment", RFC3353, August 2002. Switching (MPLS) Environment", RFC3353, August 2002.
[FRR] P. Pan, D. Gan, G. Swallow, J. P. Vasseur, D. Cooper, [FRR] P. Pan, D. Gan, G. Swallow, J. P. Vasseur, D. Cooper,
A. Atlas, M. Jork,"Fast Reroute Extensions to RSVP-TE for LSP A. Atlas, M. Jork,"Fast Reroute Extensions to RSVP-TE for LSP
Tunnels", draft-ietf-mpls-rsvp-lsp-fastreroute-03.txt, July 2003 Tunnels", draft-ietf-mpls-rsvp-lsp-fastreroute-03.txt, July 2003.
[RFC3564] F. Le Faucheur, W. Lai, "Requirements for Support of [RFC3564] F. Le Faucheur, W. Lai, "Requirements for Support of
Differentiated Services-aware MPLS Traffic Engineering", RFC3564, Differentiated Services-aware MPLS Traffic Engineering", RFC3564,
July 2003 July 2003.
[OSPF-TE] D. Katz, D. Yeung, K. Kompella, "Traffic Engineering [OSPF-TE] D. Katz, D. Yeung, K. Kompella, "Traffic Engineering
Extensions to OSPF Version 2", draft-katz-yeung-ospf-traffic-08.txt, Extensions to OSPF Version 2", draft-katz-yeung-ospf-traffic-08.txt,
September 2002 September 2002.
[IS-IS-TE] Henk Smit, Tony Li, "IS-IS extensions for Traffic [IS-IS-TE] Henk Smit, Tony Li, "IS-IS extensions for Traffic
Engineering", draft-ietf-isis-traffic-04.txt, December 2002 Engineering", draft-ietf-isis-traffic-04.txt, December 2002.
[CRANKBACK] A. Farrel, A. Satyanarayana, A. Iwata, N. Fujita, G. Ash
S. Marshall, "Crankback Signaling Extensions for MPLS Signaling",
draft-ietf-ccamp-crankback-00.txt, December 2003.
[LSP-HIER] K. Kompella, Y. Rekhter, "LSP Hierarchy with Generalized
MPLS TE", draft-ietf-mpls-lsp-hierarchy-08.txt, September 2002.
[NODE-ID] Vasseur, Ali and Sivabalan, "Definition of an RRO node-id
subobject", draft-ietf-mpls-nodeid-subobject-01.txt, June 2003.
9. Author's Addresses 9. Author's Addresses
Seisho Yasukawa Seisho Yasukawa
NTT Network Service Systems Laboratories, NTT Corporation NTT Network Service Systems Laboratories, NTT Corporation
9-11, Midori-Cho 3-Chome 9-11, Midori-Cho 3-Chome
Musashino-Shi, Tokyo 180-8585 Japan Musashino-Shi, Tokyo 180-8585 Japan
Phone: +81 422 59 4769 Phone: +81 422 59 4769
EMail: yasukawa.seisho@lab.ntt.co.jp Email: yasukawa.seisho@lab.ntt.co.jp
Dimitri Papadimitriou (Alcatel) Dimitri Papadimitriou (Alcatel)
Francis Wellensplein 1, Francis Wellensplein 1,
B-2018 Antwerpen, Belgium B-2018 Antwerpen, Belgium
Phone : +32 3 240 8491 Phone : +32 3 240 8491
EMail: dimitri.papadimitriou@alcatel.be Email: dimitri.papadimitriou@alcatel.be
JP Vasseur JP Vasseur
Cisco Systems, Inc. Cisco Systems, Inc.
300 Beaver Brook Road 300 Beaver Brook Road
Boxborough , MA - 01719 Boxborough, MA 01719
USA USA
Email: jpv@cisco.com Email: jpv@cisco.com
Yuji Kamite Yuji Kamite
NTT Communications Corporation NTT Communications Corporation
Innovative IP Architecture Center, Tokyo Opera City Tower
Tokyo Opera City Tower 21F, 3-20-2 Nishi Shinjuku, Shinjuku-ku, Tokyo
20-2, 3-chome, Nishi-Shinjuku, Shinjuku-ku, 163-1421, Japan
Tokyo, 163-1421, Japan. Email: y.kamite@ntt.com
EMail: y.kamite@ntt.com
Rahul Aggarwal Rahul Aggarwal
Juniper Networks Juniper Networks
1194 North Mathilda Ave. 1194 North Mathilda Ave.
Sunnyvale, CA 94089 Sunnyvale, CA 94089
Email: rahul@juniper.net Email: rahul@juniper.net
Alan Kullberg Alan Kullberg
Motorola Computer Group Motorola Computer Group
120 Turnpike Rd. 120 Turnpike Rd.
Southborough, MA 01772 Southborough, MA 01772
Email: alan.kullberg@motorola.com Email: alan.kullberg@motorola.com
Adrian Farrel Adrian Farrel
Old Dog Consulting Old Dog Consulting
Phone: +44 (0) 1978 860944 Phone: +44 (0) 1978 860944
EMail: adrian@olddog.co.uk Email: adrian@olddog.co.uk
Markus Jork Markus Jork
Avici Systems Avici Systems
101 Billerica Avenue 101 Billerica Avenue
N. Billerica, MA 01862 N. Billerica, MA 01862
email: mjork@avici.com Phone: +1 978 964 2142
phone: +1 978 964 2142 Email: mjork@avici.com
Andrew G. Malis Andrew G. Malis
Tellabs Tellabs
2730 Orchard Parkway 2730 Orchard Parkway
San Jose, CA 95134 San Jose, CA 95134
Phone: +1 408 383 7223 Phone: +1 408 383 7223
Email: andy.malis@tellabs.com Email: andy.malis@tellabs.com
Jean-Louis Le Roux
France Telecom
2, avenue Pierre-Marzin
22307 Lannion Cedex
France
Email: jeanlouis.leroux@francetelecom.com
10. Intellectual Property Consideration
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The IETF invites any interested party to bring to its
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11. Full Copyright Statement
Copyright (C) The Internet Society (2004). All Rights
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