draft-ietf-mpls-mp-ldp-reqs-00.txt   draft-ietf-mpls-mp-ldp-reqs-01.txt 
Network Working Group J.-L. Le Roux (Editor) Network Working Group J.-L. Le Roux (Editor)
Internet Draft France Telecom Internet Draft France Telecom
Category: Informational Category: Informational
Expires: November 2006 T. Morin Expires: January 2007 T. Morin
France Telecom France Telecom
Vincent Parfait Vincent Parfait
Equant Equant
Luyuan Fang Luyuan Fang
AT&T AT&T
Lei Wang Lei Wang
Telenor Telenor
Yuji Kamite Yuji Kamite
NTT Communications NTT Communications
Shane Amante Shane Amante
Level 3 Communications Level 3 Communications
Requirements for point-to-multipoint extensions to Requirements for point-to-multipoint extensions to
the Label Distribution Protocol the Label Distribution Protocol
draft-ietf-mpls-mp-ldp-reqs-00.txt draft-ietf-mpls-mp-ldp-reqs-01.txt
Status of this Memo Status of this Memo
By submitting this Internet-Draft, each author represents that any By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware applicable patent or other IPR claims of which he or she is aware
have been or will be disclosed, and any of which he or she becomes have been or will be disclosed, and any of which he or she becomes
aware will be disclosed, in accordance with Section 6 of BCP 79. aware will be disclosed, in accordance with Section 6 of BCP 79.
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 other Task Force (IETF), its areas, and its working groups. Note that other
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3.1. Problem Statement...........................................5 3.1. Problem Statement...........................................5
3.2. Requirements overview.......................................5 3.2. Requirements overview.......................................5
4. Application scenario........................................6 4. Application scenario........................................6
5. Detailed Requirements.......................................7 5. Detailed Requirements.......................................7
5.1. P2MP LSPs...................................................7 5.1. P2MP LSPs...................................................7
5.2. P2MP LSP FEC................................................7 5.2. P2MP LSP FEC................................................7
5.3. P2MP LDP routing............................................8 5.3. P2MP LDP routing............................................8
5.4. Setting up, tearing down and modifying P2MP LSPs............8 5.4. Setting up, tearing down and modifying P2MP LSPs............8
5.5. Label Advertisement.........................................8 5.5. Label Advertisement.........................................8
5.6. Data Duplication............................................8 5.6. Data Duplication............................................8
5.7. Avoiding loops..............................................8 5.7. Avoiding loops..............................................9
5.8. P2MP LSP Re-routing.........................................9 5.8. P2MP LSP Re-routing.........................................9
5.8.1. Rerouting upon Network Failure..............................9 5.8.1. Rerouting upon Network Failure..............................9
5.8.2. Rerouting on a Better Path..................................9 5.8.2. Rerouting on a Better Path..................................9
5.8.3. Rerouting upon Planned Maintenance..........................9 5.8.3. Rerouting upon Planned Maintenance.........................10
5.9. Support for LAN interfaces.................................10 5.9. Support for LAN interfaces.................................10
5.10. Support for encapsulation in P2P and P2MP TE tunnels........10 5.10. Support for encapsulation in P2P and P2MP TE tunnels.......10
5.11. Label spaces................................................10 5.11. Label spaces...............................................10
5.12. IPv4/IPv6 support...........................................10 5.12. IPv4/IPv6 support..........................................11
5.13. Multi-Area LSPs.............................................10 5.13. Multi-Area LSPs............................................11
5.14. OAM.........................................................11 5.14. OAM........................................................11
5.15. Graceful Restart and Fault Recovery.........................11 5.15. Graceful Restart and Fault Recovery........................11
5.16. Robustness..................................................11 5.16. Robustness.................................................11
5.17. Scalability.................................................11 5.17. Scalability................................................11
5.17.1. Orders of magnitude of the expected numbers of P2MP 5.17.1. Orders of magnitude of the expected numbers of P2MP
LSPs in operational networks.............................11 LSPs in operational networks.............................12
5.18. Backward Compatibility......................................12 5.18. Backward Compatibility.....................................12
6. Shared Trees...............................................12 6. Shared Trees...............................................12
6.1. MP2MP LSPs.................................................12 6.1. Requirements for MP2MP LSPs................................13
7. Evaluation criteria........................................13 7. Evaluation criteria........................................14
7.1. Performances...............................................13 7.1. Performances...............................................14
7.2. Complexity and Risks.......................................13 7.2. Complexity and Risks.......................................14
8. Security Considerations....................................13 8. Security Considerations....................................14
9. Acknowledgments............................................13 9. Acknowledgments............................................14
10. References.................................................14 10. References.................................................14
10.1. Normative references.......................................14
10.2. Informative references.....................................15
11. Editor Address.............................................15 11. Editor Address.............................................15
12. Contributors Addresses.....................................15 12. Contributors Addresses.....................................16
13. Intellectual Property Statement............................16 13. Intellectual Property Statement............................17
1. Terminology 1. Terminology
LSR: Label Switching Router LSR: Label Switching Router
LSP: MPLS Label Switched Path LSP: MPLS Label Switched Path
Ingress LSR: Router acting as a sender of an LSP Ingress LSR: Router acting as a sender of an LSP
Egress LSR: Router acting as a receiver of an LSP Egress LSR: Router acting as a receiver of an LSP
P2P LSP: A LSP that has one unique Ingress LSR and one unique P2P LSP: A LSP that has one unique Ingress LSR and one unique
Egress LSR Egress LSR
MP2P LSP: A LSP that has one or more Ingress LSRs and one unique MP2P LSP: A LSP that has one or more Ingress LSRs and one unique
Egress LSR Egress LSR
P2MP LSP: A LSP that has one unique Ingress LSR and one or more P2MP LSP: A LSP that has one unique Ingress LSR and one or more
Egress LSRs Egress LSRs
Leaf LSR: Egress LSR of a P2MP LSP MP2MP LSP: A LSP that as one or more Leaf LSRs acting
indifferently as Ingress or Egress LSR
Leaf LSR: Egress LSR of a P2MP LSP or Ingress/Egress LSR of a
MP2MP LSP
Transit LSR: A LSR of a P2MP LSP that has one or more downstream Transit LSR: A LSR of a P2MP LSP that has one or more downstream
LSRs LSRs
Branch LSR: A LSR of a P2MP LSP that has more than one downstream Branch LSR: A LSR of a P2MP LSP that has more than one downstream
LSR LSR
Bud LSR: A LSR of a P2MP LSP that is an egress but also has one or Bud LSR: A LSR of a P2MP LSP that is an egress but also has one or
more directly connected downstream LSRs more directly connected downstream LSRs
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They meet requirements expressed in [P2MP-TE-REQ]. This approach is They meet requirements expressed in [P2MP-TE-REQ]. This approach is
useful, in network environments where P2MP Traffic Engineering useful, in network environments where P2MP Traffic Engineering
capabilities are needed (Optimization, QoS, Fast recovery). capabilities are needed (Optimization, QoS, Fast recovery).
However for operators who want to support point-to-multipoint traffic However for operators who want to support point-to-multipoint traffic
delivery on an MPLS backbone, without Traffic Engineering needs, and delivery on an MPLS backbone, without Traffic Engineering needs, and
have already deployed LDP for P2P traffic, an interesting and useful have already deployed LDP for P2P traffic, an interesting and useful
approach would be to rely on LDP extensions in order to setup point- approach would be to rely on LDP extensions in order to setup point-
to-multipoint (P2MP) LSPs. This would bring consistency with P2P MPLS to-multipoint (P2MP) LSPs. This would bring consistency with P2P MPLS
applications and would ease the delivery of point-to-multipoint applications and would ease the delivery of point-to-multipoint
applications in an MPLS backbone. services in an MPLS backbone.
This document focuses on the LDP approach for setting up P2MP LSPs. This document focuses on the LDP approach for setting up P2MP LSPs.
It lists a detailed set of requirements for P2MP extensions to LDP, It lists a detailed set of requirements for P2MP extensions to LDP,
so as to deliver P2MP traffic over a LDP-enabled MPLS infrastructure. so as to deliver P2MP traffic over a LDP-enabled MPLS infrastructure.
These requirements should be used as guidelines when specifying LDP These requirements should be used as guidelines when specifying LDP
extensions. It is intended that solutions that specify LDP procedures extensions. It is intended that solutions that specify LDP procedures
for P2MP LSP setup, satisfy these requirements. for P2MP LSP setup, satisfy these requirements.
Note that generic requirements for P2MP extensions to MPLS are out of Note that generic requirements for P2MP extensions to MPLS are out of
the scope of this document. Rather this document describes solution the scope of this document. Rather this document describes solution
specific requirements related to LDP extensions in order to set up specific requirements related to LDP extensions in order to set up
P2MP LSPs. P2MP LSPs.
Note also that other mechanisms could be used for setting up P2MP Note also that other mechanisms could be used for setting up P2MP
LSPs, such as for instance PIM extensions, but these are out of the LSPs, such as for instance PIM extensions, but these are out of the
scope of this document. The objective is not to compare these scope of this document. The objective is not to compare these
mechanisms but rather to focus on the requirements for an LDP mechanisms but rather to focus on the requirements for an LDP
extension approach. extension approach.
The document is structured as follows: The document is structured as follows:
- Section 3 points out the problem statement. - Section 3 points out the problem statement;
- Section 4 illustrates an application scenario. - Section 4 illustrates an application scenario;
- Section 5 addresses detailed requirements. - Section 5 addresses detailed requirements for P2MP LSPs;
- Section 6 finally discusses group communication. - Section 6 finally discusses group communication, and
requirements for MP2MP LSPs.
3. Problem Statement and Requirements Overview 3. Problem Statement and Requirements Overview
3.1. Problem Statement 3.1. Problem Statement
Many operators have deployed LDP [LDP] for setting up P2P and MP2P Many operators have deployed LDP [LDP] for setting up P2P and MP2P
MPLS LSPs as PE-to-PE tunnels so as to carry point-to-point traffic MPLS LSPs as PE-to-PE tunnels so as to carry point-to-point traffic
essentially in Layer 3 and Layer 2 VPN networks. There are emerging essentially in Layer 3 and Layer 2 VPN networks. There are emerging
requirements for supporting multicast traffic delivery within these requirements for supporting multicast traffic delivery within these
VPN infrastructures ([L3VPN-MCAST-REQ] and [L2VPN-MCAST-REQ]). For VPN infrastructures ([L3VPN-MCAST-REQ] and [L2VPN-MCAST-REQ]). For
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The following gives a set of guidelines that a specification of LDP The following gives a set of guidelines that a specification of LDP
extensions for setting up P2MP LSPs should follow. extensions for setting up P2MP LSPs should follow.
3.2. Requirements overview 3.2. Requirements overview
The P2MP LDP mechanism MUST support setting up P2MP LSPs, i.e. LSPs The P2MP LDP mechanism MUST support setting up P2MP LSPs, i.e. LSPs
with one Ingress LSR and one or more Egress LSRs, with traffic with one Ingress LSR and one or more Egress LSRs, with traffic
replication at some Branch LSRs. replication at some Branch LSRs.
The P2MP LDP mechanism MUST allow the arbitrary addition or removal The P2MP LDP mechanism MUST allow the addition or removal of leaves
of leaves associated with a P2MP LSP. associated with a P2MP LSP.
The P2MP LDP mechanism MUST interoperate seamlessly with existing P2P The P2MP LDP mechanism MUST co-exist with current LDP mechanisms and
and MP2P LDP mechanisms. inherit its capability sets from [LDP]. It is of paramount importance
It is of paramount importance that the P2MP LDP mechanism MUST NOT that the P2MP LDP mechanism MUST NOT impede the operation of existing
impede the operation of existing P2P/MP2P LSPs. P2P/MP2P LSPs.
Note that the P2MP LDP mechanism MAY also allow setting up The P2MP LDP mechanism MAY also allow setting up multipoint-to-
multipoint-to-multipoint (MP2MP) LSPs connecting a group of Leaf LSRs multipoint (MP2MP) LSPs connecting a group of Leaf LSRs acting
acting indifferently as Ingress LSR or Egress LSR. This may allow indifferently as Ingress LSR or Egress LSR. This may allow a
a reduction in the amount of LDP state that must be reduction in the amount of LDP state that needs to be maintained by a
maintained by a LSR. Detailed requirements for MP2MP LSPs are left LSR.
for further study.
4. Application scenario 4. Application scenario
Figure 1 below illustrates an LDP enabled MPLS provider network, used Figure 1 below illustrates an LDP enabled MPLS provider network, used
to carry both unicast and multicast traffic of VPN customers to carry both unicast and multicast traffic of VPN customers
following for instance the architecture defined in [2547-MCAST] for following for instance the architecture defined in [2547-MCAST] for
BGP/MPLS VPNs, or the one defined in [VPLS-MCAST]. BGP/MPLS VPNs, or the one defined in [VPLS-MCAST].
MP2P LDP LSPs are setup between PE routers to carry unicast VPN A set of MP2P LDP LSPs are setup between PE routers to carry unicast
traffic. VPN traffic within the MPLS backbone.
A set of P2MP LDP LSPs are setup between PE routers acting as Ingress A set of P2MP LDP LSPs are setup between PE routers acting as Ingress
LSRs and PE routers acting as Egress LSRs, so as to support multicast LSRs and PE routers acting as Egress LSRs, so as to support multicast
VPN traffic delivery within the MPLS backbone. VPN traffic delivery within the MPLS backbone.
For instance, a P2MP LDP LSP is setup between Ingress LSR PE1 and For instance, a P2MP LDP LSP is setup between Ingress LSR PE1 and
Egress LSRs PE2, PE3, and PE4. It is used to transport multicast Egress LSRs PE2, PE3, and PE4. It is used to transport multicast
traffic from PE1 to PE2, PE3 and PE4. P1 is a Branch LSR, it traffic from PE1 to PE2, PE3 and PE4. P1 is a Branch LSR, it
replicates MPLS traffic sent by PE1 to P2, P3 and PE2. P2 and P3 are replicates MPLS traffic sent by PE1 to P2, P3 and PE2. P2 and P3 are
non-branch transit LSRs, they forward MPLS traffic sent by P1 to PE3 non-branch transit LSRs, they forward MPLS traffic sent by P1 to PE3
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network and a large amount of leaf LSRs for a single P2MP LSP. network and a large amount of leaf LSRs for a single P2MP LSP.
In order to scale well with a large number of leaves it is In order to scale well with a large number of leaves it is
RECOMMENDED to follow a leaf-initiated P2MP LSP setup approach. For RECOMMENDED to follow a leaf-initiated P2MP LSP setup approach. For
that purpose, leaves will have to be aware of the P2MP LSP that purpose, leaves will have to be aware of the P2MP LSP
identifier. The ways a Leaf LSR discovers P2MP LSPs identifiers rely identifier. The ways a Leaf LSR discovers P2MP LSPs identifiers rely
on the applications that will use P2MP LSPs, and are out of the scope on the applications that will use P2MP LSPs, and are out of the scope
of this document. of this document.
The P2MP LDP mechanism MUST allow the dynamic addition and removal of The P2MP LDP mechanism MUST allow the dynamic addition and removal of
leaves to and from a P2MP LSP. It is RECOMMENDED that these leaves to and from a P2MP LSP, without any restriction (provided
there is network connectivity). It is RECOMMENDED that these
operations be leaf-initiated. operations be leaf-initiated.
It is RECOMMENDED that these operations do not cause any additional These operations MUST not impact the data transfer (packet loss,
processing except on the path from the added/removed Leaf LSR to duplication, delay) towards other leaves. It is RECOMMENDED that
the Branch LSR. these operations do not cause any additional processing except on the
path from the added/removed Leaf LSR to the Branch LSR.
5.5. Label Advertisement 5.5. Label Advertisement
The P2MP LDP mechanism SHOULD support downstream unsolicited label The P2MP LDP mechanism SHOULD support downstream unsolicited label
advertisement mode. This is well suited to a leaf-initiated approach advertisement mode. This is well suited to a leaf-initiated approach
and is consistent with P2P/MP2P LDP operations. and is consistent with P2P/MP2P LDP operations.
5.6. Data Duplication 5.6. Data Duplication
Data duplication refers to the receipt of multiple copies of a packet Data duplication refers to the receipt of multiple copies of a packet
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Furthermore, the P2MP LDP mechanism MUST avoid routing loops that may Furthermore, the P2MP LDP mechanism MUST avoid routing loops that may
trigger unexpected non-localized exponential growth of traffic. Note trigger unexpected non-localized exponential growth of traffic. Note
that any loop-avoidance mechanism MUST respect scalability that any loop-avoidance mechanism MUST respect scalability
requirements. requirements.
5.8. P2MP LSP Re-routing 5.8. P2MP LSP Re-routing
The P2MP LDP mechanism MUST support the rerouting of a P2MP LSP in The P2MP LDP mechanism MUST support the rerouting of a P2MP LSP in
the following cases: the following cases:
- Network failure (link or node) - Network failure (link or node);
- A better path exists (e.g. new link, metric change) - A better path exists (e.g. new link, metric change);
- Planned maintenance - Planned maintenance.
Given that P2MP LDP routing must rely on the RIB, the achievement of Given that P2MP LDP routing should rely on the RIB, the achievement
the following requirements also implies the underlying routing of the following requirements also implies the underlying routing
protocols (IGP, etc.). protocols (IGP, etc.).
5.8.1. Rerouting upon Network Failure 5.8.1. Rerouting upon Network Failure
The P2MP LDP mechanism MUST allow for rerouting of a P2MP LSP in case The P2MP LDP mechanism MUST allow for rerouting of a P2MP LSP in case
of link or node failure(s). The rerouting time SHOULD be minimized as of link or node failure(s). The rerouting time SHOULD be minimized as
much as possible so as to reduce traffic disruption. much as possible so as to reduce traffic disruption.
A mechanism MUST be defined to prevent constant P2MP LSP teardown and A mechanism MUST be defined to prevent constant P2MP LSP teardown and
rebuild which may be caused by the instability of a specific rebuild which may be caused by the instability of a specific
link/node in the network. link/node in the network.
5.8.2. Rerouting on a Better Path 5.8.2. Rerouting on a Better Path
The P2MP LDP mechanism MUST allow for rerouting of a P2MP LSP in case The P2MP LDP mechanism MUST allow for rerouting of a P2MP LSP in case
a better path is created in the network, for instance as a result of a better path is created in the network, for instance as a result of
a metric change, or the addition of links or nodes. a metric change, a link repair, or the addition of links or nodes.
Traffic disruption SHOULD be minimized as much as possible during Traffic disruption and data duplication SHOULD be minimized as much
such rerouting. It SHOULD be feasible to avoid packet loss during as possible during such rerouting.
such rerouting. There is actually a tension between packet loss minimization and
Unnecessary data duplication during such rerouting SHOULD also be packet duplication minimization objectives.
minimized as much as possible. It SHOULD be feasible to avoid either data duplication or packet loss
during such rerouting.
Note that there is likely to be a tension between packet loss A solution MAY provide the operator with means to choose between
minimization and packet duplication minimization objectives. favoring avoiding packet loss at the expense of potential packet
duplication, and favoring avoiding duplication against packet loss.
5.8.3. Rerouting upon Planned Maintenance 5.8.3. Rerouting upon Planned Maintenance
The P2MP LDP mechanism MUST support planned maintenance operations. The P2MP LDP mechanism MUST support planned maintenance operations.
It MUST be possible to reroute a P2MP LSP before a link/node is It MUST be possible to reroute a P2MP LSP before a link/node is
deactivated for maintenance purposes. Traffic disruption SHOULD be deactivated for maintenance purposes.
minimized as much as possible during such rerouting. It SHOULD be Traffic disruption and data duplication SHOULD be minimized as much
feasible to avoid packet loss during such rerouting. as possible during such planned maintenance.
Unnecessary traffic duplication during such rerouting SHOULD also be There is actually a tension between packet loss minimization and
minimized as much as possible. packet duplication minimization objectives.
It SHOULD be feasible to avoid either data duplication or packet loss
Note that there is likely to be a tension between packet loss during such rerouting.
minimization and packet duplication minimization objectives. A solution MAY provide the operator with means to choose between
favoring avoiding packet loss at the expense of packet duplication,
and favoring avoiding duplication against packet loss.
5.9. Support for LAN interfaces 5.9. Support for LAN interfaces
The P2MP LDP mechanism MUST provide a way for a Branch LSR to send a The P2MP LDP mechanism MUST provide a way for a Branch LSR to send a
single copy of the data onto an Ethernet LAN interface and reach single copy of the data onto an Ethernet LAN interface and reach
multiple adjacent downstream nodes. This requires that the same label multiple adjacent downstream nodes. This requires that the same label
be negotiated with all downstream LSRs for the LSP. be negotiated with all downstream LSRs for the LSP.
When there are several candidate upstream LSRs on a LAN interface, When there are several candidate upstream LSRs on a LAN interface,
the P2MP LDP mechanism MUST provide a way for all downstream LSRs of the P2MP LDP mechanism MUST provide a way for all downstream LSRs of
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on the P2MP LSP, which are also Egress LSRs of the tunnel. As with on the P2MP LSP, which are also Egress LSRs of the tunnel. As with
LAN interfaces, this requires that the same LDP label be negotiated LAN interfaces, this requires that the same LDP label be negotiated
with all downstream LSRs for the P2MP LDP LSP. with all downstream LSRs for the P2MP LDP LSP.
5.11. Label spaces 5.11. Label spaces
Labels for P2MP LSPs and P2P/MP2P LSPs MAY be assigned from shared or Labels for P2MP LSPs and P2P/MP2P LSPs MAY be assigned from shared or
dedicated label spaces. dedicated label spaces.
Note that dedicated label spaces will require the establishment of Note that dedicated label spaces will require the establishment of
separate P2MP LDP sessions. separate P2P and P2MP LDP sessions.
5.12. IPv4/IPv6 support 5.12. IPv4/IPv6 support
The P2MP LDP mechanism MUST be equally applicable to IPv4 and IPv6 The P2MP LDP mechanism MUST be equally applicable to IPv4 and IPv6
traffic. Likewise, it SHOULD be possible to convey both kinds of traffic. Likewise, it SHOULD be possible to convey both kinds of
traffic in a given P2MP LSP facility. traffic in a given P2MP LSP facility.
Also the P2MP LDP mechanism MUST support the establishment of LDP Also the P2MP LDP mechanism MUST support the establishment of LDP
sessions over both IPv4 and IPv6 control planes. sessions over both IPv4 and IPv6 control planes.
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purpose are out of the scope of this document and are addressed in purpose are out of the scope of this document and are addressed in
[P2MP-OAM-REQ]. [P2MP-OAM-REQ].
5.15. Graceful Restart and Fault Recovery 5.15. Graceful Restart and Fault Recovery
LDP Graceful Restart mechanisms [LDP-GR] and Fault Recovery [LDP-FT] LDP Graceful Restart mechanisms [LDP-GR] and Fault Recovery [LDP-FT]
mechanisms SHOULD be enhanced to support P2MP LDP LSPs. mechanisms SHOULD be enhanced to support P2MP LDP LSPs.
5.16. Robustness 5.16. Robustness
A solution SHOULD avoid single points of failures or propose some A solution MUST avoid single points of failures provided there is
technical solutions for a failover mechanism. enough network connectivity.
5.17. Scalability 5.17. Scalability
Scalability is a key requirement for the P2MP LDP mechanism. Scalability is a key requirement for the P2MP LDP mechanism.
It MUST be designed to scale well with an increase in the number of It MUST be designed to scale well with an increase in the number of
any of the following: any of the following:
- number of Leaf LSRs per P2MP LSP - number of Leaf LSRs per P2MP LSP;
- number of Downstream LSRs per Branch LSR - number of Downstream LSRs per Branch LSR;
- number of P2MP LSPs per LSR - number of P2MP LSPs per LSR.
In order to scale well with an increase in the number of leaves, it In order to scale well with an increase in the number of leaves, it
is RECOMMENDED that the size of a P2MP LSP state on a LSR, for one is RECOMMENDED that the size of a P2MP LSP state on a LSR, for one
particular LSP, depend only on the number of adjacent LSRs on the particular LSP, depend only on the number of adjacent LSRs on the
LSP. LSP.
5.17.1. Orders of magnitude of the expected numbers of P2MP LSPs in 5.17.1. Orders of magnitude of the expected numbers of P2MP LSPs in
operational networks operational networks
Typical orders of magnitude that we expect should be supported are: Typical orders of magnitude that we expect should be supported are:
- tens of thousands of P2MP trees spread out across core network - tens of thousands of P2MP trees spread out across core network
routers routers;
- hundreds, or a few thousands, of leaves per tree - hundreds, or a few thousands, of leaves per tree;
See also section 4.2 of [L3VPN-MCAST-REQ]. See also section 4.2 of [L3VPN-MCAST-REQ].
5.18. Backward Compatibility 5.18. Backward Compatibility
In order to allow for a smooth migration, the P2MP LDP mechanism In order to allow for a smooth migration, the P2MP LDP mechanism
SHOULD offer as much backward compatibility as possible. In SHOULD offer as much backward compatibility as possible. In
particular, the solution SHOULD allow the setup of a P2MP LSP along particular, the solution SHOULD allow the setup of a P2MP LSP along
non Branch Transit LSRs that do not support P2MP LDP extensions. non-Branch Transit LSRs that do not support P2MP LDP extensions.
Also, the P2MP LDP solution MUST interoperate seamlessly with current Also, the P2MP LDP solution MUST co-exist with current LDP mechanisms
LDP mechanisms and inherit its capability sets from [LDP]. The P2MP and inherit its capability sets from [LDP]. The P2MP LDP solution
LDP solution MUST not impede the operation of P2P/MP2P LSPs. A P2MP MUST not impede the operation of P2P/MP2P LSPs. A P2MP LDP solution
LDP solution MUST be designed in such a way that it allows P2P/MP2P MUST be designed in such a way that it allows P2P/MP2P and P2MP LSPs
and P2MP LSPs to be signalled on the same interface. to be signalled on the same interface.
6. Shared Trees 6. Shared Trees
For traffic delivery between a group of N Leaf LSRs which are acting For traffic delivery between a group of N Leaf LSRs which are acting
indifferently as Ingress or Egress LSRs, it may be useful to indifferently as Ingress or Egress LSRs, it may be useful to
setup a shared tree connecting all these LSRs, instead of having N setup a shared tree connecting all these LSRs, instead of having N
P2MP LSPs. This would reduce the amount of control and forwarding P2MP LSPs. This would reduce the amount of control and forwarding
state that has to be maintained on a given LSR. state that has to be maintained on a given LSR.
There are actually two main options for supporting such shared trees: There are actually two main options for supporting such shared trees:
- This could rely on the applications protocols that use LDP - This could rely on the applications protocols that use LDP
LSPs. A shared tree could consist of the combination of a LSPs. A shared tree could consist of the combination of a
MP2P LDP LSP from Leafs LSRs to a given root node, with a P2MP MP2P LDP LSP from Leafs LSRs to a given root node, with a P2MP
LSP from this root to all Leaf LSRs. LSP from this root to all Leaf LSRs. For instance with
For instance with Multicast L3 VPN applications, it would be Multicast L3 VPN applications, it would be possible to build a
possible to build a shared tree by combining: shared tree by combining:
- a MP2P unicast LDP LSP, from each PE of the group to a - a MP2P unicast LDP LSP, from each PE of the group to a
particular root PE acting as tree root, particular root PE acting as tree root,
- with a P2MP LDP LSP from the root PE to all PEs of the - with a P2MP LDP LSP from this root PE to each PEs of the
Group (see also [2547-MCAST]). Group.
- Or this could rely on a specific LDP mechanism allowing to - Or this could rely on a specific LDP mechanism allowing to
setup multipoint-to-multipoint MPLS LSPs (MP2MP LSPs). setup multipoint-to-multipoint MPLS LSPs (MP2MP LSPs).
The former approach (Combination of MP2P and P2MP LSPs at the The former approach (Combination of MP2P and P2MP LSPs at the
application level) is out of the scope of this document while the application level) is out of the scope of this document while the
latter (MP2MP LSPs) belong to the scope of this document. latter (MP2MP LSPs) belong to the scope of this document.
Requirements for the set up of MP2MP LSPs are listed below. Requirements for the set up of MP2MP LSPs are listed below.
6.1. MP2MP LSPs 6.1. Requirements for MP2MP LSPs
*Editorial note: There is currently no clear analysis of the gain of A MP2MP LSP is a LSP connecting a group of Leaf LSRs acting
the MP2MP MPLS approach (with the potential impact on LDP), versus indifferently as Ingress or Egress LSRs. Traffic sent by any Leaf
using application-level shared trees. This is why the requirement for LSRs is received by all other Leaf LSRs of the group.
MP2MP LSPs is currently optional*
The P2MP LDP mechanism MAY allow setting up MP2MP LSP. A MP2MP LSP is Procedures for setting up MP2MP LSPs SHOULD be specified.
a LSP connecting a group of Leaf LSRs acting indifferently as Ingress An implementation that support P2MP LDP LSPs MAY also support MP2MP
or Egress LSRs. Traffic sent by any Leaf LSRs is received by all LDP LSP.
other Leaf LSRs of the group. A sender LSR does not receive back the
traffic sent.
All detailed requirements for P2MP LSPs listed in section 5, apply The MP2MP LDP procedures MUST not impede the operations of P2MP LSP.
equally to MP2MP LSPs. Particularly it is RECOMMENDED that the size
of MP2MP state on a LSR, for one particular MP2MP LSP, depend only on
the number of adjacent LSRs on the LSP, and not on the number of Leaf
LSRs.
Additional detailed requirements specific to MP2MP LSPs are left for Requirements for P2MP LSPs set forth in section 5 apply equally to
further study. MP2MP LSPs. Particular attention should be given on the below
requirements:
- The solution MUST support recovery upon link and transit node
failure and there MUST be no single point of failure (provided
network connectivity is redundant). Note that transit node
failure recovery is likely to be more complex to handle with MP2MP
LSPs than with P2MP LSPs;
- The size of MP2MP state on a LSR, for one particular MP2MP LSP,
SHOULD only depend on the number of adjacent LSRs on the LSP;
- Furthermore, the MP2MP LDP mechanism MUST avoid routing loops that
may trigger exponential growth of traffic. Note that this
requirement is more challenging with MP2MP LSPs as a LSR can
receive traffic for a given LSP on multiple interfaces.
There are additional requirements specific to MP2MP LSPs:
- It is RECOMMENDED that a MP2MP MPLS LSP follow shortest paths to a
specific LSR called root LSR;
- It is RECOMMENDED to define several root LSRs (e.g. a primary and
a backup) to ensure redundancy upon root LSR failure;
- The receiver SHOULD not receive back a packet it has sent on the
MP2MP LSP;
- The solution SHOULD avoid that all traffic between any pair of
leaves is traversing a root LSR, and SHOULD as much as possible
minimize the distance between two leaves (similarly to PIM-Bidir
trees);
- It MUST be possible to check connectivity of a MP2MP LSP in both
directions.
7. Evaluation criteria 7. Evaluation criteria
7.1. Performances 7.1. Performances
The solution will be evaluated with respect to the following The solution will be evaluated with respect to the following
criteria: criteria:
(1) Time to add or remove a Leaf LSR; (1) Time to add or remove a Leaf LSR;
(2) Time to repair a P2MP LSP in case of link or node (2) Time to repair a P2MP LSP in case of link or node
failure; failure;
(3) Scalability (state size, number of messages, message size). (3) Scalability (state size, number of messages, message size).
Particularly, the P2MP LDP mechanism SHOULD be designed so that Particularly the P2MP LDP mechanism SHOULD be designed with as key
convergence times in case of link or node failure are minimized, in objective to minimize the additional amount of state and additional
order to limit traffic disruption. processing required in the network when deploying P2MP LDP.
Also, the P2MP LDP mechanism SHOULD be designed so that convergence
times in case of link or node failure are minimized, in order to
limit traffic disruption.
7.2. Complexity and Risks 7.2. Complexity and Risks
The proposed solution SHOULD not introduce complexity to the current The proposed solution SHOULD not introduce complexity to the current
LDP operations to such a degree that it would affect the stability LDP operations to such a degree that it would affect the stability
and diminish the benefits of deploying such P2MP LDP solution. and diminish the benefits of deploying such P2MP LDP solution.
The proposed solution SHOULD not require deploying a new routing
protocol.
8. Security Considerations 8. Security Considerations
This document does not introduce any new security issue beyond those This document does not introduce any new security issue beyond those
inherent to LDP, and a P2MP LDP solution may rely on the security inherent to LDP, and a P2MP LDP solution may rely on the security
mechanisms defined in [LDP] (e.g. TCP MD5 Signature). mechanisms defined in [LDP] (e.g. TCP MD5 Signature).
9. Acknowledgments 9. Acknowledgments
We would like to thank Christian Jacquenet (France Telecom), We would like to thank Christian Jacquenet (France Telecom),
Hitoshi Fukuda (NTT Communications), Ina Minei (Juniper), Dean Hitoshi Fukuda (NTT Communications), Ina Minei (Juniper), Dean
Cheng (Cisco Systems), and Benjamin Niven-Jenkins (British Telecom), Cheng (Cisco Systems), and Benjamin Niven-Jenkins (British Telecom),
for their highly useful comments and suggestions. for their highly useful comments and suggestions.
We would also like to thank authors of [P2MP-TE-REQ] from which some We would also like to thank authors of [P2MP-TE-REQ] from which some
text of this document has been inspired. text of this document has been inspired.
10. References 10. References
10.1. 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.
[RFC3667] Bradner, S., "IETF Rights in Contributions", BCP 78, RFC
3667, February 2004.
[BCP79] Bradner, S., "Intellectual Property Rights in IETF
Technology", RFC 3979, March 2005.
[LDP] L. Andersson, P. Doolan, N. Feldman, A. Fredette, B. Thomas, [LDP] L. Andersson, P. Doolan, N. Feldman, A. Fredette, B. Thomas,
"LDP Specification", RFC 3036, January 2001 "LDP Specification", RFC 3036, January 2001
[L3VPN-MCAST-REQ] T. Morin, Ed., "Requirements for Multicast in L3
Provider-Provisioned VPNs", draft-ietf-l3vpn-ppvpn-mcast-reqts, work
in progress.
[L2VPN-MCAST-REQ] Y. Kamite et al. "Requirements for Multicast
Support in Virtual Private LAN Services", draft-ietf-l2vpn-vpls-
mcast-reqts, work in progress
[P2MP-TE-REQ] S. Yasukawa, et. al., "Requirements for Point-to-
Multipoint capability extension to MPLS", RFC4461, April 2006.
[P2MP-TE-RSVP] R. Aggarwal, D. Papadimitriou, S. Yasukawa, et. al..,
"Extensions to RSVP-TE for Point to Multipoint TE LSPs", draft-ietf-
mpls-rsvp-te-p2mp, work in progress.
[LDP-MIB] J. Cuchiarra et al. "Definitions of Managed Objects for the [LDP-MIB] J. Cuchiarra et al. "Definitions of Managed Objects for the
Multiprotocol Label Switching (MPLS), Label Distribution Protocol Multiprotocol Label Switching (MPLS), Label Distribution Protocol
(LDP)", RFC3815, June 2004. (LDP)", RFC3815, June 2004.
[LDP-GR] M. Leelanivas, Y. Rekhter, R. Aggarwal, " Graceful Restart [LDP-GR] M. Leelanivas, Y. Rekhter, R. Aggarwal, " Graceful Restart
Mechanism for Label Distribution Protocol" RFC3478, February 2003. Mechanism for Label Distribution Protocol" RFC3478, February 2003.
[LDP-FT] A. Farrel, " Fault Tolerance for the Label Distribution [LDP-FT] A. Farrel, " Fault Tolerance for the Label Distribution
Protocol (LDP)", RFC3479, February 2003. Protocol (LDP)", RFC3479, February 2003.
10.2. Informative references
[L3VPN-MCAST-REQ] T. Morin, Ed., "Requirements for Multicast in L3
Provider-Provisioned VPNs", draft-ietf-l3vpn-ppvpn-mcast-reqts, work
in progress.
[L2VPN-MCAST-REQ] Y. Kamite et al. "Requirements for Multicast
Support in Virtual Private LAN Services", draft-ietf-l2vpn-vpls-
mcast-reqts, work in progress.
[2547-MCAST] E. Rosen, R. Aggarwal, et. al., "Multicast in MPLS/BGP [2547-MCAST] E. Rosen, R. Aggarwal, et. al., "Multicast in MPLS/BGP
IP VPNs", draft-ietf-l3vpn-2547bis-mcast, work in progress. IP VPNs", draft-ietf-l3vpn-2547bis-mcast, work in progress.
[VPLS-MCAST] R.Aggarwal, Y Kamite, L Fang, “VPLS Multicast” draft-
ietf-l2vpn-vpls-mcast, work in progress.
[P2MP-OAM-REQ] S. Yasukawa, A. Farrel, D. King, T. Nadeau, "OAM [P2MP-OAM-REQ] S. Yasukawa, A. Farrel, D. King, T. Nadeau, "OAM
Requirements for Point-To-Multipoint MPLS Networks", draft-ietf-mpls- Requirements for Point-To-Multipoint MPLS Networks", draft-ietf-mpls-
p2mp-oam-reqs, work in progress. p2mp-oam-reqs, work in progress.
[VPLS-MCAST] R.Aggarwal, Y Kamite, L Fang, “VPLS Multicast” draft- [P2MP-TE-REQ] S. Yasukawa, et. al., "Requirements for Point-to-
ietf-l2vpn-vpls-mcast, work in progress. Multipoint capability extension to MPLS", RFC4461, April 2006.
[P2MP-TE-RSVP] R. Aggarwal, D. Papadimitriou, S. Yasukawa, et. al..,
"Extensions to RSVP-TE for Point to Multipoint TE LSPs", draft-ietf-
mpls-rsvp-te-p2mp, work in progress.
11. Editor Address 11. Editor Address
Jean-Louis Le Roux Jean-Louis Le Roux
France Telecom France Telecom
2, avenue Pierre-Marzin 2, avenue Pierre-Marzin
22307 Lannion Cedex 22307 Lannion Cedex
FRANCE FRANCE
Email: jeanlouis.leroux@francetelecom.com Email: jeanlouis.leroux@orange-ft.com
12. Contributors Addresses 12. Contributors Addresses
Thomas Morin Thomas Morin
France Telecom France Telecom
2, avenue Pierre-Marzin 2, avenue Pierre-Marzin
22307 Lannion Cedex 22307 Lannion Cedex
FRANCE FRANCE
Email: thomas.morin@francetelecom.com Email: thomas.morin@orange-ft.com
Vincent Parfait Vincent Parfait
EQUANT EQUANT
1041 Route des Dolines 1041 Route des Dolines
Sophia Antipolis Sophia Antipolis
06560 Valbonne 06560 Valbonne
FRANCE FRANCE
Email: vincent.parfait@equant.com Email: vincent.parfait@orange-ft.com
Luyuan Fang Luyuan Fang
AT&T AT&T
200 Laurel Avenue 200 Laurel Avenue
Middletown, NJ 07748 Middletown, NJ 07748
USA USA
Email: luyuanfang@att.com Email: luyuanfang@att.com
Lei Wang Lei Wang
Telenor Telenor
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