draft-ietf-mpls-p2mp-sig-requirement-04.txt   rfc4461.txt 
Network Working Group Seisho Yasukawa (NTT)
Internet Draft Editor
Category: Informational
Expiration Date: June 2006 December 2005
Signaling Requirements for Point to Multipoint
Traffic Engineered MPLS LSPs
<draft-ietf-mpls-p2mp-sig-requirement-04.txt>
Status of this Memo Network Working Group S. Yasukawa, Ed.
Request for Comments: 4461 NTT
Category: Informational April 2006
By submitting this Internet-Draft, each author represents that any Signaling Requirements for Point-to-Multipoint
applicable patent or other IPR claims of which he or she is aware Traffic-Engineered MPLS Label Switched Paths (LSPs)
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Abstract Abstract
This document presents a set of requirements for the establishment This document presents a set of requirements for the establishment
and maintenance of Point-to-Multipoint (P2MP) Traffic Engineered (TE) and maintenance of Point-to-Multipoint (P2MP) Traffic-Engineered (TE)
Multiprotocol Label Switching (MPLS) Label Switched Paths (LSPs). Multiprotocol Label Switching (MPLS) Label Switched Paths (LSPs).
There is no intent to specify solution specific details nor There is no intent to specify solution-specific details or
application specific requirements in this document. application-specific requirements in this document.
The requirements presented in this document apply equally to packet The requirements presented in this document not only apply to
switched networks under the control of MPLS protocols and to but also packet-switched networks under the control of MPLS protocols, but
encompass the requirements of Layer two Switching (L2SC), Time also encompass the requirements of Layer Two Switching (L2SC), Time
Division Multiplexing (TDM), lambda, and port switching networks Division Multiplexing (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 developed to meet the requirements set out in this document must
attempt to be equally applicable to MPLS and GMPLS. attempt to be equally applicable to MPLS and GMPLS.
Table of Contents Table of Contents
1. Introduction ................................................... 3 1. Introduction ....................................................3
1.1 Non-Objectives ................................................ 5 1.1. Non-Objectives .............................................6
2. Definitions .................................................... 6 2. Definitions .....................................................6
2.1 Acronyms ...................................................... 6 2.1. Acronyms ...................................................6
2.2 Terminology ................................................... 6 2.2. Terminology ................................................6
2.2.1 Terminology for Partial LSPs ................................ 7 2.2.1. Terminology for Partial LSPs ........................8
2.3 Conventions ................................................... 8 2.3. Conventions ................................................9
3. Problem Statement .............................................. 9 3. Problem Statement ...............................................9
3.1 Motivation .................................................... 9 3.1. Motivation .................................................9
3.2. Requirements Overview......................................... 9 3.2. Requirements Overview ......................................9
4. Detailed requirements for P2MP TE extensions .................. 11 4. Detailed Requirements for P2MP TE Extensions ...................11
4.1 P2MP LSP ..................................................... 11 4.1. P2MP LSP ..................................................11
4.2 P2MP explicit routing......................................... 11 4.2. P2MP Explicit Routing .....................................12
4.3 Explicit Path Loose Hops and Widely Scoped Abstract Nodes .... 12 4.3. Explicit Path Loose Hops and Widely Scoped
4.4 P2MP TE LSP establishment, teardown, and modification mechanisms Abstract Nodes ............................................13
............................................................ 13 4.4. P2MP TE LSP Establishment, Teardown, and
4.5 Fragmentation ................................................ 14 Modification Mechanisms ...................................14
4.6 Failure Reporting and Error Recovery ......................... 14 4.5. Fragmentation .............................................14
4.7 Record route of P2MP TE LSP .................................. 15 4.6. Failure Reporting and Error Recovery ......................15
4.8 Call Admission Control (CAC) and QoS Control mechanism of 4.7. Record Route of P2MP TE LSP ...............................16
P2MP TE LSPs ............................................... 16 4.8. Call Admission Control (CAC) and QoS Control
4.9 Variation of LSP Parameters .................................. 16 Mechanism of P2MP TE LSPs .................................17
4.10 Re-optimization of P2MP TE LSPs ............................. 17 4.9. Variation of LSP Parameters ...............................17
4.11 Merging of Tree Branches .................................... 17 4.10. Re-Optimization of P2MP TE LSPs ..........................18
4.12 Data Duplication ............................................ 18 4.11. Merging of Tree Branches .................................18
4.13 IPv4/IPv6 support ........................................... 19 4.12. Data Duplication .........................................19
4.14 P2MP MPLS Label ............................................. 19 4.13. IPv4/IPv6 Support ........................................20
4.15 Advertisement of P2MP capability ............................ 19 4.14. P2MP MPLS Label ..........................................20
4.16 Multi-access LANs ........................................... 20 4.15. Advertisement of P2MP Capability .........................20
4.17 P2MP MPLS OAM ............................................... 20 4.16. Multi-Access LANs ........................................21
4.18 Scalability ................................................. 20 4.17. P2MP MPLS OAM ............................................21
4.18.1 Absolute Limits ........................................... 21 4.18. Scalability ..............................................21
4.19 Backwards Compatibility ..................................... 23 4.18.1. Absolute Limits ..................................22
4.20 GMPLS ....................................................... 23 4.19. Backwards Compatibility ..................................24
4.21 P2MP Crankback routing ...................................... 24 4.20. GMPLS ....................................................24
5. Security Considerations ....................................... 24 4.21. P2MP Crankback Routing ...................................25
6. IANA Considerations ........................................... 25 5. Security Considerations ........................................25
7. Acknowledgements .............................................. 25 6. Acknowledgements ...............................................26
8. References .................................................... 25 7. References .....................................................26
8.1 Normative References ......................................... 25 7.1. Normative References ......................................26
8.2 Informational References ..................................... 25 7.2. Informative References ....................................26
9. Editor's Address .............................................. 26
10. Authors' Addresses ........................................... 26
11. Intellectual Property Consideration .......................... 28
12. Full Copyright Statement ..................................... 28
1. Introduction 1. Introduction
Existing MPLS Traffic Engineering (MPLS-TE) allows for strict QoS Existing MPLS traffic engineering (MPLS-TE) allows for strict QoS
guarantees, resources optimization, and fast failure recovery, but guarantees, resource optimization, and fast failure recovery, but it
is limited to point-to-point (P2P) LSPs. There is a desire to support is limited to point-to-point (P2P) LSPs. There is a desire to
point-to-multipoint (P2MP) services using traffic engineered LSPs and support point-to-multipoint (P2MP) services using traffic-engineered
this clearly motivates enhancements of the base MPLS-TE tool box in LSPs, and this clearly motivates enhancements of the base MPLS-TE
order to support P2MP MPLS-TE LSPs. tool box in order to support P2MP MPLS-TE LSPs.
A P2MP TE LSP is a TE LSP in the definitions of [RFC2702] and A P2MP TE LSP is a TE LSP (per [RFC2702] and [RFC3031]) that has a
[RFC3031] that has a single ingress LSR, one or more egress LSRs, and single ingress LSR and one or more egress LSRs, and is
is unidirectional. P2MP services (that deliver data from a single unidirectional. P2MP services (that deliver data from a single
source to one or more receivers) may be supported by any combination source to one or more receivers) may be supported by any combination
of P2P and P2MP LSPs depending on the degree of optimization required of P2P and P2MP LSPs depending on the degree of optimization required
within the network, and such LSPs may be Traffic Engineered again within the network, and such LSPs may be traffic-engineered again
depending on the requirements of the network. Further, multipoint-to- depending on the requirements of the network. Further, multipoint-
multipoint (MP2MP) services (that deliver data from more than one to-multipoint (MP2MP) services (which deliver data from more than one
source to one or more receivers) may be supported by a combination source to one or more receivers) may be supported by a combination of
of P2P and P2MP LSPs. P2P and P2MP LSPs.
[RFC2702] specifies requirements for traffic engineering over MPLS. [RFC2702] specifies requirements for traffic engineering over MPLS.
In Section 2, it describes traffic engineering in some detail, and In Section 2, it describes traffic engineering in some detail, and
those definitions are equally applicable to traffic engineering in a those definitions are equally applicable to traffic engineering in a
point-to-multipoint service environment. They are not repeated here, point-to-multipoint service environment. They are not repeated here,
but it is assumed that the reader is fully familiar with them. but it is assumed that the reader is fully familiar with them.
Section 3.0 of [RFC2702] also explains how MPLS is particularly Section 3.0 of [RFC2702] also explains how MPLS is particularly
suited to traffic engineering, and presents the following eight suited to traffic engineering; it presents the following eight
reasons. reasons.
1. Explicit label switched paths which are not constrained by the 1. Explicit label switched paths that are not constrained by the
destination based forwarding paradigm can be easily created destination-based forwarding paradigm can be easily created
through manual administrative action or through automated through manual administrative action or through automated
action by the underlying protocols. action by the underlying protocols.
2. LSPs can potentially be efficiently maintained. 2. LSPs can potentially be maintained efficiently.
3. Traffic trunks can be instantiated and mapped onto LSPs. 3. Traffic trunks can be instantiated and mapped onto LSPs.
4. A set of attributes can be associated with traffic trunks which 4. A set of attributes can be associated with traffic trunks that
modulate their behavioral characteristics. modulate their behavioral characteristics.
5. A set of attributes can be associated with resources which 5. A set of attributes can be associated with resources that
constrain the placement of LSPs and traffic trunks across them. constrain the placement of LSPs and traffic trunks across them.
6. MPLS allows for both traffic aggregation and disaggregation 6. MPLS allows for both traffic aggregation and disaggregation,
whereas classical destination only based IP forwarding permits whereas classical destination-only-based IP forwarding permits
only aggregation. only aggregation.
7. It is relatively easy to integrate a "constraint-based routing" 7. It is relatively easy to integrate a "constraint-based routing"
framework with MPLS. framework with MPLS.
8. A good implementation of MPLS can offer significantly lower 8. A good implementation of MPLS can offer significantly lower
overhead than competing alternatives for Traffic Engineering. overhead than competing alternatives for traffic engineering.
These points are equally applicable to point-to-multipoint traffic These points are equally applicable to point-to-multipoint traffic
engineering. Points 1. and 7. are particularly important. Note that engineering. Points 1 and 7 are particularly important. Note that
point 3. implies that the concept of a point-to-multipoint traffic point 3 implies that the concept of a point-to-multipoint traffic
trunk is defined and is supported by (or mapped onto) P2MP LSPs. trunk is defined and is supported by (or mapped onto) P2MP LSPs.
That is, the traffic flow for a point-to-multipoint LSP is not That is, the traffic flow for a point-to-multipoint LSP is not
constrained to the path or paths that it would follow during constrained to the path or paths that it would follow during
multicast routing or shortest path destination-based routing, but can multicast routing or shortest path destination-based routing, but it
be explicitly controlled through manual or automated action. can be explicitly controlled through manual or automated action.
Further, the explicit paths that are used may be computed using Further, the explicit paths that are used may be computed using
algorithms based on a variety of constraints to produce all manner algorithms based on a variety of constraints to produce all manner of
of tree shapes. For example, an explicit path may be cost-based tree shapes. For example, an explicit path may be cost-based
[STEINER], shortest path, QoS-based, or may use some fair-cost QoS [STEINER], shortest path, or QoS-based, or it may use some fair-cost
algorithm. QoS algorithm.
[RFC2702] also describes the functional capabilities required to [RFC2702] also describes the functional capabilities required to
fully support Traffic Engineering over MPLS in large networks. fully support traffic engineering over MPLS in large networks.
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 solutions Switching (MPLS). It specifies functional requirements for solutions
to deliver P2MP TE LSPs. to deliver P2MP TE LSPs.
Solutions that specify procedures for P2MP TE LSP setup MUST satisfy Solutions that specify procedures for P2MP TE LSP setup MUST satisfy
these requirements. There is no intent to specify solution-specific these requirements. There is no intent to specify solution-specific
details nor application-specific requirements in this document. details or application-specific requirements in this document.
The requirements presented in this document apply equally to packet The requirements presented in this document apply equally to packet-
packet switched networks under the control of MPLS protocols and to switched networks under the control of MPLS protocols and to packet-
packet switched, TDM, lambda, and port switching networks managed switched, TDM, lambda, and port-switching networks managed by
by Generalized MPLS (GMPLS) protocols. Protocol solutions developed Generalized MPLS (GMPLS) protocols. Protocol solutions developed to
to meet the requirements set out in this document MUST attempt to be meet the requirements set out in this document MUST attempt to be
equally applicable to MPLS and GMPLS. equally applicable to MPLS and GMPLS.
Existing MPLS TE mechanisms such as [RFC3209] do not support P2MP TE Existing MPLS TE mechanisms such as [RFC3209] do not support P2MP TE
LSPs so new mechanisms need to be developed. This SHOULD be achieved LSPs, so new mechanisms need to be developed. This SHOULD be
with maximum re-use of existing MPLS protocols. achieved with maximum re-use of existing MPLS protocols.
Note that there is a separation between routing and signaling in Note that there is a separation between routing and signaling in MPLS
MPLS TE. In particular, the path of the MPLS TE LSP is determined by TE. In particular, the path of the MPLS TE LSP is determined by
performing a constraint-based computation (such as CSPF) on a traffic performing a constraint-based computation (such as CSPF) on a traffic
engineering database (TED). The contents of the TED may be collected engineering database (TED). The contents of the TED may be collected
through a variety of mechanisms. through a variety of mechanisms.
This document focuses on requirements for establishing and This document focuses on requirements for establishing and
maintaining P2MP MPLS TE LSPs through signaling protocols; and maintaining P2MP MPLS TE LSPs through signaling protocols; routing
routing protocols are out of scope. No assumptions are made about protocols are out of scope. No assumptions are made about how the
how the TED used as the basis for path computations for P2MP LSPs is TED used as the basis for path computations for P2MP LSPs is formed.
formed.
This requirements document assumes the following conditions for P2MP This requirements document assumes the following conditions for P2MP
MPLS TE LSP establishment and maintenance: MPLS TE LSP establishment and maintenance:
o A P2MP TE LSP will be set up with TE constraints and will allow o A P2MP TE LSP will be set up with TE constraints and will allow
efficient packet or data replication at various branching points in efficient packet or data replication at various branching points in
the network. Although replication is a data plane issue, it is the the network. Although replication is a data plane issue, it is the
responsibility of the control plane (acting in conjunction with the responsibility of the control plane (acting in conjunction with the
path computation component) to install LSPs in the network such path computation component) to install LSPs in the network such
that replication can be performed efficiently. Note that the notion that replication can be performed efficiently. Note that the
of "efficient" replication is relative and may have different notion of "efficient" replication is relative and may have
meanings depending on the objectives (see section 4.2). different meanings depending on the objectives (see Section 4.2).
o P2MP TE LSP setup mechanisms must include the ability to add/remove o P2MP TE LSP setup mechanisms must include the ability to add/remove
receivers to/from the P2MP service supported by an existing P2MP TE receivers to/from the P2MP service supported by an existing P2MP TE
LSP. LSP.
o Tunnel endpoints of P2MP TE LSP will be modified by adding/removing o Tunnel endpoints of P2MP TE LSP will be modified by adding/removing
egress LSRs to/from an existing P2MP TE LSP. It is assumed that the egress LSRs to/from an existing P2MP TE LSP. It is assumed that
rate of change of leaves of a P2MP LSP (that is, the rate at the rate of change of leaves of a P2MP LSP (that is, the rate at
which new egress LSRs join, or old egress LSRs are pruned) is "not which new egress LSRs join, or old egress LSRs are pruned) is "not
so high" because P2MP TE LSPs are assumed to be utilized for TE so high" because P2MP TE LSPs are assumed to be utilized for TE
applications. This issue is discussed at greater length in section applications. This issue is discussed at greater length in Section
4.18.1. 4.18.1.
o A P2MP TE LSP may be protected by fast error recovery mechanisms o A P2MP TE LSP may be protected by fast error recovery mechanisms to
to minimize disconnection of a P2MP service. minimize disconnection of a P2MP service.
o And a set of attributes of the P2MP TE LSP (e.g. bandwidth, etc.) o A set of attributes of the P2MP TE LSP (e.g., bandwidth, etc.) may
may be modified by some mechanism (e.g. make-before-break etc.) be modified by some mechanism (e.g., make-before-break, etc.) to
to accommodate attribute changes to the P2MP service without accommodate attribute changes to the P2MP service without impacting
impacting data traffic. These issues are discussed in section 4.6 data traffic. These issues are discussed in Sections 4.6 and 4.10.
and 4.10.
It is not a requirement that the ingress LSR must control the It is not a requirement that the ingress LSR must control the
addition or removal of leaves from the P2MP tree. addition or removal of leaves from the P2MP tree.
It is this document's objective that a solution compliant to the It is this document's objective that a solution compliant to the
requirements set out in this document MUST operate these P2MP requirements set out in this document MUST operate these P2MP TE
TE capabilities in a scalable fashion. capabilities in a scalable fashion.
1.1 Non-Objectives 1.1. Non-Objectives
For clarity, this section lists some items that are out of scope of For clarity, this section lists some items that are out of scope of
this document. this document.
It is assumed that some information elements describing the P2MP TE It is assumed that some information elements describing the P2MP TE
LSP are known to the ingress LSR prior to LSP establishment. For LSP are known to the ingress LSR prior to LSP establishment. For
example, the ingress LSRs knows the IP addresses that identify the example, the ingress LSRs know the IP addresses that identify the
egress LSRs of the P2MP TE LSP. The mechanisms by which the ingress egress LSRs of the P2MP TE LSP. The mechanisms by which the ingress
LSR obtains this information is outside the scope of P2MP TE LSR obtains this information is outside the scope of P2MP TE
signaling and so is not included in this document. Other documents signaling and so is not included in this document. Other documents
may complete the description of this function by providing may complete the description of this function by providing automated,
automated, protocol-based ways of passing this information to the protocol-based ways of passing this information to the ingress LSR.
ingress LSR.
This document does not specify any requirements for the following This document does not specify any requirements for the following
functions. functions.
- Non-TE LSPs (such as per-hop, routing-based LSPs). - Non-TE LSPs (such as per-hop, routing-based LSPs).
- Discovery of egress leaves for a P2MP LSP. - Discovery of egress leaves for a P2MP LSP.
- Hierarchical P2MP LSPs. - Hierarchical P2MP LSPs.
- OAM for P2MP LSPs. - OAM for P2MP LSPs.
- Inter-area and inter-AS P2MP TE LSPs. - Inter-area and inter-AS P2MP TE LSPs.
- Applicability of P2MP MPLS TE LSPs to service scenarios. - Applicability of P2MP MPLS TE LSPs to service scenarios.
- Specific application or application requirements. - Specific application or application requirements.
- Algorithms for computing P2MP distribution trees. - Algorithms for computing P2MP distribution trees.
- Multipoint-to-point LSPs. - Multipoint-to-point LSPs.
- Multipoint-to-multipoint LSPs. - Multipoint-to-multipoint LSPs.
- Routing protocols. - Routing protocols.
- Construction of the traffic engineering database. - Construction of the traffic engineering database.
- Distribution of the information used to construct the traffic - Distribution of the information used to construct the traffic
engineering database. engineering database.
2. Definitions 2. Definitions
2.1 Acronyms 2.1. Acronyms
P2P:
Point-to-point
P2MP: P2P: Point-to-point
Point-to-multipoint P2MP: Point-to-multipoint
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].
The following terms are defined for use in the context of P2MP TE The following terms are defined for use in the context of P2MP TE
LSPs only. LSPs only.
P2MP tree: P2MP tree:
The ordered set of LSRs and TE links that comprise the path of a The ordered set of LSRs and TE links that comprise the path of a
skipping to change at page 7, line 27 skipping to change at page 7, line 31
An LSR that is an egress LSR, but also has one or more directly An LSR that is an egress LSR, but also has one or more directly
connected downstream LSRs. connected downstream LSRs.
branch LSR: branch LSR:
An LSR that has more than one directly connected downstream LSR. An LSR that has more than one directly connected downstream LSR.
P2MP-ID (P2ID): P2MP-ID (P2ID):
A unique identifier of a P2MP TE LSP, that is constant for the A unique identifier of a P2MP TE LSP, which is constant for the
whole LSP regardless of the number of branches and/or leaves. whole LSP regardless of the number of branches and/or leaves.
source: source:
The sender of traffic that is carried on a P2MP service supported The sender of traffic that is carried on a P2MP service supported
by a P2MP LSP. The sender is not necessarily the ingress LSR of by a P2MP LSP. The sender is not necessarily the ingress LSR of
the P2MP LSP. the P2MP LSP.
receiver: receiver:
A recipient of traffic carried on a P2MP service supported by a A recipient of traffic carried on a P2MP service supported by a
P2MP LSP. A receiver is not necessarily an egress LSR of the P2MP P2MP LSP. A receiver is not necessarily an egress LSR of the P2MP
LSP. Zero, one or more receivers may receive data through a given LSP. Zero, one, or more receivers may receive data through a
egress LSR. given egress LSR.
2.2.1 Terminology for Partial LSPs 2.2.1. Terminology for Partial LSPs
It is convenient to sub-divide P2MP trees for functional and It is convenient to sub-divide P2MP trees for functional and
representational reasons. A tree may be divided in two dimensions: representational reasons. A tree may be divided in two dimensions:
- A division may be made along the length of the tree. For example, - A division may be made along the length of the tree. For example,
the tree may be split into two components each running from the the tree may be split into two components each running from the
ingress LSR to a discrete set of egress LSRs. Upstream LSRs (for ingress LSR to a discrete set of egress LSRs. Upstream LSRs (for
example, the ingress LSR) may be members of both components. example, the ingress LSR) may be members of both components.
- A tree may be divided at a branch LSR (or any transit LSR) to - A tree may be divided at a branch LSR (or any transit LSR) to
skipping to change at page 8, line 14 skipping to change at page 8, line 24
- A tree may be divided at a branch LSR (or any transit LSR) to - A tree may be divided at a branch LSR (or any transit LSR) to
produce a component of the tree that runs from the branch (or produce a component of the tree that runs from the branch (or
transit) LSR to all egress LSRs downstream of this point. transit) LSR to all egress LSRs downstream of this point.
These two methods of splitting the P2MP tree can be combined, so it These two methods of splitting the P2MP tree can be combined, so it
is useful to introduce some terminology to allow the partitioned is useful to introduce some terminology to allow the partitioned
trees to be clearly described. trees to be clearly described.
Use the following designations: Use the following designations:
Source (ingress) LSR - S Source (ingress) LSR - S
Leaf (egress) LSR - L Leaf (egress) LSR - L
Branch LSR - B Branch LSR - B
Transit LSR - X (any single, arbitrary LSR that is not a source, Transit LSR - X (any single, arbitrary LSR that is not a source,
leaf or branch) leaf or branch)
All - A All - A
Partial (i.e. not all) - P Partial (i.e., not all) - P
Define a new term: Define a new term:
Sub-LSP Sub-LSP:
A segment of a P2MP TE LSP that runs from one of the LSP's LSRs A segment of a P2MP TE LSP that runs from one of the LSP's LSRs
to one or more of its other LSRs. to one or more of its other LSRs.
Using these new concepts we can define any combination or split of Using these new concepts, we can define any combination or split of
the P2MP tree. For example: the P2MP tree. For example:
S2L sub-LSP S2L sub-LSP:
The path from the source to one specific leaf. The path from the source to one specific leaf.
S2PL sub-LSP S2PL sub-LSP:
The path from the source to a set of leaves. The path from the source to a set of leaves.
B2AL sub-LSP B2AL sub-LSP:
The path from a branch LSR to all downstream leaves. The path from a branch LSR to all downstream leaves.
X2X sub-LSP X2X sub-LSP:
A component of the P2MP LSP that is a simple path thatwith A component of the P2MP LSP that is a simple path that does not
does not branches. branch.
Note that the S2AL sub-LSP is equivalent to the P2MP LSP. Note that the S2AL sub-LSP is equivalent to the P2MP LSP.
2.3 Conventions 2.3. Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
this document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
3. Problem Statement 3. Problem Statement
3.1 Motivation 3.1. Motivation
As described in section 1, Traffic Engineering and Constraint Based As described in Section 1, traffic engineering and constraint-based
Routing (including Call Admission Control(CAC), explicit source routing (including Call Admission Control (CAC), explicit source
routing, and bandwidth reservation) are required to enable efficient routing, and bandwidth reservation) are required to enable efficient
resource usage and strict QoS guarantees. Such mechanisms also make resource usage and strict QoS guarantees. Such mechanisms also make
it possible to provide services across a congested network where it possible to provide services across a congested network where
conventional "shortest path first" forwarding paradigms would fail. conventional "shortest path first" forwarding paradigms would fail.
Existing MPLS TE mechanisms [RFC3209] and GMPLS TE mechanisms Existing MPLS TE mechanisms [RFC3209] and GMPLS TE mechanisms
[RFC3473] only provide support for P2P TE LSPs. While it is possible [RFC3473] only provide support for P2P TE LSPs. While it is possible
to provide P2MP TE services using P2P TE LSPs, any such approach is to provide P2MP TE services using P2P TE LSPs, any such approach is
potentially suboptimal since it may result in data replication at potentially suboptimal since it may result in data replication at the
the ingress LSR, or in duplicate data traffic within the network. ingress LSR, or in duplicate data traffic within the network.
Hence, to provide P2MP MPLS TE services in a fully efficient manner Hence, to provide P2MP MPLS TE services in a fully efficient manner,
it is necessary to specify specific requirements. These requirements it is necessary to specify specific requirements. These requirements
can then be used when defining mechanisms for the use of existing can then be used when defining mechanisms for the use of existing
protocols and/or extensions to existing protocols and/or new protocols and/or extensions to existing protocols and/or new
protocols. protocols.
3.2. Requirements Overview 3.2. Requirements Overview
This document states basic requirements for the setup of P2MP TE This document states basic requirements for the setup of P2MP TE
LSPs. The requirements apply to the signaling techniques only, and LSPs. The requirements apply to the signaling techniques only, and
no assumptions are made about which routing protocols are run within no assumptions are made about which routing protocols are run within
the network, nor about how the information that is used to construct the network, or about how the information that is used to construct
the Traffic Engineering Database (TED) is distributed. These factors the Traffic Engineering Database (TED) is distributed. These factors
are out of the scope of this document. are out of the scope of this document.
A P2MP TE LSP path computation will take into account various A P2MP TE LSP path computation will take into account various
constraints such as bandwidth, affinities, required level of constraints such as bandwidth, affinities, required level of
protection and so on. The solution MUST allow for the computation of protection and so on. The solution MUST allow for the computation of
P2MP TE LSP paths satisfying constraints with the objective of P2MP TE LSP paths that satisfy constraints, with the objective of
supporting various optimization criteria such as delays, bandwidth supporting various optimization criteria such as delays, bandwidth
consumption in the network, or any other combinations. This is likely consumption in the network, or any other combinations. This is
to require the presence of a TED, as well as the ability to signal likely to require the presence of a TED, as well as the ability to
the explicit path of an LSP. signal the explicit path of an LSP.
A desired requirement is also to maximize the re-use of existing A desired requirement is also to maximize the re-use of existing MPLS
MPLS TE techniques and protocols where doing so does not adversely TE techniques and protocols where doing so does not adversely impact
impact the function, simplicity or scalability of the solution. the function, simplicity, or scalability of the solution.
This document does not restrict the choice of signaling protocol This document does not restrict the choice of signaling protocol used
used to set up a P2MP TE LSP, but it should be noted that [RFC3468] to set up a P2MP TE LSP, but note that [RFC3468] states
states
... the consensus reached by the Multiprotocol Label Switching ...the consensus reached by the Multiprotocol
(MPLS) Working Group within the IETF to focus its efforts on Label Switching (MPLS) Working Group within the IETF to focus its
"Resource Reservation Protocol (RSVP)-TE: Extensions to RSVP for efforts on "Resource Reservation Protocol (RSVP)-TE: Extensions to
Label-Switched Paths (LSP) Tunnels" (RFC 3209) as the MPLS signaling RSVP for Label-Switched Paths (LSP) Tunnels" (RFC 3209) as the MPLS
protocol for traffic engineering applications... signalling protocol for traffic engineering applications...
The P2MP TE LSP setup mechanism MUST include the ability to The P2MP TE LSP setup mechanism MUST include the ability to
add/remove egress LSRs to/from an existing P2MP TE LSP and MUST add/remove egress LSRs to/from an existing P2MP TE LSP and MUST allow
allow for the support of all the TE LSP management procedures for the support of all the TE LSP management procedures already
already defined for P2P TE LSP. Further, when new TE LSP procedures defined for P2P TE LSP. Further, when new TE LSP procedures are
are developed for P2P TE LSPs, equivalent or identical procedures developed for P2P TE LSPs, equivalent or identical procedures SHOULD
SHOULD be developed for P2MP TE LSPs. be developed for P2MP TE LSPs.
The computation of P2MP trees is implementation dependent and is The computation of P2MP trees is implementation dependent and is
beyond the scope of the solutions that are built with this document beyond the scope of the solutions that are built with this document
as a guideline. as a guideline.
Consider the following figure. Consider the following figure.
Source 1 (S1) Source 1 (S1)
| |
I-LSR1 I-LSR1
skipping to change at page 10, line 36 skipping to change at page 10, line 50
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
Figure 1 shows a single ingress LSR (I-LSR1), and four egress LSRs Figure 1 shows a single ingress LSR (I-LSR1), and four egress LSRs
(E-LSR2, E-LSR3, E-LSR4 and E-LSR5). I-LSR1 is attached to a traffic (E-LSR2, E-LSR3, E-LSR4, and E-LSR5). I-LSR1 is attached to a
source that is generating traffic for a P2MP application. Receivers traffic source that is generating traffic for a P2MP application.
R1, R2, R3 and R4 are attached to E-LSR2, E-LSR3 and E-LSR4.
Receivers R1, R2, R3, and R4 are attached to E-LSR2, E-LSR3, and
E-LSR4.
The following are the objectives of P2MP LSP establishment and use. The following are the objectives of P2MP LSP establishment and use.
a) A P2MP tree which satisfies various constraints is a) A P2MP tree that satisfies various constraints is pre-
pre-determined and details are supplied to I-LSR1. determined, and details are supplied to I-LSR1.
Note that no assumption is made on whether the tree is Note that no assumption is made about whether the tree is
provided to I-LSR1 or computed by I-LSR1. The provided to I-LSR1 or computed by I-LSR1. The solution SHOULD
solution SHOULD also allow for the support of a partial path by also allow for the support of a partial path by means of loose
means of loose routing. routing.
Typical constraints are bandwidth requirements, resource class Typical constraints are bandwidth requirements, resource class
affinities, fast rerouting, preemption. There should not be any affinities, fast rerouting, and preemption. There should not
restriction on the possibility to support the set of be any restriction on the possibility of supporting the set of
constraints already defined for point to point TE LSPs. A new constraints already defined for point-to-point TE LSPs. A new
constraint may specify which LSRs should be used as branch LSRs constraint may specify which LSRs should be used as branch LSRs
for the P2MP LSR in order to take into account LSR capabilities for the P2MP LSR in order to take into account LSR capabilities
or network constraints. or network constraints.
b) A P2MP TE LSP is set up from I-LSR1 to E-LSR2, E-LSR3 and b) A P2MP TE LSP is set up from I-LSR1 to E-LSR2, E-LSR3, and
E-LSR4 using the tree information. E-LSR4 using the tree information.
c) In this case, the branch LSR1 should replicate incoming c) In this case, the branch LSR1 should replicate incoming packets
packets or data and send them to E-LSR3 and E-LSR4. or data and send them to E-LSR3 and E-LSR4.
d) If a new receiver (R5) expresses an interest in receiving d) If a new receiver (R5) expresses an interest in receiving
traffic, a new tree is determined and a B2L sub-LSP from LSR2 traffic, a new tree is determined, and a B2L sub-LSP from LSR2
to E-LSR5 is grafted onto the P2MP TE LSP. LSR2 becomes a to E-LSR5 is grafted onto the P2MP TE LSP. LSR2 becomes a
branch LSR. branch LSR.
4. Detailed requirements for P2MP TE extensions 4. Detailed Requirements for P2MP TE Extensions
4.1 P2MP LSP 4.1. P2MP LSP
The P2MP TE extensions MUST be applicable to the signaling of LSPs The P2MP TE extensions MUST be applicable to the signaling of LSPs
for different switching types. For example, it MUST be possible to for different switching types. For example, it MUST be possible to
signal a P2MP TE LSP in any switching medium being packet or signal a P2MP TE LSP in any switching medium, whether it is packet or
non-packet based (including frame, cell, TDM, lambda, etc.). non-packet based (including frame, cell, TDM, lambda, etc.).
As with P2P MPLS technology [RFC3031], traffic is classified with a As with P2P MPLS technology [RFC3031], traffic is classified with a
FEC in this extension. All packets which belong to a particular FEC FEC in this extension. All packets that belong to a particular FEC
and which travel from a particular node MUST follow the same P2MP and that travel from a particular node MUST follow the same P2MP
tree. tree.
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 a unique identifier (the P2MP ID or P2ID) that is be identified by a unique identifier (the P2MP ID or P2ID) that is
constant for the whole LSP regardless of the number of branches constant for the whole LSP regardless of the number of branches
and/or leaves. and/or leaves.
4.2 P2MP explicit routing 4.2. P2MP Explicit Routing
Various optimizations in P2MP tree formation need to be applied to Various optimizations in P2MP tree formation need to be applied to
meet various QoS requirements and operational constraints. meet various QoS requirements and operational constraints.
Some P2MP applications may request a bandwidth guaranteed P2MP tree Some P2MP applications may request a bandwidth-guaranteed P2MP tree
which satisfies end-to-end delay requirements. And some operators that satisfies end-to-end delay requirements. And some operators may
may want to set up a cost minimum P2MP tree by specifying branch want to set up a cost-minimum P2MP tree by specifying branch LSRs
LSRs explicitly. explicitly.
The P2MP TE solution therefore MUST provide a means of establishing The P2MP TE solution therefore MUST provide a means of establishing
arbitrary P2MP trees under the control of an external tree arbitrary P2MP trees under the control of an external tree
computation process or path configuration process or dynamic tree computation process, path configuration process, or dynamic tree
computation process located on the ingress LSR. Figure 2 shows two computation process located on the ingress LSR. Figure 2 shows two
typical examples. 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 tree SPF P2MP tree Steiner P2MP tree SPF P2MP tree
Figure 2 Examples of P2MP TE LSP topology Figure 2: Examples of P2MP TE LSP topology
One example is the Steiner P2MP tree (Cost minimum P2MP tree) One example is the Steiner P2MP tree (cost-minimum P2MP tree)
[STEINER]. This P2MP tree is suitable for constructing a cost [STEINER]. This P2MP tree is suitable for constructing a cost-
minimum P2MP tree so as to minimize the bandwidth consumption in minimum P2MP tree so as to minimize the bandwidth consumption in the
the core. To realize this P2MP tree, several intermediate LSRs must core. To realize this P2MP tree, several intermediate LSRs must be
be both MPLS data terminating LSRs and transit LSRs (LSRs E, F, G, both MPLS data terminating LSRs and transit LSRs (LSRs E, F, G, H, I,
H, I, J and K in the figure 2). Therefore, the P2MP TE solution MUST J, and K in Figure 2). Therefore, the P2MP TE solution MUST support
support a mechanism that can setup this kind of bud LSR between an a mechanism that can set up this kind of bud LSR between an ingress
ingress LSR and egress LSRs. Note that this includes constrained LSR and egress LSRs. Note that this includes constrained Steiner
Steiner trees that allow for the computation of a minimal cost trees trees that allow for the computation of a minimal cost trees with
with some other constraints such as a bounded delay between the some other constraints such as a bounded delay between the source and
source and every receiver. every receiver.
Another example is a CSPF (Constraint Shortest Path First) P2MP Another example is a CSPF (Constraint Shortest Path First) P2MP tree.
tree. By some metric (which can be set upon any specific criteria By some metric (which can be set upon any specific criteria like the
like the delay, bandwidth, a combination of those), one can delay, bandwidth, or a combination of those), one can calculate a
calculate a shortest path P2MP tree. This P2MP tree is suitable for shortest-path P2MP tree. This P2MP tree is suitable for carrying
carrying real-time traffic. real-time traffic.
The solution MUST allow the operator to make use of any tree The solution MUST allow the operator to make use of any tree
computation technique. In the former case an efficient/optimal tree computation technique. In the former case, an efficient/optimal tree
is defined as a minimal cost tree (Steiner tree) whereas in the is defined as a minimal cost tree (Steiner tree), whereas in the
later case it is defined as the tree that provides shortest path later case, it is defined as the tree that provides shortest path
between the source and any receiver. between the source and any receiver.
To support explicit setup of any reasonable P2MP tree shape, a P2MP To support explicit setup of any reasonable P2MP tree 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 tree which can explicitly include particular LSRs as of the P2MP tree that can explicitly include particular LSRs as
branch LSRs. This can be used by the ingress LSR to setup the P2MP branch LSRs. This can be used by the ingress LSR to setup the P2MP
TE LSP. For instance, a P2MP TE LSP can be simply represented as a TE LSP. For instance, a P2MP TE LSP can be represented simply as a
whole tree or by its individual branches. whole tree or by its individual branches.
4.3 Explicit Path Loose Hops and Widely Scoped Abstract Nodes 4.3. Explicit Path Loose Hops and Widely Scoped Abstract Nodes
A P2MP tree is completely specified if all of the required branches A P2MP tree is completely specified if all the required branches and
and hops between a sender and leaf LSR are indicated. hops between a sender and leaf LSR are indicated.
A P2MP tree is partially specified if only a subset of intermediate A P2MP tree is partially specified if only a subset of intermediate
branches and hops are indicated. This may be achieved using loose branches and hops is indicated. This may be achieved using loose
hops in the explicit path, or using widely scoped abstract nodes hops in the explicit path, or using widely scoped abstract nodes
(that is, abstract nodes that are not simple [RFC3209]) such as IPv4 (that is, abstract nodes that are not simple [RFC3209]) such as IPv4
prefixes shorter than 32 bits, or AS numbers. A partially specified prefixes shorter than 32 bits, or AS numbers. A partially specified
P2MP tree might be particularly useful in inter-area and inter-AS P2MP tree might be particularly useful in inter-area and inter-AS
situations although P2MP requirements for inter-area and inter-AS are situations, although P2MP requirements for inter-area and inter-AS
beyond the scope of this document. are beyond the scope of this document.
Protocol solutions SHOULD include a way to specify loose hops and Protocol solutions SHOULD include a way to specify loose hops and
widely scoped abstract nodes in the explicit source-based control of widely scoped abstract nodes in the explicit source-based control of
the P2MP tree as defined in the previous section. Where this support the P2MP tree as defined in the previous section. Where this support
is provided, protocol solutions MUST allow downstream LSRs to apply is provided, protocol solutions MUST allow downstream LSRs to apply
further explicit control to the P2MP tree to resolve a partially further explicit control to the P2MP tree to resolve a partially
specified tree into a (more) completely specified tree. specified tree into a (more) completely specified tree.
Protocol solutions MUST allow the P2MP tree to be completely Protocol solutions MUST allow the P2MP tree to be completely
specified at the ingress LSR where sufficient information exists to specified at the ingress LSR where sufficient information exists to
allow the full tree to be computed and where policies along the path allow the full tree to be computed and where policies along the path
(such as at domain boundaries) support full specification. (such as at domain boundaries) support full specification.
In all cases, the egress LSRs of the P2MP TE LSP must be fully In all cases, the egress LSRs of the P2MP TE LSP must be fully
specified either individually or through some collective identifier. specified either individually or through some collective identifier.
Without this information, it is impossible to know to where the TE Without this information, it is impossible to know where the TE LSP
LSP should be routed. should be routed to.
In case of a tree being computed by some downstream LSRs (e.g. the In case of a tree being computed by some downstream LSRs (e.g., the
case of hops specified as loose hops), the solution MUST provide case of hops specified as loose hops), the solution MUST provide
protocol mechanisms for the ingress LSR of the P2MP TE LSP to learn protocol mechanisms for the ingress LSR of the P2MP TE LSP to learn
the full P2MP tree. Note that this information may not always be the full P2MP tree. Note that this information may not always be
obtainable owing to policy considerations, but where part of the path obtainable owing to policy considerations, but where part of the path
remains confidential it MUST be reported through aggregation (for remains confidential, it MUST be reported through aggregation (for
example, using an AS number). example, using an AS number).
4.4 P2MP TE LSP establishment, teardown, and modification mechanisms 4.4. P2MP TE LSP Establishment, Teardown, and Modification Mechanisms
The P2MP TE solution MUST support establishment, maintenance and The P2MP TE solution MUST support establishment, maintenance, and
teardown of P2MP TE LSPs in a manner that is at least scalable in a teardown of P2MP TE LSPs in a manner that is at least scalable in a
linear way. This MUST include both the existence of very many LSPs at linear way. This MUST include both the existence of very many LSPs
once, and the existence of very many destinations for a single P2MP at once, and the existence of very many destinations for a single
LSP. P2MP LSP.
In addition to P2MP TE LSP establishment and teardown mechanisms, it In addition to P2MP TE LSP establishment and teardown mechanisms, the
SHOULD support a partial P2MP tree modification mechanism. solution SHOULD support a partial P2MP tree modification mechanism.
For the purpose of adding sub-P2MP TE LSPs to an existing P2MP TE For the purpose of adding sub-P2MP TE LSPs to an existing P2MP TE
LSP, the extensions SHOULD support a grafting mechanism. For the LSP, the extensions SHOULD support a grafting mechanism. For the
purpose of deleting a sub-P2MP TE LSPs from an existing P2MP TE LSP, purpose of deleting a sub-P2MP TE LSPs from an existing P2MP TE LSP,
the extensions SHOULD support a pruning mechanism. the extensions SHOULD support a pruning mechanism.
It is RECOMMENDED that these grafting and pruning operations cause It is RECOMMENDED that these grafting and pruning operations cause no
no additional processing in nodes that are not along the path to additional processing in nodes that are not along the path to the
the grafting or pruning node, or that are downstream of the grafting grafting or pruning node, or that are downstream of the grafting or
or pruning node toward the grafted or pruned leaves. Moreover, both pruning node toward the grafted or pruned leaves. Moreover, both
grafting and pruning operations MUST NOT disrupt traffic currently grafting and pruning operations MUST NOT disrupt traffic currently
forwarded along the P2MP tree. forwarded along the P2MP tree.
There is no assumption that the explicitly routed P2MP LSP remains on There is no assumption that the explicitly routed P2MP LSP remains on
an optimal path after several grafts and prunes have occurred. In an optimal path after several grafts and prunes have occurred. In
this context, scalable refers to the signaling process for the P2MP this context, scalable refers to the signaling process for the P2MP
TE LSP. The TE nature of the LSP allows that re-optimization may take TE LSP. The TE nature of the LSP allows that re-optimization may
place from time to time to restore the optimality of the LSP. take place from time to time to restore the optimality of the LSP.
4.5 Fragmentation 4.5. Fragmentation
The P2MP TE solution MUST handle the situation where a single The P2MP TE solution MUST handle the situation where a single
protocol message cannot contain all of the information necessary to protocol message cannot contain all the information necessary to
signal the establishment of the P2MP LSP. It MUST be possible to signal the establishment of the P2MP LSP. It MUST be possible to
establish the LSP in these circumstances. establish the LSP in these circumstances.
This situation may arise in either of the following circumstances. This situation may arise in either of the following circumstances.
a. The ingress LSR cannot signal the whole tree in a single a. The ingress LSR cannot signal the whole tree in a single
message. message.
b. The information in a message expands to be too large (or is b. The information in a message expands to be too large (or is
discovered to be too large) at some transit node. This may discovered to be too large) at some transit node. This may
occur because of some increase in the information that needs occur because of some increase in the information that needs to
to be signaled or because of a reduction in the size of be signaled or because of a reduction in the size of signaling
signaling message that is supported. message that is supported.
The solution to these problems SHOULD NOT rely on IP fragmentation of The solution to these problems SHOULD NOT rely on IP fragmentation of
protocol messages and it is RECOMMENDED to rely on some protocol protocol messages, and it is RECOMMENDED to rely on some protocol
procedures specific to the signaling solution. procedures specific to the signaling solution.
In the event that fragmented IP packets containing protocol messages In the event that fragmented IP packets containing protocol messages
are received, it is NOT RECOMMENDED that they are reassembled at the are received, it is NOT RECOMMENDED that they are reassembled at the
receiving LSR. receiving LSR.
4.6 Failure Reporting and Error Recovery 4.6. Failure Reporting and Error Recovery
Failure events may cause egress LSRs or sub-P2MP LSPs to become Failure events may cause egress LSRs or sub-P2MP LSPs to become
detached from the P2MP TE LSP. These events MUST be reported upstream detached from the P2MP TE LSP. These events MUST be reported
as for a P2P LSP. upstream as for a P2P LSP.
The solution SHOULD provide recovery techniques such as protection The solution SHOULD provide recovery techniques, such as protection
and restoration allowing recovery of any impacted sub-P2MP TE LSPs. and restoration, allowing recovery of any impacted sub-P2MP TE LSPs.
In particular, a solution MUST provide fast protection mechanisms In particular, a solution MUST provide fast protection mechanisms
applicable to P2MP TE LSP similar to the solutions specified in applicable to P2MP TE LSP similar to the solutions specified in
[RFC4090] for P2P TE LSPs. Note also that no assumption is made on [RFC4090] for P2P TE LSPs. Note also that no assumption is made
whether backup paths for P2MP TE LSPs should or should not be shared about whether backup paths for P2MP TE LSPs should or should not be
with P2P TE LSPs backup paths. shared with P2P TE LSPs backup paths.
Note that the functions specified in [RFC4090] are currently specific Note that the functions specified in [RFC4090] are currently specific
to packet environments and do not apply to non-packet environments. to packet environments and do not apply to non-packet environments.
Thus, while solutions MUST provide fast protection mechanisms similar Thus, while solutions MUST provide fast protection mechanisms similar
to those specified in [RFC4090], this requirement is limited to the to those specified in [RFC4090], this requirement is limited to the
subset of the solution space that applies to packet switched networks subset of the solution space that applies to packet-switched networks
only. only.
Note that the requirements expressed in this document are general to Note that the requirements expressed in this document are general to
all MPLS TE P2MP signaling, and any solution that meets them will all MPLS TE P2MP signaling, and any solution that meets them will
therefore be general. Specific applications may have additional therefore be general. Specific applications may have additional
requirements, or may want to relax some requirements stated in this requirements or may want to relax some requirements stated in this
document. This may lead to variations in the solution. document. This may lead to variations in the solution.
The solution SHOULD also support the ability to meet other network The solution SHOULD also support the ability to meet other network
recovery requirements such as bandwidth protection and bounded recovery requirements such as bandwidth protection and bounded
propagation delay increase along the backup path during failure. propagation delay increase along the backup path during failure.
A P2MP TE solution MUST support P2MP fast protection mechanism to A P2MP TE solution MUST support the P2MP fast protection mechanism to
handle P2MP applications sensitive to traffic disruption. handle P2MP applications sensitive to traffic disruption.
If the ingress LSR is informed of the failure of delivery to fewer If the ingress LSR is informed of the failure of delivery to fewer
than all of the egress LSRs this SHOULD NOT cause automatic teardown than all the egress LSRs, this SHOULD NOT cause automatic teardown of
of the P2MP TE LSP. That is, while some egress LSRs remain connected the P2MP TE LSP. That is, while some egress LSRs remain connected to
to the P2MP tree it SHOULD be a matter of local policy at the ingress the P2MP tree, it SHOULD be a matter of local policy at the ingress
LSR whether the P2MP LSP is retained. LSR whether the P2MP LSP is retained.
When all egress LSRs downstream of a branch LSR have become When all egress LSRs downstream of a branch LSR have become
disconnected from the P2MP tree, and some branch LSR is unable disconnected from the P2MP tree, and some branch LSR is unable to
to restore connectivity to any of them by means of some recovery or restore connectivity to any of them by means of some recovery or
protection mechanisms, the branch LSR MAY remove itself from the protection mechanisms, the branch LSR MAY remove itself from the P2MP
P2MP tree provided that it is not also an egress LSR (that is, a tree provided that it is not also an egress LSR (that is, a bud).
bud). Since the faults that severed the various downstream egress Since the faults that severed the various downstream egress LSRs from
LSRs from the P2MP tree may be disparate, the branch LSR MUST the P2MP tree may be disparate, the branch LSR MUST report all such
report all such errors to its upstream neighbor. An upstream LSR or errors to its upstream neighbor. An upstream LSR or the ingress LSR
the ingress LSR can then decide to re-compute the path to those can then decide to re-compute the path to those particular egress
particular egress LSRs, around the failure point. LSRs around the failure point.
Solutions MAY include the facility for transit LSRs and particularly Solutions MAY include the facility for transit LSRs and particularly
branch LSRs to recompute sub-P2MP trees to restore them after branch LSRs to recompute sub-P2MP trees to restore them after
failures. In the event of successful repair, error notifications failures. In the event of successful repair, error notifications
SHOULD NOT be reported to upstream nodes, but the new paths are SHOULD NOT be reported to upstream nodes, but the new paths are
reported if route recording is in use. Crankback requirements are reported if route recording is in use. Crankback requirements are
discussed in Section 4.21. discussed in Section 4.21.
4.7 Record route of P2MP TE LSP 4.7. Record Route of P2MP TE LSP
Being able to identify the established topology of P2MP TE LSP is Being able to identify the established topology of P2MP TE LSP is
very important for various purposes such as management and operation very important for various purposes such as management and operation
of some local recovery mechanisms like Fast Reroute [RFC4090]. A of some local recovery mechanisms like Fast Reroute [RFC4090]. A
network operator uses this information to manage P2MP TE LSPs. network operator uses this information to manage P2MP TE LSPs.
Therefore the P2MP TE solution MUST support a mechanism which can Therefore, the P2MP TE solution MUST support a mechanism that can
collect and update P2MP tree topology information after P2MP LSP collect and update P2MP tree topology information after the P2MP LSP
establishment and modification process. establishment and modification process.
It is RECOMMENDED that the information is collected in a data format It is RECOMMENDED that the information is collected in a data format
which allows easy recognition of the P2MP tree topology. that allows easy recognition of the P2MP tree topology.
The solution MUST support mechanisms for the recording of both The solution MUST support mechanisms for the recording of both
outgoing interfaces and node-ids. outgoing interfaces and node-ids.
The solution MUST gracefully handle scaling issues concerned with the The solution MUST gracefully handle scaling issues concerned with the
collection of P2MP tree information including the case where the collection of P2MP tree information, including the case where the
collected information is too large to be carried in a single protocol collected information is too large to be carried in a single protocol
message. message.
4.8 Call Admission Control (CAC) and QoS Control mechanism of 4.8. Call Admission Control (CAC) and QoS Control Mechanism of
P2MP TE LSPs P2MP TE LSPs
P2MP TE LSPs may share network resource with P2P TE LSPs. Therefore P2MP TE LSPs may share network resource with P2P TE LSPs. Therefore,
it is important to use CAC and QoS in the same way as P2P TE LSPs it is important to use CAC and QoS in the same way as P2P TE LSPs for
for easy and scalable operation. easy and scalable operation.
P2MP TE solutions MUST support both resource sharing and exclusive P2MP TE solutions MUST support both resource sharing and exclusive
resource utilization to facilitate co-existence with other LSPs to resource utilization to facilitate coexistence with other LSPs to the
the same destination(s). same destination(s).
P2MP TE solutions MUST be applicable to DiffServ-enabled networks P2MP TE solutions MUST be applicable to DiffServ-enabled networks
that can provide consistent QoS control in P2MP LSP traffic. that can provide consistent QoS control in P2MP LSP traffic.
Any solution SHOULD also satisfy the DS-TE requirements [RFC3564] Any solution SHOULD also satisfy the DS-TE requirements [RFC3564] and
and interoperate smoothly with current P2P DS-TE protocol interoperate smoothly with current P2P DS-TE protocol specifications.
specifications.
Note that this requirement document does not make any assumption on Note that this requirement document does not make any assumption on
the type of bandwidth pool used for P2MP TE LSPs which can either be the type of bandwidth pool used for P2MP TE LSPs, which can either be
shared with P2P TE LSP or be dedicated for P2MP use. shared with P2P TE LSP or be dedicated for P2MP use.
4.9 Variation of LSP Parameters 4.9. Variation of LSP Parameters
Certain parameters (such as priority and bandwidth) are associated Certain parameters (such as priority and bandwidth) are associated
with an LSP. The parameters are installed by the signaling exchanges with an LSP. The parameters are installed by the signaling exchanges
associated with establishing and maintaining the LSP. associated with establishing and maintaining the LSP.
Any solution MUST NOT allow for variance of these parameters within Any solution MUST NOT allow for variance of these parameters within a
a single P2MP LSP. That is: single P2MP LSP. That is:
- No attributes set and signaled by the ingress LSR of a P2MP LSP may - No attributes set and signaled by the ingress LSR of a P2MP LSP may
be varied by downstream LSRs. be varied by downstream LSRs.
- There MUST be homogeneous QoS from the root to all leaves of a - There MUST be homogeneous QoS from the root to all leaves of a
single P2MP LSP. single P2MP LSP.
Changing the parameters for the whole tree MAY be supported, but the Changing the parameters for the whole tree MAY be supported, but the
change MUST apply to the whole tree from ingress LSR to all egress change MUST apply to the whole tree from ingress LSR to all egress
LSRs. LSRs.
4.10 Re-optimization of P2MP TE LSPs 4.10. Re-Optimization of P2MP TE LSPs
The detection of a more optimal path (for example, one with a lower The detection of a more optimal path (for example, one with a lower
overall cost) is an example of a situation where P2MP TE LSP overall cost) is an example of a situation where P2MP TE LSP re-
re-routing may be required. While re-routing is in progress, an routing may be required. While re-routing is in progress, an
important requirement is avoiding double bandwidth reservation important requirement is to avoid double bandwidth reservation (over
(over the common parts between the old and new LSP) thorough the use the common parts between the old and new LSP) thorough the use of
of resource sharing. resource sharing.
Make-before-break MUST be supported for a P2MP TE LSP to ensure that Make-before-break MUST be supported for a P2MP TE LSP to ensure that
there is minimal traffic disruption when the P2MP TE LSP is there is minimal traffic disruption when the P2MP TE LSP is re-
re-routed. routed.
Make-before-break that only applies to a sub-P2MP tree without Make-before-break that only applies to a sub-P2MP tree without
impacting the data on all of the other parts of the P2MP tree MUST be impacting the data on all the other parts of the P2MP tree MUST be
supported. supported.
The solution SHOULD allow for make-before-break re-optimization of The solution SHOULD allow for make-before-break re-optimization of
any subdivision of the P2MP LSP (S2PL sub-LSP, S2X sub-LSP, S2L any subdivision of the P2MP LSP (S2PL sub-LSP, S2X sub-LSP, S2L sub-
sub-LSP, X2AL sub-LSP, B2PL sub-LSP, X2AL sub-LSP, or B2AL tree). LSP, X2AL sub-LSP, B2PL sub-LSP, X2AL sub-LSP, or B2AL tree).
Further it SHOULD do so minimizing the signaling impact on the rest Further, it SHOULD do so by minimizing the signaling impact on the
of the P2MP LSP, and without affecting the ability of the management rest of the P2MP LSP, and without affecting the ability of the
plane to manage the LSP. management plane to manage the LSP.
The solution SHOULD also provide the ability for the ingress LSR to The solution SHOULD also provide the ability for the ingress LSR to
have strict control over the re-optimization process. The ingress have strict control over the re-optimization process. The ingress
LSR SHOULD be able to limit all re-optimization to be LSR SHOULD be able to limit all re-optimization to be source-
source-initiated. initiated.
Where sub-LSP re-optimization is allowed by the ingress LSR, such Where sub-LSP re-optimization is allowed by the ingress LSR, such
re-optimization MAY be initiated by a downstream LSR that is the re-optimization MAY be initiated by a downstream LSR that is the root
root of the sub-LSP that is to be re-optimized. Sub-LSP of the sub-LSP that is to be re-optimized. Sub-LSP re-optimization
re-optimization initiated by a downstream LSR MUST be carried out initiated by a downstream LSR MUST be carried out with the same
with the same regard to minimizing the impact on active traffic as regard to minimizing the impact on active traffic as was described
was described above for other re-optimization. above for other re-optimization.
4.11 Merging of Tree Branches 4.11. Merging of Tree Branches
It is possible for a single transit LSR to receive multiple signaling It is possible for a single transit LSR to receive multiple signaling
messages for the same P2MP LSP but for different sets of messages for the same P2MP LSP but for different sets of
destinations. These messages may be received from the same or destinations. These messages may be received from the same or
different upstream nodes and may need to be passed on to the same or different upstream nodes and may need to be passed on to the same or
different downstream nodes. different downstream nodes.
This situation may arise as the result of the signaling solution This situation may arise as the result of the signaling solution
definition or implementation options within the signaling solution. definition or implementation options within the signaling solution.
Further, it may happen during make-before-break reoptimization Further, it may happen during make-before-break re-optimization
(section 4.10). (Section 4.10).
It is even possible that it is necessary to construct distinct It is even possible that it is necessary to construct distinct
upstream branches in order to achieve the correct label choices in upstream branches in order to achieve the correct label choices in
certain switching technologies managed by GMPLS (for example, certain switching technologies managed by GMPLS (for example,
photonic cross-connects where the selection of a particular lambda photonic cross-connects where the selection of a particular lambda
for the downstream branches is only available on different upstream for the downstream branches is only available on different upstream
switches). switches).
The solution MUST support the case where multiple signaling The solution MUST support the case where multiple signaling messages
messages for the same P2MP LSP are received at a single transit LSR for the same P2MP LSP are received at a single transit LSR and refer
and refer to the same upstream interface. In this case the result of to the same upstream interface. In this case, the result of the
the protocol procedures SHOULD be a single data flow on the upstream protocol procedures SHOULD be a single data flow on the upstream
interface. interface.
The solution SHOULD support the case where multiple signaling The solution SHOULD support the case where multiple signaling
messages for the same P2MP LSP are received at a single transit LSR messages for the same P2MP LSP are received at a single transit LSR
and refer to different upstream interfaces, and where each signaling and refer to different upstream interfaces, and where each signaling
message results in the use of different downstream interfaces. This message results in the use of different downstream interfaces. This
case represents data flows that cross at the LSR but which do not case represents data flows that cross at the LSR but that do not
merge. merge.
The solution MAY support the case where multiple signaling messages The solution MAY support the case where multiple signaling messages
for the same P2MP LSP are received at a single transit LSR and refer for the same P2MP LSP are received at a single transit LSR and refer
to different upstream interfaces, and where the downstream interfaces to different upstream interfaces, and where the downstream interfaces
are shared across the received signaling messages. This case are shared across the received signaling messages. This case
represents the merging of data flows. A solution that supports this represents the merging of data flows. A solution that supports this
case MUST ensure that data is not replicated on the downstream case MUST ensure that data is not replicated on the downstream
interfaces. interfaces.
An alternative to supporting this last case is for the signaling An alternative to supporting this last case is for the signaling
protocol to indicate an error such that the merge may be resolved by protocol to indicate an error such that the merge may be resolved by
the upstream LSRs. the upstream LSRs.
4.12 Data Duplication 4.12. Data Duplication
Data duplication refers to the receipt by any recipient of duplicate Data duplication refers to the receipt by any recipient of duplicate
instances of the data. In a packet environment this means the instances of the data. In a packet environment, this means the
receipt of duplicate packets. Although small-scale packet duplication receipt of duplicate packets. Although small-scale packet
(that is, a few packets over a relatively short period of time) duplication (that is, a few packets over a relatively short period of
should be a harmless (if inefficient) situation, certain existing and time) should be a harmless (if inefficient) situation, certain
deployed applications will not tolerate packet duplication. Sustained existing and deployed applications will not tolerate packet
packet duplication is, at best, a waste of network and processing duplication. Sustained packet duplication is, at best, a waste of
resources, and at worst may cause congestion and the inability to network and processing resources and, at worst, may cause congestion
process the data correctly. and the inability to process the data correctly.
In a non-packet environment data duplication means the duplication of In a non-packet environment, data duplication means the duplication
some part of the signal that may lead to the replication of data or of some part of the signal that may lead to the replication of data
to the scrambling of data. or to the scrambling of data.
Data duplication may legitimately arise in various scenarios Data duplication may legitimately arise in various scenarios
including re-optimization of active LSPs as described in the including re-optimization of active LSPs as described in the previous
previous section, and protection of LSPs. Thus, it is impractical to section, and protection of LSPs. Thus, it is impractical to regulate
regulate against data duplication in this document. against data duplication in this document.
Instead, the solution: Instead, the solution:
- SHOULD limit to bounded transitory conditions the cases where - SHOULD limit to bounded transitory conditions the cases where
network bandwidth is wasted by the existence of duplicate delivery network bandwidth is wasted by the existence of duplicate delivery
paths. paths.
- MUST limit the cases where duplicate data is delivered to an - MUST limit the cases where duplicate data is delivered to an
application to bounded transitory conditions. application to bounded transitory conditions.
4.13 IPv4/IPv6 support 4.13. IPv4/IPv6 Support
Any P2MP TE solution MUST support IPv4 and IPv6 addressing. Any P2MP TE solution MUST support IPv4 and IPv6 addressing.
4.14 P2MP MPLS Label 4.14. P2MP MPLS Label
A P2MP TE solution MUST allow the continued use of existing A P2MP TE solution MUST allow the continued use of existing
techniques to establish P2P LSPs (TE and otherwise) within the same techniques to establish P2P LSPs (TE and otherwise) within the same
network, and MUST allow the co-existence of P2P LSPs within the same network, and MUST allow the coexistence of P2P LSPs within the same
network as P2MP TE LSPs. network as P2MP TE LSPs.
A P2MP TE solution MUST be specified in such a way that it allows A P2MP TE solution MUST be specified in such a way that it allows
P2MP and P2P TE LSPs to be signaled on the same interface. P2MP and P2P TE LSPs to be signaled on the same interface.
4.15 Advertisement of P2MP capability 4.15. Advertisement of P2MP Capability
Several high-level requirements have been identified to determine the Several high-level requirements have been identified to determine the
capabilities of LSRs within a P2MP network. The aim of such capabilities of LSRs within a P2MP network. The aim of such
information is to facilitate the computation of P2MP trees using TE information is to facilitate the computation of P2MP trees using TE
constraints within a network that contains LSRs that do not all have constraints within a network that contains LSRs that do not all have
the same capabilities levels with respect to P2MP signaling and data the same capability levels with respect to P2MP signaling and data
forwarding. forwarding.
These capabilities include, but are not limited to: These capabilities include, but are not limited to:
- 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 LSR and a branch LSR for - The ability of an LSR to act as an egress LSR and a branch LSR for
the same LSP. the same LSP.
- The ability of an LSR to support P2MP MPLS-TE signaling. - The ability of an LSR to support P2MP MPLS-TE signaling.
4.16 Multi-access LANs 4.16. Multi-Access LANs
P2MP MPLS TE may be used to traverse network segments that are P2MP MPLS TE may be used to traverse network segments that are
provided by multi-access media such as Ethernet. In these cases, it provided by multi-access media such as Ethernet. In these cases, it
is also possible that the entry point to the network segment is a is also possible that the entry point to the network segment is a
branch LSR of the P2MP LSP. branch LSR of the P2MP LSP.
Two options clearly exist: Two options clearly exist:
- the branch LSR replicates the data and transmits multiple copies - the branch LSR replicates the data and transmits multiple copies
onto the segment onto the segment.
- the branch LSR sends a single copy of the data to the segment - the branch LSR sends a single copy of the data to the segment and
and relies on the exit points to determine whether to receive and relies on the exit points to determine whether to receive and
forward the data. forward the data.
The first option has a significant data plane scaling issue since all The first option has a significant data plane scaling issue since all
replicated data must be sent through the same port and carried on the replicated data must be sent through the same port and carried on the
same segment. Thus, a solution SHOULD provide a mechanism for a same segment. Thus, a solution SHOULD provide a mechanism for a
branch LSR to send a single copy of the data onto a multi-access branch LSR to send a single copy of the data onto a multi-access
network and reach multiple (adjacent) downstream nodes. The second network to reach multiple (adjacent) downstream nodes. The second
option may have control plane scaling issues. option may have control plane scaling issues.
4.17 P2MP MPLS OAM 4.17. P2MP MPLS OAM
The MPLS and GMPLS MIB modules MUST be enhanced to provide P2MP TE The MPLS and GMPLS MIB modules MUST be enhanced to provide P2MP TE
LSP management in line with whatever signaling solutions are LSP management in line with whatever signaling solutions are
developed. developed.
In order to facilitate correct management, P2MP TE LSPs MUST have In order to facilitate correct management, P2MP TE LSPs MUST have
unique identifiers since otherwise it is impossible to determine unique identifiers, since otherwise it is impossible to determine
which LSP is being managed. which LSP is being managed.
Further discussions of OAM are out of scope for this document. Further discussions of OAM are out of scope for this document. See
See [P2MP-OAM] for more details. [P2MP-OAM] for more details.
4.18 Scalability 4.18. Scalability
Scalability is a key requirement in P2MP MPLS systems. Solutions MUST Scalability is a key requirement in P2MP MPLS systems. Solutions
be designed to scale well with an increase in the number of any of MUST be designed to scale well with an increase in the number of any
the following: of the following:
- the number of recipients - the number of recipients
- the number of egress LSRs - the number of egress LSRs
- the number of branch LSRs - the number of branch LSRs
- the number of branches. - the number of branches
Both scalability of control plane operation (setup, maintenance, Both scalability of control plane operation (setup, maintenance,
modification and teardown) MUST be considered. modification, and teardown) MUST be considered.
Key considerations MUST include: Key considerations MUST include:
- the amount of refresh processing associated with maintaining
a P2MP TE LSP. - the amount of refresh processing associated with maintaining a P2MP
- the amount of protocol state that must be maintained by ingress TE LSP.
and transit LSRs along a P2MP tree. - the amount of protocol state that must be maintained by ingress and
transit LSRs along a P2MP tree.
- the number of protocol messages required to set up or tear down a - the number of protocol messages required to set up or tear down a
P2MP LSP as a function of the number of egress LSRs. P2MP LSP as a function of the number of egress LSRs.
- the number of protocol messages required to repair a P2MP LSP after - the number of protocol messages required to repair a P2MP LSP after
failure or perform make-before-break. failure or to perform make-before-break.
- the amount of protocol information transmitted to manage - the amount of protocol information transmitted to manage a P2MP TE
a P2MP TE LSP (i.e. the message size). LSP (i.e., the message size).
- the amount of additional data distributed in potential routing - the amount of additional data distributed in potential routing
extensions. extensions.
- the amount of additional control plane processing required in - the amount of additional control plane processing required in the
the network to detect whether an add/delete of a new branch is network to detect whether an add/delete of a new branch is
required, and in particular, the amount of processing in steady required, and in particular, the amount of processing in steady
state when no add/delete is requested state when no add/delete is requested
- the amount of control plane processing required by the ingress, - the amount of control plane processing required by the ingress,
transit and egress LSRs to add/delete a branch LSP to/from an transit, and egress LSRs to add/delete a branch LSP to/from an
existing P2MP LSP. existing P2MP LSP.
It is expected that the applicability of each solution will be It is expected that the applicability of each solution will be
evaluated with regards to the aforementioned scalability criteria. evaluated with regards to the aforementioned scalability criteria.
4.18.1 Absolute Limits 4.18.1. Absolute Limits
In order to achieve the best solution for the problem space it is In order to achieve the best solution for the problem space, it is
helpful to clarify the boundaries for P2MP TE LSPs. helpful to clarify the boundaries for P2MP TE LSPs.
- Number of egress LSRs. - Number of egress LSRs.
A scaling bound is placed on the solution mechanism such that a A scaling bound is placed on the solution mechanism such that a
P2MP TE LSP MUST reduce to similar scaling properties as a P2P LSP P2MP TE LSP MUST reduce to similar scaling properties as a P2P LSP
when the number of egress LSRs reduces to one. That is, when the number of egress LSRs reduces to one. That is,
establishing a P2MP TE LSP to a single egress LSR should cost establishing a P2MP TE LSP to a single egress LSR should cost
approximately as much as establishing a P2P LSP. approximately as much as establishing a P2P LSP.
It is important to classify the issues of scaling within the It is important to classify the issues of scaling within the
context of Traffic Engineering. It is anticipated that the initial context of traffic engineering. It is anticipated that the initial
deployments of P2MP TE LSPs will be limited to a maximum of around deployments of P2MP TE LSPs will be limited to a maximum of around
a hundred egress LSRs, but that within five years deployments may a hundred egress LSRs, but that within five years deployments may
increase this to several hundred, and that future deployments may increase this to several hundred, and that future deployments may
require significantly larger numbers. require significantly larger numbers.
An acceptable upper bound for a solution, therefore, is one that An acceptable upper bound for a solution, therefore, is one that
scales linearly with the number of egress LSRs. It is expected that scales linearly with the number of egress LSRs. It is expected
solutions will scale better than linearly. that solutions will scale better than linearly.
Solutions that scale worse than linear (that is, exponential or Solutions that scale worse than linearly (that is, exponentially or
polynomial) are not acceptable whatever the number of egress LSRs polynomially) are not acceptable whatever the number of egress LSRs
they could support. they could support.
- Number of branch LSRs. - Number of branch LSRs.
Solutions MUST support all possibilities from one extreme of a Solutions MUST support all possibilities from one extreme of a
single branch LSR that forks to all leaves on a separate branch, single branch LSR that forks to all leaves on a separate branch, to
to the greatest number of branch LSRs which is (n-1) for n egress the greatest number of branch LSRs which is (n-1) for n egress
LSRs. Assumptions MUST NOT be made in the solution regarding which LSRs. Assumptions MUST NOT be made in the solution regarding which
topology is more common, and the solution MUST be designed to topology is more common, and the solution MUST be designed to
ensure scalability in all topologies. ensure scalability in all topologies.
- Dynamics of P2MP tree. - Dynamics of P2MP tree.
Recall that the mechanisms for determining which egress LSRs should Recall that the mechanisms for determining which egress LSRs should
be added to an LSP, and for adding and removing egress LSRs from be added to an LSP and for adding and removing egress LSRs from
that group are out of the scope of this document. Nevertheless, it that group are out of the scope of this document. Nevertheless, it
is useful to understand the expected rates of arrival and is useful to understand the expected rates of arrival and departure
departure of egress LSRs since this can impact the selection of of egress LSRs, since this can impact the selection of solution
solution techniques. techniques.
Again, it must be recalled that this document is limited to Traffic Again, this document is limited to traffic engineering, and in this
Engineering, and in this model the rate of change of LSP egress model the rate of change of LSP egress LSRs may be expected to be
LSRs may be expected to be lower than the rate of change of lower than the rate of change of recipients in an IP multicast
recipients in an IP multicast group. group.
Although the absolute number of egress LSRs coming and going is the Although the absolute number of egress LSRs coming and going is the
important element for determining the scalability of a solution, important element for determining the scalability of a solution,
it may be noted that a percentage may be a more comprehensible note that a percentage may be a more comprehensible measure, but
measure, but that this is not as significant for LSPs with a small that this is not as significant for LSPs with a small number of
number of recipients. recipients.
A working figure for an established P2MP TE LSP is less than 10% A working figure for an established P2MP TE LSP is less than 10%
churn per day. That is, a relatively slow rate of churn. churn per day; that is, a relatively slow rate of churn.
We could say that a P2MP LSP would be shared by multiple multicast We could say that a P2MP LSP would be shared by multiple multicast
groups and so the dynamics of the P2MP LSP would be relatively groups, so the dynamics of the P2MP LSP would be relatively small.
small.
Solutions MUST optimize for such relatively low rates of change and Solutions MUST optimize for such relatively low rates of change and
are not required to optimize for significantly higher rates of are not required to optimize for significantly higher rates of
change. change.
- Rate of change within the network. - Rate of change within the network.
It is also important to understand the scaling with regard to It is also important to understand the scaling with regard to
changes within the network. That is, one of the features of a P2MP changes within the network. That is, one of the features of a P2MP
TE LSP is that it can be robust or protected against network TE LSP is that it can be robust or protected against network
failures, and can be re-optimized to take advantage of newly failures, and it can be re-optimized to take advantage of newly
available network resources. available network resources.
It is more important that a solution be optimized for scaling with It is more important that a solution be optimized for scaling with
respect to recovery and re-optimization of the LSP than for change respect to recovery and re-optimization of the LSP than for change
in the egress LSRs, because P2MP is used as a TE tool. in the egress LSRs, because P2MP is used as a TE tool.
The solution MUST follow this distinction and optimize accordingly. The solution MUST follow this distinction and optimize accordingly.
4.19 Backwards Compatibility 4.19. Backwards Compatibility
It SHOULD be an aim of any P2MP solution to offer as much backward It SHOULD be an aim of any P2MP solution to offer as much backward
compatibility as possible. An ideal which is probably impossible to compatibility as possible. An ideal that is probably impossible to
achieve would be to offer P2MP services across legacy MPLS networks achieve would be to offer P2MP services across legacy MPLS networks
without any change to any LSR in the network. without any change to any LSR in the network.
If this ideal cannot be achieved, the aim SHOULD be to use legacy If this ideal cannot be achieved, the aim SHOULD be to use legacy
nodes as both transit non-branch LSRs and egress LSRs. nodes as both transit non-branch LSRs and egress LSRs.
It is a further requirement for the solution that any LSR that It is a further requirement for the solution that any LSR that
implements the solution SHALL NOT be prohibited by that act from implements the solution SHALL NOT be prohibited by that act from
supporting P2P TE LSPs using existing signaling mechanisms. That is, supporting P2P TE LSPs using existing signaling mechanisms. That is,
unless administratively prohibited, P2P TE LSPs MUST be supported unless doing so is administratively prohibited, P2P TE LSPs MUST be
through a P2MP network. supported through a P2MP network.
Also, it is a requirement that P2MP TE LSPs MUST be able to co-exist Also, it is a requirement that P2MP TE LSPs MUST be able to coexist
with IP unicast and IP multicast networks. with IP unicast and IP multicast networks.
4.20 GMPLS 4.20. GMPLS
The requirement for P2MP services for non-packet switch interfaces The requirement for P2MP services for non-packet switch interfaces is
is similar to that for Packet-Switch Capable (PSC) interfaces. similar to that for Packet-Switch Capable (PSC) interfaces.
Therefore, it is a requirement that reasonable attempts must be made Therefore, it is a requirement that reasonable attempts must be made
to make all the features/mechanisms (and protocol extensions) that to make all the features/mechanisms (and protocol extensions) that
will be defined to provide MPLS P2MP TE LSPs equally applicable to will be defined to provide MPLS P2MP TE LSPs equally applicable to
P2MP PSC and non-PSC TE-LSPs. If the requirements of non-PSC networks P2MP PSC and non-PSC TE-LSPs. If the requirements of non-PSC
over-complicate the PSC solution a decision may be taken to separate networks over-complicate the PSC solution a decision may be taken to
the solutions. separate the solutions.
Solutions for MPLS P2MP TE-LSPs when applied to GMPLS P2MP PSC or Solutions for MPLS P2MP TE-LSPs, when applied to GMPLS P2MP PSC or
non-PSC TE-LSPs MUST be compatible with the other features of GMPLS non-PSC TE-LSPs, MUST be compatible with the other features of GMPLS
including: including:
- control and data plane separation, - control and data plane separation;
- full support of numbered and unnumbered TE links, - full support of numbered and unnumbered TE links;
- use of the arbitrary labels and labels for specific technologies, - use of the arbitrary labels and labels for specific technologies,
as well as negotiation of labels where necessary to support limited as well as negotiation of labels, where necessary, to support
label processing and swapping capabilities, limited label processing and swapping capabilities;
- the ability to apply external control to the labels selected on - the ability to apply external control to the labels selected on
each hop of the LSP, and to control the next hop each hop of the LSP, and to control the next hop
label/port/interface for data after it reaches the egress LSR, label/port/interface for data after it reaches the egress LSR;
- support for graceful and alarm-free enablement and termination of - support for graceful and alarm-free enablement and termination of
LSPs, LSPs;
- full support for protection including link level protection, - full support for protection including link-level protection,
end-to-end protection and segment protection, end-to-end protection, and segment protection;
- the ability to teardown an LSP from a downstream LSR, in particular - the ability to teardown an LSP from a downstream LSR, in
from the egress LSR, particular, from the egress LSR;
- handling of Graceful Deletion procedures, - handling of Graceful Deletion procedures; and
- support for failure and restart or reconnection of the control - support for failure and restart or reconnection of the control
plane without any disruption of the data plane. plane without any disruption of the data plane.
In addition, since non-PSC TE-LSPs may have to be processed in In addition, since non-PSC TE-LSPs may have to be processed in
environments where the "P2MP capability" could be limited, specific environments where the "P2MP capability" could be limited, specific
constraints may also apply during the P2MP TE Path computation. constraints may also apply during the P2MP TE Path computation.
Being technology specific, these constraints are outside the scope Being technology specific, these constraints are outside the scope of
of this document. However, technology independent constraints this document. However, technology-independent constraints (i.e.,
(i.e. constraints that are applicable independently of the LSP constraints that are applicable independently of the LSP class)
class) SHOULD be allowed during P2MP TE LSP message processing. SHOULD be allowed during P2MP TE LSP message processing. It has to
It has to be emphasized that path computation and management be emphasized that path computation and management techniques shall
techniques shall be as close as possible to those being used for be as close as possible to those being used for PSC P2P TE LSPs and
PSC P2P TE LSPs and P2MP TE LSPs. P2MP TE LSPs.
4.21 P2MP Crankback routing 4.21. P2MP Crankback Routing
P2MP solutions SHOULD support crankback requirements as defined in P2MP solutions SHOULD support crankback requirements as defined in
[CRANKBACK]. In particular, they SHOULD provide sufficient [CRANKBACK]. In particular, they SHOULD provide sufficient
information to a branch LSR from downstream LSRs to allow the branch information to a branch LSR from downstream LSRs to allow the branch
LSR to re-route a sub-LSP around any failures or problems in the LSR to re-route a sub-LSP around any failures or problems in the
network. network.
5. Security Considerations 5. Security Considerations
This requirements document does not define any protocol extensions This requirements document does not define any protocol extensions
skipping to change at page 24, line 42 skipping to change at page 25, line 45
5. Security Considerations 5. Security Considerations
This requirements document does not define any protocol extensions This requirements document does not define any protocol extensions
and does not, therefore, make any changes to any security models. and does not, therefore, make any changes to any security models.
It is a requirement that any P2MP solution developed to meet some or It is a requirement that any P2MP solution developed to meet some or
all of the requirements expressed in this document MUST include all of the requirements expressed in this document MUST include
mechanisms to enable the secure establishment and management of P2MP mechanisms to enable the secure establishment and management of P2MP
MPLS-TE LSPs. This includes, but is not limited to: MPLS-TE LSPs. This includes, but is not limited to:
- mechanisms to ensure that the ingress LSR of a P2MP LSP is - mechanisms to ensure that the ingress LSR of a P2MP LSP is
identified identified;
- mechanisms to ensure that communicating signaling entities can - mechanisms to ensure that communicating signaling entities can
verify each other's identities verify each other's identities;
- mechanisms to ensure that control plane messages are protected - mechanisms to ensure that control plane messages are protected
against spoofing and tampering against spoofing and tampering;
- mechanisms to ensure that unauthorized leaves or branches are not - mechanisms to ensure that unauthorized leaves or branches are not
added to the P2MP LSP added to the P2MP LSP; and
- mechanisms to protect signaling messages from snooping. - mechanisms to protect signaling messages from snooping.
It should be noted that P2MP signaling mechanisms built on P2P Note that P2MP signaling mechanisms built on P2P RSVP-TE signaling
RSVP-TE signaling are likely to inherit all of the security are likely to inherit all the security techniques and problems
techniques and problems associated with RSVP-TE. These problems may associated with RSVP-TE. These problems may be exacerbated in P2MP
be exacerbated in P2MP situations where security relationships may situations where security relationships may need to maintained
need to maintained between an ingress LSR and multiple egress LSRs. between an ingress LSR and multiple egress LSRs. Such issues are
Such issues are similar to security issues for IP multicast. similar to security issues for IP multicast.
It is a requirement that documents offering solutions for P2MP LSPs It is a requirement that documents offering solutions for P2MP LSPs
MUST have detailed security sections. MUST have detailed security sections.
6. IANA Considerations 6. Acknowledgements
This informational draft does not introduce any new encodings or code
points. It requires no action from IANA.
7. Acknowledgements
The authors would like to thank George Swallow, Ichiro Inoue, Dean The authors would like to thank George Swallow, Ichiro Inoue, Dean
Cheng, Lou Berger and Eric Rosen for their review and suggestions. Cheng, Lou Berger, and Eric Rosen for their review and suggestions.
Thanks to Loa Andersson for his help resolving the final issues in Thanks to Loa Andersson for his help resolving the final issues in
this document and to Harald Alvestrand for a thorough GenArt review. this document and to Harald Alvestrand for a thorough GenArt review.
8. References 7. References
8.1 Normative References 7.1. 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.
[RFC2702] D. Awduche, J. Malcolm, J. Agogbua, M. O'Dell, J. [RFC2702] Awduche, D., Malcolm, J., Agogbua, J., O'Dell, M., and
McManus, "Requirements for Traffic Engineering Over J. McManus, "Requirements for Traffic Engineering Over
MPLS", RFC2702, September 1999. MPLS", RFC2702, September 1999.
[RFC3031] Rosen, E., Viswanathan, A. and R. Callon, [RFC3031] Rosen, E., Viswanathan, A., and R. Callon,
"Multiprotocol Label Switching Architecture", RFC 3031, "Multiprotocol Label Switching Architecture", RFC 3031,
January 2001. January 2001.
[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 V., and G. Swallow, "RSVP-TE: Extensions to RSVP for
Tunnels", RFC 3209, December 2001. LSP Tunnels", RFC 3209, December 2001.
8.2 Informational References 7.2. Informative References
[RFC3473] Berger, L., Editor, "Generalized Multi-Protocol Label [RFC3468] Andersson, L. and G. Swallow, "The Multiprotocol Label
Switching (GMPLS) Signaling - Resource ReserVation Switching (MPLS) Working Group decision on MPLS
Protocol-Traffic Engineering (RSVP-TE) Extensions", signaling protocols", RFC 3468, February 2003.
RFC 3473, January 2003.
[RFC3564] F. Le Faucheur, W. Lai, "Requirements for Support of [RFC3473] Berger, L., "Generalized Multi-Protocol Label Switching
Differentiated Services-aware MPLS Traffic (GMPLS) Signaling Resource ReserVation Protocol-Traffic
Engineering (RSVP-TE) Extensions", RFC 3473, January
2003.
[RFC3564] Le Faucheur, F. and W. Lai, "Requirements for Support
of Differentiated Services-aware MPLS Traffic
Engineering", RFC 3564, July 2003. Engineering", RFC 3564, July 2003.
[RFC4090] P. Pan, G. Swallow, A. Atlas, "Fast Reroute Extensions [RFC4090] Pan, P., Swallow, G., and A. Atlas, "Fast Reroute
to RSVP-TE for LSP Tunnels", RFC 4090, May 2005. Extensions to RSVP-TE for LSP Tunnels", RFC 4090, May
2005.
[STEINER] H. Salama, et al., "Evaluation of Multicast Routing [STEINER] H. Salama, et al., "Evaluation of Multicast Routing
Algorithm for Real-Time Communication on High-Speed Algorithm for Real-Time Communication on High-Speed
Networks," IEEE Journal on Selected Area in Networks," IEEE Journal on Selected Area in
Communications, pp.332-345, 1997. Communications, pp.332-345, 1997.
[CRANKBACK] A. Farrel, A. Satyanarayana, A. Iwata, N. Fujita, G. [CRANKBACK] A. Farrel, A. Satyanarayana, A. Iwata, N. Fujita, G.
Ash, S. Marshall, "Crankback Signaling Extensions for Ash, S. Marshall, "Crankback Signaling Extensions for
MPLS Signaling", draft-ietf-ccamp-crankback, work in MPLS Signaling", Work in Progress, May 2005.
progress.
[P2MP-OAM] S. Yasukawa, A. Farrel, D. King, and T. Nadeau, "OAM [P2MP-OAM] S. Yasukawa, A. Farrel, D. King, and T. Nadeau, "OAM
Requirements for Point-to-Multipoint MPLS Networks", Requirements for Point-to-Multipoint MPLS Networks",
draft-yasukawa-mpls-p2mp-oam-reqs, work in progress. Work in Progress, February 2006.
9. Editor's Address Editor's Address
Seisho Yasukawa Seisho Yasukawa
NTT Corporation NTT Corporation
9-11, Midori-Cho 3-Chome 9-11, Midori-Cho 3-Chome
Musashino-Shi, Tokyo 180-8585, Musashino-Shi, Tokyo 180-8585,
Japan 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
10. Authors' Addresses Authors' Addresses
Dimitri Papadimitriou Dimitri Papadimitriou
Alcatel Alcatel
Francis Wellensplein 1, Francis Wellensplein 1,
B-2018 Antwerpen, B-2018 Antwerpen,
Belgium 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
Tokyo Opera City Tower Tokyo Opera City Tower
3-20-2 Nishi Shinjuku, Shinjuku-ku, 3-20-2 Nishi Shinjuku, Shinjuku-ku,
Tokyo 163-1421, Tokyo 163-1421,
Japan 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
Quarry Technologies Quarry Technologies
8 New England Executive Park 8 New England Executive Park
Burlington, MA 01803 Burlington, MA 01803
EMail: mjork@quarrytech.com EMail: mjork@quarrytech.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 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
11. Intellectual Property Consideration EMail: jeanlouis.leroux@francetelecom.com
Full Copyright Statement
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Copyright (C) The Internet Society (2005). This document is Acknowledgement
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This document and the information contained herein are provided Funding for the RFC Editor function is provided by the IETF
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