draft-ietf-mpls-ldp-interarea-04.txt   rfc5283.txt 
Network Working Group B. Decraene Network Working Group B. Decraene
Internet Draft J.L. Le Roux Request for Comments: 5283 JL. Le Roux
Document: draft-ietf-mpls-ldp-interarea-04.txt France Telecom Category: Standards Track France Telecom
Intended status: Standards Track I. Minei
Expiration Date: December 2008 I. Minei
Juniper Networks, Inc. Juniper Networks, Inc.
LDP extension for Inter-Area LSP LDP Extension for Inter-Area Label Switched Paths (LSPs)
Status of this Memo
By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware
have been or will be disclosed, and any of which he or she becomes
aware will be disclosed, in accordance with Section 6 of BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that other
groups may also distribute working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at Status of This Memo
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at This document specifies an Internet standards track protocol for the
http://www.ietf.org/shadow.html. Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Abstract Abstract
To facilitate the establishment of Label Switched Paths (LSP) that To facilitate the establishment of Label Switched Paths (LSPs) that
would span multiple IGP areas in a given Autonomous System (AS), this would span multiple IGP areas in a given Autonomous System (AS), this
document describes a new optional Longest Match Label Mapping document describes a new optional Longest-Match Label Mapping
Procedure for the Label Distribution Protocol (LDP). Procedure for the Label Distribution Protocol (LDP).
This procedure allows the use of a label if the Forwarding This procedure allows the use of a label if the Forwarding
Equivalence Class (FEC) Element matches an entry in the routing table Equivalence Class (FEC) Element matches an entry in the Routing
(RIB). Matching is defined by an IP longest match search and does not Information Base (RIB). Matching is defined by an IP longest-match
mandate an exact match. search and does not mandate an exact match.
Table of Contents Table of Contents
1. Conventions used in this document...........................2 1. Introduction ....................................................2
2. Terminology.................................................2 2. Conventions Used in This Document ...............................2
3. Introduction................................................2 3. Terminology .....................................................2
4. Problem statement...........................................3 4. Problem Statement ...............................................3
5. Longest Match Label Mapping Message Procedure...............4 5. Longest-Match Label Mapping Message Procedure ...................4
6. Application examples........................................6 6. Application Examples ............................................6
6.1. Inter-area LSPs.............................................6 6.1. Inter-Area LSPs ............................................6
6.2. Use of static routes........................................7 6.2. Use of Static Routes .......................................7
7. Caveats for deployment......................................8 7. Caveats for Deployment ..........................................8
7.1. Deployment considerations...................................8 7.1. Deployment Considerations ..................................8
7.2. Routing convergence time considerations.....................8 7.2. Routing Convergence Time Considerations ....................8
8. Security Considerations.....................................9 8. Security Considerations .........................................9
9. IANA Considerations.........................................9 9. References ......................................................9
10. References..................................................9 9.1. Normative References .......................................9
10.1. Normative References........................................9 9.2. Informative References .....................................9
10.2. Informative References......................................9 10. Acknowledgments ...............................................11
11. Acknowledgments............................................10
12. Authors' Addresses.........................................11
1. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC 2119].
2. Terminology
IGP Area: OSPF Area or IS-IS level
ABR: OSPF Area Border Router or IS-IS L1/L2 router
LSP: Label Switched Path
Intra-area LSP: LSP that does not traverse any IGP area boundary.
Inter-area LSP: LSP that traverses at least one IGP area boundary.
3. Introduction 1. Introduction
Link state Interior Gateway Protocols (IGPs) such as OSPF [OSPFv2] Link state Interior Gateway Protocols (IGPs) such as OSPF [OSPFv2]
and IS-IS [IS-IS] allow the partition of an autonomous system into and IS-IS [IS-IS] allow the partition of an autonomous system into
areas or levels so as to increase routing scalability within a areas or levels so as to increase routing scalability within a
routing domain. routing domain.
However, [LDP] recommends that the IP address of the FEC Element However, [LDP] recommends that the IP address of the FEC Element
should *exactly* match an entry in the IP RIB: according to [LDP] should *exactly* match an entry in the IP Routing Information Base
section 3.5.7.1 (Label Mapping Messages Procedures) "A Label (RIB). According to [LDP], section 3.5.7.1 ("Label Mapping Messages
Switching Router (LSR) receiving a Label Mapping message from a Procedures"):
downstream LSR for a Prefix SHOULD NOT use the label for forwarding
unless its routing table contains an entry that exactly matches the An LSR [Label Switching Router] receiving a Label Mapping message
FEC Element.". from a downstream LSR for a Prefix SHOULD NOT use the label for
forwarding unless its routing table contains an entry that exactly
matches the FEC Element.
Therefore, MPLS LSPs between Label Edge Routers (LERs) in different Therefore, MPLS LSPs between Label Edge Routers (LERs) in different
areas/levels are not setup unless the specific (e.g. /32 for IPv4) areas/levels are not set up unless the specific (e.g., /32 for IPv4)
loopback addresses of all the LERs are redistributed across all loopback addresses of all the LERs are redistributed across all
areas. areas.
The problem statement is discussed in section 4. Then, in section 5 The problem statement is discussed in section 4. Then, in section 5
we extend the Label Mapping Procedure defined in [LDP] so as to we extend the Label Mapping Procedure defined in [LDP] so as to
support the setup of contiguous inter-area LSPs while maintaining IP support the setup of contiguous inter-area LSPs while maintaining IP
prefix aggregation on the ABRs. This consists of allowing for longest prefix aggregation on the ABRs. This consists of allowing for
match based Label Mapping. longest-match-based Label Mapping.
4. Problem statement 2. Conventions Used in This Document
Provider based MPLS (Multi Protocol Label Switching) networks are The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
expanding with the success of Layer 3 VPN (Virtual Private Networks "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
[L3-VPN]) and the new deployments of layer 2 VPNs ([VPLS-BGP], [VPLS- document are to be interpreted as described in [RFC2119].
LDP]). Service providers MPLS backbones are significantly growing
both in terms of density with the addition of Provider Edge (PE) 3. Terminology
routers to connect new customers and in terms of footprint as
traditional layer two aggregation networks may be replaced by IP/MPLS IGP Area: OSPF Area or IS-IS level
networks.
As a consequence many providers need to introduce IGP areas. Inter- ABR: OSPF Area Border Router or IS-IS L1/L2 router
area LSPs, that is LSPs that traverse at least two IGP areas, are
required to ensure MPLS connectivity between PEs located in distinct LSP: Label Switched Path
IGP areas.
Intra-area LSP: LSP that does not traverse any IGP area boundary.
Inter-area LSP: LSP that traverses at least one IGP area boundary.
4. Problem Statement
Provider-based MPLS (Multiprotocol Label Switching) networks are
expanding with the success of Layer 3 Virtual Private Networks
[L3-VPN] and the new deployments of Layer 2 VPNs ([VPLS-BGP],
[VPLS-LDP]). Service providers' MPLS backbones are significantly
growing both in terms of density with the addition of Provider Edge
(PE) routers to connect new customers and in terms of footprint as
traditional Layer 2 aggregation networks may be replaced by IP/MPLS
networks. As a consequence many providers need to introduce IGP
areas. Inter-area LSPs (that is, LSPs that traverse at least two IGP
areas) are required to ensure MPLS connectivity between PEs located
in distinct IGP areas.
To set up the required MPLS LSPs between PEs in different IGP areas, To set up the required MPLS LSPs between PEs in different IGP areas,
service providers have currently three solutions: 1) LDP with IGP service providers currently have three solutions: 1) LDP with IGP
route leaking, 2) BGP [MPLS-BGP] over LDP with MPLS hierarchy, and 3) route leaking, 2) BGP [MPLS-BGP] over LDP with MPLS hierarchy, and 3)
inter-area RSVP-TE (Resource Reservation Protocol-Traffic Engineering inter-area RSVP-TE (Resource Reservation Protocol-Traffic Engineering
[RSVP-TE]). [RSVP-TE]).
IGP route leaking consists in redistributing all specific PE loopback IGP route leaking consists of redistributing all specific PE loopback
addresses across area boundaries. As a result, LDP finds in the addresses across area boundaries. As a result, LDP finds in the RIB
Routing Information Base (RIB) an exact match for its FEC and sets up an exact match for its FEC and sets up the LSP. As a consequence,
the LSP. As a consequence, the potential benefits that a multi-area the potential benefits that a multi-area domain may yield are
domain may yield are significantly diminished since a lot of significantly diminished since a lot of addresses have to be
addresses have to be redistributed by ABRs, and the number of IP redistributed by ABRs, and the number of IP entries in the IGP Link
entries in the IGP Link State DataBase (LSDB), RIB and FIB maintained State Database (LSDB), RIB, and Forwarding Information Base (FIB)
by every LSR of the domain (whatever the area/level it belongs to) maintained by every LSR of the domain (whatever the area/level it
cannot be minimized. belongs to) cannot be minimized.
Service providers may also set up these inter-area LSPs by using MPLS Service providers may also set up these inter-area LSPs by using MPLS
hierarchy with BGP [MPLS-BGP] as a label distribution protocol hierarchy with BGP [MPLS-BGP] as a label distribution protocol
between areas. The BGP next hop would typically be the ABRs and the between areas. The BGP next hop would typically be the ABRs, and the
BGP-created LSPs would be nested within intra-area LSPs setup by LDP BGP-created LSPs would be nested within intra-area LSPs setup by LDP
between PEs and ABRs and between ABRs. between PEs and ABRs and between ABRs.
This solution is not adequate for service providers which don't want This solution is not adequate for service providers which don't want
to run BGP on their P routers as it requires BGP on all ABRs. In to run BGP on their provider routers as it requires BGP on all ABRs.
addition, MPLS hierarchy does not allow locally protecting the LSP In addition, MPLS hierarchy does not allow locally protecting the LSP
against ABR failures (IP/LDP Fast Reroute), and hence ensuring sub- against ABR failures (IP/LDP Fast Reroute), and hence ensuring sub-
50ms recovery upon ABR failure. The resulting convergence time may 50ms recovery upon ABR failure. The resulting convergence time may
not be acceptable for stringent Service Level Agreements (SLAs) not be acceptable for stringent Service Level Agreements (SLAs)
required for voice or mission critical applications. Finally, this required for voice or mission-critical applications. Finally, this
solution requires a significant migration effort for service solution requires a significant migration effort for service
providers which started with LDP and IGP route leaking to quickly providers that started with LDP and IGP route leaking to quickly set
set-up the first inter-area LSPs. up the first inter-area LSPs.
Service providers may also setup these inter-area LSPs by using Service providers may also setup these inter-area LSPs by using
inter-area RSVP-TE [RSVP-TE]. This is a relevant solution when RSVP- inter-area RSVP-TE [RSVP-TE]. This is a relevant solution when RSVP-
TE is already used for setting up intra-area LSPs, and inter-area TE is already used for setting up intra-area LSPs, and inter-area
traffic engineering features are required. In return this is not a traffic engineering features are required. In return, this is not a
desired solution when LDP is already used for setting up intra-area desired solution when LDP is already used for setting up intra-area
LSPs, and inter-area traffic engineering features are not required. LSPs, and inter-area traffic engineering features are not required.
To avoid the above drawbacks, there is a need for an LDP based To avoid the above drawbacks, there is a need for an LDP-based
solution which allows setting up contiguous inter-area LSPs while solution that allows setting up contiguous inter-area LSPs while
avoiding leaking of specific PE loopback addresses across area avoiding leaking of specific PE loopback addresses across area
boundaries, and hence keeping all the benefits of IGP hierarchy. boundaries, thereby keeping all the benefits of IGP hierarchy.
In that context, this document defines a new LDP Label Mapping In that context, this document defines a new LDP Label Mapping
Procedure so as to support the setup of contiguous inter-area LSPs Procedure so as to support the setup of contiguous inter-area LSPs
while maintaining IP prefix aggregation on the ABRs. This procedure while maintaining IP prefix aggregation on the ABRs. This procedure
is similar to the one defined in [LDP] but performs an IP longest is similar to the one defined in [LDP] but performs an IP longest
match when searching the FEC element in the RIB. match when searching the FEC element in the RIB.
5. Longest Match Label Mapping Message Procedure 5. Longest-Match Label Mapping Message Procedure
This document defines a new Label Mapping Procedure for [LDP]. It is This document defines a new Label Mapping Procedure for [LDP]. It is
applicable to IPv4 and IPv6 prefix FEC elements (address families 1 applicable to IPv4 and IPv6 prefix FEC elements (address families 1
and 2 as per [ASSIGNED_AF]). It SHOULD be possible to activate / and 2 as per the "Address Family Numbers" registry on the IANA site).
deactivate this procedure by configuration and it SHOULD be It SHOULD be possible to activate/deactivate this procedure by
deactivated by default. It MAY be possible to activate it on a per configuration, and it SHOULD be deactivated by default. It MAY be
prefix basis. possible to activate it on a per-prefix basis.
With this new Longest Match Label Mapping Procedure, an LSR receiving With this new Longest-Match Label Mapping Procedure, an LSR receiving
a Label Mapping message from a neighbor LSR for a Prefix Address FEC a Label Mapping message from a neighbor LSR for a Prefix Address FEC
Element FEC1 SHOULD use the label for MPLS forwarding if its routing Element FEC1 SHOULD use the label for MPLS forwarding if its routing
table contains an entry that matches the FEC Element FEC1 and the table contains an entry that matches the FEC Element FEC1 and the
advertising LSR is a next hop to reach FEC1. If so, it SHOULD advertising LSR is a next hop to reach FEC1. If so, it SHOULD
advertise the received FEC Element FEC1 and a label to its LDP peers. advertise the received FEC Element FEC1 and a label to its LDP peers.
By "matching FEC Element", one should understand an IP longest match. By "matching FEC Element", one should understand an IP longest match.
That is, either the LDP FEC element exactly matches an entry in the That is, either the LDP FEC element exactly matches an entry in the
IP RIB or the FEC element is a subset of an IP RIB entry. There is no IP RIB or the FEC element is a subset of an IP RIB entry. There is
match for other cases such as the FEC element is a superset of a RIB no match for other cases (i.e., if the FEC element is a superset of a
entry. RIB entry, it is not considered a match).
Note that LDP re-advertises to its peers the specific FEC element Note that LDP re-advertises to its peers the specific FEC element
FEC1, and not the aggregated prefix found in the IP RIB during the FEC1, and not the aggregated prefix found in the IP RIB during the
longest match search. longest-match search.
Note that with this Longest Match Label Mapping Procedure, each LSP Note that with this Longest-Match Label Mapping Procedure, each LSP
established by LDP still strictly follows the shortest path(s) established by LDP still strictly follows the shortest path(s)
defined by the IGP. defined by the IGP.
FECs selected by this Longest Match Label Mapping Procedure are FECs selected by this Longest-Match Label Mapping Procedure are
distributed in an ordered way. In case of LER failure, the removal of distributed in an ordered way. In case of LER failure, the removal
reachability to the FEC occurs using LDP ordered label distribution of reachability to the FEC occurs using LDP ordered label
mode procedures. As defined in [LDP] in section A.1.5, the FEC will distribution mode procedures. As defined in [LDP] in section A.1.5,
be removed in an ordered way through the propagation of Label the FEC will be removed in an ordered way through the propagation of
Withdraw messages. The use of this (un)reachability information by Label Withdraw messages. The use of this (un)reachability
application layers using this MPLS LSP (e.g., [MP-BGP]) is outside information by application layers using this MPLS LSP (e.g.,
the scope of this document. [MP-BGP]) is outside the scope of this document.
As per [LDP], LDP has already some interactions with the RIB. In As per [LDP], LDP already has some interactions with the RIB. In
particular, it needs to be aware of the following events: particular, it needs to be aware of the following events:
- prefix up when a new IP prefix appears in the RIB, - prefix up when a new IP prefix appears in the RIB,
- prefix down when an existing IP prefix disappears, - prefix down when an existing IP prefix disappears,
- next hop change when an existing IP prefix has a new next hop
- next-hop change when an existing IP prefix has a new next hop
following a routing change. following a routing change.
With this Longest Match Label Mapping Message Procedure, multiple With this Longest-Match Label Mapping Message Procedure, multiple
FECs may be concerned by a single RIB prefix change. The LSR MUST FECs may be concerned by a single RIB prefix change. The LSR MUST
check all the FECs which are a subset of this RIB prefix. So some LDP check all the FECs that are a subset of this RIB prefix. So, some
reactions following a RIB event are changed: LDP reactions following a RIB event are changed:
- When a new prefix appears in the RIB, the LSR MUST check if this - When a new prefix appears in the RIB, the LSR MUST check if this
prefix is a better match for some existing FECs. E.g. the FEC prefix is a better match for some existing FECs. For example,
elements 192.0.2.1/32 and 192.0.2.2/32 used the IP RIB entry the FEC elements 192.0.2.1/32 and 192.0.2.2/32 used the IP RIB
192.0.2.0/24 and a new more specific IP RIB entry 192.0.2.0/26 entry 192.0.2.0/24, and a new more specific IP RIB entry
appears. This may result in changing the LSR used as next hop 192.0.2.0/26 appears. This may result in changing the LSR used
and hence the Next Hop Label Forwarding Entry (NHLFE) for this as next hop and hence the Next Hop Label Forwarding Entry
FEC. (NHLFE) for this FEC.
- When a prefix disappears in the RIB, the LSR MUST check all FEC - When a prefix disappears in the RIB, the LSR MUST check all FEC
elements which are using this RIB prefix as best match. For each elements that are using this RIB prefix as best match. For each
FEC, if another RIB prefix is found as best match, LDP MUST use FEC, if another RIB prefix is found as best match, LDP MUST use
it. This may result in changing the LSR used as next hop and it. This may result in changing the LSR used as next hop and
hence the NHLFE for this FEC. Otherwise, the LSR MUST remove the hence the NHLFE for this FEC. Otherwise, the LSR MUST remove
FEC binding and send a Label Withdraw message. the FEC binding and send a Label Withdraw message.
- When the next hop of a RIB prefix changes, the LSR MUST change - When the next hop of a RIB prefix changes, the LSR MUST change
the NHLFE of all the FEC elements using this prefix. the NHLFE of all the FEC elements using this prefix.
Future work may define new management objects to the MPLS LDP MIB Future work may define new management objects to the MPLS LDP MIB
modules [LDP-MIB] to activate/deactivate this Longest Match Label modules [LDP-MIB] to activate/deactivate this Longest-Match Label
Mapping Message Procedure, possibly on a per prefix basis. Mapping Message Procedure, possibly on a per-prefix basis.
6. Application examples 6. Application Examples
6.1. Inter-area LSPs 6.1. Inter-Area LSPs
Consider the following example of an autonomous system with one Consider the following example of an autonomous system with one
backbone area and two edge areas: backbone area and two edge areas:
Area "B" Area "B"
Level 2 / Backbone area Level 2 / Backbone area
+--------------------------+ +--------------------------+
Area "A" | | Area "C" Area "A" | | Area "C"
skipping to change at page 6, line 35 skipping to change at page 6, line 31
+----------+ +-------------+ +----------+ +-------------+
| | P2 | PE1 | 192.0.2.1/32 | | P2 | PE1 | 192.0.2.1/32
| | | | | | | |
|PE4 ABR2 ABR1 PE2 | 192.0.2.2/32 |PE4 ABR2 ABR1 PE2 | 192.0.2.2/32
| | P3 | | | | P3 | |
| | | PE3 | 192.0.2.3/32 | | | PE3 | 192.0.2.3/32
+----------+ +-------------+ +----------+ +-------------+
| | | |
+--------------------------+ +--------------------------+
Figure 1: An IGP domain with two areas attached to the Backbone Figure 1: An IGP domain with two areas
Area. attached to the Backbone Area.
Note that this applies equally to IS-IS and OSPF. An ABR refers here Note that this applies equally to IS-IS and OSPF. An ABR refers here
either to an OSPF ABR or to an IS-IS L1/L2 node. either to an OSPF ABR or to an IS-IS L1/L2 node.
All routers are MPLS enabled and MPLS connectivity (i.e. an LSP) is All routers are MPLS enabled, and MPLS connectivity (i.e., an LSP) is
required between all PE routers. required between all PE routers.
In the "egress" area "C", the records available are: In the "egress" area "C", the records available are:
IGP RIB LDP FEC elements: IGP RIB LDP FEC elements:
192.0.2.1/32 192.0.2.1/32 192.0.2.1/32 192.0.2.1/32
192.0.2.2/32 192.0.2.2/32 192.0.2.2/32 192.0.2.2/32
192.0.2.3/32 192.0.2.3/32 192.0.2.3/32 192.0.2.3/32
The area border router ABR1 advertises in the backbone area: The area border router ABR1 advertises in the backbone area:
- the aggregated IP prefix 192.0.2.0/26 in the IGP - the aggregated IP prefix 192.0.2.0/26 in the IGP
- all the specific IP FEC elements (/32) in LDP - all the specific IP FEC elements (/32) in LDP
In the "backbone" area "B", the records available are: In the "backbone" area "B", the records available are:
IGP RIB LDP FEC elements: IGP RIB LDP FEC elements:
192.0.2.0/26 192.0.2.1/32 192.0.2.0/26 192.0.2.1/32
192.0.2.2/32 192.0.2.2/32
192.0.2.3/32 192.0.2.3/32
The area border router ABR2 advertises in the area "A": The area border router ABR2 advertises in the area "A":
- an aggregated IP prefix 192.0.2.0/24 in the IGP - an aggregated IP prefix 192.0.2.0/24 in the IGP
- all the individual IP FEC elements (/32) in LDP - all the individual IP FEC elements (/32) in LDP
In the "ingress" area "A", the records available are: In the "ingress" area "A", the records available are:
skipping to change at page 7, line 15 skipping to change at page 7, line 16
IGP RIB LDP FEC elements: IGP RIB LDP FEC elements:
192.0.2.0/26 192.0.2.1/32 192.0.2.0/26 192.0.2.1/32
192.0.2.2/32 192.0.2.2/32
192.0.2.3/32 192.0.2.3/32
The area border router ABR2 advertises in the area "A": The area border router ABR2 advertises in the area "A":
- an aggregated IP prefix 192.0.2.0/24 in the IGP - an aggregated IP prefix 192.0.2.0/24 in the IGP
- all the individual IP FEC elements (/32) in LDP - all the individual IP FEC elements (/32) in LDP
In the "ingress" area "A", the records available are: In the "ingress" area "A", the records available are:
IGP RIB LDP FEC elements: IGP RIB LDP FEC elements:
192.0.2.0/24 192.0.2.1/32 192.0.2.0/24 192.0.2.1/32
192.0.2.2/32 192.0.2.2/32
192.0.2.3/32 192.0.2.3/32
In this situation, one LSP is established between the ingress PE4 and In this situation, one LSP is established between the ingress PE4 and
every egress PE of area C while maintaining IP prefix aggregation on every egress PE of area C while maintaining IP prefix aggregation on
the ASBRs. the ABRs.
6.2. Use of static routes 6.2. Use of Static Routes
Consider the following example where a LER is dual-connected to two Consider the following example where a LER is dual-connected to two
LSRs: LSRs:
+--------LSR1---- +--------LSR1----
| | | |
LER | LER |
| | | |
+--------LSR2---- +--------LSR2----
Figure 2: LER dual-connected to two LSRs. Figure 2: LER dual-connected to two LSRs.
In some situations, especially on the edge of the network, it is In some situations, especially on the edge of the network, it is
valid to use static IP routes between the LER and the two LSRs. If valid to use static IP routes between the LER and the two LSRs. If
necessary, the BFD protocol ([BFD]) can be used to quickly detect necessary, the Bidirectional Forwarding Detection protocol [BFD] can
loss of connectivity. be used to quickly detect loss of connectivity.
The LDP specification defined in [LDP] would require on the ingress The LDP specification defined in [LDP] would require on the ingress
LER the configuration and the maintenance of one IP route per egress LER the configuration and the maintenance of one IP route per egress
LER and per outgoing interface. LER and per outgoing interface.
The Longest Match Label Mapping Procedure described in this document The Longest-Match Label Mapping Procedure described in this document
only requires one IP route per outgoing interface. only requires one IP route per outgoing interface.
7. Caveats for deployment 7. Caveats for Deployment
7.1. Deployment considerations 7.1. Deployment Considerations
LSRs compliant with this document are backward compatible with LSRs LSRs compliant with this document are backward compatible with LSRs
that comply with [LDP]. that comply with [LDP].
For the successful establishment of end-to-end MPLS LSPs whose FEC For the successful establishment of end-to-end MPLS LSPs whose FECs
are aggregated in the RIB, this specification must be implemented on are aggregated in the RIB, this specification must be implemented on
all LSRs in all areas where IP aggregation is used. If an LSR on the all LSRs in all areas where IP aggregation is used. If an LSR on the
path does not support this procedure, then the LSP initiated on the path does not support this procedure, then the LSP initiated on the
egress LSR stops at this non compliant LSR. There are no other egress LSR stops at this non-compliant LSR. There are no other
adverse effects. adverse effects.
This extension can be deployed incrementally: This extension can be deployed incrementally:
- It can be deployed on a per area or routing domain basis and
does not necessarily require an AS wide deployment. For example, - It can be deployed on a per-area or per-routing-domain basis and
if all specific IP prefixes are leaked in the IGP backbone area does not necessarily require an AS-wide deployment. For
and only stub areas use IP aggregation, LSRs in the backbone example, if all specific IP prefixes are leaked in the IGP
area don't need to be compliant with this document. backbone area and only stub areas use IP aggregation, LSRs in
the backbone area don't need to be compliant with this document.
- Within each routing area, LSRs can be upgraded independently, at - Within each routing area, LSRs can be upgraded independently, at
any time, in any order and without service disruption. During any time, in any order, and without service disruption. During
deployment, if those LSPs are already used, one should only make deployment, if those LSPs are already used, one should only make
sure that ABRs keep advertising the specific IP prefixes in the sure that ABRs keep advertising the specific IP prefixes in the
IGP until all LSR of this area are successfully upgraded. Then, IGP until all LSRs of this area are successfully upgraded.
the ABRs can advertise the aggregated prefix only and stop Then, the ABRs can advertise the aggregated prefix only and stop
advertising the specific ones. advertising the specific ones.
A service provider currently leaking specific LER's loopback A service provider currently leaking specific LER loopback addresses
addresses in the IGP and now considering performing IP aggregation on in the IGP and considering performing IP aggregation on ABR should be
ABR should be aware that this may result in suboptimal routing as aware that this may result in suboptimal routing as discussed in
discussed in [RFC 2966]. [RFC2966].
7.2. Routing convergence time considerations 7.2. Routing Convergence Time Considerations
IP and MPLS traffic restoration time is based on two factors: the IP and MPLS traffic restoration time is based on two factors: the
Shortest Path First (SPF) calculation in the control plane and Shortest Path First (SPF) calculation in the control plane and
Forwarding Information Base (FIB)/Label FIB (LFIB) update time in the Forwarding Information Base (FIB) / Label FIB (LFIB) update time in
forwarding plane. The SPF calculation scales O(N*Log(N)) where N is the forwarding plane. The SPF calculation scales O(N*Log(N)) where N
the number of Nodes. The FIB/LFIB update scales O(P) where P is the is the number of Nodes. The FIB/LFIB update scales O(P) where P is
number of modified prefixes. Currently, with most routers the number of modified prefixes. Currently, with most routers
implementations, the FIB/LFIB update is the dominant component [1] implementations, the FIB/LFIB update is the dominant component
and therefore the bottleneck that should be addressed in priority. [IGP-CONV], and therefore the bottleneck that should be addressed in
The solution documented in this draft reduces the link state database priority. The solution documented in this document reduces the link
size in the control plane and the number of FIB entries in the state database size in the control plane and the number of FIB
forwarding plane. As such it solves the scaling of pure IP routers entries in the forwarding plane. As such, it solves the scaling of
sharing the IGP with MPLS routers. However, it does not decrease the pure IP routers sharing the IGP with MPLS routers. However, it does
number of LFIB entries so is not sufficient to solve the scaling of not decrease the number of LFIB entries so is not sufficient to solve
MPLS routers. For this, an additional mechanism is required (e.g. the scaling of MPLS routers. For this, an additional mechanism is
introducing some MPLS hierarchy in LDP). This is out of scope of this required (e.g., introducing some MPLS hierarchy in LDP). This is out
document. of scope for this document.
Compared to [LDP], for all failures except LER failure (i.e. links, Compared to [LDP], for all failures except LER failure (i.e., links,
Ps and ABRs nodes), the failure notification and the convergence is provider routers, and ABRs), the failure notification and the
unchanged. For LER failure, given that the IGP aggregates IP routes convergence is unchanged. For LER failure, given that the IGP
on ABRs and no longer advertise specific prefixes, the control plane aggregates IP routes on ABRs and no longer advertises specific
and more specifically the routing convergence behavior of protocols prefixes, the control plane and more specifically the routing
(e.g. [MP-BGP]) or applications (e.g. [L3-VPN]) may be changed in convergence behavior of protocols (e.g., [MP-BGP]) or applications
case of failure of the egress LER node. For protocols and (e.g., [L3-VPN]) may be changed in case of failure of the egress LER
applications which need to track egress LER availability, several node. For protocols and applications which need to track egress LER
solutions can be used, for example: availability, several solutions can be used, for example:
- Rely on the LDP ordered label distribution control mode - as
defined in [LDP] - to know the availability of the LSP toward the - Rely on the LDP ordered label distribution control mode -- as
defined in [LDP] -- to know the availability of the LSP toward the
egress LER. The egress to ingress propagation time of that egress LER. The egress to ingress propagation time of that
unreachability information is expected to be comparable to the IGP unreachability information is expected to be comparable to the IGP
(but this may be implementation dependant). (but this may be implementation dependent).
- Advertise LER reachability in the IGP for the purpose of the - Advertise LER reachability in the IGP for the purpose of the
control plane in a way that do not create IP FIB entries in the control plane in a way that does not create IP FIB entries in the
forwarding plane. forwarding plane.
8. Security Considerations 8. Security Considerations
The Longest Match Label Mapping procedure described in this document The Longest-Match Label Mapping procedure described in this
does not introduce any change as far as the Security Consideration document does not introduce any change as far as the Security
section of [LDP] is concerned. Considerations section of [LDP] is concerned.
9. IANA Considerations 9. References
This document has no actions for IANA. 9.1. Normative References
10. References [LDP] Andersson, L., Ed., Minei, I., Ed., and B. Thomas, Ed.,
"LDP Specification", RFC 5036, October 2007.
10.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[LDP] Andersson, L., Minei, I., Thomas, B., "LDP 9.2. Informative References
Specification", RFC 5036, October 2007
[ASSIGNED_AF] http://www.iana.org/assignments/address-family- [L3-VPN] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
numbers Networks (VPNs)", RFC 4364, February 2006.
[RFC 2119] Bradner, S., "Key words for use in RFCs to Indicate [MP-BGP] Bates, T., Chandra, R., Katz, D., and Y. Rekhter,
"Multiprotocol Extensions for BGP-4", RFC 4760, January
2007.
10.2. Informative References [MPLS-BGP] Rekhter, Y. and E. Rosen, "Carrying Label Information
in BGP-4", RFC 3107, May 2001.
[L3-VPN] Rosen, E., Rekhter, Y. ," BGP/MPLS IP Virtual Private [IS-IS] Callon, R., "Use of OSI IS-IS for routing in TCP/IP and
Networks (VPNs) ", RFC 4374, February 2006 dual environments", RFC 1195, December 1990.
[MP-BGP] Bates, T., Chandra, R., Katz, D., Rekhter, Y., [VPLS-BGP] Kompella, K., Ed., and Y. Rekhter, Ed., "Virtual
"Multiprotocol Extensions for BGP-4", RFC 4760, January 2007 Private LAN Service (VPLS) Using BGP for Auto-Discovery
[MPLS-BGP] Rekhter, Y., Rosen, E., "Carrying Label Information in and Signaling", RFC 4761, January 2007.
[IS-IS] Callon, R., "Use of OSI IS-IS for Routing in TCP/IP and
Dual Environments", RFC 1195, December 1990
[VPLS-BGP] Kompella, K., Rekhter, Y., "Virtual Private LAN Service [VPLS-LDP] Lasserre, M., Ed., and V. Kompella, Ed., "Virtual
(VPLS) Using BGP for Auto-discovery and Signaling", RFC 4761, Private LAN Service (VPLS) Using Label Distribution
January 2007. Protocol (LDP) Signaling", RFC 4762, January 2007.
[VPLS-LDP] Lasserre, M., Kompella, V., "Virtual Private LAN Service [RFC2966] Li, T., Przygienda, T., and H. Smit, "Domain-wide
(VPLS) Using Label Distribution Protocol (LDP) Signaling", RFC Prefix Distribution with Two-Level IS-IS", RFC 2966,
4762, January 2007. October 2000.
[RFC 2966] Li, T., Przygienda, T., Smit, H., "Domain-wide Prefix [RSVP-TE] Farrel, A., Ed., Ayyangar, A., and JP. Vasseur,
Distribution with Two-Level IS-IS", RFC 2966, October 2000. "Inter-Domain MPLS and GMPLS Traffic Engineering --
Resource Reservation Protocol-Traffic Engineering
(RSVP-TE) Extensions", RFC 5151, February 2008.
[RSVP-TE] Farrel, Ayyangar, Vasseur, "Inter domain MPLS and GMPLS [LDP-MIB] Cucchiara, J., Sjostrand, H., and J. Luciani,
Traffic Engineering - RSVP-TE extensions", RFC 5151, February "Definitions of Managed Objects for the Multiprotocol
2008. Label Switching (MPLS), Label Distribution Protocol
(LDP)", RFC 3815, June 2004.
[LDP-MIB] Cucchiara, J., Sjostrand, H., Luciani, J., "Definitions [BFD] Katz, D. and D. Ward, "Bidirectional Forwarding
of Managed Objects for the Multiprotocol Label Switching Detection", Work in Progress, March 2008.
(MPLS), Label Distribution Protocol (LDP)", RFC 3815, June
2004.
[BFD] Katz, D., Ward, D., "Bidirectional Forwarding Detection", [IGP-CONV] Francois, P., Filsfils, C., and Evans, J., "Achieving
draft-ietf-bfd-base-08.txt, March 2008. sub-second IGP convergence in large IP networks". ACM
SIGCOMM Computer Communications Review, July 2005.
[1] Francois, P., Filsfils, C., and Evans, J. 2005. "Achieving sub- [OSPFv2] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April
second IGP convergence in large IP networks". ACM SIGCOMM 1998.
11. Acknowledgments 10. Acknowledgments
Authors would like to thank Yakov Rekhter, Stefano Previdi, Vach The authors would like to thank Yakov Rekhter, Stefano Previdi, Vach
Kompella, Bob Thomas, Clarence Filsfils, Kireeti Kompella, Luca Kompella, Bob Thomas, Clarence Filsfils, Kireeti Kompella, Luca
Martini, Sina Mirtorabi, Dave McDysan, Benoit Fondeviole, Gilles Martini, Sina Mirtorabi, Dave McDysan, Benoit Fondeviole, Gilles
Bourdon and Christian Jacquenet for the useful discussions on this Bourdon, and Christian Jacquenet for the useful discussions on this
subject, their review and comments. subject, their reviews, and comments.
12. Authors' Addresses Authors' Addresses
Bruno Decraene Bruno Decraene
France Telecom France Telecom
38 rue du General Leclerc 38 rue du General Leclerc
92794 Issy Moulineaux cedex 9 92794 Issy Moulineaux cedex 9
France France
EMail: bruno.decraene@orange-ftgroup.com EMail: bruno.decraene@orange-ftgroup.com
Jean-Louis Le Roux Jean-Louis Le Roux
skipping to change at page 11, line 28 skipping to change at page 11, line 36
22307 Lannion Cedex 22307 Lannion Cedex
France France
EMail: jeanlouis.leroux@orange-ftgroup.com EMail: jeanlouis.leroux@orange-ftgroup.com
Ina Minei Ina Minei
Juniper Networks Juniper Networks
1194 N. Mathilda Ave. 1194 N. Mathilda Ave.
Sunnyvale, CA 94089 Sunnyvale, CA 94089
Email: ina@juniper.net EMail: ina@juniper.net
Intellectual Property Considerations Full Copyright Statement
Copyright (C) The IETF Trust (2008).
This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors
retain all their rights.
This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Intellectual Property
The IETF takes no position regarding the validity or scope of any The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information made any independent effort to identify any such rights. Information
on the procedures with respect to rights in RFC documents can be on the procedures with respect to rights in RFC documents can be
found in BCP 78 and BCP 79. found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat and any Copies of IPR disclosures made to the IETF Secretariat and any
assurances of licenses to be made available, or the result of an assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use of attempt made to obtain a general license or permission for the use of
such proprietary rights by implementers or users of this such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository at specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr. http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at ietf- this standard. Please address the information to the IETF at
ipr@ietf.org. ietf-ipr@ietf.org.
Copyright Statement
Copyright (C) The IETF Trust (2008).
This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors
retain all their rights.
Disclaimer of Validity
This document and the information contained herein are provided
on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE
REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE
IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL
WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY
WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE
ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS
FOR A PARTICULAR PURPOSE.
Acknowledgment
Funding for the RFC Editor function is currently provided by the
Internet Society.
 End of changes. 90 change blocks. 
244 lines changed or deleted 263 lines changed or added

This html diff was produced by rfcdiff 1.35. The latest version is available from http://tools.ietf.org/tools/rfcdiff/