Internet DRAFT - draft-wijnands-mpls-mldp-vpn-in-band-signaling
draft-wijnands-mpls-mldp-vpn-in-band-signaling
Network Working Group IJ. Wijnands, Ed.
Internet-Draft Cisco Systems, Inc.
Intended status: Standards Track P. Hitchen
Expires: April 9, 2012 BT
N. Leymann
Deutsche Telekom
W. Henderickx
Alcatel-Lucent
October 7, 2011
Multipoint Label Distribution Protocol
In-Band Signaling in a VPN Context
draft-wijnands-mpls-mldp-vpn-in-band-signaling-00
Abstract
Sometimes an IP multicast distribution tree (MDT) traverses both
MPLS-enabled and non-MPLS-enabled regions of a network. Typically
the MDT begins and ends in non-MPLS regions, but travels through an
MPLS region. In such cases, it can be useful to begin building the
MDT as a pure IP MDT, then convert it to an MPLS Multipoint LSP
(Label Switched Path) when it enters an MPLS-enabled region, and then
convert it back to a pure IP MDT when it enters a non-MPLS-enabled
region. [I-D.ietf-mpls-mldp-in-band-signaling] specifies the
procedures for building such a hybrid MDT, using Protocol Independent
Multicast (PIM) as the control protocol in the non-MPLS region of the
network, and using Multipoint Extensions to Label Distribution
Protocol (mLDP) in the MPLS region. This document extends those
procedures so that they will work when the links between the MPLS and
non-MPLS regions are [RFC4364] interfaces. While these procedures do
not provide a good general multicast VPN solution, they are useful in
certain specific situations.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
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."
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This Internet-Draft will expire on April 9, 2012.
Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
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described in the Simplified BSD License.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Conventions used in this document . . . . . . . . . . . . 5
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5
2. VPN In-band signaling for MP LSPs . . . . . . . . . . . . . . 6
3. Encoding the Opaque Value of an LDP MP FEC . . . . . . . . . . 7
3.1. Transit VPNv4 Source TLV . . . . . . . . . . . . . . . . . 7
3.2. Transit VPNv6 Source TLV . . . . . . . . . . . . . . . . . 8
3.3. Transit VPNv4 bidir TLV . . . . . . . . . . . . . . . . . 9
3.4. Transit VPNv6 bidir TLV . . . . . . . . . . . . . . . . . 10
4. Security Considerations . . . . . . . . . . . . . . . . . . . 11
5. IANA considerations . . . . . . . . . . . . . . . . . . . . . 11
6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 11
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
7.1. Normative References . . . . . . . . . . . . . . . . . . . 11
7.2. Informative References . . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12
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1. Introduction
Sometimes an IP multicast distribution tree (MDT) traverses both
MPLS-enabled and non-MPLS-enabled regions of a network. In such
cases, it can be useful to begin building the MDT as a pure IP MDT,
then convert it to an MPLS Multipoint LSP (Label Switched Path) when
it enters an MPLS-enabled region, and then convert it back to a pure
IP MDT when it enters a non-MPLS-enabled region.
[I-D.ietf-mpls-mldp-in-band-signaling] specifies the procedures for
building such a hybrid MDT, using Protocol Independent Multicast
(PIM) [RFC4601] as the control protocol in the non-MPLS region of the
network, and using Multipoint Extensions to Label Distribution
Protocol (mLDP) [I-D.ietf-mpls-ldp-p2mp] in the MPLS region.
For a given tree, one or more routers that are at the border between
a non-MPLS-enabled region and an MPLS-enabled region receive PIM
control messages from the non-MPLS-enabled region, and convert them
to mLDP control messages to be sent into the MPLS-enabled region.
Another router that is at the border between a non-MPLS-enabled
region and an MPLS-enabled region receives mLDP control messages from
the MPLS-enabled region and converts them to PIM control messages to
be sent into a non-MPLS-enabled region.
In PIM, a tree is identified by a source address (or in the case of
bidirectional trees [RFC5015], a rendezvous point address or "RPA")
and a group address. The tree is built from the leaves up, by
sending PIM control messages in the direction of the source address
or the RPA. In mLDP, a tree is identified by a root address and an
"opaque value", and is built by sending mLDP control messages in the
direction of the root. The procedures of
[I-D.ietf-mpls-mldp-in-band-signaling] explain how to convert a PIM
<source address or RPA, group address> pair into an mLDP <root node,
opaque value> pair;, and how to convert the mLDP <root node, opaque
value> pair back into the original PIM <source address or RPA, group
address> pair.
However, those procedures assume that the routers doing the PIM/mLDP
conversion have routes to the source address or RPA in their global
routing tables. Thus the procedures cannot be applied exactly as
specified when the interfaces connecting the non-MPLS-enabled region
to the MPLS-enabled region are interfaces that belong to a VPN as
described in [RFC4364]. This specification extends the procedures of
[I-D.ietf-mpls-mldp-in-band-signaling] so that they may be applied in
the VPN context.
As in [I-D.ietf-mpls-mldp-in-band-signaling], the scope of this
document is limited to the case where the multicast content is
distributed in the non-MPLS-enabled regions via PIM-created Source-
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Specific or Bidirectional trees. Bidirectional trees are always
mapped onto Multipoint-to-Multipoint LSPs, and source-specific trees
are always mapped onto Point-to-Multipoint LSPs.
Each multicast tree in the non-MPLS enabled region is mapped 1-1 onto
a multipoint LSP in the MPLS-enabled region. For a variety of
reasons (discussed in [I-D.ietf-l3vpn-2547bis-mcast]), this is not a
suitable for a general purpose multicast VPN solution. But the
procedures described herein are much simpler than the general purpose
MVPN procedures, and are applicable when the 1-1 mapping is
acceptable, and when it is acceptable to use mLDP as the protocol for
setting up the multipoint LSPs. For example, some service providers
offer multicast content to their customers, but have chosen to use
VPNs to isolate the various customers and services. This is a very
different scenario than the general MVPN scenario, in which the
customers provide their own multicast content, out of the control of
the service provider.
Due to the 1-1 mapping and the multicast source and group information
being encoded in the mLDP FEC, there is deterministic mapping beween
the multicast tree and the mLDP LSP in the core network. This
improves and simplifies fault resolution.
In order to use the mLDP in-band signaling procedures for a
particular group address in a particular VPN, the Provider Edge (PE)
routers that attach to that VPN MUST be configured with a range of
multicast group addresses for which mLDP in-band signaling is to be
enabled. This configuration is per VRF ("Virtual Routing and
Forwarding table", defined in [RFC4364]). For those groups, and
those groups only, the procedures of this document are used instead
of the general purpose Multicast VPN procedures. This configuration
must be present in all PE routers that attach to sites containing
senders or receivers for the given set of group addresses.
1.1. 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 [RFC2119].
1.2. Terminology
IP multicast tree : An IP multicast distribution tree identified by
an source IP address and/or IP multicast destination address, also
referred to as (S,G) and (*,G).
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mLDP : Multicast LDP.
In-band signaling : Using the opaque value of a mLDP FEC element to
encode the (S,G) or (*,G) identifying a particular IP multicast
tree.
P2MP LSP: An LSP that has one Ingress LSR and one or more Egress
LSRs (see [I-D.ietf-mpls-ldp-p2mp]).
MP2MP LSP: An LSP that connects a set of leaf nodes, acting
indifferently as ingress or egress (see [I-D.ietf-mpls-ldp-p2mp]).
MP LSP: A multipoint LSP, either a P2MP or an MP2MP LSP.
Ingress LSR: Source of a P2MP LSP, also referred to as root node.
2. VPN In-band signaling for MP LSPs
Suppose that a PE router, PE1, attaching to a particular VPN,
receives a PIM Join(S,G) message over one of its VRF interfaces.
Following the procedure of section 5.1 of
[I-D.ietf-l3vpn-2547bis-mcast], PE1 determines the "upstream RD", the
"upstream PE", and the "upstream multicast hop" (UMH) for the source
address S. Please note that sections 5.1.1 and 5.1.2 of
[I-D.ietf-l3vpn-2547bis-mcast] are applicable.
In order to transport the multicast tree via a MP LSP using VPN in-
band signaling, an mLDP Label Mapping Message is sent by PE1. This
message will contain either a P2MP FEC or an MP2MP FEC (see
[I-D.ietf-mpls-ldp-p2mp], depending upon whether the PIM tree being
transported is a source-specific tree, or a bidirectional tree,
respectively. The FEC contains a "root" and an "opaque value".
If the UMH and the upstream PE have the same IP address (i.e., the
Upstream PE is the UMH), then the root of the Multipoint FEC is set
to the IP address of the Upstream PE. If, in the context of this
VPN, (S,G) refers to a source-specific MDT, then the values of S, G,
and the upstream RD are encoded into the opaque value. If, in the
context of this VPN, G is a bidirectional group address, then S is
replaced with the value of the RPA associated with G. The coding
details are specified in Section 3. Conceptually, the Multipoint FEC
can be thought of as an ordered pair: <root=Upstream-PE,
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opaque_value=<S or RPA ,G ,Upstream-RD>. The mLDP Label Mapping
Message is then sent by PE1 on its LDP session to the "next hop" on
its path to the upstream PE. The "next hop" is usually the IGP next
hop, but see [I-D.napierala-mpls-targeted-mldp] for cases in which
the next hop is not the IGP next hop.
If the UMH and the upstream PE do not have the same IP address, the
procedures of section 2 of [I-D.ietf-mpls-mldp-recurs-fec] should be
applied. The root node of the multipoint FEC is set to the UMH. The
recursive opaque value is then set as follows: the root node is set
to the upstream PE, and the opaque value is set to the multipoint FEC
described in the previous paragraph. That is, the multipoint FEC can
be thought of as the following recursive ordered pair: <root=UMH,
opaque_value=<root=Upstream-PE, opaque_value =<S or RPA, G,
Upstream-RD>>.
The encoding of the multipoint FEC also specifies the "type" of PIM
MDT being spliced onto the multipoint LSP. Four types of MDT are
defined: IPv4 source-specific tree, IPv6 source-specific tree, IPv4
bidirectional tree, and IPv6 bidirectional tree.
When a PE router receives an mLDP message with a P2MP or MP2MP FEC,
where the PE router itself is the root node, and the opaque value is
one of the types defined in Section 3, then it uses the RD encoded in
the opaque value field to determine the VRF context. (This RD will
be associated with one of the PEs VRFs.) Then, in the context of
that VRF, the PE follows the procedure specified in section 2 of
[I-D.ietf-mpls-mldp-in-band-signaling].
3. Encoding the Opaque Value of an LDP MP FEC
This section documents the different transit opaque encodings.
3.1. Transit VPNv4 Source TLV
This opaque value type is used when transporting a source-specific
mode multicast tree whose source and group addresses are IPv4
addresses.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Source
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Group
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ RD |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: (to be assigned by IANA).
Length: 16
Source: IPv4 multicast source address, 4 octets.
Group: IPv4 multicast group address, 4 octets.
RD: Route Distinguisher, 8 octets.
3.2. Transit VPNv6 Source TLV
This opaque value type is used when transporting a source-specific
mode multicast tree whose source and group addresses are IPv6
addresses.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Source ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ | Group ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ | ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ RD |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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Type: (to be assigned by IANA).
Length: 40
Source: IPv6 multicast source address, 16 octets.
Group: IPv6 multicast group address, 16 octets.
RD: Route Distinguisher, 8 octets.
3.3. Transit VPNv4 bidir TLV
This opaque value type is used when transporting a bidirectional
multicast tree whose group address is an IPv4 address. The RP
address is also an IPv4 address in this case.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Mask Len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RP |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Group |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ RD |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: (to be assigned by IANA).
Length: 17
Mask Len: The number of contiguous one bits that are left justified
and used as a mask, 1 octet.
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RP: Rendezvous Point (RP) IPv4 address used for encoded Group, 4
octets.
Group: IPv4 multicast group address, 4 octets.
RD: Route Distinguisher, 8 octets.
3.4. Transit VPNv6 bidir TLV
This opaque value type is used when transporting a bidirectional
multicast tree whose group address is an IPv6 address. The RP
address is also an IPv6 address in this case.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Mask Len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RP ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Group ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ RD |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: (to be assigned by IANA).
Length: 41
Mask Len: The number of contiguous one bits that are left justified
and used as a mask, 1 octet.
RP: Rendezvous Point (RP) IPv6 address used for encoded group, 16
octets.
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Group: IPv6 multicast group address, 16 octets.
RD: Route Distinguisher, 8 octets.
4. Security Considerations
The same security considerations apply as for the base LDP
specification, described in [RFC5036], and the base mLDP
specification, described in [I-D.ietf-mpls-ldp-p2mp]
5. IANA considerations
[I-D.ietf-mpls-ldp-p2mp] defines a registry for "The LDP MP Opaque
Value Element Basic Type". This document requires the assignment of
four new code points in this registry:
Transit VPNv4 Source TLV type - requested 10
Transit VPNv6 Source TLV type - requested 11
Transit VPNv4 Bidir TLV type - requested 12
Transit VPNv6 Bidir TLV type - requested 13
6. Acknowledgments
Thanks to Eric Rosen and Andy Green for their comments on the draft.
7. References
7.1. Normative References
[RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
Networks (VPNs)", RFC 4364, February 2006.
[RFC4601] Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas,
"Protocol Independent Multicast - Sparse Mode (PIM-SM):
Protocol Specification (Revised)", RFC 4601, August 2006.
[RFC5015] Handley, M., Kouvelas, I., Speakman, T., and L. Vicisano,
"Bidirectional Protocol Independent Multicast (BIDIR-
PIM)", RFC 5015, October 2007.
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[RFC5036] Andersson, L., Minei, I., and B. Thomas, "LDP
Specification", RFC 5036, October 2007.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[I-D.ietf-mpls-ldp-p2mp]
Minei, I., Kompella, K., Wijnands, I., and B. Thomas,
"Label Distribution Protocol Extensions for Point-to-
Multipoint and Multipoint-to-Multipoint Label Switched
Paths", draft-ietf-mpls-ldp-p2mp-11 (work in progress),
October 2010.
[I-D.ietf-mpls-mldp-in-band-signaling]
Wijnands, I., Eckert, T., Leymann, N., and M. Napierala,
"mLDP based in-band signaling for Point-to-Multipoint and
Multipoint-to- Multipoint Label Switched Paths",
draft-ietf-mpls-mldp-in-band-signaling-02 (work in
progress), July 2010.
[I-D.ietf-mpls-mldp-recurs-fec]
Wijnands, I., Rosen, E., Napierala, M., and N. Leymann,
"Using mLDP through a Backbone where there is no Route to
the Root", draft-ietf-mpls-mldp-recurs-fec-00 (work in
progress), October 2010.
[I-D.ietf-l3vpn-2547bis-mcast]
Aggarwal, R., Bandi, S., Cai, Y., Morin, T., Rekhter, Y.,
Rosen, E., Wijnands, I., and S. Yasukawa, "Multicast in
MPLS/BGP IP VPNs", draft-ietf-l3vpn-2547bis-mcast-10 (work
in progress), January 2010.
7.2. Informative References
[I-D.napierala-mpls-targeted-mldp]
Napierala, M., Rosen, E., and I. Wijnands, "Using LDP
Multipoint Extensions on Targeted LDP Sessions",
draft-napierala-mpls-targeted-mldp-00 (work in progress),
January 2011.
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Authors' Addresses
IJsbrand Wijnands (editor)
Cisco Systems, Inc.
De kleetlaan 6a
Diegem 1831
Belgium
Email: ice@cisco.com
Paul Hitchen
BT
BT Adastral Park
Ipswich IP53RE
UK
Email: paul.hitchen@bt.com
Nicolai Leymann
Deutsche Telekom
Winterfeldtstrasse 21
Berlin 10781
Germany
Email: n.leymann@telekom.de
Wim Henderickx
Alcatel-Lucent
Copernicuslaan 50
Antwerp 2018
Belgium
Email: wim.henderickx@alcatel-lucent.com
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