Internet DRAFT - draft-ietf-mpls-mldp-in-band-signaling
draft-ietf-mpls-mldp-in-band-signaling
Network Working Group IJ. Wijnands, Ed.
Internet-Draft T. Eckert
Intended status: Standards Track Cisco Systems, Inc.
Expires: June 2, 2013 N. Leymann
Deutsche Telekom
M. Napierala
AT&T Labs
November 29, 2012
Multipoint LDP in-band signaling for Point-to-Multipoint and Multipoint-
to-Multipoint Label Switched Paths
draft-ietf-mpls-mldp-in-band-signaling-08
Abstract
Consider an IP multicast tree, constructed by Protocol Independent
Multicast (PIM), needs to pass through an MPLS domain in which
Multipoint LDP (mLDP) Point-to-Multipoint and/or Multipoint-to-
Multipoint Labels Switched Paths (LSPs) can be created. The part of
the IP multicast tree that traverses the MPLS domain can be
instantiated as a multipoint LSP. When a PIM Join message is
received at the border of the MPLS domain, information from that
message is encoded into mLDP messages. When the mLDP messages reach
the border of the next IP domain, the encoded information is used to
generate PIM messages that can be sent through the IP domain. The
result is an IP multicast tree consisting of a set of IP multicast
sub-trees that are spliced together with a multipoint LSP. This
document describes procedures how IP multicast trees are spliced
together with multipoint LSPs.
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."
This Internet-Draft will expire on June 2, 2013.
Wijnands, et al. Expires June 2, 2013 [Page 1]
Internet-Draft In-band signaling with mLDP November 2012
Copyright Notice
Copyright (c) 2012 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
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Conventions used in this document . . . . . . . . . . . . 3
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. In-band signaling for MP LSPs . . . . . . . . . . . . . . . . 4
2.1. Transiting Unidirectional IP multicast Shared Trees . . . 6
2.2. Transiting IP multicast source trees . . . . . . . . . . . 6
2.3. Transiting IP multicast bidirectional trees . . . . . . . 7
3. LSP opaque encodings . . . . . . . . . . . . . . . . . . . . . 7
3.1. Transit IPv4 Source TLV . . . . . . . . . . . . . . . . . 7
3.2. Transit IPv6 Source TLV . . . . . . . . . . . . . . . . . 8
3.3. Transit IPv4 bidir TLV . . . . . . . . . . . . . . . . . . 9
3.4. Transit IPv6 bidir TLV . . . . . . . . . . . . . . . . . . 9
4. Security Considerations . . . . . . . . . . . . . . . . . . . 10
5. IANA considerations . . . . . . . . . . . . . . . . . . . . . 10
6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 10
7. Contributing authors . . . . . . . . . . . . . . . . . . . . . 11
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
8.1. Normative References . . . . . . . . . . . . . . . . . . . 11
8.2. Informative References . . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12
Wijnands, et al. Expires June 2, 2013 [Page 2]
Internet-Draft In-band signaling with mLDP November 2012
1. Introduction
The mLDP (Multipoint LDP) [RFC6388] specification describes
mechanisms for creating point-to-multipoint (P2MP) and multipoint-to-
multipoint (MP2MP) LSPs (Label Switched Paths). These LSPs are
typically used for transporting end-user multicast packets. However,
the mLDP specification does not provide any rules for associating
particular end-user multicast packets with any particular LSP. Other
documents, like [RFC6513], describe applications in which out-of-band
signaling protocols, such as PIM and BGP, are used to establish the
mapping between an LSP and the multicast packets that need to be
forwarded over the LSP.
This document describes an application in which the information
needed to establish the mapping between an LSP and the set of
multicast packets to be forwarded over it is carried in the "opaque
value" field of an mLDP FEC (Forwarding Equivalence Class) element.
When an IP multicast tree (either a source-specific tree or a
bidirectional tree) enters the MPLS network the (S,G) or (*,G)
information from the IP multicast control plane state is carried in
the opaque value field of the mLDP FEC message. As the tree leaves
the MPLS network, this information is extracted from the FEC element
and used to build the IP multicast control plane. PIM messages can
be sent outside the MPLS domain. Note that although the PIM control
messages are sent periodically, the mLDP messages are not.
Each IP multicast tree is mapped one-to-one to a P2MP or MP2MP LSP in
the MPLS network. A network operator should expect to see as many
LSPs in the MPLS network as there are IP multicast trees. A network
operator should be aware how IP multicast state is created in the
network to ensure it does not exceed the scalability numbers of the
protocol, either PIM or mLDP.
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
a IP multicast Group address and optionally a Source IP address,
also referred to as (S,G) and (*,G).
Wijnands, et al. Expires June 2, 2013 [Page 3]
Internet-Draft In-band signaling with mLDP November 2012
RP: The PIM Rendezvous Point.
SSM: PIM Source Specific Multicast.
ASM: PIM Any Source Multicast.
mLDP : Multipoint LDP.
Transit LSP : A P2MP or MP2MP LSP whose FEC element contains the
(S,G) or (*,G) identifying a particular IP multicast distribution
tree.
In-band signaling : Using the opaque value of a mLDP FEC element to
carry 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.
MP2MP LSP: An LSP that connects a set of leaf nodes that may each
independently act as ingress or egress.
MP LSP: A multipoint LSP, either a P2MP or an MP2MP LSP.
Ingress LSR: Source of the P2MP LSP, also referred to as root node.
Egress LSR: One of potentially many destinations of an LSP, also
referred to as leaf node in the case of P2MP and MP2MP LSPs.
Transit LSR: An LSR that has one or more directly connected
downstream LSRs.
2. In-band signaling for MP LSPs
Consider the following topology;
Wijnands, et al. Expires June 2, 2013 [Page 4]
Internet-Draft In-band signaling with mLDP November 2012
|--- IPM ---|--- MPLS --|--- IPM ---|
S/RP -- (A) - (U) - (C) - (D) -- (B) -- R
Figure 1.
Nodes A and B are IP Multicast capable routers and respectively
connect to a Source/RP and a Receiver. Nodes U, C and D are MPLS
Label Switched Routers (LSRs).
Label Switched Router D is attached to a network that is capable of
MPLS multicast and IP multicast (see figure 1), and D is required to
create a IP multicast tree due to a certain IP multicast event, like
a PIM Join, MSDP Source Announcement (SA) [RFC3618], BGP Source
Active auto-discovery route [I-D.rekhter-pim-sm-over-mldp] or
Rendezvous Point (RP) discovery. Suppose that D can determine that
the IP multicast tree needs to travel through the MPLS network until
it reaches LSR U. For instance, when D looks up the route to the
Source or RP [RFC4601] of the IP multicast tree, it may discover that
the route is a BGP route with U as the BGP next hop. Then D may
chose to set up a P2MP or MP2MP LSP, with U as root, and to make that
LSP become part of the IP multicast distribution tree. Note that
other methods are possible to determine that an IP multicast tree is
to be transported across an MPLS network using P2MP or MP2MP LSPs,
these methods are outside the scope of this document.
In order to establish a multicast tree via a P2MP or MP2MP LSP using
"in-band signaling", LSR D encodes a P2MP or MP2MP FEC Element, with
the IP address of LSR U as the "Root Node Address", and with the
source and the group encoded into the "opaque value" ([RFC6388],
section 2.2 and 3.2). Several different opaque value types are
defined in this document; LSR D MUST NOT use a particular opaque
value type unless it knows (through provisioning, or through some
other means outside the scope of this document) that LSR U supports
the root node procedures for that opaque value type.
The particular type of FEC Element and opaque value used depends on
the IP address family being used, and on whether the multicast tree
being established is a source specific or a bidirectional multicast
tree.
When an LSR receives a label mapping or withdraw whose FEC Element
contains one of the opaque value types defined in this document, and
that LSR is not the one identified by the "Root Node Address" field
of that FEC element, the LSR follows the procedures of RFC 6388.
When an LSR receives a label mapping or withdraw whose FEC Element
contains one of the opaque value types defined in this document, and
Wijnands, et al. Expires June 2, 2013 [Page 5]
Internet-Draft In-band signaling with mLDP November 2012
that LSR is the one identified by the "Root Node Address" field of
that FEC element, then the following procedure is executed. The
multicast source and group are extracted and passed to the multicast
code. If a label mapping is being processed, the multicast code will
add the downstream LDP neighbor to the olist of the corresponding
(S,G) or (*,G) state, creating such state if it does not already
exist. If a label withdraw is being processed, the multicast code
will remove the downstream LDP neighbor from the olist of the
corresponding (S,G) or (*,G) state. From this point on normal PIM
processing will occur.
Note that if the LSR identified by the "Root Node Address" field does
not recognize the opaque value type, the MP LSP will be established,
but the root node will not send any multicast data packets on it.
Source or RP addresses that are reachable in a VPN context are
outside the scope of this document.
Multicast groups that operate in PIM Dense-Mode are outside the scope
of this document.
2.1. Transiting Unidirectional IP multicast Shared Trees
Nothing prevents PIM shared trees, used by PIM-SM in the ASM service
model, from being transported across a MPLS core. However, it is not
possible to prune individual sources from the shared tree without the
use of an additional out-of-band signaling protocol, like PIM or BGP
[I-D.rekhter-pim-sm-over-mldp]. For that reason transiting Shared
Trees across a Transit LSP is outside the scope of this document.
2.2. Transiting IP multicast source trees
IP multicast source trees can either be created via PIM operating in
SSM mode [RFC4607] or ASM mode [RFC4601]. When PIM-SM is used in ASM
mode, the usual means of discovering active sources is to join a
sparse mode shared tree. However, this document does not provide any
method of establishing a sparse mode shared tree across an MPLS
network. To apply the technique of this document to PIM-SM in ASM
mode, there must be some other means of discovering the active
sources. One possible means is the use of MSDP [RFC3618]. Another
possible means is to use BGP Source Active auto-discovery routes, as
documented in [I-D.rekhter-pim-sm-over-mldp]. However, the method of
discovering the active sources is outside the scope of this document,
and as a result this document does not specify everything that is
needed to support the ASM service model using in-band signaling.
The source and group addresses are encoded into the a transit TLV as
specified in Section 3.1 and Section 3.2.
Wijnands, et al. Expires June 2, 2013 [Page 6]
Internet-Draft In-band signaling with mLDP November 2012
2.3. Transiting IP multicast bidirectional trees
If a Bidirectional IP multicast trees [RFC5015] has to be transported
over a MPLS network using in-band signaling, as described in this
document, it MUST be transported using a MP2MP LSPs. A bidirectional
tree does not have a specific source address; the group address,
subnet mask and RP are relevant for multicast forwarding. This
document does not provide procedures to discover RP to group mappings
dynamically across an MPLS network and assumes the RP is statically
defined. Support of dynamic RP mappings in combination with in-band
signaling is outside the scope of his document.
The RP for the group is used to select the ingress LSR and root of
the LSP. The group address is encoded according to the rules of
Section 3.3 or Section 3.4, depending on the IP version. The subnet
mask associated with the bidirectional group is encoded in the
Transit TLV. There are two types of bidirectional states in IP
multicast, the group specific state and the RP state. The first type
is typically created due to receiving a PIM join and has a subnet
mask of 32 for IPv4 and 128 for IPv6. The latter is typically
created via the static RP mapping and has a variable subnet mask.
The RP state is used to build a tree to the RP and used for sender
only branches. Each state (group specific and RP state) will result
in a separate MP2MP LSP. The merging of the two MP2MP LSPs will be
done by PIM on the root LSR. No special procedures are necessary for
PIM to merge the two LSPs, each LSP is effectively treated as a PIM
enabled interface. Please see [RFC5015] for more details.
For transporting the packets of a sender only branch we create a
MP2MP LSP. Other sender only branches will receive these packets and
will not forward them because there are no receivers. These packets
will be dropped. If that affect is undesireable some other means of
transport has to be established to forward packets to the root of the
tree, like a Multi-Point to Point LSP for example. A technique to
unicast packets to the root of a P2MP or MP2MP LSP is documented in
[I-D.rosen-l3vpn-mvpn-mspmsi] section 3.2.2.1.
3. LSP opaque encodings
This section documents the different transit opaque encodings.
3.1. Transit IPv4 Source TLV
Wijnands, et al. Expires June 2, 2013 [Page 7]
Internet-Draft In-band signaling with mLDP November 2012
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 3 (to be assigned by IANA).
Length: 8 (octet size of Source and Group fields)
Source: IPv4 multicast source address, 4 octets.
Group: IPv4 multicast group address, 4 octets.
3.2. Transit IPv6 Source TLV
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 ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 4 (to be assigned by IANA).
Length: 32 (octet size of Source and Group fields)
Source: IPv6 multicast source address, 16 octets.
Wijnands, et al. Expires June 2, 2013 [Page 8]
Internet-Draft In-band signaling with mLDP November 2012
Group: IPv6 multicast group address, 16 octets.
3.3. Transit IPv4 bidir TLV
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 5 (to be assigned by IANA).
Length: 9 (octet size of Mask Len, RP and Group fields)
Mask Len: The number of contiguous one bits that are left justified
and used as a mask, 1 octet. Maximum value allowed is 32.
RP: Rendezvous Point (RP) IPv4 address used for encoded Group, 4
octets.
Group: IPv4 multicast group address, 4 octets.
3.4. Transit IPv6 bidir TLV
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 ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Wijnands, et al. Expires June 2, 2013 [Page 9]
Internet-Draft In-band signaling with mLDP November 2012
~ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 6 (to be assigned by IANA).
Length: 33 (octet size of Mask Len, RP and Group fields)
Mask Len: The number of contiguous one bits that are left justified
and used as a mask, 1 octet. Maximum value allowed is 128.
RP: Rendezvous Point (RP) IPv6 address used for encoded group, 16
octets.
Group: IPv6 multicast group address, 16 octets.
4. Security Considerations
The same security considerations apply as for the base LDP
specification, as described in [RFC5036].
5. IANA considerations
This document requires allocation from the 'LDP MP Opaque Value
Element basic type' name space managed by IANA. The values requested
are:
Transit IPv4 Source TLV type - 3
Transit IPv6 Source TLV type - 4
Transit IPv4 Bidir TLV type - 5
Transit IPv6 Bidir TLV type - 6
6. Acknowledgments
Thanks to Eric Rosen for his valuable comments on this document.
Also thanks to Yakov Rekhter, Adrian Farrel, Uwe Joorde, Loa
Andersson and Arkadiy Gulko for providing comments on this document.
Wijnands, et al. Expires June 2, 2013 [Page 10]
Internet-Draft In-band signaling with mLDP November 2012
7. Contributing authors
Below is a list of the contributing authors in alphabetical order:
Toerless Eckert
Cisco Systems, Inc.
170 Tasman Drive
San Jose, CA, 95134
USA
E-mail: eckert@cisco.com
Nicolai Leymann
Deutsche Telekom
Winterfeldtstrasse 21
Berlin, 10781
Germany
E-mail: n.leymann@telekom.de
Maria Napierala
AT&T Labs
200 Laurel Avenue
Middletown, NJ 07748
USA
E-mail: mnapierala@att.com
IJsbrand Wijnands
Cisco Systems, Inc.
De kleetlaan 6a
1831 Diegem
Belgium
E-mail: ice@cisco.com
8. References
8.1. Normative References
[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.
[RFC6388] Wijnands, IJ., Minei, I., Kompella, K., and B. Thomas,
"Label Distribution Protocol Extensions for Point-to-
Wijnands, et al. Expires June 2, 2013 [Page 11]
Internet-Draft In-band signaling with mLDP November 2012
Multipoint and Multipoint-to-Multipoint Label Switched
Paths", RFC 6388, November 2011.
8.2. Informative References
[RFC4601] Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas,
"Protocol Independent Multicast - Sparse Mode (PIM-SM):
Protocol Specification (Revised)", RFC 4601, August 2006.
[RFC4607] Holbrook, H. and B. Cain, "Source-Specific Multicast for
IP", RFC 4607, August 2006.
[RFC5015] Handley, M., Kouvelas, I., Speakman, T., and L. Vicisano,
"Bidirectional Protocol Independent Multicast (BIDIR-
PIM)", RFC 5015, October 2007.
[RFC3618] Fenner, B. and D. Meyer, "Multicast Source Discovery
Protocol (MSDP)", RFC 3618, October 2003.
[RFC6513] Rosen, E. and R. Aggarwal, "Multicast in MPLS/BGP IP
VPNs", RFC 6513, February 2012.
[I-D.rekhter-pim-sm-over-mldp]
Rekhter, Y. and R. Aggarwal, "Carrying PIM-SM in ASM mode
Trees over P2MP mLDP LSPs",
draft-rekhter-pim-sm-over-mldp-04 (work in progress),
August 2011.
[I-D.rosen-l3vpn-mvpn-mspmsi]
Cai, Y., Rosen, E., Wijnands, I., Napierala, M., and A.
Boers, "MVPN: Optimized use of PIM via MS-PMSIs",
draft-rosen-l3vpn-mvpn-mspmsi-10 (work in progress),
February 2012.
Authors' Addresses
IJsbrand Wijnands (editor)
Cisco Systems, Inc.
De kleetlaan 6a
Diegem 1831
Belgium
Email: ice@cisco.com
Wijnands, et al. Expires June 2, 2013 [Page 12]
Internet-Draft In-band signaling with mLDP November 2012
Toerless Eckert
Cisco Systems, Inc.
170 Tasman Drive
San Jose CA, 95134
USA
Email: eckert@cisco.com
Nicolai Leymann
Deutsche Telekom
Winterfeldtstrasse 21
Berlin 10781
Germany
Email: n.leymann@telekom.de
Maria Napierala
AT&T Labs
200 Laurel Avenue
Middletown NJ 07748
USA
Email: mnapierala@att.com
Wijnands, et al. Expires June 2, 2013 [Page 13]
