Internet Engineering Task Force (IETF) IJ. Wijnands, Ed.

Internet Engineering Task Force (IETF) IJ. Wijnands, Ed.
Request for Comments: 7438 Cisco Systems, Inc.
Updates: 6826, 7246 E. Rosen
Category: Standards Track Juniper Networks, Inc.
ISSN: 2070-1721 A. Gulko
Thomson Reuters
U. Joorde
Deutsche Telekom
J. Tantsura
Ericsson
January 2015

Multipoint LDP (mLDP) In-Band Signaling with Wildcards

Abstract

There are scenarios in which an IP multicast tree traverses an MPLS
domain. In these scenarios, it can be desirable to convert the IP
multicast tree "seamlessly" into an MPLS Multipoint Label Switched
Path (MP-LSP) when it enters the MPLS domain, and then to convert it
back to an IP multicast tree when it exits the MPLS domain. Previous
documents specify procedures that allow certain kinds of IP multicast
trees (either Source-Specific Multicast trees or Bidirectional
Multicast trees) to be attached to an MPLS Multipoint Label Switched
Path (MP-LSP). However, the previous documents do not specify
procedures for attaching IP Any-Source Multicast trees to MP-LSPs,
nor do they specify procedures for aggregating multiple IP multicast
trees onto a single MP-LSP. This document specifies the procedures
to support these functions. It does so by defining "wildcard"
encodings that make it possible to specify, when setting up an MP-
LSP, that a set of IP multicast trees, or a shared IP multicast tree,
should be attached to that MP-LSP. Support for non-bidirectional IP
Any-Source Multicast trees is subject to certain applicability
restrictions that are discussed in this document. This document
updates RFCs 6826 and 7246.

Wijnands, et al. Standards Track [Page 1]

RFC 7438 mLDP In-Band Signaling with Wildcards January 2015

Status of This Memo

This is an Internet Standards Track document.

This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.

Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc7438.

Copyright Notice

Copyright (c) 2015 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.

Wijnands, et al. Standards Track [Page 2]

RFC 7438 mLDP In-Band Signaling with Wildcards January 2015

Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology and Definitions . . . . . . . . . . . . . . . . . 5
3. Wildcards in mLDP Opaque Value TLVs . . . . . . . . . . . . . 7
3.1. Encoding the Wildcards . . . . . . . . . . . . . . . . . 7
3.2. Wildcard Semantics . . . . . . . . . . . . . . . . . . . 8
3.3. Backwards Compatibility . . . . . . . . . . . . . . . . . 8
3.4. Applicability Restrictions with Regard to ASM . . . . . . 9
4. Some Wildcard Use Cases . . . . . . . . . . . . . . . . . . . 9
4.1. PIM Shared Tree Forwarding . . . . . . . . . . . . . . . 9
4.2. IGMP/MLD Proxying . . . . . . . . . . . . . . . . . . . . 11
4.3. Selective Source Mapping . . . . . . . . . . . . . . . . 11
5. Procedures for Wildcard Source Usage . . . . . . . . . . . . 11
6. Procedures for Wildcard Group Usage . . . . . . . . . . . . . 13
7. Determining the MP-LSP Root (Ingress LSR) . . . . . . . . . . 13
8. Anycast RP . . . . . . . . . . . . . . . . . . . . . . . . . 13
9. Security Considerations . . . . . . . . . . . . . . . . . . . 14
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 14
10.1. Normative References . . . . . . . . . . . . . . . . . . 14
10.2. Informative References . . . . . . . . . . . . . . . . . 14
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16

1. Introduction

[RFC6826] and [RFC7246] specify procedures for mLDP (Multipoint LDP)
that allow an IP multicast tree (either a Source-Specific Multicast
tree or a Bidirectional Multicast tree) to be attached "seamlessly"
to an MPLS Multipoint Label Switched Path (MP-LSP). This can be
useful, for example, when there is multicast data that originates in
a domain that supports IP multicast, which then has to be forwarded
across a domain that supports MPLS multicast and then has to
forwarded across another domain that supports IP multicast. By
attaching an IP multicast tree to an MP-LSP, data that is traveling
along the IP multicast tree can be moved seamlessly to the MP-LSP
when it enters the MPLS multicast domain. The data then travels
along the MP-LSP through the MPLS domain. When the data reaches the
boundary of the MPLS domain, it can be moved seamlessly to an IP
multicast tree. This ability to attach IP multicast trees to MPLS
MP-LSPs can be useful in either VPN context or global context.

In mLDP, every MP-LSP is identified by the combination of a "root
node" (or "Ingress Label Switching Router (LSR)") and an "Opaque
Value" that, in the context of the root node, uniquely identifies the
MP-LSP. These are encoded into an mLDP "Forwarding Equivalence Class
(FEC) Element". To set up an MP-LSP, the Egress LSRs originate mLDP

Wijnands, et al. Standards Track [Page 3]

RFC 7438 mLDP In-Band Signaling with Wildcards January 2015

control messages containing the FEC element. A given FEC Element
value identifies a single MP-LSP and is passed upstream from the
Egress LSRs, through the intermediate LSRs, to the Ingress LSR.

In IP multicast, a multicast tree is identified by the combination of
an IP source address ("S") and an IP group address ("G"), usually
written as "(S,G)". A tree carrying traffic of multiple sources is
identified by its group address, and the identifier is written as
"(*,G)".

When an MP-LSP is being set up, the procedures of [RFC6826] and
[RFC7246], known as "mLDP in-band signaling", allow the Egress LSRs
of the MP-LSP to encode the identifier of an IP multicast tree in the
"Opaque Value" field of the mLDP FEC Element that identifies the MP-
LSP. Only the Egress and Ingress LSRs are aware that the mLDP FEC
Elements contain encodings of the IP multicast tree identifier;
intermediate nodes along the MP-LSP do not take any account of the
internal structure of the FEC Element's Opaque Value, and the
internal structure of the Opaque Value does not affect the operation
of mLDP. By using mLDP in-band signaling, the Egress LSRs of an MP-
LSP inform the Ingress LSR that they expect traffic of the identified
IP multicast tree (and only that traffic) to be carried on the MP-
LSP. That is, mLDP in-band signaling not only sets up the MP-LSP, it
also binds a given IP multicast tree to the MP-LSP.

If multicast is being done in a VPN context [RFC7246], then the mLDP
FEC elements also contain a "Route Distinguisher" (RD) (see
[RFC7246]), as the IP multicast trees are identified not merely by
"(S,G)" but by "(RD,S,G)". The procedures of this document are also
applicable in this case. Of course, when an Ingress LSR processes an
in-band signaling Opaque Value that contains an RD, it does so in the
context of the VPN associated with that RD.

If mLDP in-band signaling is not used, then some other protocol must
be used to bind an IP multicast tree to the MP-LSP; this requires
additional communication mechanisms between the Ingress LSR and the
Egress LSRs of the MP-LSP. The purpose of mLDP in-band signaling is
to eliminate the need for these other protocols.

When following the procedures of [RFC6826] and [RFC7246] for non-
bidirectional trees, the Opaque Value has an IP source address (S)
and an IP group address (G) encoded into it, thus enabling it to
identify a particular IP multicast (S,G) tree. Only a single IP
source-specific multicast tree (i.e., a single "(S,G)") can be
identified in a given FEC element. As a result, a given MP-LSP can
carry data from only a single IP source-specific multicast tree
(i.e., a single "(S,G) tree"). However, there are scenarios in which
it would be desirable to aggregate a number of (S,G) trees on a

Wijnands, et al. Standards Track [Page 4]

RFC 7438 mLDP In-Band Signaling with Wildcards January 2015

single MP-LSP. Aggregation allows a given number of IP multicast
trees to use a smaller number of MP-LSPs, thus saving state in the
network.

In addition, [RFC6826] and [RFC7246] do not support the attachment of
an Any-Source Multicast (ASM) shared tree to an MP-LSP, except in the
case where the ASM shared tree is a bidirectional tree (i.e., a tree
set up by BIDIR-PIM [RFC5015]). However, there are scenarios in
which it would be desirable to attach a non-bidirectional ASM shared
tree to an MP-LSP.

This document specifies a way to encode an mLDP "Opaque Value" in
which either the "S" or the "G" or both are replaced by a "wildcard"
(written as "*"). Procedures are described for using the wildcard
encoding to map non-bidirectional ASM shared trees to MP-LSPs and for
mapping multiple (S,G) trees (with a common value of S or a common
value of G) to a single MP-LSP.

Some example scenarios where wildcard encoding is useful are

o PIM shared tree forwarding with "threshold infinity";

o IGMP/Multicast Listener Discovery (MLD) proxying; and

o Selective Source mapping.

These scenarios are discussed in Section 4. Note that this list of
scenarios is not meant to be exhaustive.

This document specifies only the mLDP procedures that are specific to
the use of wildcards. mLDP in-band signaling procedures that are not
specific to the use of wildcards can be found in [RFC6826] and
[RFC7246]. Unless otherwise specified in this document, those
procedures still apply when wildcards are used.

2. Terminology and Definitions

Readers of this document are assumed to be familiar with the
terminology and concepts of the documents listed as Normative
References. For convenience, some of the more frequently used terms
appear below.

IGMP:
Internet Group Management Protocol.

Wijnands, et al. Standards Track [Page 5]

RFC 7438 mLDP In-Band Signaling with Wildcards January 2015

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. This document
also allows (S,*) to be encoded in the opaque value; see
Section 6.

Ingress LSR:
Root node of a MP-LSP. When mLDP in-band signaling is used, the
Ingress LSR receives mLDP messages about a particular MP-LSP from
downstream and emits IP multicast control messages upstream. The
set of IP multicast control messages that are emitted upstream
depends upon the contents of the LDP Opaque Value TLVs. The
Ingress LSR also receives IP multicast data messages from upstream
and sends them downstream as MPLS packets on an MP-LSP.

IP multicast tree:
An IP multicast distribution tree identified by an IP multicast
group address and optionally a source IP address, also referred to
as (S,G) and (*,G).

MLD:
Multicast Listener Discovery.

mLDP:
Multipoint LDP.

MP-LSP:
A Point-to-Multipoint (P2MP) or Multipoint-to-Multipoint (MP2MP)
LSP.

PIM:
Protocol Independent Multicast.

PIM-ASM:
PIM Any-Source Multicast.

PIM-SM:
PIM Sparse Mode.

PIM-SSM:
PIM Source-Specific Multicast.

RP:
The PIM Rendezvous Point.

Wijnands, et al. Standards Track [Page 6]

RFC 7438 mLDP In-Band Signaling with Wildcards January 2015

Egress LSR:
The Egress LSRs of an MP-LSP are LSPs that receive MPLS multicast
data packets from upstream on that MP-LSP, and that forward that
data downstream as IP multicast data packets. The Egress LSRs
also receive IP multicast control messages from downstream and
send mLDP control messages upstream. When in-band signaling is
used, the Egress LSRs construct Opaque Value TLVs that contain IP
source and/or group addresses based on the contents of the IP
multicast control messages received from downstream.

Threshold Infinity:
A PIM-SM procedure where no source-specific multicast (S,G) trees
are created for multicast packets that are forwarded down the
shared tree (*,G).

TLV:
A protocol element consisting of a type field, followed by a
length field, followed by a value field. Note that the value
field of a TLV may be subdivided into a number of subfields.

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in RFC
2119 [RFC2119].

3. Wildcards in mLDP Opaque Value TLVs

[RFC6826] and [RFC7246] define the following Opaque Value TLVs:
Transit IPv4 Source TLV, Transit IPv6 Source TLV, Transit VPNv4
Source TLV, and Transit VPNv6 Source TLV. The value field of each
such TLV is divided into a number of subfields, one of which contains
an IP source address, and one of which contains an IP group address.
Per those documents, these fields must contain valid IP addresses.

This document extends the definition of those TLVs by allowing either
the IP source address field or the IP group address field (or both)
to specify a "wildcard" rather than a valid IP address.

3.1. Encoding the Wildcards

A value of all zeroes in the IP source address subfield is used to
represent a wildcard source address. A value of all zeroes in the IP
group address subfield is used to represent the wildcard group
address. Note that the lengths of these subfields are as specified
in the previous documents.

Wijnands, et al. Standards Track [Page 7]

RFC 7438 mLDP In-Band Signaling with Wildcards January 2015

3.2. Wildcard Semantics

If the IP source address subfield contains the wildcard, and the IP
group address subfield contains an IP multicast group address that is
NOT in the SSM address range (see Section 4.8 of [RFC4601]), then the
TLV identifies a PIM-SM shared tree. Please see Section 3.4 for the
applicability restrictions that apply to this case.

If the IP source address subfield contains the wildcard, and the IP
group address subfield contains an IP multicast group address that is
in the SSM address range, then the TLV identifies the collection of
PIM trees with the given group address.

If the IP source address subfield contains a non-zero IP address, and
the IP group address subfield contains the wildcard, the TLV
identifies the collection of PIM-SSM trees that have the source
address as their root.

Procedures for the use of the wildcards are discussed in Sections 4,
5, and 6. Please note that, as always, the structure of an Opaque
Value TLV does not affect the operation of mLDP. The structure is
meaningful only to the IP multicast modules at the Ingress and Egress
LSRs.

Procedures for the use of a wildcard group in the following TLVs
(defined in [RFC6826] or [RFC7246]) are outside the scope of the
current document: Transit IPv4 Bidir TLV, Transit IPv6 Bidir TLV,
Transit VPNv4 Bidir TLV, and Transit VPNv6 Bidir TLV.

Procedures for the use of both a wildcard source and a wildcard group
in the same TLV are outside the scope of the current document.

Note that the Bidir TLVs do not have a source address subfield, and
hence the notion of a wildcard source is not applicable to them.

3.3. Backwards Compatibility

The procedures of this document do not change the behavior described
in [RFC6826] and [RFC7246].

A correctly operating Egress LSR that supports [RFC6826] and/or
[RFC7246], but that does not support this document, will never
generate mLDP FEC Element Opaque values that contain source or group
wildcards.

Neither [RFC6826] nor [RFC7246] specifies the behavior of an Ingress
LSR that receives mLDP FEC Element Opaque values that contain zeroes
in the source address or group address subfields. However, if an

Wijnands, et al. Standards Track [Page 8]

RFC 7438 mLDP In-Band Signaling with Wildcards January 2015

Ingress LSR supports [RFC6826] and/or [RFC7246], but does not support
this document, then it has no choice but to treat any such received
FEC elements as invalid; the procedures specified in [RFC6826] and
[RFC7246] do not work when the Opaque values contain zeroes in the
source address or group address subfields.

The procedures of this document thus presuppose that if an Egress LSR
uses wildcard encodings when setting up an MP-LSP, then the Ingress
LSR (i.e., the root of the multipoint LSP) supports the procedures of
this document. An Egress LSR MUST NOT use wildcard encodings when
setting up a particular multipoint LSP unless it is known a priori
that the Ingress LSR supports the procedures of this document. How
this is known is outside the scope of this document.

3.4. Applicability Restrictions with Regard to ASM

In general, support for non-bidirectional PIM-ASM trees requires (a)
a procedure for determining the set of sources for a given ASM tree
("source discovery"), and (b) a procedure for pruning a particular
source off a shared tree ("source pruning"). No such procedures are
specified in this document. Therefore, the combination of a wildcard
source with an ASM group address MUST NOT be used unless it is known
a priori that neither source discovery nor source pruning are needed.
How this is known is outside the scope of this document. Section 4
describes some use cases in which source discovery and source pruning
are not needed.

There are, of course, use cases where source discovery and/or source
pruning is needed. These can be handled with procedures such as
those specified in [RFC6513], [RFC6514], and [GTM]. Use of mLDP in-
band signaling is NOT RECOMMENDED for those cases.

4. Some Wildcard Use Cases

This section discusses a number of wildcard use cases. The set of
use cases here is not meant to be exhaustive. In each of these use
cases, the Egress LSRs construct mLDP Opaque Value TLVs that contain
wildcards in the IP source address or IP group address subfields.

4.1. PIM Shared Tree Forwarding

PIM [RFC4601] has the concept of a "shared tree", identified as
(*,G). This concept is only applicable when G is an IP multicast
group address that is not in the SSM address range (i.e., is an ASM
group address). Every ASM group is associated with a Rendezvous
Point (RP), and the (*,G) tree is built towards the RP (i.e., its
root is the RP). The RP for group G is responsible for forwarding

Wijnands, et al. Standards Track [Page 9]

RFC 7438 mLDP In-Band Signaling with Wildcards January 2015

packets down the (*,G) tree. The packets forwarded down the (*,G)
tree may be from any multicast source, as long as they have an IP
destination address of G.

The RP learns about all the multicast sources for a given group and
then joins a source-specific tree for each such source. That is,
when the RP for G learns that S has multicast data to send to G, the
RP joins the (S,G) tree. When the RP receives multicast data from S
that is destined to G, the RP forwards the data down the (*,G) tree.
There are several different ways that the RP may learn about the
sources for a given group. The RP may learn of sources via PIM
Register messages [RFC4601], via Multicast Source Discovery Protocol
(MSDP) [RFC3618], or by observing packets from a source that is
directly connected to the RP.

In PIM, a PIM router that has receivers for a particular ASM
multicast group G (known as a "last hop" router for G) will first
join the (*,G) tree. As it receives multicast traffic on the (*,G)
tree, it learns (by examining the IP headers of the multicast data
packets) the sources that are transmitting to G. Typically, when a
last hop router for group G learns that source S is transmitting to
G, the last hop router joins the (S,G) tree and "prunes" S off the
(*,G) tree. This allows each last hop router to receive the
multicast data along the shortest path from the source to the last
hop router. (Full details of this behavior can be found in
[RFC4601].)

In some cases, however, a last hop router for group G may decide not
to join the source trees, but rather to keep receiving all the
traffic for G from the (*,G) tree. In this case, we say that the
last hop router has "threshold infinity" for group G. This is
optional behavior documented in [RFC4601]. "Threshold infinity" is
often used in deployments where the RP is between the multicast
sources and the multicast receivers for group G, i.e., in deployments
where it is known that the shortest path from any source to any
receiver of the group goes through the RP. In these deployments,
there is no advantage for a last hop router to join a source tree
since the data is already traveling along the shortest path. The
only effect of executing the complicated procedures for joining a
source tree and pruning the source off the shared tree would be to
increase the amount of multicast routing state that has to be
maintained in the network.

To efficiently use mLDP in-band signaling in this scenario, it is
necessary for the Egress LSRs to construct an Opaque Value TLV that
identifies a (*,G) tree. This is done by using the wildcard in the
IP source address subfield and setting the IP group address subfield
to G.

Wijnands, et al. Standards Track [Page 10]

RFC 7438 mLDP In-Band Signaling with Wildcards January 2015

Note that these mLDP in-band signaling procedures do not support PIM-
ASM in scenarios where "threshold infinity" is not used.

4.2. IGMP/MLD Proxying

There are scenarios where the multicast senders and receivers are
directly connected to an MPLS routing domain, and where it is desired
to use mLDP rather than PIM to set up "trees" through that domain.

In these scenarios, we can apply "IGMP/MLD proxying" and eliminate
the use of PIM. The senders and receivers consider the MPLS domain
to be single hop between each other. [RFC4605] documents procedures
where a multicast routing protocol is not necessary to build a
"simple tree". Within the MPLS domain, mLDP will be used to build an
MP-LSP, but this is hidden from the senders and receivers. The
procedures defined in [RFC4605] are applicable since the senders and
receivers are considered to be one hop away from each other.

For mLDP to build the necessary MP-LSP, it needs to know the root of
the tree. Following the procedures as defined in [RFC4605], we
depend on manual configuration of the mLDP root for the ASM multicast
group. Since the MP-LSP for a given ASM multicast group will carry
traffic from all the sources for that group, the Opaque Value TLV
used to construct the MP-LSP will contain a wildcard in the IP source
address subfield.

4.3. Selective Source Mapping

In many IPTV deployments, the content servers are gathered into a
small number of sites. Popular channels are often statically
configured and forwarded over a core MPLS network to the Egress
routers. Since these channels are statically defined, they MAY also
be forwarded over a multipoint LSP with wildcard encoding. The sort
of wildcard encoding that needs to be used (source and/or group)
depends on the source/group allocation policy of the IPTV provider.
Other options are to use MSDP [RFC3618] or BGP "Auto-Discovery"
procedures [RFC6513] for source discovery by the Ingress LSR. Based
on the received wildcard, the Ingress LSR can select from the set of
IP multicast streams for which it has state.

5. Procedures for Wildcard Source Usage

The decision to use mLDP in-band signaling is made by the IP
multicast component of an Egress LSR, based on provisioned policy.
The decision to use (or not to use) a wildcard in the IP source
address subfield of an mLDP Opaque Value TLV is also made by the IP
multicast component, again based on provisioned policy. Following
are some example policies that may be useful:

Wijnands, et al. Standards Track [Page 11]

RFC 7438 mLDP In-Band Signaling with Wildcards January 2015

1. Suppose that PIM is enabled, an Egress LSR needs to join a non-
bidirectional ASM group G, and the RP for G is reachable via a
BGP route. The Egress LSR may choose the BGP Next Hop of the
route to the RP to be the Ingress LSR (root node) of the MP-LSP
corresponding to the (*,G) tree (see also Section 7). The Egress
LSR may identify the (*,G) tree by using an mLDP Opaque Value TLV
whose IP source address subfield contains a wildcard, and whose
IP group address subfield contains G.

2. Suppose that PIM is not enabled for group G, and an IGMP/MLD
group membership report for G has been received by an Egress LSR.
The Egress LSR may determine the "proxy device" for G (see
Section 4.2). It can then set up an MP-LSP for which the proxy
device is the Ingress LSR. The Egress LSR needs to signal the
Ingress LSR that the MP-LSP is to carry traffic belonging to
group G; it does this by using an Opaque Value TLV whose IP
source address subfield contains a wildcard, and whose IP group
address subfield contains G.

As the policies needed in any one deployment may be very different
than the policies needed in another, this document does not specify
any particular set of policies as being mandatory to implement.

When the Ingress LSR receives an mLDP Opaque Value TLV that has been
defined for in-band signaling, the information from the subfields of
that TLV is passed to the IP multicast component of the Ingress LSR.
If the IP source address subfield contains a wildcard, the IP
multicast component must determine how to process it. The processing
MUST follow the rules below:

1. If PIM is enabled and the group identified in the Opaque Value
TLV is a non-bidirectional ASM group, the Ingress LSR acts as if
it had received a (*,G) IGMP/MLD report from a downstream node,
and the procedures defined in [RFC4601] are followed.

2. If PIM is enabled and the identified group is a PIM-SSM group,
all multicast sources known for the group on the Ingress LSR are
to be forwarded down the MP-LSP. In this scenario, it is assumed
that the Ingress LSR is already receiving all the necessary
traffic. How the Ingress LSR receives this traffic is outside
the scope of this document.

3. If PIM is not enabled for the identified group, the Ingress LSR
acts as if it had received a (*,G) IGMP/MLD report from a
downstream node, and the procedures as defined in [RFC4605] are
followed. The Ingress LSR should forward the (*,G) packets to
the Egress LSR through the MP-LSP identified by the Opaque Value
TLV. (See also Section 4.2.)

Wijnands, et al. Standards Track [Page 12]

RFC 7438 mLDP In-Band Signaling with Wildcards January 2015

6. Procedures for Wildcard Group Usage

The decision to use mLDP in-band signaling is made by the IP
multicast component of an Egress LSR based on provisioned policy.
The decision to use (or not to use) a wildcard in the IP group
address subfield of an mLDP Opaque Value TLV is also made by the IP
multicast component of the Egress LSR, again based on provisioned
policy. As the policies needed in any one deployment may be very
different than the policies needed in another, this document does not
specify any particular set of policies as being mandatory to
implement.

When the Ingress LSR (i.e., the root node of the MP-LSP) receives an
mLDP Opaque Value TLV that has been defined for in-band signaling,
the information from the subfields of that TLV is passed to the IP
multicast component of the Ingress LSR. If the IP group address
subfield contains a wildcard, then the Ingress LSR examines its IP
multicast routing table to find all the IP multicast streams whose IP
source address is the address specified in the IP source address
subfield of the TLV. All these streams SHOULD be forwarded down the
MP-LSP identified by the Opaque Value TLV. Note that some of these
streams may have SSM group addresses, while some may have ASM group
addresses.

7. Determining the MP-LSP Root (Ingress LSR)

[RFC6826] and [RFC7246] describe procedures by which an Egress LSR
may determine the MP-LSP root node address corresponding to a given
(S,G) IP multicast stream. That determination is based upon the IP
address of the source ("S") of the multicast stream. To follow the
procedures of this document, it is necessary to determine the MP-LSP
root node corresponding to a given (*,G) set of IP multicast streams.
The only difference from the above mentioned procedures is that the
Proxy device or RP address is used instead of the source to discover
the mLDP root node address.

Other procedures for determining the root node are also allowed, as
determined by policy.

8. Anycast RP

In the scenarios where mLDP in-band signaling is used, it is unlikely
that the RP-to-group mappings are being dynamically distributed over
the MPLS core. It is more likely that the RP address is statically
configured at each multicast site. In these scenarios, it is
advisable to configure an Anycast RP address at each site in order to
provide redundancy. See [RFC3446] for more details.

Wijnands, et al. Standards Track [Page 13]

RFC 7438 mLDP In-Band Signaling with Wildcards January 2015

9. Security Considerations

There are no security considerations other than ones already
mentioned in [RFC5036], [RFC6826], and [RFC7246].

10. References

10.1. Normative References

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.

[RFC4601] Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas,
"Protocol Independent Multicast - Sparse Mode (PIM-SM):
Protocol Specification (Revised)", RFC 4601, August 2006,
<http://www.rfc-editor.org/info/rfc4601>.

[RFC4605] Fenner, B., He, H., Haberman, B., and H. Sandick,
"Internet Group Management Protocol (IGMP) / Multicast
Listener Discovery (MLD)-Based Multicast Forwarding
("IGMP/MLD Proxying")", RFC 4605, August 2006,
<http://www.rfc-editor.org/info/rfc4605>.

[RFC5036] Andersson, L., Minei, I., and B. Thomas, "LDP
Specification", RFC 5036, October 2007,
<http://www.rfc-editor.org/info/rfc5036>.

[RFC6826] Wijnands, IJ., Eckert, T., Leymann, N., and M. Napierala,
"Multipoint LDP In-Band Signaling for Point-to-Multipoint
and Multipoint-to-Multipoint Label Switched Paths", RFC
6826, January 2013,
<http://www.rfc-editor.org/info/rfc6826>.

[RFC7246] Wijnands, IJ., Hitchen, P., Leymann, N., Henderickx, W.,
Gulko, A., and J. Tantsura, "Multipoint Label Distribution
Protocol In-Band Signaling in a Virtual Routing and
Forwarding (VRF) Table Context", RFC 7246, June 2014,
<http://www.rfc-editor.org/info/rfc7246>.

10.2. Informative References

[GTM] Zhang, J., Giulano, L., Rosen, E., Subramanian, K.,
Pacella, D., and J. Schiller, "Global Table Multicast with
BGP-MVPN Procedures", Work in Progress, draft-ietf-bess-
mvpn-global-table-mcast-00, November 2014.

Wijnands, et al. Standards Track [Page 14]

RFC 7438 mLDP In-Band Signaling with Wildcards January 2015

[RFC3446] Kim, D., Meyer, D., Kilmer, H., and D. Farinacci, "Anycast
Rendevous Point (RP) mechanism using Protocol Independent
Multicast (PIM) and Multicast Source Discovery Protocol
(MSDP)", RFC 3446, January 2003,
<http://www.rfc-editor.org/info/rfc3446>.

[RFC3618] Fenner, B. and D. Meyer, "Multicast Source Discovery
Protocol (MSDP)", RFC 3618, October 2003,
<http://www.rfc-editor.org/info/rfc3618>.

[RFC5015] Handley, M., Kouvelas, I., Speakman, T., and L. Vicisano,
"Bidirectional Protocol Independent Multicast (BIDIR-
PIM)", RFC 5015, October 2007,
<http://www.rfc-editor.org/info/rfc5015>.

[RFC6513] Rosen, E. and R. Aggarwal, "Multicast in MPLS/BGP IP
VPNs", RFC 6513, February 2012,
<http://www.rfc-editor.org/info/rfc6513>.

[RFC6514] Aggarwal, R., Rosen, E., Morin, T., and Y. Rekhter, "BGP
Encodings and Procedures for Multicast in MPLS/BGP IP
VPNs", RFC 6514, February 2012,
<http://www.rfc-editor.org/info/rfc6514>.

Acknowledgements

We would like to thank Loa Andersson, Pranjal Dutta, Lizhong Jin, and
Curtis Villamizar for their review and comments.

Wijnands, et al. Standards Track [Page 15]

RFC 7438 mLDP In-Band Signaling with Wildcards January 2015

Authors' Addresses

IJsbrand Wijnands (editor)
Cisco Systems, Inc.
De kleetlaan 6a
Diegem 1831
Belgium

EMail: [email protected]

Eric C. Rosen
Juniper Networks, Inc.
10 Technology Park Drive
Westford, MA 01886
United States

EMail: [email protected]

Arkadiy Gulko
Thomson Reuters
195 Broadway
New York, NY 10007
United States

EMail: [email protected]

Uwe Joorde
Deutsche Telekom
Hammer Str. 216-226
Muenster D-48153
Germany

EMail: [email protected]

Jeff Tantsura
Ericsson
300 Holger Way
San Jose, CA 95134
United States

EMail: [email protected]

Wijnands, et al. Standards Track [Page 16]