Internet Engineering Task Force (IETF) J. Arango
Request for Comments: 8059 S. Venaas
Category: Experimental Cisco Systems
ISSN: 2070-1721 I. Kouvelas
Arista Networks Inc.
D. Farinacci
lispers.net
January 2017
PIM Join Attributes
for Locator/ID Separation Protocol (LISP) Environments
Abstract
This document defines two PIM Join/Prune attributes that support the
construction of multicast distribution trees where the root and
receivers are located in different Locator/ID Separation Protocol
(LISP) sites. These attributes allow the receiver site to select
between unicast and multicast underlying transport and to convey the
RLOC (Routing Locator) address of the receiver ETR (Egress Tunnel
Router) to the control plane of the root ITR (Ingress Tunnel Router).
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for examination, experimental implementation, and
evaluation.
This document defines an Experimental Protocol for the Internet
community. 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). Not
all documents approved by the IESG are a candidate for any level of
Internet Standard; see Section 2 of RFC 7841.
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/rfc8059.
Copyright Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements Notation . . . . . . . . . . . . . . . . . . . . 3
3. PIM Join/Prune Attributes . . . . . . . . . . . . . . . . . . 3
4. The Transport Attribute . . . . . . . . . . . . . . . . . . . 4
4.1. Transport Attribute Format . . . . . . . . . . . . . . . 4
4.2. Using the Transport Attribute . . . . . . . . . . . . . . 5
5. Receiver ETR RLOC Attribute . . . . . . . . . . . . . . . . . 5
5.1. Receiver RLOC Attribute Format . . . . . . . . . . . . . 6
5.2. Using the Receiver RLOC Attribute . . . . . . . . . . . . 6
6. Security Considerations . . . . . . . . . . . . . . . . . . . 7
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 8
8.1. Normative References . . . . . . . . . . . . . . . . . . 7 8
8.2. Informative References . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8 9
1. Introduction
The construction of multicast distribution trees where the root and
receivers are located in different LISP sites [RFC6830] is defined in
[RFC6831]. Creation of (root-EID,G) state in the root site requires
that unicast LISP-encapsulated Join/Prune messages be sent from an
ETR on the receiver site to an ITR on the root site. The term "EID"
is short for "Endpoint ID".
[RFC6831] specifies that (root-EID,G) data packets are to be LISP-
encapsulated into (root-RLOC,G) multicast packets. However, a wide
deployment of multicast connectivity between LISP sites is unlikely
to happen any time soon. In fact, some implementations are initially
focusing on unicast transport with head-end replication between root
and receiver sites.
The unicast LISP-encapsulated Join/Prune message specifies the
(root-EID,G) state that needs to be established in the root site, but
conveys nothing about the receiver's capability or desire to use
multicast as the underlying transport. This document specifies a
Join/Prune attribute that allows the receiver ETR to select the
desired transport.
The term "transport" in this document is intentionally somewhat
vague. Currently, it is used just to indicate whether multicast or
head-end replication is used; this means that the outer destination
address is either a unicast or multicast address. Future documents
may specify how other types of delivery, encapsulation, or underlay
are used.
Knowledge of the receiver ETR's RLOC address is essential to the
control plane of the root ITR. The RLOC address determines the
downstream destination for unicast head-end replication and
identifies the receiver ETR that needs to be notified should the root
ITR of the distribution tree move to another site. The root ITR can
change when the source EID is roaming to another LISP site.
Service providers may implement unicast reverse path forwarding
(uRPF) policies requiring that the outer source address of the LISP-
encapsulated Join/Prune message be the address of the receiver ETR's
core-facing interface used to physically transmit the message.
However, due to policy and load-balancing considerations, the outer
source address may not be the RLOC on which the receiver site wishes
to receive a particular flow. This document specifies a Join/Prune
attribute that conveys the appropriate receiver ETR's RLOC address to
the control plane of the root ITR.
This document uses terminology defined in [RFC6830], such as EID,
RLOC, ITR, and ETR.
2. Requirements Notation
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 [RFC2119].
3. PIM Join/Prune Attributes
PIM Join/Prune attributes are defined in [RFC5384] by introducing a
new Encoded-Source type that, in addition to the Join/Prune source,
can carry multiple Type-Length-Value (TLV) attributes. These
attributes apply to the individual Join/Prune sources on which they
are stored.
The attributes defined in this document conform to the format of the
encoding type defined in [RFC5384]. The attributes would typically
be the same for all the sources in the Join/Prune message. Hence, we
RECOMMEND using the hierarchical Join/Prune attribute scheme defined
in [RFC7887]. This hierarchical system allows attributes to be
conveyed in the Upstream Neighbor Address field, thus enabling the
efficient application of a single attribute instance to all the
sources in the Join/Prune message.
LISP Tunnel Routers (xTRs) do not exchange PIM Hello Messages, and
hence no Hello option is defined to negotiate support for these
attributes. Systems that support unicast head-end replication are
assumed to support these attributes.
4. The Transport Attribute
It is essential that a mechanism be provided by which the desired
transport can be conveyed by receiver sites. Root sites with
multicast connectivity will want to leverage multicast replication.
However, not all receiver sites can be expected to have multicast
connectivity. It is thus desirable that root sites be prepared to
support (root-EID,G) state with a mixture of multicast and unicast
output state. This document specifies a Join/Prune attribute that
allows the receiver to select the desired underlying transport.
4.1. Transport Attribute Format
0 1 2
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|F|E| Type = 5 | Length = 1 | Transport |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
F bit: The Transitive bit. Specifies whether the attribute is
transitive or non-transitive. MUST be set to zero. This
attribute is ALWAYS non-transitive.
E bit: End-of-Attributes bit. Specifies whether this attribute is
the last. Set to zero if there are more attributes. Set to 1 if
this is the last attribute.
Type: The Transport Attribute type is 5.
Length: The length of the Transport Attribute value. MUST be set
to 1.
Transport: The type of transport being requested. Set to zero for
multicast. Set to 1 for unicast. The values from 2 to 255 may be
assigned in the future.
4.2. Using the Transport Attribute
Hierarchical Join/Prune attribute instances [RFC7887] SHOULD be used
when the same Transport Attribute is to be applied to all the sources
within the Join/Prune message or all the sources within a group set.
The root ITR MUST accept Transport Attributes in the Upstream
Neighbor Encoded-Unicast address, Encoded-Group addresses, and
Encoded-Source addresses.
There MUST NOT be more than one Transport Attribute within the same
encoded address. If an encoded address has more than one instance of
the attribute, the root ITR MUST discard all affected Join/Prune
sources. The root ITR MUST also discard all affected Join/Prune
sources if the Transport Attribute value is unknown.
5. Receiver ETR RLOC Attribute
When a receiver ETR requests unicast head-end replication for a given
(root-EID,G) entry, the PIM control plane of the root ITR must
maintain an outgoing interface list ("oif-list") entry for the
receiver ETR and its corresponding RLOC address. This allows the
root ITR to perform unicast LISP-encapsulation of multicast data
packets to each and every receiver ETR that has requested unicast
head-end replication.
The PIM control plane of the root ITR could potentially determine the
RLOC address of the receiver ETR from the outer source address field
of the LISP-encapsulated Join/Prune message. However, receiver ETRs
are subject to uRPF checks by the network providers on each core-
facing interface. The outer source address must therefore be the
RLOC of the core-facing interface used to physically transmit the
LISP-encapsulated Join/Prune message. Due to policy and load-
balancing considerations, that may not be the RLOC on which the
receiver site wishes to receive a particular flow. This document
specifies a Join/Prune attribute that conveys the appropriate
receiver RLOC address to the PIM control plane of the root ITR.
To support root-EID mobility, receiver ETRs must also be tracked by
the LISP control plane of the root ITR, regardless of the underlying
transport. When the root-EID moves to a new root ITR in a different
LISP site, the receiver ETRs do not know the root-EID has moved and
therefore do not know the RLOC of the new root ITR. This is true for
both unicast and multicast transport modes. The new root ITR does
not have any receiver ETR state. Therefore, it is the responsibility
of the old root ITR to inform the receiver ETRs that the root-EID has
moved. When the old root ITR detects that the root-EID has moved, it
sends a LISP Solicit-Map-Request (SMR) message to each receiver ETR.
The receiver ETRs do a mapping database lookup to retrieve the RLOC
of the new root ITR. The old root ITR detects that the root-EID has
moved when it receives a Map-Notify from the Map-Server. The
transmission of the Map-Notify is triggered when the new root ITR
registers the root-EID [EID-MOBILITY]. When a receiver ETR
determines that the root ITR has changed, it will send a LISP-
encapsulated PIM prune message to the old root xTR and a LISP-
encapsulated PIM join message to the new root xTR.
5.1. Receiver RLOC Attribute Format
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|F|E| Type = 6 | Length | Addr Family | Receiver RLOC
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...
F bit: The Transitive bit. Specifies whether this attribute is
transitive or non-transitive. MUST be set to zero. This
attribute is ALWAYS non-transitive.
E bit: End-of-Attributes bit. Specifies whether this attribute is
the last. Set to zero if there are more attributes. Set to 1 if
this is the last attribute.
Type: The Receiver RLOC Attribute type is 6.
Length: The length in octets of the attribute value. MUST be set
to the length in octets of the receiver RLOC address plus 1 octet
to account for the Address Family field.
Addr Family: The PIM Address Family of the receiver RLOC as defined
in [RFC7761].
Receiver RLOC: The RLOC address on which the receiver ETR wishes to
receiver the unicast-encapsulated flow.
5.2. Using the Receiver RLOC Attribute
Hierarchical Join/Prune attribute instances [RFC7887] SHOULD be used
when the same Receiver RLOC Attribute is to be applied to all the
sources within the message or all the sources within a group set.
The root ITR MUST accept Transport Attributes in the Upstream
Neighbor Encoded-Unicast address, Encoded-Group addresses, and
Encoded-Source addresses.
There MUST NOT be more than one Receiver RLOC Attribute within the
same encoded address. If an encoded address has more than one
instance of the attribute, the root ITR MUST discard all affected
Join/Prune sources. The root ITR MUST also discard all affected
Join/Prune sources if the address family is unknown or the address
length is incorrect for the specified address family.
6. Security Considerations
Security of Join/Prune attributes is only guaranteed by the security
of the PIM packet. The attributes specified herein do not enhance or
diminish the privacy or authenticity of a Join/Prune message. A site
that legitimately or maliciously sends and delivers a Join/Prune
message to another site will equally be able to append these and any
other attributes it wishes. See [RFC5384] for general security
considerations for Join/Prune attributes.
7. IANA Considerations
Two new PIM Join/Prune attribute types have been assigned: value 5
for the Transport Attribute and value 6 for the Receiver RLOC
Attribute.
The "PIM Join/Prune Transport Types" registry has been created for
the Join/Prune Transport attribute. The registration policy is IETF
Review [RFC5226], and the values are in the range 0-255. This
document assigns value 0 for multicast and value 1 for unicast.
8. References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC5384] Boers, A., Wijnands, I., and E. Rosen, "The Protocol
Independent Multicast (PIM) Join Attribute Format",
RFC 5384, DOI 10.17487/RFC5384, November 2008,
<http://www.rfc-editor.org/info/rfc5384>.
[RFC6830] Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "The
Locator/ID Separation Protocol (LISP)", RFC 6830,
DOI 10.17487/RFC6830, January 2013,
<http://www.rfc-editor.org/info/rfc6830>.
[RFC6831] Farinacci, D., Meyer, D., Zwiebel, J., and S. Venaas, "The
Locator/ID Separation Protocol (LISP) for Multicast
Environments", RFC 6831, DOI 10.17487/RFC6831, January
2013, <http://www.rfc-editor.org/info/rfc6831>.
[RFC7761] Fenner, B., Handley, M., Holbrook, H., Kouvelas, I.,
Parekh, R., Zhang, Z., and L. Zheng, "Protocol Independent
Multicast - Sparse Mode (PIM-SM): Protocol Specification
(Revised)", STD 83, RFC 7761, DOI 10.17487/RFC7761, March
2016, <http://www.rfc-editor.org/info/rfc7761>.
[RFC7887] Venaas, S., Arango, J., and I. Kouvelas, "Hierarchical
Join/Prune Attributes", RFC 7887, DOI 10.17487/RFC7887,
June 2016, <http://www.rfc-editor.org/info/rfc7887>.
8.2. Informative References
[EID-MOBILITY]
Portoles-Comeras, M., Ashtaputre, V., Moreno, V., Maino,
F., and D. Farinacci, "LISP L2/L3 EID Mobility Using a
Unified Control Plane", Work in Progress, draft-portoles-
lisp-eid-mobility-01, October 2016.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
DOI 10.17487/RFC5226, May 2008,
<http://www.rfc-editor.org/info/rfc5226>.
Authors' Addresses
Jesus Arango
Cisco Systems
170 Tasman Drive
San Jose, CA 95134
United States of America
Email: jearango@cisco.com
Stig Venaas
Cisco Systems
170 Tasman Drive
San Jose, CA 95134
United States of America
Email: stig@cisco.com
Isidor Kouvelas
Arista Networks Inc.
5453 Great America Parkway
Santa Clara, CA 95054
United States of America
Email: kouvelas@arista.com
Dino Farinacci
lispers.net
San Jose, CA
United States of America
Email: farinacci@gmail.com