RFC 8059 EXPERIMENTAL MULTICAST · LISP · PIM
PIM Join Attributes for Locator/ID Separation Protocol (LISP) Environments
Two PIM Join/Prune attributes that let LISP receiver sites pick unicast or multicast transport and report their RLOC.
RFC EDITOR
Arango, J., Venaas, S., Kouvelas, I., and D. Farinacci, "PIM Join Attributes for Locator/ID Separation Protocol (LISP) Environments", RFC 8059, DOI 10.17487/RFC8059, January 2017, <https://www.rfc-editor.org/info/rfc8059>.
BIBTEX
@misc{rfc8059,
series = {Request for Comments},
number = 8059,
howpublished = {RFC 8059},
publisher = {RFC Editor},
doi = {10.17487/RFC8059},
url = {https://www.rfc-editor.org/info/rfc8059},
author = {J. Arango and S. Venaas and I. Kouvelas and D. Farinacci},
title = {{PIM Join Attributes for Locator/ID Separation Protocol (LISP) Environments}},
pagetotal = 9,
year = 2017,
month = jan,
} RFC text
Contents
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
Copyright (c) 2017 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 . . . . . . . . . . . . . . . . . . . . . . . . 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 . . . . . . . . . . . . . . . . . . . . . . . . . 8
8.1. Normative References . . . . . . . . . . . . . . . . . . 8
8.2. Informative References . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 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
AI ELI5
On this page
PROBLEMWhen a multicast root and its receivers sit in different LISP sites, the Join/Prune message says nothing about whether the receiver wants multicast or unicast head-end replication, and its outer source address may not be the RLOC the receiver wants to use.
MECHANISMThe document defines the Transport attribute (type 5) to choose multicast (0) or unicast (1), and the Receiver RLOC attribute (type 6) to carry the receiver ETR's RLOC address to the root ITR's control plane.
STATUS TODAYIt is an Experimental specification. It is updated by RFC 9798.
§1The Problem Between LISP Sites
In the Locator/ID Separation Protocol (LISP), multicast trees that span sites need a unicast LISP-encapsulated Join/Prune message sent from an ETR on the receiver site to an ITR on the root site. That message names the (root-EID,G) state to create but conveys nothing about whether the receiver can or wants to use multicast as the underlying transport.
The authors note that wide deployment of multicast connectivity between LISP sites is unlikely to happen soon, and some implementations focus first on unicast transport with head-end replication. The document therefore lets the receiver say which it wants.
A second gap is the receiver's RLOC. Providers may apply uRPF policies that require the outer source address to be the address of the core-facing interface, which may not be the RLOC on which the site wants to receive a flow.
The sender does not know if the receiving building can get a broadcast or needs a personal delivery, or which door to use. These attributes let the building say so.
§3Using PIM Join/Prune Attributes
The attributes follow the format defined in RFC 5384, which lets Join/Prune messages carry Type-Length-Value (TLV) attributes attached to individual sources. Because these attributes are typically the same for all sources in a message, the document RECOMMENDS the hierarchical scheme of RFC 7887, which lets one attribute in the Upstream Neighbor Address field apply to all sources.
LISP Tunnel Routers do not exchange PIM Hello messages, so there is no Hello option to negotiate support. Systems that support unicast head-end replication are assumed to support these attributes.
Instead of writing a note for every single item, you can put one sticky note on the whole package.
§4The Transport Attribute
The Transport attribute lets a receiver pick the underlying transport. Root sites with multicast connectivity can use multicast replication, but not every receiver site has it, so a root should be ready to support a mixture of multicast and unicast output state.
The attribute has type 5 and length 1, and always has the F (transitive) bit set to zero. Its one-octet value is 0 for multicast and 1 for unicast; values 2 to 255 may be assigned in the future.
An encoded address MUST NOT carry more than one Transport attribute. If it does, or if the value is unknown, the root ITR MUST discard all affected Join/Prune sources.
It is a checkbox on the request: deliver by broadcast, or deliver to me personally. Fill in two boxes or an unknown one, and the request is thrown away.
| Field | Name | Size | Value | Description |
|---|---|---|---|---|
F | F | 1 bits | Transitive bit; MUST be zero. | |
E | E | 1 bits | End-of-Attributes bit; 1 if this is the last attribute. | |
TYPE | Type | 6 bits | 5 | Attribute type. |
LENGTH | Length | 1 byte | 1 | Length of the value; MUST be 1. |
TRANSPORT | Transport | 1 byte | 0 for multicast, 1 for unicast. |
§5The Receiver ETR RLOC Attribute
For unicast head-end replication, the root ITR's PIM control plane keeps an outgoing interface list entry for each receiver ETR and its RLOC, so it can unicast-encapsulate multicast data to each one. The RLOC could be guessed from the outer source address of the Join/Prune message, but uRPF checks and load-balancing policy can make that the wrong address.
The Receiver RLOC attribute (type 6) carries the right address: an Address Family octet defined in RFC 7761 followed by the RLOC. Its length is the address length plus one octet for the family. The root ITR MUST discard affected sources if the attribute is duplicated, the address family is unknown, or the address length is wrong.
Receiver ETRs must also be tracked for root-EID mobility. When the root moves to a new site, the old root ITR learns of it through a Map-Notify and sends a Solicit-Map-Request to each receiver ETR. The receiver then looks up the new root ITR, sends a PIM prune to the old one and a join to the new one.
The receiver writes its exact address on the request so deliveries go to the right door. If the sender moves, the old sender tells everyone to look up the new address.
§6Security and IANA
Security of Join/Prune attributes is only as good as the security of the PIM packet. These attributes neither enhance nor diminish privacy or authenticity. A site that can deliver a Join/Prune message can also append these attributes, as the general considerations in RFC 5384 say.
IANA assigned attribute types 5 (Transport) and 6 (Receiver RLOC) and created the "PIM Join/Prune Transport Types" registry with IETF Review as the policy and values in the range 0 to 255. Values 0 (multicast) and 1 (unicast) are assigned here.
The new notes are only as trustworthy as the envelope they come in, and the registry is a public list of what each number means.
§6References
[RFC5384]RFC 5384Boers, A., Wijnands, I., and E. Rosen, "The Protocol Independent Multicast (PIM) Join Attribute Format", RFC 5384, November 2008.November 2008[RFC6830]RFC 6830Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "The Locator/ID Separation Protocol (LISP)", RFC 6830, January 2013.January 2013[RFC6831]RFC 6831Farinacci, D., Meyer, D., Zwiebel, J., and S. Venaas, "The Locator/ID Separation Protocol (LISP) for Multicast Environments", RFC 6831, January 2013.January 2013[RFC7761]RFC 7761Fenner, B., et al., "Protocol Independent Multicast - Sparse Mode (PIM-SM): Protocol Specification (Revised)", STD 83, RFC 7761, March 2016.March 2016[RFC7887]RFC 7887Venaas, S., Arango, J., and I. Kouvelas, "Hierarchical Join/Prune Attributes", RFC 7887, June 2016.June 2016