LISP Working Group A. Rodriguez-Natal
Internet-Draft V. Ermagan
Intended status: Experimental J. Leong
Expires: October 27, 2018 F. Maino
Cisco Systems
A. Cabellos-Aparicio
Technical University of Catalonia
S. Barkai
Fermi Serverless
D. Farinacci
lispers.net
M. Boucadair
C. Jacquenet
Orange
S. Secci
LIP6 UPMC
April 25, 2018
Publish/Subscribe Functionality for LISP
draft-ietf-lisp-pubsub-00
Abstract
This document specifies an extension to the use of Map-Request to
enable Publish/Subscribe (PubSub) operation for LISP.
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
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This Internet-Draft will expire on October 27, 2018.
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Copyright Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3
3. Deployment Assumptions . . . . . . . . . . . . . . . . . . . 3
4. Map-Request Additions . . . . . . . . . . . . . . . . . . . . 4
5. Mapping Request Subscribe Procedures . . . . . . . . . . . . 5
6. Mapping Notification Publish Procedures . . . . . . . . . . . 7
7. Security Considerations . . . . . . . . . . . . . . . . . . . 8
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 8
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
10. Normative References . . . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
The Locator/ID Separation Protocol (LISP) [RFC6830] splits current IP
addresses in two different namespaces, Endpoint Identifiers (EIDs)
and Routing Locators (RLOCs). LISP uses a map-and-encap approach
that relies on (1) a Mapping System (basically a distributed
database) that stores and disseminates EID-RLOC mappings and on (2)
LISP tunnel routers (xTRs) that encapsulate and decapsulate data
packets based on the content of those mappings.
ITRs/RTRs/PITRs pull EID-to-RLOC mapping information from the Mapping
System by means of an explicit request message. [RFC6830] indicates
how ETRs can tell ITRs/RTRs/PITRs about mapping changes. This
document presents a Publish/Subscribe (PubSub) extension in which the
Mapping System can notify ITRs/RTRs/PITRs about mapping changes.
When this mechanism is used, mapping changes can be notified faster
and can be managed in the Mapping System versus the LISP sites.
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In general, when an ITR/RTR/PITR wants to be notified for mapping
changes for a given EID-prefix, the following steps occur:
(1) The ITR/RTR/PITR sends a Map-Request for that EID-prefix.
(2) The ITR/RTR/PITR sets the Notification-Requested bit (N-bit) on
the Map-Request and includes its xTR-ID.
(3) The Map-Request is forwarded to one of the Map-Servers that the
EID-prefix is registered to.
(4) The Map-Server creates subscription state for the ITR/RTR/PITR
on the EID-prefix.
(5) The Map-Server sends a Map-Notify to the ITR/RTR/PITR to
acknowledge the successful subscription.
(6) When there is an RLOC-set change for the EID-prefix, the Map-
Server sends a Map-Notify message to each ITR/RTR/PITR in the
subscription list.
(7) Each ITR/RTR/PITR sends a Map-Notify-Ack to acknowledge the
received Map-Notify.
This operation is repeated for all EID-prefixes for which ITR/RTR/
PITR want to be notified. The ITR/RTR/PITR can set the N-bit for
several EID-prefixes within a single Map-Request
2. Requirements Language
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. Deployment Assumptions
The specification described in this document makes the following
deployment assumptions:
(1) A unique 128-bit xTR-ID identifier is assigned to each xTR.
(2) Map-Servers are configured in proxy-reply mode, i.e., they are
solicited to generate and send Map-Reply messages for the
mappings they are serving.
(3) There can be either a soft-state or hard-state security
association between the xTRs and the Map-Servers.
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The distribution of xTR-IDs and the management of security
associations are out of the scope of this document.
4. Map-Request Additions
Figure 1 shows the format of the updated Map-Request
[I-D.ietf-lisp-rfc6833bis] to support the PubSub functionality.
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=1 |A|M|P|S|p|s|m|I| Reserved | IRC | Record Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Nonce . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| . . . Nonce |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source-EID-AFI | Source EID Address ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ITR-RLOC-AFI 1 | ITR-RLOC Address 1 ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ITR-RLOC-AFI n | ITR-RLOC Address n ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ |N| Reserved | EID mask-len | EID-Prefix-AFI |
Rec +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\ | EID-Prefix ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Map-Reply Record ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ xTR-ID +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Map-Request with N-bit and xTR-ID
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The meaning of the fields is exactly the same as defined in
[I-D.ietf-lisp-rfc6833bis]. The only addition is a flag bit in the
EID-Record field. The meaning of this flag bit is as follows:
Notification-Requested bit (N-bit): the first bit in the EID-
Record section of a Map-Request message. The N-bit of an EID-
record is set to 1 to specify that the xTR wants to be notified of
updates for that mapping record.
The PubSub functionality requires to include an xTR-ID in the Map-
Request. This is done by setting the xTR-ID bit (I-bit) defined in
[I-D.ietf-lisp-rfc6833bis]. When the I-bit of a Map-Request message
is set, a 128-bit xTR-ID field is appended to the end of the Map-
Request, immediately following the last EID-Record (or the Map-Reply
Record, if present). The xTR-ID field uniquely identifies each xTR
of a given LISP deployment. Provisioning of unique xTR-IDs is out of
the scope of this document.
5. Mapping Request Subscribe Procedures
The xTR subscribes for RLOC-set changes for a given EID-prefix by
sending a Map-Request to the Mapping System with the N-bit set on the
EID-Record. The xTR builds a Map-Request according to [RFC6830] but
also does the following:
(1) The xTR MUST set the I-bit of the Map-Request message to 1, to
specify the presence of an xTR-ID field that uniquely identifies
the xTR.
(2) The xTR MUST set the N-bit to 1 for each EID-Record to which the
xTR wants to subscribe.
The Map-Request is forwarded to the appropriate Map-Server through
the Mapping System. This document does not assume that a Map-Server
is pre-assigned to handle the subscription state for a given xTR.
The Map-Server that receives the Map-Request will be the Map-Server
responsible to notify that specific xTR about future mapping changes
for the subscribed mapping records.
Upon reception of the Map-Request, the Map-Server processes it as
described in [RFC6830]. Upon processing, for each EID-Record that
has the N-bit set to 1, the Map-Server proceeds adding the xTR-ID
contained in the Map-Request to the list of xTR that have requested
to be subscribed to that mapping record.
If the xTR-ID is added to the list, the Map-Server MUST send a Map-
Notify message back to the xTR to acknowledge the successful
subscription. The Map-Server MUST follow the specification in
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Section 6.1.7 of [RFC6830] to build the Map-Notify with the following
considerations.
(1) The Map-Server MUST use the nonce from the Map-Request as the
nonce for the Map-Notify.
(2) The Map-Server MUST use its security association with the xTR
(see Section 3) to compute the authentication data of the Map-
Notify.
(3) The Map-Server MUST send the Map-Notify to one of the ITR-RLOCs
received in the Map-Request.
When the xTR receives a Map-Notify with a nonce that matches one in
the list of outstanding Map-Request messages sent with an N-bit set,
it knows that the Map-Notify is to acknowledge a successful
subscription. The xTR processes this Map-Notify as described in
[RFC6830] with the following considerations. The xTR MUST use its
security association with the Map-Server (see Section 3) to validate
the authentication data on the Map-Notify. The xTR MUST use the Map-
Notify to populate its map-cache with the returned EID-prefix and
RLOC-set.
The subscription of an xTR-ID to the list of subscribers for the EID-
Record may fail for a number of reasons. For example, because of
local configuration policies (such as white/black lists of
subscribers), or because the Map-Server has exhausted the resources
to dedicate to the subscription of that EID-Record (e.g., the number
of subscribers excess the capacity of the Map-Server).
If the subscription fails, the Map-Server MUST send a Map-Reply to
the originator of the Map-Request, as described in [RFC6830]. This
is also the case when the Map-Server does not support PubSub
operation. The xTR processes the Map-Reply as specified in
[RFC6830].
If an xTR-ID is successfully added to the list of subscribers for an
EID-Record, the Map-Server MUST extract the ITR-RLOCs present in the
Map-Request, and store the association between the xTR-ID and those
RLOCs. Any already present state regarding ITR-RLOCs for the same
xTR-ID MUST be overwritten.
If the Map-Request only has one ITR-RLOC with AFI = 0 (i.e. Unknown
Address), the Map-Server MUST remove the subscription state for that
xTR-ID. In this case, the Map-Server MUST send the Map-Notify to the
source RLOC of the Map-Request. When the TTL for the EID-record
expires, the EID-prefix is removed from the Map-Server's subscription
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cache. On EID-Record removal, the Map-Server notifies the
subscribers via a Map-Notify with TTL equal 0.
6. Mapping Notification Publish Procedures
The publish procedure is implemented via Map-Notify messages that the
Map-Server sends to xTRs. The xTRs acknowledge the reception of Map-
Notifies via sending Map-Notify-Ack messages back to the Map-Server.
The complete mechanism works as follows.
When a mapping stored in a Map-Server is updated (e.g. via a Map-
Register from an ETR), the Map-Server MUST notify the subscribers of
that mapping via sending Map-Notify messages with the most updated
mapping information. The Map-Notify message sent to each of the
subscribers as a result of an update event MUST follow the exact
encoding and logic defined in [RFC6830] for Map-Notify, except for
the following:
(1) The Map-Notify MUST be sent to one of the ITR-RLOCs associated
with the xTR-ID of the subscriber.
(2) The nonce of the Map-Notify MUST be the one the subscriber sent
in the Map-Request. If the subscriber sent no Map-Request (e.g.
was subscribed via configuration at the Map-Server) the nonce
MUST be randomly generated by the Map-Server.
(3) The Map-Server MUST use its security association with the xTR to
compute the authentication data of the Map-Notify.
When the xTR receives a Map-Notify with a nonce sent previously in a
Map-Request, or with a nonce not present in any list of previously
sent nonces but with an EID not local to the xTR, the xTR knows that
the Map-Notify has been received to update an entry on its map-cache.
Processing of unsolicited Map-Notify messages MUST be explicitly
enabled via configuration at the xTR.
The xTR processes the received Map-Notify as specified in [RFC6830],
with the following considerations. The xTR MUST use its security
association with the Map-Server (see Section 3) to validate the
authentication data on the Map-Notify. The xTR MUST use the mapping
information carried in the Map-Notify to update its internal map-
cache. The xTR MUST acknowledge the Map-Notify by sending back a
Map-Notify-Ack (specified in [I-D.ietf-lisp-rfc6833bis]), with the
nonce from the Map-Notify, to the Map-Server. If after a
configurable timeout, the Map-Server has not received back the Map-
Notify-Ack, it CAN try to send the Map-Notify to a different ITR-RLOC
for that xTR-ID.
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7. Security Considerations
The way to provide a security association between the ITRs and the
Map-Servers must be evaluated according to the size of the
deployment. For small deployments, it is possible to have a shared
key (or set of keys) between the ITRs and the Map-Servers. For
larger and Internet-scale deployments, scalability is a concern and
further study is needed.
8. Acknowledgments
This work is partly funded by the ANR LISP-Lab project #ANR-
13-INFR-009 (https://lisplab.lip6.fr).
9. IANA Considerations
This document makes no request to IANA.
10. Normative References
[I-D.ietf-lisp-rfc6833bis]
Fuller, V., Farinacci, D., and A. Cabellos-Aparicio,
"Locator/ID Separation Protocol (LISP) Control-Plane",
draft-ietf-lisp-rfc6833bis-10 (work in progress), March
2018.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC6830] Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "The
Locator/ID Separation Protocol (LISP)", RFC 6830,
DOI 10.17487/RFC6830, January 2013,
<https://www.rfc-editor.org/info/rfc6830>.
Authors' Addresses
Alberto Rodriguez-Natal
Cisco Systems
170 Tasman Drive
San Jose, CA
USA
Email: natal@cisco.com
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Vina Ermagan
Cisco Systems
170 Tasman Drive
San Jose, CA
USA
Email: vermagan@cisco.com
Johnson Leong
Cisco Systems
170 Tasman Drive
San Jose, CA
USA
Email: joleong@cisco.com
Fabio Maino
Cisco Systems
170 Tasman Drive
San Jose, CA
USA
Email: fmaino@cisco.com
Albert Cabellos-Aparicio
Technical University of Catalonia
Barcelona
Spain
Email: acabello@ac.upc.edu
Sharon Barkai
Fermi Serverless
CA
USA
Email: sharon@fermicloud.io
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Dino Farinacci
lispers.net
San Jose, CA
USA
Email: farinacci@gmail.com
Mohamed Boucadair
Orange
Rennes 35000
France
Email: mohamed.boucadair@orange.com
Christian Jacquenet
Orange
Rennes 35000
France
Email: christian.jacquenet@orange.com
Stefano Secci
LIP6 UPMC
France
Email: stefano.secci@lip6.fr
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