MS-originated SMRs
draft-rodrigueznatal-lisp-ms-smr-13
LISP Working Group A. Rodriguez-Natal
Internet-Draft Cisco Systems
Intended status: Informational A. Cabellos-Aparicio
Expires: 14 April 2022 Technical University of Catalonia
V. Ermagan
Google
F. Maino
Cisco Systems
S. Barkai
Nexar Inc.
11 October 2021
MS-originated SMRs
draft-rodrigueznatal-lisp-ms-smr-13
Abstract
This document extends [I-D.ietf-lisp-rfc6833bis] to allow Map Servers
to send SMR messages.
This extension is intended to be used in some SDN deployments that
use LISP as a southbound protocol with (P)ITRs that are compliant
with [I-D.ietf-lisp-rfc6833bis]. In this use-case mapping updates do
not come from ETRs, but rather from a centralized controller that
pushes the updates directly to the Mapping System. In such
deployments, Map Servers will benefit from having a mechanism to
inform directly (P)ITRs about updates in the mappings they are
serving. Although implementations of this extension exist, this
extension is deprecated by [I-D.ietf-lisp-pubsub] and it is being
documented for informational purposes. Newer implementations should
look into [I-D.ietf-lisp-pubsub] to support PubSub in LISP
deployments.
Status of This Memo
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This Internet-Draft will expire on 14 April 2022.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Map Server extension . . . . . . . . . . . . . . . . . . . . 3
3. Interoperability with legacy (P)ITRs . . . . . . . . . . . . 4
4. Deployment considerations . . . . . . . . . . . . . . . . . . 4
5. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
7. Security Considerations . . . . . . . . . . . . . . . . . . . 5
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
8.1. Normative References . . . . . . . . . . . . . . . . . . 5
8.2. Informative References . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
The Locator/ID Separation Protocol (LISP) [I-D.ietf-lisp-rfc6833bis]
splits current IP addresses in two different namespaces, Endpoint
Identifiers (EIDs) and Routing Locators (RLOCs). LISP uses a map-
and-encap approach that relies in two entities, the Mapping System
and the Tunnel Routers. The Tunnel Routers are deployed at LISP
sites edge points and perform encapsulation and decapsulation of LISP
data packets. The Mapping System is a distributed database that
stores and disseminates EID-RLOC bindings across different Map-
Servers. LISP Tunnel Routers keep a cache of EID-RLOC mappings
pulled from the Mapping System.
There are several ways to keep this cache updated as described in
[I-D.ietf-lisp-rfc6833bis]. Among them, the Solicit Map-Request
(SMR) message allows to explicitly signal (P)ITRs to let them know
that some of their cached mappings may be outdated. However, vanilla
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LISP as described in [I-D.ietf-lisp-rfc6833bis] only considers SMR
messages to be sent by an ETR. This document extends
[I-D.ietf-lisp-rfc6833bis] to cover the case where SMRs can be sent
also by a Map Server (MS).
This document introduces changes in the MS specification allowing
them to send SMR messages, however it does not require any
modification in the (P)ITRs. This document is backwards compatible
and enables upgraded MSs to interoperate via SMRs with legacy (P)ITRs
that only implement [I-D.ietf-lisp-rfc6833bis].
This document offers a basic form of Publish/Subscribe (PubSub)
compatible with legacy LISP devices. The LISP WG is currently
working on [I-D.ietf-lisp-pubsub] as the comprehensive mechanism to
enable PubSub in LISP which deprecates this document. Newer
implementations should look into [I-D.ietf-lisp-pubsub] to support
PubSub in LISP deployments.
1.1. 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 RFC 2119 [RFC2119].
2. Map Server extension
This document enables MS to generate and send SMR messages towards
(P)ITRs. SMRs originated in a MS follow the same format described in
[I-D.ietf-lisp-rfc6833bis]. Besides the fact that they are sent from
a MS, there is no difference between an SMR originated in an ETR and
one originated in a MS.
A MS supporting the extension described in this document is supposed
to keep track of the Map-Requests received for the mappings it is
serving. When receiving a Map-Request, the MS should extract the
source EID and ITR-RLOCs from the message and keep them associated
with the requested mapping. The MS is expected to keep this state
for a period equal to the TTL of the mapping. When the mapping
changes, the MS should build and send an SMR to the (P)ITR that
requested the mapping using the stored EID and ITR-RLOCs, as
described below.
When a MS generates an SMR, it uses as source-EID the EID-prefix it
wants the (P)ITR to send the SMR-invoked Map-Request for (i.e. the
EID of the mapping that changed). The EID included in the EID-record
field is the one belonging to the (P)ITR the MS sends the SMR towards
and that was extracted from the original Map-Request. The
destination locator is one of the ITR-RLOCs associated with the EID
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of the (P)ITR that were received in the Map-Request. As source
locator for the SMR message, the MS uses one of its available
locators. This has implications in the processing of the SMR at the
(P)ITR as described in Section 4
As specified in [I-D.ietf-lisp-rfc6833bis] and noted in Section 7,
SMRs MUST be rate-limited. It must be noted as well that, as
described in Section 3, a MS that sends an SMR may not necessarily
receive the SMR-invoked Map-Request that the (P)ITR generates as
response to the SMR.
3. Interoperability with legacy (P)ITRs
This document introduces no changes in the specification of (P)ITRs
and thus it is backwards compatible with legacy equipment only
compliant with [I-D.ietf-lisp-rfc6833bis]. However, since SMRs were
designed to be sent by ETRs, and legacy (P)ITRs expect to receive
SMRs only from ETRs, the implications of sending SMRs from a MS are
discussed in this section.
As indicated in Section 2, the MS generates the SMR message using one
of its locators as source locator. However, this locator will not be
present in the Locator-Set cached for that EID-prefix at the (P)ITR.
Following [I-D.ietf-lisp-rfc6833bis], upon receiving the SMR message,
the (P)ITR will check if the source locator is in the Locator-Set
cached for that EID-record. Since it is not, the (P)ITR will send
the SMR-invoked Map-Request always to the Mapping System and never to
the source locator of the SMR message. This means that a MS can not
force an SMR-invoked Map-Request to be sent directly towards itself.
However, it is possible that the Mapping System in use is
instantiated (even partially) by the MS originator of the SMR. In
that case, it may be that the SMR-invoked Map Request will eventually
reach the MS, either directly or after being internally forwarded
through the Mapping System.
4. Deployment considerations
The extension defined in this document may be useful in scenarios
where the MS wants to signal (P)ITRs about changes on mappings it is
serving. For instance, when the MS is keeping track of the (P)ITRs
that are requesting its mappings and wants to inform them
intermediately whenever a mapping is updated.
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SDN deployments that use LISP as a southbound protocol are
particularly suitable to take advantage of this extension. On the
SDN scenario, mapping updates will unlikely come from ETRs, but
rather from a centralized entity that pushes the updates directly to
the Mapping System. In such deployments, Map Servers will benefit
from having a mechanism to inform directly (P)ITRs about updates in
the mappings they are serving.
Due to scalability and security concerns, it is RECOMMENDED that this
extension is only applied in intra-domain scenarios where all LISP
devices are within a single administrative domain.
To limit the impact of the extension and to ease its integration with
the rest of LISP signaling and operation, it is RECOMMENDED that the
MS only sends SMR messages for those mappings it is proxy-replying
for.
5. Acknowledgments
The authors would like to thank Joel Halpern and Luigi Iannone for
their guidance regarding this document.
6. IANA Considerations
This memo includes no request to IANA.
7. Security Considerations
As described in [I-D.ietf-lisp-rfc6833bis], the SMR messages and the
SMR-invoked Map-Request MUST be rate-limited. This does not change
with the extension proposed in this document.
The (P)ITRs receiving SMRs from the MS will send Map-Request messages
to the Mapping System to retrieve authoritative mappings. It is
RECOMMENDED that the security mechanism described in
[I-D.ietf-lisp-sec] and [RFC8111] are in place to secure the mapping
retrieval and protect against unsolicited messages or hijacking
attacks.
8. References
8.1. Normative References
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[I-D.ietf-lisp-rfc6833bis]
Farinacci, D., Maino, F., Fuller, V., and A. Cabellos,
"Locator/ID Separation Protocol (LISP) Control-Plane",
Work in Progress, Internet-Draft, draft-ietf-lisp-
rfc6833bis-30, 18 November 2020,
<https://www.ietf.org/archive/id/draft-ietf-lisp-
rfc6833bis-30.txt>.
[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>.
[RFC8111] Fuller, V., Lewis, D., Ermagan, V., Jain, A., and A.
Smirnov, "Locator/ID Separation Protocol Delegated
Database Tree (LISP-DDT)", RFC 8111, DOI 10.17487/RFC8111,
May 2017, <https://www.rfc-editor.org/info/rfc8111>.
8.2. Informative References
[I-D.ietf-lisp-pubsub]
Rodriguez-Natal, A., Ermagan, V., Cabellos, A., Barkai,
S., and M. Boucadair, "Publish/Subscribe Functionality for
LISP", Work in Progress, Internet-Draft, draft-ietf-lisp-
pubsub-09, 28 June 2021, <https://www.ietf.org/archive/id/
draft-ietf-lisp-pubsub-09.txt>.
[I-D.ietf-lisp-sec]
Maino, F., Ermagan, V., Cabellos, A., and D. Saucez,
"LISP-Security (LISP-SEC)", Work in Progress, Internet-
Draft, draft-ietf-lisp-sec-23, 22 September 2021,
<https://www.ietf.org/archive/id/draft-ietf-lisp-sec-
23.txt>.
Authors' Addresses
Alberto Rodriguez-Natal
Cisco Systems
170 Tasman Drive
San Jose, CA
United States of America
Email: natal@cisco.com
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Albert Cabellos-Aparicio
Technical University of Catalonia
Barcelona
Spain
Email: acabello@ac.upc.edu
Vina Ermagan
Google
United States of America
Email: ermagan@gmail.com
Fabio Maino
Cisco Systems
170 Tasman Drive
San Jose, CA
United States of America
Email: fmaino@cisco.com
Sharon Barkai
Nexar Inc.
CA
United States of America
Email: sharon.barkai@getnexar.com
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