Internet DRAFT - draft-kompella-spring-dhcp
draft-kompella-spring-dhcp
Network Working Group K. Kompella
Internet-Draft R. Bonica
Intended status: Standards Track Juniper Networks
Expires: January 8, 2020 July 7, 2019
Using DHCP to Manage Node and Ring SID Assignment
draft-kompella-spring-dhcp-00
Abstract
Node and ring segment identifiers (SIDs) assignements in a particular
domain (such as an IGP area) must follow certain rules: they must be
allocated from a configured set of SID blocks; they must be unique;
and the values should be sticky, i.e., the same value(s) should be
assigned to a node should its assignment expire (as might happen if
the node resets). This memo suggests the use of the Dynamic Host
Configuration Protocol to handle such assignments.
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].
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on January 8, 2020.
Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Operational Requirements . . . . . . . . . . . . . . . . . . 2
3. Theory of Operation . . . . . . . . . . . . . . . . . . . . . 3
4. Security Considerations . . . . . . . . . . . . . . . . . . . 4
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
6.1. Normative References . . . . . . . . . . . . . . . . . . 4
6.2. Informative References . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
Fundamental to SPRING forwarding is the notion of Segment Identifiers
(SIDs) [RFC8402]. At a high level, there are two types of SIDs:
those that are locally assigned by the advertising node, such as
adjacency and binding SIDs; and those that are globally unique within
a given SPRING domain, such as node and ring SIDs. Node SIDs are
often manually configured on routers today; this is not only tedious,
but error-prone as well; the addition of ring SIDs which must be
managed per ring makes manual assignment even more fraught
([I-D.kompella-spring-rmr]).
This document describes the use of the Dynamic Host Configuration
Protocol (DHCP [RFC2132]) for managing global SID allocation. The
description is limited to the use of node and ring SIDs for MPLS
([I-D.ietf-spring-segment-routing-mpls]); other types of SID
allocation, such as for SRv6+ ([I-D.bonica-spring-srv6-plus]) will be
described in a future version.
2. Operational Requirements
Node SID assignments must satisfy the following properties:
A SID allocation is an index within a block. This block is
defined by a base value (SRGB) and a range; the SID value MUST
fall within the range.
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SID assignments MUST be unique. Duplicate assignments can have
serious forwarding consequences, such as loops and packet
misdelivery.
and should have the following properties:
Assignments SHOULD have a long lease time.
Assignments SHOULD be "sticky", i.e., a node re-requesting a
global SID of the same type that it had previously requested
SHOULD be assigned the same SID (if possible).
An expired SID SHOULD NOT be re-assigned to another node until
sufficient time has passed. This time SHOULD be configurable on
the DHCP server.
3. Theory of Operation
A DHCP server to be used for global SID assignment SHOULD be told the
following:
The type of SID (node, anycast, ring, ...)
The block or set of blocks for each type: SRGB and range.
The default lease time and hold time (before re-assigning a SID to
a different node).
The DHCP server need know nothing about SID semantics; the only thing
it needs to know is that ring SIDs are allocated in pairs, and all
other SIDs are allocated singly.
A node taking part in a SPRING network MAY be configured to use DHCP
to get node SIDs. This configuration should say whether to use DHCP
for its loopback address, for anycast SIDs and/or for ring SIDs.
A node configured to use DHCP to obtain a SID for its loopback and/or
any other prefix sends a request to the DHCP server including the
following information:
the type of SID
the prefix
A node that participates in an RMR ring and is configured to use DHCP
to obtain a pair of ring SIDs sends, once ring identification is
complete ([I-D.ietf-mpls-rmr]), a DHCP request including:
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the type of SID (ring SID)
the ring ID
The DHCP server replies to such requests by:
1. looking up the type of SID request;
2. checking if it has previously allocated a SID for this node and
prefix (or pair of SIDs for this node and ring ID);
3. if so, checking if the same SID (or pair of SIDs) is available;
if so, allocating that SID (or pair of SIDs) and returning.
4. Otherwise, allocating a new SID/pair of SIDs, noting this in its
database, and returning.
4. Security Considerations
DHCP is a very widely used protocol, and thus ensuring its continuing
secure and robust operation is vital. When the requirements of DHCP
in this context are better understood, this section will be filled
out.
5. IANA Considerations
Should this document be deemed useful, relevant IANA code points
would be requested.
6. References
6.1. Normative References
[I-D.ietf-mpls-rmr]
Kompella, K. and L. Contreras, "Resilient MPLS Rings",
draft-ietf-mpls-rmr-11 (work in progress), June 2019.
[I-D.ietf-spring-segment-routing-mpls]
Bashandy, A., Filsfils, C., Previdi, S., Decraene, B.,
Litkowski, S., and R. Shakir, "Segment Routing with MPLS
data plane", draft-ietf-spring-segment-routing-mpls-22
(work in progress), May 2019.
[I-D.kompella-spring-rmr]
Kompella, K., Deshmukh, A., and R. Torvi, "Resilient MPLS
Rings", draft-kompella-spring-rmr-00 (work in progress),
October 2018.
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[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>.
[RFC2132] Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor
Extensions", RFC 2132, DOI 10.17487/RFC2132, March 1997,
<https://www.rfc-editor.org/info/rfc2132>.
[RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
July 2018, <https://www.rfc-editor.org/info/rfc8402>.
6.2. Informative References
[I-D.bonica-spring-srv6-plus]
Bonica, R., Hegde, S., Kamite, Y., Alston, A., Henriques,
D., Halpern, J., and J. Linkova, "IPv6 Support for Segment
Routing: SRv6+", draft-bonica-spring-srv6-plus-03 (work in
progress), July 2019.
Authors' Addresses
Kireeti Kompella
Juniper Networks
1194 N. Mathilda Ave.
Sunnyvale, CA 94089
US
Email: kireeti.kompella@gmail.com
Ron Bonica
Juniper Networks
1194 N. Mathilda Ave.
Sunnyvale, CA 94089
US
Email: rbonica@juniper.net
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