All,
Jim and I have updated the Automatic Prefix Delegation draft
to take into account comments and suggestions made in the last few
months. I submitted it to the I-D editor last week, but have not
seen it posted yet so it is attached. Comments and suggestions are
always welcome.
Brian
Individual Submission B. Haberman
Internet Draft J. Martin
draft-haberman-ipngwg-auto-prefix-02.txt
February 2002
Expires August 2002
Automatic Prefix Delegation Protocol for
Internet Protocol Version 6 (IPv6)
<draft-haberman-ipngwg-auto-prefix-02.txt>
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts. Internet-Drafts are draft documents valid for a maximum of
six months and may be updated, replaced, or obsoleted by other
documents at any time. It is inappropriate to use Internet- Drafts
as reference material or to cite them other than as "work in
progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
Abstract
The expansion of the IP address space provided by IPv6 makes it both
possible and reasonable to allocate entire subnets to environments
that had been previously limited to a few individual IP addresses.
Other protocols such as Neighbor Discovery and Stateless Address
Autoconfiguration allow hosts within those subnets to be
automatically configured. The router between this subnet and the
upstream world requires just one more piece to make this process
automatic, a network prefix.
This document describes a mechanism for the automated delegation of
an IPv6 network prefix. It allows routers to request either a
specific prefix or any prefix. Upon authorizing the request the
delegating router then returns a prefix and a lifetime for the use
of the prefix. Optionally, the delegating and requesting routers
can exchange routing protocol information.
Haberman, Martin 1
Internet Draft <Automatic Prefix Delegation> February 2002
1. Introduction
This specification defines the Prefix Delegation (PD) protocol for
Internet Protocol Version 6 (IPv6). Routers use Prefix Delegation to
request a network prefix for use on directly attached networks.
Upon receipt of the request, the delegating router may authenticate
the request, and will establish if the requested prefix size is
acceptable. The delegating router then specifies the prefix for use
and the length of time for which that prefix is delegated.
The Prefix Delegation protocol supports extensible options. These
options may be used to negotiate additional operational parameters,
such as routing protocol information.
2. Terminology
2.1 General
This document uses the terminology defined in [RFC 2460] and [RFC
2461] and in addition:
- Requesting Router - The router that is requesting that a
prefix be assigned
- Delegating Router - The router that is responding to the
prefix request
2.2 Requirements
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].
3. Scope of Work
This proposal is meant to give a singly homed leaf router the
ability to obtain an IPv6 prefix that can be used within its leaf
network. Future revisions of this document may support a more
generic approach to dynamic prefix delegation.
It is also assumed that the delegating server/router shares a
network connection with the requesting router. Future revisions may
remove this restriction and allow for either multi-hop messages or a
relay function.
4. Protocol Overview
Haberman, Martin 2
Internet Draft <Automatic Prefix Delegation> February 2002
The Prefix Delegation protocol defines two new ICMP message types,
the Prefix Request and the Prefix Delegation. The Prefix Request is
used by the Requesting Router to communicate requests to the
Delegating Router. Conversely, the Prefix Delegation is used by the
Delegating Router to communicate prefix and error information with
the Requesting Router.
4.1 Delegator Query
The Requesting Router begins the Prefix Delegation process by
sending a Prefix Request message of type [DELEGATOR QUERY] to the
All-Routers link-local multicast address (FF02::2).
Upon receipt of the Delegator query, a Delegating Router determines
if it is configured to provide prefixes of the specified scope. If
so, it unicasts a Prefix Delegation of type [PREFIX DELEGATOR] to
the Requestor. If not, the message is silently discarded.
After sending the query, the Requestor waits for Query Interval
(Default: 5) seconds for one or more Delegating Routers to respond.
If there is no response, the Delegator Query is sent again up to Max
Query times (Default: 3). If no response is received, there are no
Prefix Delegation services available, and Prefix Delegation has
failed.
If more than one response is received to the query within the Query
Interval, the response with the numerically highest source IP
address is used.
4.2 Initial Request
Once a Delegating Router is chosen, the Requestor sends a Prefix
Request message of type Initial Request to the unicast IP address of
the chosen Delegating Router.
The Requestor may or may not have a Security Association with the
Delegating Router, however if Authentication is required and no SA
is present, the Delegator will reject the request with an error
response indicating that Authentication is required. The Requestor
then builds a Security Association with the Delegator and sends
another Initial Request including the SA information.
If no response is heard within Request Timeout seconds (Default: 5),
the Initial Request should be sent again, up to Max Initial Request
(Default: 3) tries. If no response is heard, a Delegator Query is
sent and the process restarted. If this cycle is repeated Max
Delegation Attempts times (Default: 3), Prefix Delegation has
failed.
4.3 Message Security
Haberman, Martin 3
Internet Draft <Automatic Prefix Delegation> February 2002
Upon receipt of the Prefix Request of any type, the Delegating
Router establishes if there is a need for Authentication and/or
Encryption, based upon local policy. If either is required and none
is provided, the Delegator will return a Prefix Delegation message,
with a code of Authentication Required.
The building of a Security Association between the Delegator and the
Requestor is based on the Authentication and/or Encapsulated
Security Payload extension headers defined in [RFC 2402] and [RFC
2406].
4.4 Prefix Delegation
After the request is verified to be acceptable, the Delegating
Router allocates the requested prefix size from its pool of
available addresses. The creation and management of that pool is
beyond the scope of this document, but it can be supposed that
minimalistically a Delegating Router will be statically configured
with a fixed pool. If no acceptable prefix is available, a Prefix
Delegation message with a code of Prefix Unavailable is returned.
The Delegating Router then sends a Prefix Delegation message to the
Requesting Router containing a code of Prefix Delegation and all of
the prefix information. The Requesting Router then activates the
prefix on its interface of choice.
4.5 Prefix Refresh
All Prefix Delegations have a lifetime that MUST follow the rules
defined in Section 4.6.2 of [RFC 2461]. Upon receiving a Prefix
Delegation, the requesting router initiates a timer such that before
the lifetime expires, the Requesting Router sends a Prefix Request
with code=REFRESH directly to the Delegating router.
If the Requestor receives no response within [RENEWAL TIMEOUT]
seconds (Default: 5), the Renewal Request should be sent again, up
to [MAX RENEWAL REQUEST] (Default: 3) tries. If no response is
heard the previously allocated prefix is not renewed.
A Requesting Router receiving the Prefix Unavailable code, or no
response at all, has not had the prefix renewed. It will expire at
the end of the initial lifetime. To acquire a new prefix, the
Requesting Router must begin anew as described in Section 4.1.
4.6 Prefix Return
If the Requesting Router no longer requires the use of a prefix, it
can return that prefix to the control of the Delegating Router
through the use of the Prefix Return code in a Prefix Request. The
requesting router sends a Prefix Request directly to the Delegating
Router.
Haberman, Martin 4
Internet Draft <Automatic Prefix Delegation> February 2002
Upon receipt and verification (if needed) of this message, the
Delegating Router returns the prefix to the pool and issues a Prefix
Delegation with a code of Prefix Returned.
5. Messages
All messages have the following general 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Code | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ Message Body +
| |
The following sections describe the specific messages and options
used in delegating IPv6 prefixes.
5.1 Prefix Request Message
The Prefix Request Message is sent to request, renew, or release a
prefix.
IP Fields
Source Address
An IP address assigned to the sending interface.
Destination Address
The All-Routers link-local multicast address (FF02::2)for
Delegator Query messages. All other Prefix Request messages
should be sent to a unicast address of the Delegating Router.
Authentication Header
If a Security Association for the IP Authentication Header
exists between the sender and the destination address, then
the sender SHOULD include this header. No such header is
required for the initial prefix request that is multicast,
but may be required for further progress.
ICMP Fields
Type
XXX (Where XXX is assigned by IANA)
Haberman, Martin 5
Internet Draft <Automatic Prefix Delegation> February 2002
Code
They Type of Request Code:
Delegator Query (0)
The Delegator Query is used by the Requestor to
identify potential Delegating Routers. It is sent to
the All-Routers link-local multicast address with no
Authentication Header.
Initial Request (1)
The Initial Request is used to initiate the request
process. It is sent to the unicast IP address of the
Delegating Router, and may carry an Authentication
Header. Unused fields MUST be set to zero. An Initial
Request code MAY contain a Prefix Option.
Renewal Request (2)
The Renewal Request is used to renew a prefix that has
been previously allocated. It is sent to a unicast IP
address of the Delegating Router and may carry an
Authentication Header. A Renewal Request code MUST
contain at least one Prefix Option.
Prefix Return (3)
The Prefix Return is used to return an unused prefix,
or portion of a prefix to the control of the Delegating
Router. It is sent to a unicast IP address of the
Delegating Router and may carry an Authentication
Header. A Prefix Return code MUST contain at least one
Prefix Option.
Checksum
The ICMP checksum as defined in [RFC 2463].
5.2 Prefix Delegation Message Format
The Prefix Delegation Messages are sent to provide the addresses of
available Prefix Delegators, to provide prefix data, and for error
returns.
IP Fields
Source Address
An IP address assigned to the sending interface.
Destination Address
The IP address of the Requestor as specified by the IP Source
Address in the Prefix Request message.
Authentication Header
Haberman, Martin 6
Internet Draft <Automatic Prefix Delegation> February 2002
If a Security Association for the IP Authentication Header
exists between the sender and the destination address, then
the sender SHOULD include this header.
ICMP Fields
Type
XXX+1 (Where XXX+1 is assigned by IANA)
Code
The Type of Response Code:
Prefix Delegator (0)
The Prefix Delegator is used by the Delegator to inform
the Requestor that it is available to provide prefixes
of the desired type. It is sent to the unicast IP
address in the Source Address portion of the Prefix
Request packet. Unused fields MUST be set to zero.
Authentication Required (1)
The Authentication Required message indicates to the
Requestor that a Security Association must be
established before a prefix can be delegated. It is
sent to the unicast IP address in the Source Address
portion of the Prefix Request packet. Unused fields
MUST be set to zero.
Authorization Failed (2)
The Authorization Failed message indicates to the
Requestor that either it is not authorized to request a
prefix, or that the prefix requested fell outside of
local policy. It is sent to the unicast IP address in
the Source Address portion of the Prefix Request
packet. Unused fields MUST be set to zero.
Prefix Unavailable (3)
The Prefix Unavailable indicates that the Prefix
Request was acceptable, but the Delegator does not have
sufficient available address space to fulfill the
request. It is sent to the unicast IP address in the
Source Address portion of the Prefix Request packet.
Unused fields MUST be set to zero.
Prefix Delegated (4)
The Prefix Delegated message actually provides the
prefix information that the Requestor has requested. It
is sent to the unicast IP address in the Source Address
portion of the Prefix Request packet. For this message,
a Prefix Option MUST be included.
Prefix Returned (5)
Haberman, Martin 7
Internet Draft <Automatic Prefix Delegation> February 2002
The Prefix Return is used to confirm the return of a
prefix. It is sent to the unicast IP address in the
Source Address portion of the Prefix Request packet.
For this message, the Prefix Option MUST be included.
Checksum
The ICMP checksum.
5.3 Prefix Option
The Subnet Prefix Option is used to relay prefix information between
Requestors and Delegators. It has the following 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Prefix Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Prefix +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Prefix Option Fields
Type = 0x01
This field identifies the presence of a subnet prefix. This
option MUST follow either a Prefix Request header or a Prefix
Delegation header.
Length
The length of the prefix contained in the option.
Reserved
This field is unused. It MUST be initialized to zero by the
sender and MUST be ignored by the receiver.
Prefix Lifetime
The lifetime of the prefix contained in the option.
IPv6 Prefix
The Prefix field is used to carry a subnet prefix. The host
portion of the IP address MUST be padded with zeros.
Haberman, Martin 8
Internet Draft <Automatic Prefix Delegation> February 2002
6. Security Considerations
The ability to automate the delegation of prefixes opens several
security vulnerabilities. Rogue delegators can issue bogus prefixes
to requestors. This may cause denial of service due to
unreachability. Rogue requestors may consume valuable resources
from legitimate delegators, thus denying others the use of the
prefixes. For these reasons, the use of IPSec-based Authentication
and/or Encryption is suggested.
7. To Do's
- Additional security discussion
- Relay functionality
- Routing capabilities option
8. Acknowledgements
We would like to acknowledge and thank Jun-ichiro itojun Hagino,
Dave Thaler, Yamasaki Toshi, Ole Troan, and Kazuaki Tsuchiya for
their feedback and suggestions on this document.
9. References
[RFC 2460] S. Deering and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, December 1998.
[RFC 2461] T. Narten, E. Nordmark, and W. Simpson, "Neighbor
Discovery for IP Version 6 (IPv6)", RFC 2461, December
1998.
[RFC 2119] S. Bradner, "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119, BCP 14, March 1997.
[RFC 2463] A. Conta and S. Deering, "Internet Control Message
Protocol (ICMPv6) for the Internet Protocol Version 6
(IPv6) Specification", RFC 2463, December 1998.
Authors' Addresses
Brian Haberman
[EMAIL PROTECTED]
Jim Martin
[EMAIL PROTECTED]
Haberman, Martin 9
