One document matched: draft-wing-pcp-proposed-packet-format-00.txt
PCP Working Group D. Wing
Internet-Draft Cisco
Intended status: Informational October 6, 2010
Expires: April 9, 2011
Proposed PCP Packet Format
draft-wing-pcp-proposed-packet-format-00
Abstract
A proposed packet format for PCP.
This document is for discussion purposes. It is not intended to be
published as an RFC.
Status of this Memo
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Internet-Draft Proposed PCP Packet Format October 2010
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Request and Response Packet Format . . . . . . . . . . . . . . 3
2.1. Request . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.2. Response . . . . . . . . . . . . . . . . . . . . . . . . . 6
3. NAT-PMP Backwards Compatibility . . . . . . . . . . . . . . . . 6
4. Security Considerations . . . . . . . . . . . . . . . . . . . . 7
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
6. Normative References . . . . . . . . . . . . . . . . . . . . . 7
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 7
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1. Introduction
NAT-PMP [I-D.cheshire-nat-pmp] is a lightweight, UDP-based request/
response protocol that forms a good basis to obtain mappings from a
NAT. This document proposes a packet format, based on NAT-PMP, which
provides the necessary extensions and support for PCP.
This document is for discussion purposes. It is not intended to be
published as an RFC.
2. Request and Response Packet Format
The request and response packet formats take the same space and
layout. It is intended to be backwards compatible with NAT-PMP, so
that if a PCP message is sent to a NAT-PMP server it will be rejected
with an error code we can parse. The PCP request uses Version=1,
which if processed by a NAT-PMP server will cause a version conflict
(the NAT-PMP server will see this as NAT-PMP version 16) and an error
returned in the same place we're looking for it (last couple of bits
of the 4th byte).
2.1. Request
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Ver=1 |reserve| OpCode | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: :
: Internal IP address (32 or 128) :
: :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: :
: Requested external IP address (32 or 128) :
: :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Requested lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| internal port | requested external port |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: (optional) Informational Elements :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Request Packet Format
The Informational Elements (IE) allow extending PCP, without defining
a new PCP version and without consuming additional opcodes. They can
be used in requests and responses, and are defined in documents
specific to each IE. An IANA registry will be created for IEs. IEs
are useful in a request when additional information is being
specified in the request. Examples that have been discussed, which
might be standardized in the future, include mapping DSCP bits,
indicating which interface is requested for a mapping on a multi-
interface NAT (e.g., internal corporate network address versus an
Internet-facing address). IEs will use a Type-Length-Value format.
IEs that aren't understood by the server are ignored.
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the Opcode has the following format:
+-+-+-+-+-+-+-+-+
|P|0|0|I|E|proto|
+-+-+-+-+-+-+-+-+
P=Request=0, Response=1
two zero bits
I, Internal address: 0=IPv4, 1=IPv6
E, External address: 0=IPv4, 1=IPv6
proto: 1=UDP, 2=TCP, 0=all (used only for delete)
which yields the following values:
1 = NAT44 or IPv4 firewall, UDP
2 = NAT44 or IPv4 firewall, TCP
9 = NAT46, UDP
10 = NAT46, TCP
17 = NAT64, UDP
18 = NAT64, TCP
25 = IPv6 firewall, UDP
26 = IPv6 firewall, TCP
Figure 2: Opcode format
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2.2. Response
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Ver=1 |reserve| Opcode+128 | Reserved | Result Code |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Epoch |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: :
: Internal IP address (32 or 128) :
: :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: :
: Assigned external IP address (32 or 128) :
: :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Assigned lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| internal port | assigned external port |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: (optional) Informational Elements :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: Response Packet Format
3. NAT-PMP Backwards Compatibility
Because NAT-PMP and PCP share the same port, it is important that a
NAT-PMP client receive a NAT-PMP error message. This is done by
examining the version number of the incoming PCP message; if it is
zero, the message is from a NAT-PMP client. A valid NAT-PMP response
(rather than a PCP response) is necessary, shown below.
A server which supports both NAT-PMP and PCP would be able to process
both NAT-PMP and PCP requests normally, and (if necessary) proxy
between the protocols.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0 | OP = 128 + x | Result Code=1 (unsupp. vers.) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| 0 (96 bits) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: NAT-PMP response
4. Security Considerations
TBD.
5. IANA Considerations
TBD.
6. Normative References
[I-D.cheshire-nat-pmp]
Cheshire, S., "NAT Port Mapping Protocol (NAT-PMP)",
draft-cheshire-nat-pmp-03 (work in progress), April 2008.
Author's Address
Dan Wing
Cisco Systems, Inc.
170 West Tasman Drive
San Jose, California 95134
USA
Email: dwing@cisco.com
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