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Internet Engineering Task Force M. Sustrik, Ed.
Internet-Draft
Intended status: Informational March 24, 2014
Expires: September 25, 2014
UDP Mapping for Scalability Protocols
sp-udp-mapping-01
Abstract
This document defines the UDP mapping for scalability protocols.
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
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
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."
This Internet-Draft will expire on September 25, 2014.
Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Sustrik Expires September 25, 2014 [Page 1]
Internet-Draft UDP mapping for SPs March 2014
1. Underlying protocol
This mapping should be layered directly on the top of UDP.
There's no fixed UDP port to use for the communication. Instead,
port numbers are assigned to individual services by the user.
2. Message delimitation
Each UDP packet maps to exacrly one SP message.
There is no way to split one SP message into mutliple UDP packets and
therefore SP messages larger than existing path MTU will be dropped
silently.
There is also no way to pack multiple SP messages into a single UDP
packet.
3. Packet layout
Each packet consists of an 8-byte header followed by the opaque
message payload:
+------+------+------+--------------+------------+----------------+----------
| 0x00 | 0x53 | 0x50 | version (8b) | type (16b) | reserved (16b) | payload
+------+------+------+--------------+------------+----------------+----------
First four bytes of the protocol header are used to make sure that
the peer's protocol is compatible with the protocol used by the local
endpoint. Keep in mind that this protocol is designed to run on an
arbitrary UDP port, thus the standard compatibility check -- if it
runs on port X and protocol Y is assigned to X by IANA, it speaks
protocol Y -- does not apply. We have to use an alternative
mechanism.
First four bytes of the protocol header MUST be set to 0x00, 0x53,
0x50 and 0x00 respectively. If the protocol header received from the
peer differs, the UDP packets MUST be ignored.
The fact that the first byte of the protocol header is binary zero
eliminates any text-based protocols that were accidentally connected
to the endpiont. Subsequent two bytes make the check even more
rigorous. At the same time they can be used as a debugging hint to
indicate that the connection is supposed to use one of the
scalability protocols -- ASCII representation of these bytes is 'SP'
that can be easily spotted in when capturing the network traffic.
Finally, the fourth byte rules out any incompatible versions of this
protocol.
Sustrik Expires September 25, 2014 [Page 2]
Internet-Draft UDP mapping for SPs March 2014
Fifth and sixth bytes of the header form a 16-bit unsigned integer in
network byte order representing the type of SP endpoint on the layer
above. The value SHOULD NOT be interpreted by the mapping, rather
the interpretation should be delegated to the scalability protocol
above the mapping. For informational purposes, it should be noted
that the field encodes information such as SP protocol ID, protocol
version and the role of endpoint within the protocol. Individual
values are assigned by IANA.
Finally, the last two bytes of the protocol header are reserved for
future use and must be set to binary zeroes. If the protocol header
from the peer contains anything else than zeroes in this field, the
implementation MUST ignore the UDP packet.
Packet header is followed by opaque message payload which spans all
the way to the end of the packet.
Author's Address
Martin Sustrik (editor)
Email: sustrik@250bpm.com
Sustrik Expires September 25, 2014 [Page 3]
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