[Sis-ipo] Another question concerning Encapsulating IP

[Greg Kazz]

To: CCSDS SIS-IPO WG members,

Following up on this earlier email (sent on Aug. 14), another 
question has come up which we will also address at the Fall SIS-IPO 
meeting in Berlin.

Background: This RID (viewgraphs attached) against IP over CCSDS and 
Space Link Identifiers is pushing for all IP data to be identified in 
the protocol shim byte (including IPv4, IPv6 and all IP header 
compression types) which comes directly after the CCSDS Encapsulation 
header. In that spirit, the Encapsulation Protocol IDs (PIDs) already 
identified in Space Link Identifiers for IPv4, IPv6 would be 
eliminated, in favor of this homogeneous approach. Other non-IP 
protocols such as SCP-NP or CFDP would continue to be identified by 
their corresponding 3-bit PID. So this RID advocates a "CCSDS iMPE or 
CCSDS internet multi-protocol extension shim only.

The Question is:  Should the PIDs for IPv4 and IPv6 continue to be 
defined as 3-bit PIDs or should they be incorporated by this proposed 
protocol shim ? The concern is to reduce the number of alternative 
ways of identifying IP over the CCSDS space link.

Your responses to this question before the meeting are most welcome!

 From the previous message sent on Aug 14:

Attached is a set of viewgraphs for your consideration. They 
summarize the RID that has been written by the NASA Constellation 
Project against the IP over CCSDS Red book. (this RID was sent to you 
in a previous email).

It offers a solution to the NASA Constellation requirement to do IP 
header compression using RFC 2507 and 2508.

I believe it is a reasonable solution given that it does not impact 
the format of the CCSDS Encapsulation Packet, rather it adds a shim 
byte after the Encapsulation packet header (See page 6) but before 
the user data frame or packet.

This RID wil be discussed at the IP over CCSDS meeting in Berlin.

Questions for all:

1. This RID which advocates the use of a shim byte has provision for 
additional bytes so that other protocol/packet formats can be added 
at a later date if needed. Does anyone foresee such a need?

2. If this RID is approved, in which CCSDS book should this 
information go?  A new and separate blue book that addresses this 
Shim protocol? Perhaps if protocols other than IP need to be 
addressed. Or at this time, since we know this shim involves IP 
header compression, it only belongs in the IP over CCSDS magenta 
book.  You thoughts?

best regards,

Greg Kazz
Chairman IP over CCSDS WG
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