Subject: IP/CRTP compression protocol numbers

From: Karl Fox <[email-masked]>
Date: Thu, 11 Dec 1997 13:41:25 -0800

At the Tuesday meeting in Washington, D.C. the (slim) consensus of the
group was that the 16-bit protocol numbers you had requested should be
moved from the 0x2000 range to the 0x8000 range.  Somebody at the
meeting mentioned that they thought some document somewhere reserved
ranges by function, so I went searching and found little or nothing.
The one thing I found that seems relevant is that many CCP compression
algorithms will only compress protocols in the range 0x0001-0x3FFF.

Should messages in these protocols be CCP compressed?

    Protocol Numbers for IP/CRTP Header Compression

    Name			Old #	New #
    FULL_HEADER			0061	0061
    COMPRESSED_TCP		0063	0063
    COMPRESSED_NON_TCP		0065	0065
    COMPRESSED_UDP_8		0067	0067
    COMPRESSED_RTP_8		0069	0069

    COMPRESSED_TCP_NODELTA	2063	8063
    CONTEXT_STATE		2065	8065
    COMPRESSED_UDP_16		2067	8067
    COMPRESSED_RTP_16		2069	8069

-- 
Karl Fox, servant of God, employee of Ascend Communications
655 Metro Place South, Suite 370, Dublin, Ohio  43017   +1 614 760 4041

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From: Carsten Bormann <[email-masked]>
Date: Fri, 12 Dec 1997 02:21:48 +0100 (MET)

> Should messages in these protocols be CCP compressed?

Yes, definitely.

>     COMPRESSED_TCP_NODELTA	2063	8063

This is a form of semi-header-compressed TCP.

>     CONTEXT_STATE		2065	8065

I wouldn't care much about this -- it's a status message, but there is
little reason why it should NOT be compressed.

>     COMPRESSED_RTP_16		2069	8069

These are just the same as the 8-bit versions, except that they use
16-bit IDs for the compression context.  

While there is some reason to believe that RTP packets will often
already have been application-compressed, this is true of both RTP_8
and RTP_16.

So, it seems we should stick to 20xx.

BTW, the document that assigns a meaning to 80xx is
ftp://ftp.isi.edu/in-notes/iana/assignments/ppp-numbers.

Somebody should update the guidance in there.

Gruesse, Carsten

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From: Stephen Casner <[email-masked]>
Date: Thu, 11 Dec 1997 21:36:16 -0800 (PST)

> > algorithms will only compress protocols in the range 0x0001-0x3FFF.
...
> So, it seems we should stick to 20xx.

Karl, I am about to resubmit draft-engan-ip-compress-01.txt with the
selected PPP assignments inserted.

Shall I use 20xx rather than 80xx, based on the above discussion?

							-- Steve

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From: Karl Fox <[email-masked]>
Date: Fri, 12 Dec 1997 05:15:31 -0800

> Shall I use 20xx rather than 80xx, based on the above discussion?

I would say yes, since we now have a solid reason to prefer 20xx over
80xx.