Re: Payload Type number assignments

[Paul Tsuchiya <[e-mail]>]

>  
>  The IANA has assigned a couple of new IP Protocol values for use in the
>  SIP Payload Type field to identify the SIP Source Route header and
>  the SIP Fragment header.  There was also a previously assigned IP Protocol
>  value for IPAE, which has been renamed "SIP", which is used in an IP packet
>  to identify an encapsulated SIP packet (it may also be used in a SIP Payload
>  Type field, for SIP encapsulated in SIP).  The numbers are as follows:
>  
>          41  SIP
>          43  SIP Source Route
>          44  SIP Fragment
>  

Given that the SIP header itself is distinguishable from Pip
and everything else by virtue of the first nibble, is it
necessary to have a separate number for each of SIP, Pip, CLNP,
and IPv7 encapsulated over IP?  We are all going to have to do
this as part of transition, so why not just make value
41 = "IP", and let the version number distinguish......

I know it involves some extra work to examine both the
protocol and version number fields instead of just the
protocol field, but perhaps there is the possibility
of someday running out of protocol numbers in IP.....

Actually, I can go either way.  I'm just wondering if I
need to ask Jon for the analogous number for Pip.....

PX