Re: terminology (was: [16NG] Re: Last Call: draft-ietf-16ng-ipv6-over-ipv6cs)

Alex,

On 3/14/07 12:52 PM, "ext Alexandru Petrescu" <alexandru.petrescu@gmail.com>
wrote:

> Basavaraj Patil wrote:
>> 
>> On 3/14/07 12:04 PM, "ext James Carlson" <james.d.carlson@sun.com> wrote:
>> 
>>> Basavaraj Patil writes:
>>>> On 3/14/07 11:14 AM, "ext James Carlson" <james.d.carlson@sun.com> wrote:
>>>>> That issue is the exclusive use of IPv4 or IPv6 on Packet CS.  Why
>>>>> must it be exclusive?  The first four bits of the datagram tell you
>>>>> conclusively whether you're looking at IPv4 or IPv6, so why is strict
>>>>> segregation needed?
>>>> Not sure I understand what you mean by segregation... The same packet CS is
>>>> used for IPv4 as well as IPv6. There are no separate CS' per se.
>>>> The classification rules segregate an IPv4 packet from an IPv6 packet and
>>>> map it to the appropriate transport connection (CID) over the air
>>>> interface.
>>> That's not what I meant.
>>> 
>>> A single CID using just Packet CS could handle both IPv4 and IPv6
>>> traffic on the same interface.
>>> 
>>> You'd do this (on the receiver side) by looking at the first four bits
>>> of the inbound IP datagram.  They're '4', then it's IPv4.  If they're
>>> '6', then it's IPv6.  If it's anything else, discard.
>> 
>> Okay.. I see what you mean. I don't really have a comment about it.
> 
> Sorry for interfering here, sorry if I misunderstand anything.  Just one
> thought: terminology.
> 
> I think this boils down again to that terminology issue, that longer
> IEEE definition of what IETF calls "IPv6 CS".  By IEEE, it's actually
> "the IPv6 classifiers of the IP specific part of Packet CS".  So this
> document could be named "Prefix Assignment, Router Discovery, MTU and
> IPv6 Addressing for the IPv6 classifiers of the IP specific part of the
> Packet CS".  Which doesn't make much sense, because one wouldn't run
> Router Discovery over some classifiers.
> 
> We need that "IPv6 _over_ foo" tint.  And these IPv6 classifiers aren't
> _a_ foo.
> 
> Throughout the IEEE spec these IPv6 specific classifiers are mainly used
> for PHS (packet header suppression) and recomposing.  This is the most
> use of these IPv6 classifiers.
To quite the IEEE spec:
" A  classification rule is a set of matching criteria applied to each
packet entering the IEEE std  802.16 network. It consists of some
protocol-specific packet matching criteria (destination IP address, for
example), a classification rule priority, and a reference to the CID.
"

PHS is optional. A packet after classification may be mapped to a specific
PHS rule. If there is a PHS rule, there is the 8 bit PHSI (index) in the MAC
SDU. 

So I do not think that classifiers exist solely for the purpose of PHS.

> 
> In this context I'd comment on why IEEE is using this PHS, and not ROHC,
> an IETF standardized protocol, for various link-layers.  Or maybe any
> other IETF-specified header compression (for ppp and for others).

I think we are digressing when we start to discuss why IEEE chose PHS and
not ROHC or something else. I don't see the relevance of discussing IEEE
design decisions in the IETF.

-Raj

> 
> I mean what if a Station uses ROHC and the link-layer does PHS - will
> this result in inefficiency.
> 
> Just a thought on terminology...
> 
> Alex
> 
> 
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