Subject: RE: LINK update

From: Phillip Neumiller <[email-masked]>
Date: Thu, 5 Jul 2001 18:58:33 -0400

I suppose we could start with the TOS field.  To the best of my
knowledge, this is ignored by all MACs (at least standards ones).

When sending a packet from the IP layer to the MAC:

The MAC/LLC(link) should "respect" the TOS field in the IP header.
To do this, the MAC/LLC(link) SHOULD be passed the IP packet and
the TOS value (parsed out by the IP layer and handed to the MAC
directly) upon a message send.  A "well behaved MAC" should then
treat the packet appropriately based on its interpretation of the
TOS value AND it should place the TOS value into the MAC frame 
when it drops the frame on the PHY.

In the opposite direction, when receiving IP packets from the link,
the TOS field is part of the MAC frame so that inbound packet can
be handled appropriately (for example if there is MAC layer
forwarding, or different IP input queues for different TOSs).

With some time, I am sure we could find "OTHER" useful things to
pass/retrieve between say diffserv/intserv/RSVP/COPS/etc and the 
link layer.

Thanks,

Phil Neumiller

> -----Original Message-----
> From: Phil Karn [mailto:[email-masked]]
> Sent: Thursday, July 05, 2001 4:21 PM
> To: [email-masked]
> Cc: [email-masked]
> Subject: Re: LINK update
> 
> 
> >and there are a few competing ideas.  However, one thing seems to be
> >missing to me, a "standardized method" to tie IP layer QoS to MAC
> >protocol layer (or link layer) QoS mechanisms.  I feel that this
> >linkage is critical and the ability to support a variety of radio
> >technologies with the top of the MAC sublayer or Link layer 
> hiding the
> >specifics of the MAC's own QoS techniques.  I realize
> 
> I absolutely agree, and there is text in the current draft that
> encourages subnetwork designers to make these hooks available to
> IP. But I'm not sure they're amenable to standardization, because
> every subnetwork is different. Also, LINK is meant to reflect best
> current practice, not plow new ground.
> 
> Given that, is there any text you'd like to suggest be added?
> 
> Phil
>

---

From: Phil Karn <[email-masked]>
Date: Thu, 5 Jul 2001 16:37:24 -0700 (PDT)

I'm not sure I'd recommend such a direct connection from IP to the
MAC/LLC. In ISO-ese, this is the job of the Subnetwork Dependent
Convergence Function that sits between the two. It maps IP concepts like
the TOS field into whatever features the MAC/LLC layer happens to
have, and vice versa. Since I see the SNDCF as somewhat outside the
scope of the LINK document, I think it only necessary to recommend that
the subnetwork designers make the hooks available so that some SNDCF
could be implemented to use it.

Phil