Subject: [Diffserv] Diff-Serv Router Policies on ACK packets

From: "Wenjia Fang" <[email-masked]>
Date: Mon, 22 Nov 1999 22:36:13 -0500

Hi,

I wonder what DiffServ WG has decided on router's policy
w.r.t to Acknowledgement packets, if any.   Will either 
PHBs treat ACK packets any different from data packets?
for example, never drop an ACK packet in the case of AF?

thanks,

Wenjia

_______________________________________________
diffserv mailing list
[email-masked]
http://www.ietf.org/mailman/listinfo/diffserv
Archive: http://www-nrg.ee.lbl.gov/diff-serv-arch/

---

From: Kathleen Nichols <[email-masked]>
Date: Mon, 22 Nov 1999 21:32:55 -0800

Wenjia Fang wrote:
...
> for example, never drop an ACK packet in the case of AF?

Wenjia,

PHBs are normally applied to behavior aggregates as indicated
by the DSCP in the DS field. It is a matter of local policy which
packets get put into what behavior aggregate. In the diffserv
context, it doesn't make sense to have individual routers each
looking inside an IP packet to see if the ACK flag is set. Certainly,
it doesn't seem possible to decide to never drop an ACK packet that
is marked for the AF PHB without knowing something about the
rules that are governing that particular AF class in order that
its queue is never full. 

Although the WG will discuss characteristics of behavior aggregates
that are formed subject to certain rules enforced by edge behaviors
and handled by certain configurations of particular PHBs, it
seems more a topic of research whether ACKs *should* be of the
same behavior aggregate. It would seem best to attempt to use
the same behavior aggregate for ACKs as for the DATA they are
ACK'ing in the absence of clear indicators to the contrary, but
this doesn't seem to me like a topic for standardization.

        Kathie