Subject: RE: [Diffserv] Location Diffserv traffic conditioning blocks.

From: "Prabakaran, Thirumali" <[email-masked]>
Date: Wed, 22 Aug 2001 11:00:54 -0400

Hi,

I added my views and comments,
Please see my inlined comments with [Prabakaran].
Further clarifications/corrections and comments, I am pleased to recv it.

Thanks and regards,
Prabakaran TS.
Software Engineer,
Cratos Networks, Inc.,
100 Nagog Park
Acton, MA  01720
978-263-0094 - Extn:8159

-----Original Message-----
From: Manoj Kumar Venkappa Alva [mailto:[email-masked]]
Sent: Wednesday, August 22, 2001 8:22 AM
To: [email-masked]
Cc: [email-masked]
Subject: [Diffserv] Location Diffserv traffic conditioning blocks.

Hello,
 RFC 2474 point 2 states that "A differentiated services boundary can 
be further sub-divided into ingress and egress nodes, where the 
ingress/egress nodes are the downstream/upstream nodes of a boundary 
link in a given traffic direction.".
Query :
At the "ingress" of a DS domain  shown below:

         In __________
  Interface |Ingress  |      DS domain
        ----|Router   |----
        ----|         |---- 
            |_________|Out Interface
            
1)Should Differentiated services compulsorily be applied at the "In 
interface" of the router.

[prabakaran] Need not be, but if your router supports diffserv on the 
In interface then you have to, it is again your local policy and depends on
the
the diffserv model.  If you receive the packets with DSCP values and if your
incoming interface is diffserv enabled then, you have to apply diffserv on
the
In interface. But, if you are not configured diffserv on the In Interface,
and 
diffserv is configured on the Out Interface, then you have to mark the
packets 
appropriately with the proper DSCP values based on the classifier and the 
policy etc..,

2)Or should it be at the "Out interface " or both

[prabakaran] If diffserv is enabled on the Incoming interface, if you have 
proper DSCP values associated with the interface using classifiers(diffserv
classes) then, the received packets with proper DSCP values should be given
appropriate treatment like metering, marking/re-marking and scheduling 
can be done on the incoming interface.   In general metering is done at the 
In interface and if required re-marking and then if you have scheduler at
the
incoming interface the packet is put in the appropriate queue with the
associated dropping values(if required) and then it is sent to out
interface.
The Out Interface can have meter, marker and scheduler for the outgoing
packet.

But for simple implementation the In Interface can have Meter and based on
that,
the packet can be directly put it on the out interface scheduler with the
proper
drop values(if required) and if required re-marking can be done on the
packet 
before putting it on the Out Interface scheduler, this is fully depends on 
the hardware design and its support for the diffserv.

3)What are the possible scenarios for such  cases.

[prabakaran] You have to configure/associate separate service-policy for the

incoming and outgoing (Downstream/Upstream) conditions on an interface.
please refer diffserv-model(s) for more details.

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---

From: Brian E Carpenter <[email-masked]>
Date: Wed, 22 Aug 2001 14:19:15 -0500

Indeed, the router model and the MIB allow for traffic conditioning at
both input and output interfaces, and this is largely an operational
choice depending on traffic patterns, link bandwidths, and the
particular PDBs you want to support. There is no single answer
that covers all cases.

   Brian