From: simon hart (simon.hart@btinternet.com)
Date: Tue Feb 22 2005 - 03:45:26 GMT-3
David,
You are going to be a little stuck here. It is really difficult to achieve
QOS, in the manner you ask, on a contended service. This is even true of
Frame Relay, however Frame does have several mechanisms to alleviate the
problem.
The problem you have is that at times when you Service Provider has
contention and is going to have to drop packets, there is no way of knowing
what packets he is going to drop. In addition, as you have pointed out
there is no way that the SP can indicate that Packets are being dropped
(i.e. FECN and BECN's).
You also mention that your sevice provider will offer you contention ratio's
of either 1:2 or 1:4, unfortunately this is not analogous to CIR. If you
have a 512k upstream access on a 1:2 contention, even if you shaped the
traffic at 256k there is no gaurentee that your service provider will not
drop packets (on a frame network you are gaurenteed the CIR, you are not
gaurenteed an mean transfer rate on DSL).
You mention 'Ethernet WAN', so is you traffic being bridged across the DSL
network or are you routing from the CPE (I would guess the later). What
type of DSL delivery is being adopted, is it PPPoA or PPPoE. If PPPoA is
being used then you could give some indication to your service provider as
to what packets he could drop by setting the CLP bit on the low priority
traffic. This is really hit or miss, as the service provider may remark all
traffic or just ignore your setting.
If you wish to have an issue free converged network over DSL you will really
need an uncontended service.
HTH
Simon
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
David Duncon
Sent: 22 February 2005 03:45
To: ccielab@groupstudy.com
Subject: Shaping/Congestion indicators on WAN Ethernet
Hi Group,
We are in the processes of trialing out Ethernet WAN ( WAN service is
directly delivered on to RJ 45 interface at CPE via DSL ) on couple of WAN
sites those are currently running Frame relay. Just like the Frame world ,
with in Ethernet WAN we do have bandwidth of 1:2 or 1:4 etc contentious
ratios between CIR and Access. In other words with in DSL based Ethernet
WAN, our Telco do offer us a equivalent concept of CIR and Access values.
Since we intend to run converged networks on this Ethernet WAN trail sites
as well , we got to protect Voice traffic with in given CIR from the bursty
Data traffic. Now my Q is how can I make it happen as unlike Frame relay ,
Ethernet WAN do not have a congestions indicators such as BECN , FECN and DE
s. So how we can make the shaping happen on Ethernet WAN ?
Secondly queuing can still happen , I guess with LLQ to protect RTP and
Signaling streams and should be able apply the service policy on Egress int
of Fast Ethernet on the edge routers where WAN services are terminated. I
think in the absence of effective shaping parameters on the Ethernet
interface , I guess I can still use CAR to limit the out bout traffic ??So I
am wondering what is my bets bet in terms of deploying
shaping/queuing/policing on Ethernet interface on the edge router which is
connected to Ethernet WAN.
Appreciate any feed back from people who have rolled out similar solutions
on their WAN.
Cheers
- David.
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