ATM Switch Interoperability

Martin, Christian CMartin at
Sat Jan 16 05:19:11 UTC 1999

We have it matched to the policing policy of the Network Provider.  By
increasing the CDVT, we gain some bucket depth, but we are only MUXing 5
VCCs over one VP.  There shouldn't be too much clumping, espescially
considering the load on the switches(low).  One thing is interesting,
though:  The far end (customers) are all running over DS3 using HEC

A curiosity:  Given the parameters below for the contract, particularly
the MBS and CDVT, does it appear that we are being cheated?  From my
understanding of the UNI 3.1 spec, the MBS should be adjustable
according to SCR/PCR, given the fact that CDVT is defined as the same
for both SCR and PCR buckets.  

One obstacle that myself and my colleagues have not been able to
overcome is the use (aside from bucket calculation) of the Burst
Tolerance.  It is obviously proportional to the MBS, but again, it
appears as if a contract specifying a PCR/SCR of 100000/50000 cells per
sec, should have a higher MBS than a 10000/5000 cell/sec contract.

Any insights?


-----Original Message-----
From: Danny McPherson [mailto:danny at]
Sent: Friday, January 15, 1999 11:33 PM
To: Martin, Christian
Subject: Re: ATM Switch Interoperability 

Have you attempted increasing CDVT on LS1010?


"Martin, Christian" wrote:
>Does anyone have an experience dealing with cell loss between LS1010s
>and Cascade/Ascend CBX 500s using VBRnrt?  It appears that either the
>LS1010 or the CBX is performing UPC operations differently, as we are
>seeing between .1 and 2% packet loss at the AAL, and .1 to .5% at the
>cell level.  By allowing flexibility in the policing, or by removing
>policing completely on the Cascade boxes, cell loss disappears.  It
>appears that the LS may be sending cells too close together, but we are
>unsure and cannot truly test thi without an Analyzer, of which no one
>here has any experience using (even if we had one!).  The parameters are
>as follows:
>7513 w/AIP
>PCR 30000
>SCR 15000
>mbs 3 (*32) = 96
>CDVT 600
>mbs 100 cell times
>PCR 30000 CLP0+1
>SCR 15000 CLP0
>Cascade (As far as I know)
>mbs 100
>PCR 70754 cells/sec
>SCR 35377 cells/sec
>CDVT 600
>I apologize for the vendor references, and I hope some don't view this
>as off-topic!

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