[mrtg] Getting real throughput on ATM PVC´s

Adenilson Raniery Sarges Pontes raniery at rnp.br
Fri Feb 7 14:18:38 MET 2003

Dear all,

 I´d like to get your experiences on measuring throughput on ATM PVCs
using SNMP. Basically, we have GSR 12008 routers with IOS 12.0(21)S2, and
Quad-port OC3c ATM linecards. PVCs were configured (one for each
subinterface), with SCRs ranging from 4Mbps up to 38 Mbps.

My question is: what snmp counters (and procedures) do you use to get
*real* throughput on ATM PVCs?

According to some Cisco docs, e.g

subinterface MIB counters _ifInOctets and ifOutOctets_ do not include
(deterministic) 5-byte cell header and (variable) AAL5 padding.

Counters on CISCO-AAL5-MIB _cAal5VccInOctets and cAal5VccOutOctets_ seem
to include AAL5 padding but I´m not sure, since some statements in the doc
above sounded dubious to me :(
Also, these are 32-bits counters leading to wrap problems with higher
capacity PVCs.

We´re looking for better measurements (or at least good estimatives) of
our internal traffic on PVCs. Nowadays, we´ve been using subinterface
counters but measured traffic is (obviously) lower than real traffic
injected on telcos links.

Any help would be really appreciated.


Raniery Pontes
Network Operations Center (NOC)
National Research Network - Brazil

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