[mrtg] Getting real throughput on ATM PVC´s

[Adenilson Raniery Sarges Pontes]

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
http://www.cisco.com/en/US/tech/tk39/tk51/technologies_tech_note09186a0080093c9a.shtml

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.

Regards

Raniery Pontes
:::::::::::::::::::::::::
Network Operations Center (NOC)
National Research Network - Brazil
http://www.rnp.br/index_en.html

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