explain 64-bit counters and wrapping?

phiberoptik26k · Post by **phiberoptik26k** » Wed Sep 22, 2004 11:26 am

this is my frist post and i would like to say CACTI is awesome, although i'm still new at it i can see that it has a lot of potential.....plus its free!!!! anyways

I was reading an article on cisco.com and they said the following:

A. RFC 2233 adopted expanded 64-bit counters for high capacity interfaces in which 32-bit counters do not provide enough capacity and wrap too fast.

As the speed of network media increases, the minimum time in which a 32-bit counter wraps decreases. For example, a 10 Mbps stream of back-to-back, full-size packets causes ifInOctets to wrap in just over 57 minutes. At 100 Mbps, the minimum wrap time is 5.7 minutes, and at 1 Gbps, the minimum is 34 seconds.

Note: The SNMP counters wrap, the CLI counters don't.

For interfaces that operate at 20,000,000 (20 million) bits per second or less, you must use 32-bit byte and packet counters. For interfaces that operate faster than 20 million bits per second, and slower than 650,000,000 bits per second, you must use 32-bit packet counters and 64-bit octet counters. For interfaces that operate at 650,000,000 bits/second or faster, 64-bit packet and octet counters must be used.

Correspondingly, Cisco IOS Software does not support 64-bit counters for interface speeds of less than 20Mbps. This means that 64-bit counters are not supported on 10Mb Ethernet ports, only 100 Mb Fast-Ethernet and other high speed ports support 64-bit counters.

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my question is what is wrapping? could someone explain that to me? thanks alot.

- mike

bulek · Post by **bulek** » Thu Sep 23, 2004 6:37 am

Traffic counters count number of bytes transferred through given interface. Such counters have their maximum value they can handle - in case of 32-bit counters this is (2^32)-1 = 4294967295. As soon as the counter reach the maximum value it starts counting from 0. This is called counter wrapping.

Applications that check such counters frequently (as Cacti does) may get confused if the counter wraps twice between poll attempts (they usualy can hadle 1 wrap). This can happen in case of high speed interfaces. It is therefore recommended to use 64-bit counters which wrap much less often.

- Piotr

phiberoptik26k · Post by **phiberoptik26k** » Tue Sep 28, 2004 12:21 pm

thanks. excellent response. that helped to explain a few things.

realthing3d · Post by **realthing3d** » Wed Sep 29, 2004 4:45 pm

I was just researching a problem that I think is related to this so I was glad to see a fresh thread on this topic.

But what are your options when the 64 bit counters aren't exposed in snmpwalk. I looked at the IFMIB.txt and it appears to be there as ifHCInOctects and ifHCOutOctects but neither of these are showing up. The server in question is running an e1000 family NIC....anyone have any ideas?

David

JoeNetwork · Post by **JoeNetwork** » Wed Sep 29, 2004 11:49 pm

Are you using SNMP v2c? 64-bit counters don't work w/SNMP v1.

Guest · Post by **Guest** » Thu Sep 30, 2004 9:03 am

I am using v2c....here's the output from snmpwalk

Code: Select all

snmpwalk -v2c -cgraphics localhost IF | grep '.3 ='
IF-MIB::ifIndex.3 = INTEGER: 3
IF-MIB::ifDescr.3 = STRING: eth0
IF-MIB::ifType.3 = INTEGER: ethernetCsmacd(6)
IF-MIB::ifMtu.3 = INTEGER: 1500
IF-MIB::ifSpeed.3 = Gauge32: 100000000
IF-MIB::ifPhysAddress.3 = STRING: 0:30:48:29:d8:3e
IF-MIB::ifAdminStatus.3 = INTEGER: up(1)
IF-MIB::ifOperStatus.3 = INTEGER: up(1)
IF-MIB::ifInOctets.3 = Counter32: 3312081601
IF-MIB::ifInUcastPkts.3 = Counter32: 1962820674
IF-MIB::ifInDiscards.3 = Counter32: 0
IF-MIB::ifInErrors.3 = Counter32: 0
IF-MIB::ifOutOctets.3 = Counter32: 3491158269
IF-MIB::ifOutUcastPkts.3 = Counter32: 1662434153
IF-MIB::ifOutDiscards.3 = Counter32: 0
IF-MIB::ifOutErrors.3 = Counter32: 0
IF-MIB::ifOutQLen.3 = Gauge32: 0
IF-MIB::ifSpecific.3 = OID: SNMPv2-SMI::zeroDotZero

--
David

realthing3d · Post by **realthing3d** » Thu Sep 30, 2004 9:05 am

Sorry about that last post....forgot to login.

--
David

bulek · Post by **bulek** » Sat Oct 02, 2004 1:58 am

Well... you didn't say to much about the server. It's up to device vendor if it supports 64bit counters or not. Cisco for example does not support them for interfaces slower than 20Mbps so in the same device you will find the objects for Fasteth interfaces while they do not exist for Eth.

- Piotr

realthing3d · Post by **realthing3d** » Sat Oct 02, 2004 12:55 pm

Well the server in question is running a Supermicro X5DPE-G2 motherboard which has an integrated Dual Port Intel 82546EB Gigabit Ethernet controller. Which is using the e1000 driver as a module on a 2.6.7 kernel.

Post by **TheWitness** » Sun Oct 03, 2004 9:25 am

realthing3d,

It appears as if your vendor is not supporting 64bit counters. It may be that they have a vendor specific mib with the required information (which I would consider a bug as well). Best bet would be to e-mail their support group for a fix.

TheWitness

realthing3d · Post by **realthing3d** » Mon Oct 04, 2004 12:05 pm

Thanks I'll try emailing SuperMicro and see if they have any solutions. As another option could I poll the interface's every minute by modifying some of the scripts and rra's? Sounds to me like this would be a pain when it comes to adding new data sources though. Perhaps this would be a good feature request item. To be able to pick the polling frequency on a per data source (template) basis.

--
David Miller

explain 64-bit counters and wrapping?

explain 64-bit counters and wrapping?

thanks

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