[c-nsp] 1841 suitable for BGP?

[Tony Varriale]

Based on your statement (which I'm not disagreeing with), I would say there 
are multiple possible reasons for the possible packet loss.

tv
----- Original Message ----- 
From: "Mikael Abrahamsson" <swmike at swm.pp.se>
To: "Tony Varriale" <tvarriale at comcast.net>
Cc: <cisco-nsp at puck.nether.net>
Sent: Tuesday, August 29, 2006 8:46 AM
Subject: Re: [c-nsp] 1841 suitable for BGP?


> On Tue, 29 Aug 2006, Tony Varriale wrote:
>
>> Not to butt in but I could show you real world utilization (ave and peak) 
>> for a good handful of software based Cisco platforms.
>>
>> I'm sure the gear I'm familiar with isn't crashing, but I can show you 
>> 50% peak CPU on NPE 400s because of BGP scanner running every 60 seconds 
>> (since that's it's run interval).  Also, I can show you how 1 eBGP peer 
>> reset will send that NPE400 to 100% CPU.
>>
>> Since NPEs are software based and the CPU is at 100%, what would you say 
>> are happening to the packets that should be going thru the box?  I know 
>> for sure based on my monitoring that not all the packets are being 
>> forwarded at that time.  Are all being dropped?  No.  But it's very 
>> difficult to correlate exact microsecond CPU utilization and actual 
>> packet drop.
>
> As far as I understand it, if the BGP scanner is running and a packet 
> needs servicing, the BGP scanner will be interrupted and the packet will 
> be forwarded, after that, the BGP scanner process will resume.
>
> We have quite detailed jitter and packet loss analysis going, and we have 
> plenty of NPE-300 etc that very often peak at 100% cpu util when BGP 
> scanner is running, without this noticably affecting packet performance 
> thru the box.
>
> That is how we discovered that one some (older) versions of IOS there was 
> a bug which caused some ATM interfaces and (very importantly) ISL 
> encapsulated packets to not go fast-path on 7200. We had to upgrade (after 
> TAC case) IOS and switch away from ISL to .1q to solve the issues.
>
> If BGP scanner noticably affects your packet performance while you're 
> running CEF, you should open a TAC case and try to get the issue resolved.
>
> -- 
> Mikael Abrahamsson    email: swmike at swm.pp.se
>