Lucent GBE (4 x VC4) clues needed

David Temkin dave at
Thu Sep 21 13:32:03 UTC 2006

> -----Original Message-----
> From: owner-nanog at [mailto:owner-nanog at] On 
> Behalf Of Saku Ytti
> Sent: Thursday, September 21, 2006 9:12 AM
> To: nanog at
> Subject: Lucent GBE (4 x VC4) clues needed
> (oops technical question in nanog, wearing my asbestos suit)
> Consider this topology
> GSR - 3750 --(GE over 4xVC4) - NSE100 - NSE100 --(GE over 
> 4xVC4) -- 3550 - GSR
> All other fibres are dark fibres, except marked.
> When we ping either NSE100 <-> GSR leg, when there is no 
> background traffic there is no packet loss. If there is even 
> few Mbps, lets say 10Mbps of background traffic we get 1-5% 
> packet loss on 1500 bytes, and bit less packet loss on small 
> packets. As background traffic increases packet loss quickly 
> increases.
> We tried to replace (GSR-3750) with 7600, but same issue persisted.
> We've measured both Lucent GBE legs with having loop in other 
> end and pushing tests from EXFO and Smartbits gear through 
> the loop, no errors can be detected in RFC tests.
> There isn't very much that can be configured in the Lucent, 
> and we've tried pretty much every setting. We've tried to set 
> autonego on and off in every gear in the path, without any 
> changes to observed behaviour. We've also tried to use use 
> 1xVC4, without any changes to the behaviour. All VC4's in 
> given leg are using same path.
>  Even though we test the packet loss pinging from router link 
> to router link, same packet loss is experienced for transit 
> traffic also. We've tried to turn PXF off in NSE100. Packets 
> between NSE100 <-> NSE100 over dark fibre are not lost.
> We're pretty much utterly without clues. All I can think off 
> is some obscure IFG issue, that is, NSE100 would have less 
> than perfect timing for IFG which would confuse Lucent 
> regarding what is part of which frame. Does stuff like this 
> really happen?
> NSE100 drops bad IP packets in PXF and there is only shared 
> counter, so I can't tell if I get CRC for IP, I just loose 
> the packets. But IS-IS is not handled in PXF, and I get 
> %CLNS-4-LSPCKSUM and %CLNS-3-BADPACKET messages over both 
> Lucent legs, but not between the NSE100's.
> So I assume the packets are not dropped, but broken.
> I swear next time I'll complain about some political issue, thanks,
> --
>   ++ytti

Silly question (considering that you stated that IS-IS is borked also,
which is not handled by PXF - but did you try disabling PXF?

There's a reason why Cisco discontinued every product that "features"
it.  It's broken. 

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