Packet Loss Over DWDM

j.whitehouse · ‎11-13-2003

Hello,

I have a fast ethernet FX connection running over a Nortel Optera 5200 which is showing packet loss.

I have a 7500 at one end and a 7200 at the other, both have NM-FE-FX PA's installed. We have a multimode fibre connection from the routers to a SRM card in the Optera. If we ping between the two routers we see packet loss. This seems to get worse if we increase the packet size. We have checked the optical levels on the fibre between the Optera's and these look ok. We have moved the router connections to another set of SRM cards on the Optera, but still see packet loss. I believe that the router fibre cards have been replaced too.

The product spec for the PA's states that they operate at a wavelength of 1300 nanometers. The Optera runs at 1310 nanometers. Is this an issue? Any ideas on what else I could check to resolve this issue?

Many Thanks

John

scottmac · ‎11-15-2003

1300nm is probably 1310 written by a lazy person.

Which (specifically) Interface are you using on the Optera? Model, version, firmware, etc

Are you losing a specific type of packet? (i.e., TCP versus UDP, etc)

Try stretching your IP timeout values in the gateway routers.

Good Luck

Scott

rtappend_2 · ‎11-28-2003

John,

You might already have resolved this, but if not, the following may help.

The NM-1FE-FX operates at 1300nm, however most devices incorporate a receiver that can handle a range of wavelengths (eg 1280nm - 1380nm) so connecting a 1310nm device to a 1300nm device should not be a problem.

Have you checked the power levels at the Rx of both the NM and the Optera SRM? The max Rx level at the NM input should be no more than -14dBm, but I believe the Tx from the SRM will be higher than this.

You should also be using 62.5/125 fibre.

Good luck.

j.whitehouse · ‎11-28-2003

Rob,

Thanks for this information. We currently have a case open with Nortel regarding this issue. From debugs that we have supplied them, they can see los which isn't quite long enough to flag alarms in the Optera alarm log. They have suggested adding attenuation to see if this resolves the issue. As you suggest the power levels seen at the NM may be too high which seems to tie in with Nortel's thoughts. I will let you know how we get on.

John

jholsteyns · ‎02-05-2004

John,

There was an issue with the early SRM cards. These cards lost theire syncs after a while. Ask Nortel if your hardware version is OK.