SDH Fiber Problem

Hi ,

Dont know if this is the correct forum to ask this however I have been having the following problem on SDH network.

I have been trying to create EoS however am getting the following:

I can ping on point to point
I have BGP up and running

When I try to pass traffic over the link my clients are unable to pass any meanigful traffic asn browsing is impossible.

Any assistance and direction in terms of any Fiber/SDH forums will be greatly appreciated.

Regards,
Jacob Miller

Checked your MTU settings?

I can ping on point to point
I have BGP up and running
When I try to pass traffic over the link my clients are unable to pass
any meanigful traffic asn browsing is impossible.

mtu? try various size pings.

filters?

randy

I have tried the pings and am able to ping through with a size of 1600 with the df-bit set

without the df-bit am able to get up to 9000.

The switched on bot ends hav been set to allow jumbo frames through and the system MTU size and routing MTU sizes are at 1998.
The switch is a 2960 Cisco switch.

I have set the mtu on the interface on the end router to 1600 and still unable to push meaningful traffic.

Regards,
jacob Miller

How much traffic are you trying to pass over the link?
How big is the underlying VCAT? Is it possible that this is misconfigured does not have enough bandwidth?
Depending on the underlying EoSONET/EoSDH bandwidth, you might need to pace traffic into the ADM to avoid overrunning buffers.

aj

The entire link is an STM4 that has been channelised.
We are using 3xSTM1 for the EoS service.
The VCG group is configured with 3xSTM1.

Regards,
Jacob Miller

What exactly do you mean by meaningful traffic? ICMP from port to port works, can you pass TCP? SSH between routers? Establish a TCP session over it?

Are you using Juniper SRXs ? :slight_smile:

By meanigful traffic I mean traffic like Http traffic

Am able to ssh no problem.

Most of the clients on the link are using it for browsing.
However we find that even though they are able to resolve and ping different sites.
When it comes to opening of the page we have the page reading as opening opening .. but the page never gets opened.

Regards,
Jacob Miller

It does sound like an MTU issue. Symptoms are typical. Did you try pings end to end with DF bit set and full size datagrams?

I have triend to do a ping with the DF bit set.
Maximum am able to get to is 1600.
This am guessing is because of the fact I have set the mtu size on My interface to 1600.

I have also enable all alarms on the node and am getting the following alarm which is registering as beign Minor.

"High Order Path Signal Label Mismatch"

Regards,
jacob Miller

Did you try turning it off and on again? :wink:

Did so and am able to ping through

Regards,
Jacob Miller

Have you tried doing a tcpdump to see if that shows anything meaningful?

I have been trying to create EoS however am getting the following:

I can ping on point to point
I have BGP up and running

When I try to pass traffic over the link my clients are unable to pass any meanigful traffic asn browsing is impossible.

Any assistance and direction in terms of any Fiber/SDH forums will be greatly appreciated.

Is this SDH router to router, or are you handing it off as Ethernet? I had a similar problem, and it was simply a mismatched duplex setting.

-Keith

You could extend this test by sending TCP packets across to simulate
the HTTP flow, ideally looking at the packets as they come in at the
other end. At least this way you're closer to replicating the problem
than just using ICMP.

If this doesn't get you anywhere, and as you can get ICMP packets of
1600byte across the link then have you thought about looking elsewhere
for the problem? Potentially further up the path to the Internet?

Managed to solve this problem.

It was MTU related as my routers had an MTU size set at 1600.

Removed this setting from both ends and managed to get traffic flowing.

Had earlier terminated a laptop at one end of the link just to test and found I was able to push more than 20MB.

Thanks for your assistance on this.

Regards,
Jacob Miller