Log In

Come Join Us!

Are you a
Computer / IT professional?
Join Tek-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Tek-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here


IP packet loss on ATM OC3

IP packet loss on ATM OC3

IP packet loss on ATM OC3

Hey all,

Got a problem I can't figure out. We've got an ATM OC3 connection into the local ILEC's cloud with a bunch of PVCs built to customers. Just about every single customer on this OC3 is having bandwidth problems and problems with packet loss.

If we do a ping via IP across the PVC with any packets larger than 500 bytes, we see anywhere between 3% and 10% packet loss. This does not happen with our ATM DS3s in the same router. There aren't any interface errors accumulating, and the ILEC has tested the circuit clean to a loop in our router. If we do end-to-end OAM echos on each PVC everything turns up fine with no cell loss. I'm really at a loss as to what the problem could be, but basically the ILEC is telling us we must have a problem with our Cisco config.

Non-working ATM OC3 sample config:
interface ATM1/1/0
bandwidth 155000
no ip address
load-interval 30
atm ilmi-keepalive

Sample of PVC config from non working OC3:
interface ATM1/1/0.4 point-to-point
bandwidth 20000
ip address x.x.x.x
pvc 1/103
ubr 20000
encapsulation aal5snap

Ping results from the router:
Sending 50, 1000-byte ICMP Echos to x.x.x.x, timeout is 2 seconds:
Success rate is 96 percent (48/50), round-trip min/avg/max = 1/2/4 ms

Sample config of working ATM DS3 in same chassis:
interface ATM4/1/0
bandwidth 45000
no ip address
load-interval 30
atm scrambling cell-payload
no atm ilmi-keepalive

Sample of PVC from working DS3:
interface ATM4/1/0.12 point-to-point
ip address x.x.x.x
pvc 1/53
ubr 44000
encapsulation aal5snap

Ping results:
Sending 50, 1000-byte ICMP Echos to x.x.x.x, timeout is 2 seconds:
Success rate is 100 percent (50/50), round-trip min/avg/max = 4/4/8 ms

I'd be very appreciative of any troubleshooting suggestions anyone may have.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Tek-Tips Forums free from inappropriate posts.
The Tek-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Tek-Tips forums is a member-only feature.

Click Here to join Tek-Tips and talk with other members!

Close Box

Join Tek-Tips® Today!

Join your peers on the Internet's largest technical computer professional community.
It's easy to join and it's free.

Here's Why Members Love Tek-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close