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| Author |
Message |
Mark Williams
Guest
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 Posted: Wed Apr 19, 2006 8:35 pm Post subject: Fractional T1 trouble |
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I'm troubleshooting a fractional T1 (16 timeslots) that is having some
strange problems. Using extended ping, I gathered the following
information:
-Small pings up to 1000 bytes with the default data pattern go across
the line with no problems.
-Starting at around 1400 bytes, pings with the default data pattern
fail at a rate of about 3 - 5%.
-Pings sized at 1000 bytes with a data patern of 0x0000 fail at a rate
of about 3 to 5%
-500 byte pings with a data pattern of 0x0000 go through with no
problem.
-1000 byte pings with a data pattern of 0xFFFF go through with no
problem.
-Strangley, no errors show in the counters for the interfaces on either
side of the link.
The MTU is set at 1500 bytes at both sides. I changed the queueing from
WF to FIFO with no change in results. I verified that the settings of
the (external) DSU on one side of the link is set correctly (ESF, B8ZS,
16 timeslots), but I can access the other end's DSU.
| Quote: | From what I've seen, this could be an issue with incorrect linecoding
specified somewhere along the path of the circuit. But why would the |
0x0000 pings fail only for larger packets, and not the smaller sized?
Any insight would be greatly appreciated. |
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mooron@mooron.com
Guest
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| Posted: Wed Apr 19, 2006 9:08 pm Post subject: Re: Fractional T1 trouble |
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Mark Williams wrote:
| Quote: | I'm troubleshooting a fractional T1 (16 timeslots) that is having some
strange problems. Using extended ping, I gathered the following
information:
-Small pings up to 1000 bytes with the default data pattern go across
the line with no problems.
-Starting at around 1400 bytes, pings with the default data pattern
fail at a rate of about 3 - 5%.
-Pings sized at 1000 bytes with a data patern of 0x0000 fail at a rate
of about 3 to 5%
-500 byte pings with a data pattern of 0x0000 go through with no
problem.
-1000 byte pings with a data pattern of 0xFFFF go through with no
problem.
-Strangley, no errors show in the counters for the interfaces on either
side of the link.
The MTU is set at 1500 bytes at both sides. I changed the queueing from
WF to FIFO with no change in results. I verified that the settings of
the (external) DSU on one side of the link is set correctly (ESF, B8ZS,
16 timeslots), but I can access the other end's DSU.
From what I've seen, this could be an issue with incorrect linecoding
specified somewhere along the path of the circuit. But why would the
0x0000 pings fail only for larger packets, and not the smaller sized?
Any insight would be greatly appreciated.
|
Is your provider also configured for B8ZS, ESF?
Do the interfaces show errors?
- Mooron |
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Mark Williams
Guest
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| Posted: Wed Apr 19, 2006 9:14 pm Post subject: Re: Fractional T1 trouble |
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No errors show in the interfaces. One side of the link shows some
output drops, but they don't correspond with the ping failures. |
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Mooron
Guest
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| Posted: Wed Apr 19, 2006 9:53 pm Post subject: Re: Fractional T1 trouble |
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Mark Williams wrote:
| Quote: | No errors show in the interfaces. One side of the link shows some
output drops, but they don't correspond with the ping failures.
|
Oh yeah, you did mention there were no errors.
Post a snipit of the configuration, maybe
it's something dumb.
Also, do a show service module if it's a router that has them.
Your provider could be dropping frames. That would
be the next thing to look at if there are no problems
with your configuration.
- Mooron |
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Mark Williams
Guest
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| Posted: Wed Apr 19, 2006 11:39 pm Post subject: Re: Fractional T1 trouble |
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I'm using Kentrox external CSU/DSUs on both ends of the link. I've
verified that the configuration is correct on one side of the link, but
I cannot manage the CSU on the other side.
The interface configuration on one side:
interface Serial0/0
description DO-DVS WAN Link 1
bandwidth 1024
ip address 165.196.38.254 255.255.255.128
no ip directed-broadcast
no ip proxy-arp
no ip mroute-cache
no fair-queue
invert txclock
no cdp enable
The other side:
interface Serial0/1
description DVS-DO WAN Link 1
bandwidth 1024
ip address 165.196.38.253 255.255.255.128
no ip proxy-arp
invert txclock
no fair-queue
Our service provider conducted some loop testing and didn't find any
problems; I tried to explain the symptoms to them but I got the "It's
OK at layer 1" message. |
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Mooron
Guest
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| Posted: Thu Apr 20, 2006 1:01 am Post subject: Re: Fractional T1 trouble |
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Mark Williams wrote:
| Quote: | I'm using Kentrox external CSU/DSUs on both ends of the link. I've
verified that the configuration is correct on one side of the link, but
I cannot manage the CSU on the other side.
The interface configuration on one side:
interface Serial0/0
description DO-DVS WAN Link 1
bandwidth 1024
ip address 165.196.38.254 255.255.255.128
no ip directed-broadcast
no ip proxy-arp
no ip mroute-cache
no fair-queue
invert txclock
no cdp enable
The other side:
interface Serial0/1
description DVS-DO WAN Link 1
bandwidth 1024
ip address 165.196.38.253 255.255.255.128
no ip proxy-arp
invert txclock
no fair-queue
Our service provider conducted some loop testing and didn't find any
problems; I tried to explain the symptoms to them but I got the "It's
OK at layer 1" message.
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I was wondering if the clocks might be set wrong. |
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Doug McIntyre
Guest
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| Posted: Thu Apr 20, 2006 9:14 am Post subject: Re: Fractional T1 trouble |
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"Mark Williams" <webmaster@sdps-idpa.org> writes:
| Quote: | I'm using Kentrox external CSU/DSUs on both ends of the link. I've
verified that the configuration is correct on one side of the link, but
I cannot manage the CSU on the other side.
The interface configuration on one side:
interface Serial0/0
description DO-DVS WAN Link 1
bandwidth 1024
ip address 165.196.38.254 255.255.255.128
no ip directed-broadcast
no ip proxy-arp
no ip mroute-cache
no fair-queue
invert txclock
no cdp enable
The other side:
interface Serial0/1
description DVS-DO WAN Link 1
bandwidth 1024
ip address 165.196.38.253 255.255.255.128
no ip proxy-arp
invert txclock
no fair-queue
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There's not alot you are going get out of the serial interfaces at
this level. Almost always when faced with problems in this setup, its
some sort of cockup on the CSU/DSU setup. All the router's serial
interfaces know is that they can send out data, and may get garbled
data coming back.
I urge you to get into the config of the CSU on the other side of the
link and verify its setup. You most likely will find something not set
the same there. Ie. number of channels, channel order, framing,
encoding, etc. Clocking isn't that important at this point, although
good to verify the setup on. Bad clocking will still most likely bring
the circuit up, but may have problems later.
| Quote: | Our service provider conducted some loop testing and didn't find any
problems; I tried to explain the symptoms to them but I got the "It's
OK at layer 1" message.
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They won't be able to tell anything about the CSU setup at that
level of testing, just that there seems to be a T carrier that can
push bits out over it. |
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Mark Williams
Guest
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| Posted: Fri Apr 21, 2006 1:25 am Post subject: Re: Fractional T1 trouble |
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I went on site to look at the other end's CSU/DSU, and everything
looked fine. The linecoding was set to B8ZS, framing ESF, and the
timeslot configuration matched. |
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