Path Code vs Line Code Violations

handsofqwerty

So one of the functions of one of my jobs is checking some retailers that use T1s as their primary lines. If we notice a store's connection is flapping/bouncing a lot, we'll run the following:

#show ser
Interface Serial0/0/0
Total Data (last 96 15 minute intervals):
	0 Line Code Violations, 1523 Path Code Violations
	0 Slip Secs, 129 Fr Loss Secs, 0 Line Err Secs, 25 Degraded Mins
	192 Errored Secs, 129 Bursty Err Secs, 40 Severely Err Secs, 89 Unavail Secs
Data in current interval (815 seconds elapsed):
	0 Line Code Violations, 5 Path Code Violations
	0 Slip Secs, 0 Fr Loss Secs, 0 Line Err Secs, 1 Degraded Mins
	2 Errored Secs, 2 Bursty Err Secs, 0 Severely Err Secs, 0 Unavail Secs

This is something of an abbreviated output, and I removed the router name for obvious reasons. One thing I've been told is that if we have high amounts of line code violations, it's usually an internal wiring issue, as it's between the router and the demarcation point. If it's path code violations, it's on the provider's end. My question is what are these actually, and how can the router tell the difference? Just trying to understand what I'm actually looking at.

Thanks!

PSX_Defector

They can be either. The only time you care about them is when they increment up. I once had an ATM circuit increment OAM frame errors in the 10K a second, guy was complaining about slow speed.

Only way to find out which is which is to perform testing from the telco side. Lock the port, run an MLT, see what happens. Then test the smartjack for errors. Then look at CPE.

handsofqwerty

@PSX_Defector said:

They can be either. The only time you care about them is when they increment up. I once had an ATM circuit increment OAM frame errors in the 10K a second, guy was complaining about slow speed.

Only way to find out which is which is to perform testing from the telco side. Lock the port, run an MLT, see what happens. Then test the smartjack for errors. Then look at CPE.

It's just I've been told by both my peers and the provider that path code is usually provider issues and line code is usually either with our equipment or after the demarc. Can you provide an explanation of what these both actually are?

PSX_Defector

http://www.cisco.com/c/en/us/support/docs/wan/t1-e1-t3-e3/14171-T1-error.html

"Path code violations are frame synchronization errors for SF, and cyclic redundancy check (CRC) errors for ESF. Path code violations and line code violations are typically present simultaneously. Always verify that your line coding is correct. "

Shouldn't be getting one without the other. My method is still correct, check line, check smartjack, check CPE. An MLT takes about 5 minutes, remote smartjack check on something like an Adtran should take another 5. Then it's just checking the CPE for any modifications, frame type, clock drift, etc. etc. I would assume that you have documented info and change revisions listed somewhere.

handsofqwerty

@PSX_Defector said:

http://www.cisco.com/c/en/us/support/docs/wan/t1-e1-t3-e3/14171-T1-error.html

"Path code violations are frame synchronization errors for SF, and cyclic redundancy check (CRC) errors for ESF. Path code violations and line code violations are typically present simultaneously. Always verify that your line coding is correct. "

Shouldn't be getting one without the other. My method is still correct, check line, check smartjack, check CPE. An MLT takes about 5 minutes, remote smartjack check on something like an Adtran should take another 5. Then it's just checking the CPE for any modifications, frame type, clock drift, etc. etc. I would assume that you have documented info and change revisions listed somewhere.

We often do get both, but many times we get one without the other, like in the above example.

handsofqwerty

Most of that troubleshooting is handled by the provider. If everything tests clean for them, sometimes we'll deploy a tech to check that stuff.

@PSX_Defector said:

They can be either. The only time you care about them is when they increment up. I once had an ATM circuit increment OAM frame errors in the 10K a second, guy was complaining about slow speed.

Only way to find out which is which is to perform testing from the telco side. Lock the port, run an MLT, see what happens. Then test the smartjack for errors. Then look at CPE.

Agreed. They just mean you have errors. It doesn't tell you where they are at.