Mailing List Archive

Strange DS3 Problems
I have a DS3 terminating to a cisco 7200 NPE200 NonVXR router, With a
defualt route to my ISP.

At the DS3 Dmarc it's going into a fiber-to-ds3 converter made by Transition
Networks,
This rides SM fiber over to my router where it breaks back out to coax. I
needed an Attunator, because the signal levels coming out of the
Fiber converter were too hot for the PA-T3, giving me LCV errors. I have
since fixed that.

Overview

DS3 DMARC <-> Coax to Fiber <--SM Fiber--> Fiber to Coax <-> 10db Attunator
<-> Cisco PA-T3 in router


I'm currently having two problems with the Ds3,

1) The max download speed i've ever gotten is 700kb/s, this doesn't seem
right at all for 10/10mb dedicated, 45mb burstable.
2) the Ds3 is bouncing. It goes into a down/down state and i'll have a FERF
alarm light on the router. This will clear in about 20-30secs without me
doing anything.
It seems to happen more when the Ds3 is under load, though it has happend
without any load.


What I can do,

1) I can ping the living daylight out of the ISP serial side IP, 20000 pings
3700byte packets with 0% lost, 3ms max.
In past this to me, would mean a clean working ds3.
2) I can ping everything else in the world, with decent ping times.
3) I've looped back all the way up to the dmarc, and it works just fine.
Though at this point, it's appars to be working fine to the ISP also.

Questions

1) What is the rx FEBE since last clear counter mean? I notice this is the
only sort of error i'm getting now.
2) Is a 7206 non-VXR NPE 200 strong enough for a full DS3, if i'm just doing
a default route, and a very small ACL.
3) Is it possible that i have a BAD PA-T3, I did have it connected without
the Attunator for sometime,
and i'm afraid that might have fried something.
4) Has anyone used Fiber to DS3 converters in the past? Good/Bad?

Thanks,
Adam

interface Serial1/0
description DS3 to INTERNET
ip address x.x.x.70 255.255.255.252
encapsulation ppp
dsu bandwidth 44210
framing c-bit
cablelength 10
serial restart-delay 0
======================
Serial1/0 is up, line protocol is up
Hardware is M1T-T3 pa
Description: DS3 to INTERNET
Internet address is X.X.X.X/30
MTU 4470 bytes, BW 44210 Kbit, DLY 200 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation PPP, LCP Open
Listen: CDPCP
Open: IPCP, crc 16, loopback not set
Keepalive set (10 sec)
Restart-Delay is 0 secs
Last input 00:00:00, output 00:00:00, output hang never
Last clearing of "show interface" counters 00:33:33
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 9
Queueing strategy: fifo
Output queue: 0/40 (size/max)
5 minute input rate 35000 bits/sec, 93 packets/sec
5 minute output rate 35000 bits/sec, 92 packets/sec
320718 packets input, 19987776 bytes, 0 no buffer
Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
0 parity
1 input errors, 1 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
318582 packets output, 19781951 bytes, 0 underruns
0 output errors, 0 applique, 0 interface resets
0 output buffer failures, 0 output buffers swapped out
6 carrier transitions
rxLOS inactive, rxLOF inactive, rxAIS inactive
txAIS inactive, rxRAI inactive, txRAI inactive
======================
M1T-T3 pa: show controller:
PAS unit 0, subunit 0, f/w version 3-93, rev ID 0x2800001, version 3
idb = 0x63539854, ds = 0x6353AFFC, ssb=0x6353B3B0
Clock mux=0x30, ucmd_ctrl=0x0, port_status=0x1
Serial config=0x8, line config=0x1B0202
maxdgram=4500, bufpool=128Kb, 256 particles

rxLOS inactive, rxLOF inactive, rxAIS inactive
txAIS inactive, rxRAI inactive, txRAI inactive
line state: up
cable type : T3 cable, received clockrate 44201430

base0 registers=0x3C800000, base1 registers=0x3C802000
rx_base0 registers=0x3C820000, rx_base1 registers=0x3C822000
mxt_ds=0x63B85E1C, rx ring entries=124, tx ring entries=254
statring=0x4B05A300, statr shadow=0x6353D0AC, stat_head=47
plus_pa: rx_statring=0x4B05A740, rx_statr shadow=0x6353D8D8, rx_stat_head=10
rxring=0x4B05A0C0, rxr shadow=0x6353CA80, rx_head=71
txring=0x4B05AC80, txr shadow=0x6353DD04, tx_head=157, tx_tail=157,
tx_count=0
throttled=0, enabled=0
halted=0, last halt reason=0
Microcode fatal errors=0
rx_no_eop_err=0, rx_no_stp_err=0, rx_no_eop_stp_err=0
rx_no_buf=0, rx_soft_overrun_err=0, dump_err= 0, bogus=0, mxt_flags=0x2C
tx_underrun_err=0, tx_soft_underrun_err=0, tx_limited=0(256)
tx_fullring=0, tx_started=1775246, mxt_flush_count=0
rx_int_count=5782051, tx_int_count=2357850
Framing is c-bit, Clock Source is Line
Bandwidth limit is 44210, DSU mode 0, Cable length is 10
rx FEBE since last clear counter 125585, since reset 1721663
Data in current interval (143 seconds elapsed):
0 Line Code Violations, 0 P-bit Coding Violation
0 C-bit Coding Violation
0 P-bit Err Secs, 0 P-bit Sev Err Secs
0 Sev Err Framing Secs, 0 Unavailable Secs
0 Line Errored Secs, 0 C-bit Errored Secs, 0 C-bit Sev Err Secs
Data in Interval 1:
2 Line Code Violations, 1 P-bit Coding Violation
1 C-bit Coding Violation
1 P-bit Err Secs, 0 P-bit Sev Err Secs
0 Sev Err Framing Secs, 124 Unavailable Secs
2 Line Errored Secs, 1 C-bit Errored Secs, 0 C-bit Sev Err Secs
Total Data (last 1 15 minute intervals):
2 Line Code Violations, 1 P-bit Coding Violation,
1 C-bit Coding Violation,
1 P-bit Err Secs, 0 P-bit Sev Err Secs,
0 Sev Err Framing Secs, 124 Unavailable Secs,
2 Line Errored Secs, 1 C-bit Errored Secs, 0 C-bit Sev Err Secs

No alarms detected.
Last FEAC code received: OOF
================================
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Re: Strange DS3 Problems [ In reply to ]
On Mon, 7 Jan 2008, Adam Piasecki wrote:

> 1) The max download speed i've ever gotten is 700kb/s, this doesn't seem
> right at all for 10/10mb dedicated, 45mb burstable.

Is there anything you can download directly on the other end of the DS3,
to confirm it's an issue with your DS3 and not with upstream capacity?
Also, sorry to be pedantic, but you're sure it's 700kbps and not 700kBps?

> 2) the Ds3 is bouncing. It goes into a down/down state and i'll have a FERF
> alarm light on the router. This will clear in about 20-30secs without me
> doing anything.
> It seems to happen more when the Ds3 is under load, though it has happend
> without any load.

What does the provider see on their interface stats?

> What I can do,
>
> 1) I can ping the living daylight out of the ISP serial side IP, 20000 pings
> 3700byte packets with 0% lost, 3ms max.
> In past this to me, would mean a clean working ds3.

Just to be safe, try doing a range sweep with 0xAAAA (alternating 1s and
0s). DS3s are a lot more sensitive to alternating bits, and will help
expose seemingly solid circuits. Might turn out that you need to increase
attentuation, wouldn't be the first time.

> 1) What is the rx FEBE since last clear counter mean? I notice this is the
> only sort of error i'm getting now.

It's an indicator that the far end received a c-bit parity error. It's
possible you need to attenutate the tx from your router to the fiber
converter, in addition to the rx.

> 2) Is a 7206 non-VXR NPE 200 strong enough for a full DS3, if i'm just doing
> a default route, and a very small ACL.

Definitely.

> 3) Is it possible that i have a BAD PA-T3, I did have it connected without
> the Attunator for sometime,

Have you done loopback testing with a short hard loop cable? It generally
eliminates the hardware. See:

http://www.cisco.com/en/US/tech/tk713/tk628/technologies_tech_note09186a008034418d.shtml

> 4) Has anyone used Fiber to DS3 converters in the past? Good/Bad?

I have not, so in my mind that's the most suspicious issue, especially in
the absence of detected errors on the ISP side.

> cablelength 10

Try making that > 50, see what happens. Probably nothing, but just in
case.

Andy

---
Andy Dills
Xecunet, Inc.
www.xecu.net
301-682-9972
---
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Re: Strange DS3 Problems [ In reply to ]
Adam Piasecki wrote:

> I'm currently having two problems with the Ds3,
>
> 1) The max download speed i've ever gotten is 700kb/s, this doesn't seem
> right at all for 10/10mb dedicated, 45mb burstable.

Definitely not right.

> 2) the Ds3 is bouncing. It goes into a down/down state and i'll have a FERF
> alarm light on the router. This will clear in about 20-30secs without me
> doing anything.

FERF = Far end receive failure. The other side is reporting loss of
signal from you. Other end should be seeing a boatload of input errors
and carrier transitions in this condition. Transmission to you from ISP
is fine. Transmission from you to ISP is impaired.

> It seems to happen more when the Ds3 is under load, though it has happend
> without any load.

How is the circuit clocked? Ensure that there is exactly one clock
source on the circuit and that framing and linecode match throughout
among you, your ISP and carrier. (Usually C-bit B3ZS, clock source from
ISP.)

> Questions
>
> 1) What is the rx FEBE since last clear counter mean? I notice this is the
> only sort of error i'm getting now.

Far end bit errors. The remote end is signaling to you that it is
receiving errors from you. An attenuator on the other side may be
needed, and/or the other end may have bad cabling or faulty equipment
receiving from you. The other end is likely seeing input errors
corresponding to your FEBEs. This correlates to the FERF alarm,
pointing to a problem in the direction leaving you and arriving at the
other end.

> 2) Is a 7206 non-VXR NPE 200 strong enough for a full DS3, if i'm just doing
> a default route, and a very small ACL.

Yes, without breaking a sweat.

> 3) Is it possible that i have a BAD PA-T3, I did have it connected without
> the Attunator for sometime,
> and i'm afraid that might have fried something.

If so it would be on your transmit side based on the FEBEs. Can you run
clean to a remote co-ax loop at the ISP? Can the ISP run clean to a
co-ax loop on your side?

> 4) Has anyone used Fiber to DS3 converters in the past? Good/Bad?

No direct experience but be sure to include their configuration options
when verifying clocking, linecode, framing agreement. Verify light
levels and clean optics. If dark fiber end-to-end with no intervening
repeaters, swap transmit and receive strands on both sides and see if
the direction of impairment flips. If so, this would indicate a problem
with the fiber media.

You'll need someone with clue on the other end of the circuit to help
you troubleshoot this, as the problem is coming in to their end.

--
Jay Hennigan - CCIE #7880 - Network Engineering - jay@impulse.net
Impulse Internet Service - http://www.impulse.net/
Your local telephone and internet company - 805 884-6323 - WB6RDV
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