[cisco-nas] Slips

Thu Oct 11 13:59:40 EDT 2012

Aaron,

Thanks for your help on this, we were able to resolve it.  You are right, it
was the other end (the 2400's).  In this case our AS5400 was delivering PRIs
to 7 locations:  4 had Cisco 2400s, they all had slips, 3 were to various
PBXs, none had slips.

Even though the 2400 IAD T1 controller says "Clock Source is Line.", it
doesn't seem to actually mean that.   Instead, there is an additional
configuration command that is present by default in the 2400:

               network-clock-participate T1 1/0

which seems to sync the T1 controller to the internal motherboard TDM clock.
That would be OK, but another command is needed, which is not there by
default, to then sync the internal clock to the incoming T1 line.  It is:

               network-clock-select 1 T1 1/0

With that, the internal clock picks up its clocking from the T1 which then
via the participate command controls the T1 controller.  With the addition
of the select command in each of the 2400's all slips have stopped.  

Thanks for your help!

BTW, we would appreciate a working definition for what "Clock Source is
Line" really means.  In the case of the 2400, does "Line" still have any
meaning, or does the network-clock-participate command just by-pass that?
That is, the controller's clock source can be set to ANYTHING, but is
completely ignored because the "network-clock-participate" command means use
the motherboard clock instead, or does the controller clock still retains
some meaning?

Similarly, on the AS5400, it too says "Clock Source is Line", but it seems
to actually be picking up its clocking from the TDM backplane clock which is
controlled with the "tdm clock priority ." command.   There does not seem to
be the equivalent of the participate command.

Finally, in the case of say a 7200 router talking to a 2600 router with an
ordinary Internet T1 between them, we have always configured both ends to
use "line" clock source.   That seems to work, but what does it mean?   Does
it mean transmit using your own clock, but adapt and receive whatever the
other sends (in which case the two sides of the T1 could have different
clocking) or are they somehow more coupled?    Until this evet, we never
realized that the point-to-point telco provided T1 in the middle might as
well be a plain wire: both ends are getting their clocking from the other
side?   What does "line" really mean?

Thanks,

Michael (I work with Joseph Mays)

From: cisco-nas-bounces at puck.nether.net
[mailto:cisco-nas-bounces at puck.nether.net] On Behalf Of Joseph Mays
Sent: Wednesday, October 10, 2012 5:03 PM
To: Aaron Leonard
Cc: cisco-nas at puck.nether.net
Subject: Re: [cisco-nas] Slips

Perhaps. Let me work with it. Thank you for your help, btw.

----- Original Message ----- 

From: Aaron Leonard <mailto:Aaron at cisco.com>  

To: Joseph Mays <mailto:mays at win.net>  

Cc: cisco-nas at puck.nether.net 

Sent: Wednesday, October 10, 2012 4:30 PM

Subject: Re: [cisco-nas] Slips

OK ... so I've never laid a finger on an IAD2400, but I cheated and looked
at an old email from a knowledgeable source, and here's what he says (for
the case where the IAD2400 is taking clock from one T1 and providing to
another):

network-clock base-rate [56k | 64k ] as appropriate
network-clock-select 1 T1 [0 | 1 ] as appropriate
clock source line on the appropriate controller
clock source internal on the other controller

If the peer devices are providing clocking and accepting clocking as you've
set
on the IAD, then you should get no slips.

Does this help?

Aaron

  _____  

On 10/10/2012 12:57 PM, mays at win.net (Joseph Mays) wrote:

I have noticed something that I have not noticed prior to this, which is
that all the units that are experiencing slips are IAD2400's All are set to
get clocking from the line, but does the IAD2400 behave differently with
regard to clocking than most things somehow?

----- Original Message ----- 

From: Aaron Leonard <mailto:Aaron at cisco.com>  

To: Joseph Mays <mailto:mays at win.net>  

Cc: cisco-nas at puck.nether.net 

Sent: Wednesday, October 10, 2012 3:30 PM

Subject: Re: [cisco-nas] Slips

The pri-group config is weird, but I would not think it's relevant.

My theory continues to be, until disproven, that the device that is on the
far side of the slipping span is not configured right.

  _____  

On 10/10/2012 12:21 PM, mays at win.net (Joseph Mays) wrote:

Yeah. The DACS is not the problem though, because we have two circuits going
through the DACS, in fact they are two circuits that are exactly the same,
following the same path from our AS5400 through the telco to the same router
(an IAD2400) at the same customer, one is getting slips one is not. Both go
through the DACS. The only difference between them is that one has just a
channel group for T1 service and the other has both a channel group and a
PRI group. The one with just the channel group is plugged into the native T1
port on the IAD2400. The one with both is plugged into a card that will
support multilple tdm groups on a card.

On the AS5400....

controller T1 1/0:22
 framing esf
 channel-group 0 timeslots 1-22 speed 64
 description Glass Doctor combo PRI and T1 1
!
controller T1 1/0:23
 framing esf
 channel-group 0 timeslots 1-22 speed 64
 pri-group timeslots 23-24
 description Glass Doctor combo PRI and T1 2

The second one, on 1/0:23, gets slips about once every 10 seconds.

----- Original Message ----- 

From: Aaron Leonard <mailto:Aaron at cisco.com>  

To: Joe Mays <mailto:jfmays at launchpad.win.net>  

Cc: cisco-nas at puck.nether.net 

Sent: Wednesday, October 10, 2012 2:09 PM

Subject: Re: [cisco-nas] Slips

I suppose it is possible that a DACS could introduce enough jitter into the
signal to keep the other system from deriving clock from the line.  This is
not a problem in the general case though.

  _____  

On 10/9/2012 9:31 PM, jfmays at launchpad.win.net (Joe Mays) wrote:

It has been suggested that if those circuits go through a DAX, the clocking
signal may not be making it to the other system.

----- Original Message ----- 

From: Aaron Leonard <mailto:Aaron at cisco.com>  

To: Joseph Mays <mailto:mays at win.net>  

Cc: cisco-nas at puck.nether.net 

Sent: Tuesday, October 09, 2012 7:00 PM

Subject: Re: [cisco-nas] Slips

The 5400 has only one clocking domain.  So, if you are getting clock from
slot 6 port 0, then this is the time source for the whole TDM bus.  So, all
other T1s on the 5400 will be synchronized to that source, and anything that
takes clock from those T1s should be synchronized.

http://www.cisco.com/en/US/tech/tk713/tk628/technologies_tech_note09186a0080
14f8a6.shtml

That's why I suspect that the system on the other side of T1 6/1 is not
actually taking clock from the line.  Maybe it's free running or maybe it's
taking clock from something else.

Aaron

  _____  

On 10/9/2012 2:46 PM, mays at win.net (Joseph Mays) wrote:

I would like to change port 6/1 to clocking internal, but I can't find any
way change the clocking on an individual t1 port controller to internal. Am
I missing something?

----- Original Message ----- 

From: Joseph Mays <mailto:mays at win.net>  

To: Aaron Leonard <mailto:Aaron at cisco.com>  

Cc: cisco-nas at puck.nether.net 

Sent: Tuesday, October 09, 2012 4:48 PM

Subject: Re: [cisco-nas] Slips

Thank you for your response.

Show tdm clocks shows the AS5400 is using the circuit in port 6/0 for
primary clocking.

Primary Clock:
--------------
System primary is slot 6 port 0 of priority 1
TDM Bus Master Clock Generator State = NORMAL

Backup clocks for primary:
Source  Slot  Port  DS3-Port  Priority      Status      State
-------------------------------------------------------------
Trunk   1     1       YES       2            Good        Configured
Trunk   1     2       YES       3            Good        Configured
Trunk   1     3       YES       4            Good        Configured
Trunk   1     4       YES       5            Good        Configured
Trunk   1     5       YES       6            Good        Configured
Trunk   6     1       NO        213          Good        Default
Trunk   1     28      YES       202          Good        Default
Trunk   1     27      YES       203          Good        Default

Trunk cards controllers clock health information
------------------------------------------------
      CT3         2 2 2 2 2 2 2 2 2 1 1 1 1 1 1 1 1 1 1
Slot  Port  Type  8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1
1     0      T3   G G G B B G G B B G B G B B B B B B B B B B B G G G G G

We had considered the possibility that the problem might be coming from the
mux that everything was passing through. I rewired the pinouts from telco in
order to connect them directly to a t1 port on the AS5400 (Controller 6/1),
rather than passing them through the mux and coming across a channel on the
t3. It works, but the slips are exactly the same.

ArmoryPl-AS5400#show controller t1 6/1
T1 6/1 is up.
  Applique type is Channelized T1
  Cablelength is long gain36 0db
  Description: Leonard Brush MUX Bypass
  No alarms detected.
  alarm-trigger is not set
  Version info of slot 6:  HW: 768, PLD Rev: 1
  Framer Version: 0x8

Manufacture Cookie Info:
 EEPROM Type 0x0001, EEPROM Version 0x01, Board ID 0x02,
 Board Hardware Version 3.0, Item Number 73-3996-03,
 Board Revision A0, Serial Number JAB044106K3,
 PLD/ISP Version <unset>,  Manufacture Date 11-Oct-2000.

  Framing is ESF, Line Code is B8ZS, Clock Source is Line.
  Data in current interval (638 seconds elapsed):
     0 Line Code Violations, 0 Path Code Violations
     54 Slip Secs, 0 Fr Loss Secs, 0 Line Err Secs, 0 Degraded Mins
     54 Errored Secs, 0 Bursty Err Secs, 0 Severely Err Secs, 0 Unavail Secs

Right next to it is the trunking circut plugged into 6/0, it runs fine, no
slips. I would like to change 6/1 to internal clocking, btw, so that it
should be following the clock that is being derived on 6/0, but can't find
anyway to change that on the t1 ports. So as it stands right now, both 6/1
and the customer router on the other end of that t1 are set to clock-source
line, with no mux between them. And getting slips.

----- Original Message ----- 

From: "Aaron Leonard" < <mailto:Aaron at cisco.com> Aaron at cisco.com>

To: "Joseph Mays" < <mailto:jfmays at launchpad.win.net>
jfmays at launchpad.win.net>

Cc: < <mailto:cisco-nas at puck.nether.net> cisco-nas at puck.nether.net>

Sent: Tuesday, October 09, 2012 3:21 PM

Subject: Re: [cisco-nas] Slips

> Joe,
> 
> Sounds like, conceptually, you've set things up right.  I would 
> doublecheck on the customer routers to make sure that they really are 
> taking clock from the right T1 line.
> 
> On the 5400, you should be using "tdm clock priority" to set the clock 
> source, and "show tdm clocks" to validate the clocking. 
>
<http://www.cisco.com/en/US/docs/ios/12_3/dial/command/reference/dia_s6g.htm
l#wp1140246>
http://www.cisco.com/en/US/docs/ios/12_3/dial/command/reference/dia_s6g.html
#wp1140246
> 
> Aaron
> 
> ----
> 
> On 10/9/2012 8:43 AM,  <mailto:jfmays at launchpad.win.net>
jfmays at launchpad.win.net (Joseph Mays) wrote:
>> It occurs to me that there is an assumption built into this that is
>> unproven. Does setting the AS5400 to internal clocking on the T3 cause it
to
>> provide clocking for the T1's on the T3? We have assumed that it does. If
>> not, how do we tell it to provide an outgoing clock signal for the T1's
on
>> the T3?
>>
>> ----- Original Message -----
>> From: "Joe Mays" < <mailto:mays at win.net> mays at win.net>
>> To: "cisco-nsp" < <mailto:cisco-nsp at puck.nether.net>
cisco-nsp at puck.nether.net>; < <mailto:cisco-nas at puck.nether.net>
cisco-nas at puck.nether.net>
>> Sent: Tuesday, October 09, 2012 12:57 AM
>> Subject: [cisco-nas] Slips
>>
>>
>>> We have an AS5400 that we are using to provide PRI's to customers. It
has
>>> the following circuits coming into it from the Telco (AT&T).
>>>
>>> 5 Trunking circuits that come across T1 ties into a t3 mux, and then are
>>> then delivered to a T3 port on the AS5400. ! trunking circuit that is
>>> connected into a T1 card on the AS5400. Several circuits to customers
that
>>> are delivered out of the T3 through the mux to T1 tie pairs through
AT&T,
>>> and some of which go through HDSL T1's that we provide.
>>>
>>> We have clocking set up thusly. The T1 port that has the trunk line in
it
>>> (Serial6/0) is set to clock source line, to get clocking from AT&T.
>>> The TDM clock priority on AS5400 is set to Serial6/0.
>>> The T3 that has all the other T1's is set to clock source internal, on
the
>>> assumption that the internal clock on the AS5400 should now be
>>> synchronizing to the trunk line coming in on 6/0. So all the T1 channels
>>> on the T3 should be following the Cisco clock.
>>> The mux is set to clocking is set on the t3 to clock source line, to get
>>> clocking from the T3 coming from the AS5400.
>>> The customers at the end are all set to clock source line.
>>>
>>> None of the trunks is having slips, but several of the AT&T customers
are
>>> showing a slip every 10 seconds or so. The clocking chain we have set up
>>> seems logical to me. Is there something I'm missing? Why would the
>>> customers be having slips.
>>>
>>> We asked AT&T to monitor one of the lines that we are seeing slips on.
>>> They watched it for a bit and said no slips are occurring, though I am
>>> seeing them both on the AS5400 and on the Customer router. They are
>>> performing a more indepth test now.
>>>
>>>
>>> _______________________________________________
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