Problem connecting 3 LIM system over fiber using Ascom 1

[ttcentar]

Can anyone explain why remote lims can`t see GS (LPU display shows 2020)?
Phisical connections from GJUL4 and GJUG5 to MUX equipment are OK (no alarms on Ascom), all Ascom equipment is in transparent mode, but still no connection!
We have one PRI ISDN (E1) from Telco connected to TLU76 and it`s working via same Ascom equipment.
Thanks in advance!

 

[whosrdaddy]

how many channels do you provide on the E1?

-----------------------------------------------------
What You See Is What You Get
Never underestimate tha powah of tha google!

 

[dstrang1]

Are you sure that the pins on the cables between the G and L boards and the mux ports are correct?

Are the mux ports set for HDB3 coding?

Remember that the G side has to provide synch (timing) for the circuit -- is the mux set to derive timing on the GS side from the E-1 port and the L side set to derive timing from the loop?

Also remember that the G5 board is a "dual" interface and the pinout for each port is different depending whether you use coax or twisted pair.

Good luck,

Dave Strang

 

[ttcentar]

I`m not familiar with mux equipment and people that maintain the mux are not well trained.
I was hoping that someone coul`d give us a hint what to do.
As far as I know, PCM link between G and L boards use SS7, and "transpatent" mode on mux should be enough to pass the traffic between G and L.
I don`t provide nothing specific regarding channels, all 30+2 ch. are active both PRI and GS.
I`ve tryed all kind of wireing (Rx/Tx) toward mux.
I`m using 120 ohm cables, so C32,30,28,26 is correct?

 

[fouesnant]

Hi

We encoutner different problems on that topic. Now what we are specifying is that the mux should transmit tranparently the full 2 Mbit/s links.
this mean that TS0 should be send as well; in most cases TS0 is only handled locally from GJU board to the mux, and that does not work.
I have spend a lot of time in the past on that subject, and in TS0 when you start the remote LIM, there is data transmitted.
So if your mux can do that, you can test it. Otherwise IPmux from RAD works perfectly.

 

[ttcentar]

to fouesnant,

I don`t know what TS0 is, and muxs are in transparent mode!
As I said earlyer, PRI ISDN from Telco is working perfectly, and it`s connected through mux equipment used for remote lim (one Ascom LOMIF board has 8 x 2Mbit/s, first port for Telco ISDN, second for LIM2 and third for LIM3).

 

[dstrang1]

ttcentar (TechnicalUser) 20 Mar 08 3:43 sed:

>I`m not familiar with mux equipment and people that >maintain the mux are not well trained.

OY! Seems to be a universal trend these days......you have my sympathies.

>I was hoping that someone coul`d give us a hint what to do.
>As far as I know, PCM link between G and L boards use SS7

SS7??? I don't think so......

>, and "transpatent" mode on mux should be enough to pass >the traffic between G and L.

Well.....yes, BUT.....end to end timing and correct line coding are still critical aspects of the configuration.

>I don`t provide nothing specific regarding channels, all >30+2 ch. are active both PRI and GS.

Good.

>I`ve tryed all kind of wireing (Rx/Tx) toward mux.

Here's a trick I learned many moons ago: the transmit pair for a G, L or T-1/E1 will light an LED. Therefore, you can physically verify the continuity of your cable between devices as well as proper pinout by putting the LED across the transmit pairs at each end of the circuit on the cable connector and the device connector. This has saved my butt
more times than I can count.

>I`m using 120 ohm cables, so C32,30,28,26 is correct?

For the L-board, yes. For the G-board, it depends on which port - they go from top to bottom on the G5.


Good luck,

Dave Strang

 

[ttcentar]

From Alex:
"Towards the link, time slot 0 is used as a synch channel and time slot 16 is used as a signalling channel which carries signals from/to GS based on CCITT Signalling system 7."

>Well.....yes, BUT.....end to end timing and correct line coding are still critical aspects of the configuration.

If my LIM2 is connected to GS directly, everything works OK.
When I take it to the other site, I`m using mux to make connection. Line coding and timing refers to mux configuration?

 

[dstrang1]

ttcentar (TechnicalUser) 20 Mar 08 9:57 sed:

>From Alex:
>"Towards the link, time slot 0 is used as a synch channel >and time slot 16 is used as a signalling channel which >carries signals from/to GS based on CCITT Signalling >system 7."

OK, I see where you're coming from re:ss7, but it's kind of irrelevant.....we're not really concerned with the actual content of each individual channel, only that the path for those channels between the L and G boards is transparent to the end devices.


>>Well.....yes, BUT.....end to end timing and correct line >>coding are still critical aspects of the configuration.

>If my LIM2 is connected to GS directly, everything works >OK.
>When I take it to the other site, I`m using mux to make >connection.

Yup!

>Line coding and timing refers to mux configuration?

Yes! Make the folks who maintain and configure the mux provide you the documentation so you can read it yourself. Also, make them take you thru the mux config process step by step for both ends.

I didn't ask before......are these muxes on a dedicated fiber path from point to point or is there a portion of a telco network in-between?

Good luck,

Dave Strang

 

[ttcentar]

dstrang1, I dont know if you are familiar or not whit Ascom, but I`ll describe you full path between my LIMs.
MUX equipment is on dedicated fiber path!

Site A

[LIM1(GJUl4)] Tx ---> Rx [GS 0-0 (GJUG5)]
Rx ---> Tx

[GS 0-1 (GJUG5)] Tx ---> Rx [Ascom (LOMIF)]
Rx <--- Tx

Fiber network (all equipment is Ascom)

LOMIF <--> SYNAC <--> SYNIF <--> SYNIF <--> SINAC <--> LOMI4

Site B

[Ascom (LOMI4)] Tx ---> Rx [LIM2 (GJUG5)]
Rx <--- Tx

Thanks

 

[dstrang1]

I'm not familiar w/Ascom fiber equipment specifically, BUT, the basics are the same regardless of who makes the box.

From the path you give,you could indeed have the muxes on each end set up correctly, but that one of the intermediate points is misconfigured or the channels are incorrectly mapped. (your physical connections from L and G to mux ports are correct according to your diagram).

I would argue that the path between muxes is NOT dedicated because you have 4 other devices in the path between the muxes - each one of them requires separate configuration on the in and out sides.

You're going to have to verify (or make your provider verify) connectivity of the path between every single point along that path. Don't take the provider's word for anything-make them SHOW you.....you know it's not a LIM and GS problem because they work when directly connected.

Is it possible to send a remote loopback request from the LIM 2 LOMIF port to the corresponding LOMI4 port? Or, is it possible for someone on one end to manually put a loop and verify the loop on the far end?


Good luck,

Dave Strang

 

[ttcentar]

Dave,
Thanks for all your replies!
I understand your instrunctions and I agree with you completely about fiber equipment manufacturer.I also agree that provider should be more worried about this issue than I should be.
I`ve tryed loops on LOMIx boards and all I`ve managed to do is turn off Ascom "physical" layer alarms.
Ascom maintenance staff couldn`t use my loops for testing, because they must brake all "cross connections" in order to do the testing. This can`t be done because there`s some other equipment using this fiber path and braking cross connections would impact proper functioning of that system.
Once again, I want to thank you for your interest.
BR

 

[dstrang1]

1 - Sounds like the Ascom folks are blowing smoke. they should be able to see remotely all aspects of the individual circuit paths. I'd say it's a good possibility that they've got a cross connect wrong.

2 - if a hard loop on one end clears physical layer alarms, then maybe your connections between the MD and the muxes is not correct (hence the LED test). From each mux toward the MD devices, you should have no physical or layer 1 alarms, but you should have some sort of alarm from each mux looking towards the remote mux.

3 - if the intermediate equipment is cross-connected correctly, a hard loop on one end can be verified with a BERT tester at the other end.


Good luck, it's definitely no fun being at the mercy of a provider who can't support the applications they make you pay dearly for....(been there!)


Dave Strang

 

[guma07]

Hi!
Maybe problem is in TS0 , because many MUX-es use bits 4-7 for remote administration ( you can do changes on far side of mux from one place). We use NOKIA muxes , and we must disable remote administration , if we want to conection between GS and LIM X work OK.

 

[ficac]

I wasn`t able to log using my ttcentar acount, so I opened a new one just to be able to thank you all and to respond.
Problem is solved!The cause of the problem was 2Mb port malfunction on Ascom board. They`ve simply rewired fiber connections and make new SW cross-connections, and now all is OK.
BR