Re: OC3 STS VT1.5 Mapping Issue

eknell · ‎08-04-2006

I work at a CLEC and am having to do an OC3 inter-connect with one of our ILEC's. I am only going to need/use a full DS3's worth of bandwidth out of this OC3. This is how I provisioned my circuit path:

I currently have an STS-1 built from my originating 15454's DS3 port to my destination OC3 port on another 15454. This is the OC3 port where I am connected with the ILEC, which is hanging off of one of our UPSR OC12 Rings. All I am using are the first 28 channels in the first STS of the OC3 I am handing off to the ILEC.

My question is this.... when we inter-connected the 15454 OC3 port up to the Fujiysu OC3 port, my VT1.5 mappings get all bungled up coming out of the FLM-150. For Instance, all my VT1.5 mappings are in order coming from me...1-28, just like I were handing somebody a pure channelized DS3, but when they got to his FLM-150, they are coming out in VT Group 1-7/VT 1-4 numbering order.

I will explain:

- My #1 DS1, was his VT1-1-1 (DSX T1 #1)

- My #2 DS1, was his VT1-2-1 (DSX T1 #5)

- My #3 DS1, was his VT1-3-1 (DSX T1 #9)

- My #4 DS1, was his VT1-4-1 (DSX T1 #13)

- My #5 DS1, was his VT1-5-1 (DSX T1 #17)

- My #6 DS1, was his VT1-6-1 (DSX T1 #21)

- My #7 DS1, was his VT1-7-1 (DSX T1 #25)

- My #8 DS1, was his VT1-1-2 (DSX T1 #2)

- My #9 DS1, was his VT1-2-2 (DSX T1 #6)

- etc...

As you can see, this is why we had a hard time finding exactly where my T1's were coming in. My 7th time-slot, was his 25th......My 6th time-slot was his 21st??

Even though we got it figured out, can somebody please explain to me why this happened? The Engineer at the ILEC said he had never seen a DS3 come to him like that. He said they all come in a VT Group/1-4 T1 standard. I told him, that I hand off DS3's in other ILEC CO's all over my city, and have never seen anything but a straight 1-28 channelized or clear channel DS3.

Was this a UPSR Node to BLSR Node VT squelching issue? Was it an STS-1 sourced from a DS3 to an OC3 port issue? Was it a 15454 to FLM-150 incompatibility issue?

Any help would be greatly appreciated..

JoshGH · ‎08-08-2006

Which DS3 card does your STS-1 originate from?

What equipment exists behind your originated DS3 port? M13 mux or...? What is handling VT1.5 mapping?

I dont know if I have any theories on what is going on here, but curious to understand as much as I can from this.

Josh

eknell · ‎08-08-2006

Josh,

My STS-1 originates from a DS3XM-6 port. The equipment behind my DS3 port is a digital x-connect switch, which does my VT1.5 circuit grooming. The DS1's are x-connected to voice trunks on a Class 5 phone switch. These voice trunks are the whole reason for the OC3 Interconnect.

Anyhow, I was doing some research myself and found this article on compatibility issues between an ONS 15327 and a 15454. You will see exactly what I am talking about in the "VT Mapping" section:

http://www.cisco.com/en/US/products/hw/optical/ps2006/products_white_paper09186a00800944f1.shtml

I have about 30+ 15454's and have never seen this happen before, but this was the first time I had ever dropped a STS-1 out of a fiber connection. So unfortunately, the ILEC Engineer was right, and I will just have to deal with trying to work through the jacked up T1 numbering scheme until the day it is possible to upgrade to TCC+ cards and newer software on all of my 15454's.

Thanks