Cisco Support Community
Showing results for 
Search instead for 
Did you mean: 

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. And see here for current known issues.

New Member

OC3 STS VT1.5 Mapping Issue

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...

- 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..

New Member

Re: OC3 STS VT1.5 Mapping Issue

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.


New Member

Re: OC3 STS VT1.5 Mapping Issue


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:

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.


CreatePlease to create content