ONS BITS timing options

[smunzani]

We are purchasing 3 ONS 15454 shortly. The main usage of the boxes will be to use Channelized OC12(SONET) transport delivery from TELCO, do the grooming of channels and connect to 6509s with CH. OC12 card.

The layout will be like below.

6 Telco CH. DS3 --- ONS1 --- CH. OC12 on 6509-1

6 Telco CH. DS3 --- ONS2 --- CH. OC12 on 6509-2

6 Telco CH. DS3 --- ONS3 --- CH. OC12 on 6509-1

6 Telco CH. DS3 --- ONS3 --- CH. OC12 on 6509-2

Create a 2 fiber BLSR ring between 3 ONS.

Allow VT1.5 cross-connect luxury between any to any line.

Eventually we will have CH. OC12 delivery from Telco so we will be able to extract clock from SONET transport. However we will have DS3 delivery for at least 10 months and need our SONET to be in sync with Telco network for the clocking.

What are our low cost timing source options?

[tgimmel]

I hope I read this correctly, but during the time you are running with DS3's, clocking is not a huge worry, you can run one 454 with internal timing and the other 2 can line time to that box. However the second an OC connection is made to the outside world, timing will have to change, either take timing from the OC connection or install a BITS. Symmetricom has small clocks that may fit the purpose, they receive timing from the GPS satellites.

Another gotcha is where are the VT1.5's going? If they go outside your timing "island" then real clock will be needed.

Hope this helps,

Tim

[smunzani]

Below is point a to z transport in our network NOW:

A-end: remote site

Z-end: Core data center

1. Telco aggregates 28 DS1 at remote sites to their field CO office. They mux them to a DS3 and haul to central CO

2. At central CO they are put in to an STS and rides a leased OC-48 SONET ring to core data center.

3. At core data center they take STS off SONET and feed us Channelized DS3 on DSX panel.

4. We take DS3 transport to Cisco MGX/BPX to 6509 ATM-PA to have our FRF.8 network.

Immediate Need:

We need to take 4 of those DS3s routed through our ONS OC12 ring and do grooming so that a few of VT1.5 are dropped to CH.OC12(SONET) ports on new 6509 while sending rest of the channels back to MGX.

We had set it up in lab environment with Internal clock but started having line errors at high traffic volume because of clock drift.

Long Term Plans:

Telco is requested to feed us CH.OC12 instead of DS3s at core data center. Take those OC12 drops on our ONS for grooming and feed to new 6509 SONET interfaces. In short, we get rid of FRF.8 and go with point to point. At that time we can clock from the OC12 line dropped from TELCO.

[tgimmel]

One more note.

I noticed that you were refering to the T1's as VT1.5's. Is the Telco transmuxing or do you have the transmux in your 454's? If Telco is doing standard M13 or CBit muxing then the T1's are NOT VT1.5's unless they have been transmuxed somewhere (converted and placed into the sonet payload). If I misunderstand then forget this message.

Tim

[smunzani]

Tim,

TELCO is told not to do M13 muxing since we need VT1.5 visibility in SPE.

Each ONS has 2 15454-XC-VT & 2 15454-DS3XM-6. So I guess ONS can look in SPE for VT1.5 interleaves.

The 6509 OSM is OSM-1CHOC12/T3-SI.

From that perspective, I think we should be good for VT1.5 visibility.

Thanks a lot for the BITs reference. You answered my question perfectly for the BITS timing.

[smunzani]

Please forgive my ignorance but I am dealing with a telco gear first time. Symmetricom has so many timing products I am lost. Do we need a crystal oscillator or something that sync with GPS or NTP? Any recommendation of model will help a lot. I mean what should I be looking for? What's magic word in Time & Frequency timing world?

Thanks,

[tgimmel]

Symmetricom has a unit, Timesource 3500, that can be purchased with a rubiduim oscillator and GPS antenna that would probably fit your needs. Tiis would give you a statum 1 traceable clock with a holdover of stratum 2. You could go a couple of weeks with that! Since you will be handling VT1.5's I would agree that your DS3's will need to be timed a bit more tightly.

Below is a link to Symmetricom. I don't necessarly edorse the product but there are not too many vendors in the marketplace. If you had the a clock and an OC12 from Telco, then you would have 2 sources of timing and that would be "Good Thing" for your network.

http://www.symmetricom.com/Products/Telecom_Solutions/Primary_Reference_Source/TimeSource_3500.htm

Hope this helps,

Tim