[nsp] OC3 interfaces for 7xxx vs. other OC12 transport options

[Matthew Crocker]

On Jul 12, 2004, at 1:21 PM, Mike Lewinski wrote:

> While we have always had services delivered to us via OC-3 and OC-12,  
> they have always been terminated on carrier-owned and maintained  
> equipment, and muxed out as DS3 on coax or DS1 on copper to us.
>
> So as preface let me say I've got little experience with fiber and  
> none with OC transport.
>
> We are now venturing into terminating an OC service ourselves and have  
> a couple paths. The primary service we are considering is a Qwest OC-3  
> via a standard sonet interface in a point-to-point terminal  
> configuration (1 + 1 protected) delivered on single-mode fiber  
> (standard 1310nm signal) with FC connectors. This would tie back into  
> an ICDF colo at the Qwest CO where a Loop Mux Combo (LMC) would  
> interconnect DS1 tail circuits for data and VOIP services to client  
> sites. The Qwest technician who will do this installation advises he  
> is using FLM150s on his side.
>
> The primary use for these OC3s will be terminating client T1s and  
> that's all we ever expect to use them for. So the ability to peel off  
> a single DS1 in the router is important. I understand that in this  
> type of configuration, Qwest does not do the channelization for us,  
> but that the product itself is capable of channelization and we are  
> responsible for keeping track of the correspondences between the OC3  
> and LMC (they give us a circuit ID w/ CFA which is the channel on the  
> OC3 and an APOT which specifies the DS3 termination, as I understand  
> it).
>
> Cisco has a number of OC3 interfaces for a 72xx or 75xx (we have both  
> and my preference is to probably use the 75xx so that widens my  
> choices I believe). It's not at all clear to me which interface is  
> really appropriate and I'm hoping someone here is doing something  
> similiar enough to give me good guidance. Additionally, I assume that  
> for the 1 + 1 protection what I really want are two separate  
> interfaces in case of failure (and there's just one entrance facility  
> into this building so I understand what will happen when the backhoes  
> dig it up).
>
> We are also considering an OC12 but I realize the 7xxx backplanes  
> never had enough bandwidth to justify making an OC12 interface and so  
> I'm looking at buying a 12xxx series in order to support it directly.  
> But I wonder also if anyone has advice on a standalone device to  
> (relatively cheaply) terminate an OC12 and mux out OC3s to the  
> aforementioned Ciscos 7xxxs...
>

Channelized interfaces on Cisco are insanely expensive.  You can't use  
a POS-OC-x card because you aren't running POS.  You are running  
channelized to DS-1 circuits on the OC-x.   You can terminate the OC-x  
directly into the CIsco using a channelized OC-x card or you can demux  
the circuits down to channelized DS-3 and connect them to the Cisco  
using PA-MC-2T3 cards (again,  very expensive).

For OC-3 -> DS-3 muxing take a look at the Adtran OPTI-3 mux.  works  
great and it is cheap.
For OC-[3,12,48,192] -> DS-3 muxing take a look at the Cisco ONS 15454  
with DS3-12 cards.
For ChDS-3 termination take a look at the Seranoa IPeX 200  
(www.seranoa.com)

Here is what I do.

I pick up channelized DS-3s from my carriers and my own colo cages and  
bring them into my ONS 15454 SONET ring.  The SONET ring sees them as  
clear channel DS-3 circuits (no VT grooming).   I bring them into my  
pop on OC-48 and terminate them as channelized DS-3s to a Seranoa IPeX  
200 CH12 (www.seranoa.com).  The IPeX is a layer 2 DS-1/DS-3 switch  
which strips off the HDLC frame and wraps the packet back into a 802.1q  
frame.   Think of it as a frame relay switch but instead of DLCIs you  
have VLANs.   The Seranoa outputs the dot1q frames over GigE to my  
router.   I currently have a 3550 series switch acting as my GigE  
router and it is handling it perfectly.  When I outgrow it I'll get a  
7301 to handle the VLANs.

So..  the traffic flow from my customer looks like this

CPE -> [DS-1 (HDLC)] -> CO/SCOPE M13 Mux -> [ChDS-3 (HDLC)] -> SONET ->  
[ChDS-3 (HDLC)] -> Seranoa -> GigE (dot1q) -> Router

  IP    ->  HDLC(IP)  
------------------------------------------------------------------------ 
---------------------------------------> dot1q(IP)  
---------------------->  IP

The Seranoa can handle 12 Channelized DS-3s and is about the same price  
as a couple PA-MC-2T3