Anyone familiar with the SBC product lingo?

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1

Hi All,

I'm trying to get some pricing on an OC-3 that we will be using for
voice. We already have a master agreement with SBC for our services. I
have the feeling that we are being "oversold" services and/or sold
services that are not required for what we need to accomplish. Not
doing this everyday, I'm confused about the "Feature Name" of things
like:

SONET Circuit Service OC3-c (155Mbps) $2200 vs. Central Office Node
Circuit Service OC3/3c (155Mbps) $675

Anyone that is knowledgeable about SBC lingo, please feel free to ping
me. If you have experience with OC3s even better! :wink:

Thanks!
Dan

2

SONET simply means you are on a Sonet ring: Two redundant connections to
the central office. If someone gets a little crazy with a backhoe your line
is guaranteed to stay up (ask about SLAs, and make sure they will refund
part of your monthly bill if you have an outage). That's why it costs over
twice as much.

I would imagine the other service is just a point-to-point connection,
subject to the same type of reliability you would get from any
point-to-point connection.

Hope this helps.

3

SONET simply means you are on a Sonet ring

you wish

you can easily find yourself on a linear stub

and, even if you are on a ring, you need to ensure
  o trench diversity
  o that it is actually configured to fall over
  o ...

randy

4

To take advantage of this redundancy, the entrance facilities to your
building must not be part of a "collapsed ring" where both fiber pairs
are in the same conduit/bundle.

Quite often this is not done right. If it requires two backhoes to take
it down, it requires two backhoes to build it. In other words, for SONET
redundancy to be of value to you there need to be two physically separate
fiber feeds to your location that remain physically separate throughout
the ring.

5

It is worth mentioning that the value of SONET redundancy has a lot to
do with your location to the ring. SONET's value is proportional to the
available space for backhoes between your location and the point where 1
trench splits into two trenches, if this ever occurs, prior to hitting
the SONET ring.

For instance: If you are more likely to experience digging near your
location, then SONET may not really be worth the cost as nearby
trenching activity could just as easily knock you off the ring.

SONET is very good if you are worried about the provider's metro network
confronting a backhoe.

Does anyone have any good statistics on SONET outages?

-Jim P.

6

And remember to ask questions - make sure they've actually got the two
connections routed differently. Remember that if the backhoe hits the conduit,
*all* the fiber pairs go - and if both runs were in the same conduit, you're
still dead....

(Anybody here *NOT* seen cases where the 2 fibers leave the building on opposite
sides, go down different streets - and rejoin 2 miles down the way because
there's only one convenient bridge/tunnel/etc over the river, or similar?)

7

yes. but in my case we checked it and it was okay on install but was rerouted at
some point. someone broke the ducting and we lost a bunch of oc48s which was
bad.

you'll never get better redundancy than having more than one carrier.

Steve

8

you'll never get better redundancy than having more than one carrier.

very often, they buy segments from eachother, run in the same
trench, change the dlr six months later, ... trust and test
just as you would a single carrier. trust 0 test 100.

randy

9

when this has been critical i've insisted on seeing duct maps to ensure they
really are different. but as you say even that doesnt prevent a change of path
in the future

i guess it helps us to know a bit more than the average circuit buyer tho too..

Steve

10

I've seen duct maps which "proved" the fibers were truly diverse, but somehow the circuit died with a single backhoe strike.

11

The way to somewhat solve this problem is to buy a 12 pack (or two) for
the tech(s) that are setting up your circuit. Get to know them and ask
them about the pathing and what they know about common conduits,
tunneling, railroad tracks and/or watermains subject to being dug up on
the weekend, etc.

Whatever you do, don't trust the sales or support people to know. They
mean well, but their interests aren't in keeping their butt in a warm
bed in the middle of a winter weekend night.

-Jim P.

12

SONET Circuit Service OC3-c (155Mbps) $2200 vs. Central Office Node
Circuit Service OC3/3c (155Mbps) $675

SONET is a method of transporting TDM channels over fiber. SONET is made up of building blocks calls a STS. A STS is equivalent to a DS-3 + SONET Wrapper. An OC-3 equals 3 STSes. OC-3s come in two types, 'channelized' OC-3 which is 3 DS-3s in 3 STSes and Packet Over SONET (POS), concatenated OC-3c which is 155mbps. If you are planning on using this circuit for TDM based voice (84 T1s in 3 DS-3 chunks) then you will want an OC-3 not an OC-3c. If you are planning on running 155mbps POS IP traffic you want an OC-3c.

OC-3 = 3 x STS-1 = 3 x DS-3 = 3 x 28 DS-1s, 84 DS-1s = 2016 DS0 voice channels.
OC-3c = 1 x STS-3 = 155mbps

You can use an Adtran OPTI-3 to break an OC-3 into 3 distinct DS-3 channels which can be plugged into M13 muxes (Carrier Access Widebank 28) which will break a DS-3 into 28 DS-1s.

If you want IP bandwidth you can use an OC-3 POS line card from your router vendor of choice.

-Matt

13

(Anybody here *NOT* seen cases where the 2 fibers leave the building on opposite
sides, go down different streets - and rejoin 2 miles down the way because
there's only one convenient bridge/tunnel/etc over the river, or similar?)

Even if that's not the case, and it's still perfectly separated all the way to the CO, the CO is a common point of failure. Granted, the failure modes are very unlikely to occur for a CO, but they do exist. Those two separate paths of the ring have a way of always coming together somewhere, by design.

The only way to insure that doesn't happen is to have two sources of connectivity to a building, from two separate local carriers that have fiber going in two opposite directions (eg., one carrier to the east, one to the west), to two opposite area codes/LATAs that get transit from two different transit providers that have POPs in cities that are geographically the furthest apart (one to the north, one to the south, or east west, or whatever). As long as everything keeps heading in complete opposite directions, it becomes very assured that the common modes of failure diminish with distance.

This tactic works, and works well with IP using BGP, but it's something that would be beyond my scope of expertise to attempt to implement with anything else.

(someone mentioned earlier charging the 2 9's rate for providing 5 9's service...... it was a wake up call to myself.....I'm that guy!)

On a somewhat related, but kind of a little off topic note:

It always makes me chuckle inside to hear data centers tout their "dual grid connections" as a way to insure that the power "is hardly ever interrupted" Same basic principal. Sure they might be separate distribution feeders, and they might even come from separate distribution substations, and the subtransmission that feeds the distribution substations might even come from separate transmission substations... but within about a minimum of a 60-100 mile radius, it's nearly always connected together by the transmission grid.

Now, if there was a data center that had a power feed connection to say, ERCOT, the Eastern Interconnection, and the Western Interconnection.... THAT would be something to brag about.

14

One carrier can often tell if two circuits they're providing you are
on the same route,
        and can develop processes for building circuits that are not
only installed diversely,
        but don't get rerouted onto the same path. Doesn't mean that
*every* carrier can do this ,
       or that the ones who can always do it reliably, but it's a start.
Two carriers can almost never tell if that's the case, even if neither
of them is buying
       services from the other or from a common third carrier.
       Nor are they good at developing processes together.
       They are less likely to have common equipment failures, or
common operator failures,
       but they're more likely to have common backhoe targets.

Also, while it may be possible to get diversity by deploying two
circuits at the same time,
that doesn't mean that you can get diversity by deploying one circuit
and later deploying another.
A common problem is that routes ABCDEFGZ and AHIJKLMZ are diverse,
but the first circuit you buy is on route ABCKLMZ and there's no way
to build diversity with the leftovers.
Another common problem is that routes ABCDEFGZ and AHIJKLMZ are both
more expensive than ABCKLMZ, and AHINOPQRSTUVWXYZ is much more
expensive,
and you've awarded the initial purchase to the lowest bidder and
expect others to be competitive.

15

Sure, quite often in fact. Ever been to Pittsburgh, PA? :slight_smile: The vast majority of the time, the route between point A and point B requires multiple bridge and/or tunnel crossings.

jms

16

you'll never get better redundancy than having more than one carrier.

On the contrary, you get better redundancy by sticking to
one carrier and making sure that they really provide
separacy though the entire span of the circuit. If you
have two carriers running fibre to yoiur building down
the same conduit, then you do NOT have separacy and as
a result, the redundancy is not there.

Of course, you can get separacy with two carriers but
it is generally more work to verify that the two companies
do not share fibre or conduit or tunnels.

--Michael Dillon

17

Michael.Dillon@radianz.com writes:

On the contrary, you get better redundancy by sticking to
one carrier and making sure that they really provide
separacy though the entire span of the circuit. If you
have two carriers running fibre to yoiur building down
the same conduit, then you do NOT have separacy and as
a result, the redundancy is not there.

The problem with this theory is that one carrier is completely free to
reroute your connectivity among its resources. Two carriers can
certainly move from being diverse relative to each other to sharing
common infrastructure, but if it costs money it's much less likely to
happen.

Note that many carriers, though perhaps not the LECs, will answer
questions about the underlying resources they are using if they are
sufficiently motivated, but you have to reask every now and again to
make sure that the answers are still satisfactory.

Of course, you can get separacy with two carriers but
it is generally more work to verify that the two companies
do not share fibre or conduit or tunnels.

Well, then it's a question of how much one cares about diversity. If
it's important, it may be worth some effort. If it's really important,
then you try harder to control the infrastructure in question
directly, which can mean anything from constructing your own
underground facilities to leasing someone elses - at least to get out
of the building. If it's really, really important, then you pick the
building based on the selection of providers and the redundancy
offered by the set.

18

>On the contrary, you get better redundancy by sticking to
>one carrier and making sure that they really provide
>separacy though the entire span of the circuit. If you
>have two carriers running fibre to yoiur building down
>the same conduit, then you do NOT have separacy and as
>a result, the redundancy is not there.

The problem with this theory is that one carrier is completely free to
reroute your connectivity among its resources.

One carrier can only do what your contract allows them
to do. And negotiating a contract with strong requirements
for separacy is easier with one carrier than two.

Note that many carriers, though perhaps not the LECs, will answer
questions about the underlying resources they are using if they are
sufficiently motivated, but you have to reask every now and again to
make sure that the answers are still satisfactory.

Agreed.

--Michael Dillon