DWDM Metro Access Design

Livio Zanol Puppim livio.zanol.puppim at gmail.com
Mon Mar 21 20:11:21 CDT 2011

I don't rally care about the uptime at the spokes. It's not my
responsability to maintain the spokes sites, we'll just give communication
to our network.

I know that I'll have single point of failure in my topology, like having
just one HUB, but I just don't want a spoke interfering in the opeartion of
my network. Ex.: I don't want a eletrical failure at one spoke interfering
in the operation of other spokes...

Thanks for your reply. :)

2011/3/21 Michael K. Smith - Adhost <mksmith at adhost.com>

> On 3/21/11 5:36 PM, "Livio Zanol Puppim" <livio.zanol.puppim at gmail.com>
> wrote:
> >Hello,
> >
> >I don't know if this is the appropriate list for this kind of subject, so
> >if
> >anyone knows another specific list, please tell me...
> >
> >I'm analysing several DWDM designs to implement at my city, but I'm still
> >a
> >bit confusing about the Metro acess design. I'm supposed to build a
> >physical
> >ring topology with 6 pairs of fiber with an hub-and-spoke logical
> >topology.
> >The ring will have about 40Km. At the HUB we'll install our
> >point-of-presence with a MPLS equipment, and at the spokes we'll use only
> >IP
> >routers. We need an flexible design where we can add or remove spokes as
> >needed with the minimum effort possible. We are planning to have, at a
> >initial deployment, about 200 hundred spokes, and all these spokes are
> >talking only with the HUB site. Everything should work like in an FTTH or
> >FTTB design, no other type of transportation is allowed (wireless and
> >copper).
> >
> >We can't use SONET/SDH. The solution must be only IPoDWDM or complemented
> >with TDMoIP at the access equipment.
> >
> >The problem, is that all documents that I'm reading specifies that we
> >should
> >be worried with faults scenarios at the spokes, so that the optical
> >network
> >does not stops. For example, if the OADM equipment at the spoke is down,
> >the
> >lambda dropped at that site will be down too... Or at least, if we use a
> >lot
> >of lambdas, we need to keep and eye at the points where we have
> >regenerators.
> >
> >We need bandwidth from 10Mbps to 1000Mbps at these spokes.
> >
> >My question is:
> >Is it possible to make such a network in a way that we don't need to worry
> >about faults (electrical or others) at the spokes? If so, how can I do
> >this?
> >
> >I don't want the spokes sites interfering directly at the operation for
> >the
> >whole network.
> >
> >Thanks for your help.
> Hello Livio:
> At some point you will have a single point of failure, it's just a matter
> of where.  If you are running a single-threaded lambda or set of them into
> a spoke site, that node will go down should your transport gear fail.  If
> you want your add-drop sites to be redundant through the network layer you
> will have to feed each spoke site from the East and West side of your ring
> on separate add-drop gear.
> That will be expensive.  If price is no object, you can do that and then
> use your upper layer protocols to determine path availability.  Or, you
> can build your add drop site with a single device and built-in redundancy
> (controller cards, power supplies, etc.) to keep the cost down.
> Long story short, if you need those sites to stay up regardless of
> anything else, you have to build two of everything at each site.  It can
> certainly be done and many a vendor would like to talk to you about
> solutions I'm sure!  :-)
> Mike
> --
> Michael K. Smith - CISSP, GSEC, GISP
> Chief Technical Officer - Adhost Internet LLC mksmith at adhost.com
> w: +1 (206) 404-9500 f: +1 (206) 404-9050
> PGP: B49A DDF5 8611 27F3  08B9 84BB E61E 38C0 (Key ID: 0x9A96777D)


Lívio Zanol Puppim

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