SONET/SDH Becoming Obsolete?
bey...@my-deja.com
technologies like IP over DWDM and Gigabit Ethernet becoming more widely
deployed is an interoperable standard like SONET/SDH really necessary?
If SONET/SDH is on the way out, when will this happen?
I'm looking for some views on this subject for publication, so any help
you can give will be appreciated.
Sent via Deja.com
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Bill Vermillion
Everything is becoming obsolete. Some places are now replacing
DWDM with Ramman technology. That looks to make the bandwidth
gains seen with DWDM small by comparison.
--
Bill Vermillion - bv @ wjv . com
Byrautor
In what is going to follow Sonet and SDH are considered identical.
The debate general present door on the opposition that between the
transmissions by circuits (establish) as SDH and the transmissions by
datagram, independent and isolated packets.
ONE perceives, with MPLS in Internet, that the rebirth of virtual circuits
as in X25, ATM, relay of plot and SDH and SONET is under way.
For my part I am partisan of the SDH model, independent and that himself
support on a technology rather cabled that software; in SDH it is the
position of the bit in relation to a scorer of plot (framing bytes in Sonet,
bytes A1, A2 in SDH G.707 ITU) that indicates its function; there is not to
analyze the value of a byte or a set of bytes; this technology should be
always the fastest.
Sonet and SDH have again of beautiful days before them; for several reasons:
1) first the quantity of SDH facilities installed and the quantity of
facilities to install again requires an interview and a constant management
therefore a lot of work for a lot of people and for a long time because when
its functions there is anything to make that to supervise; there are a lot
of SDH facilities that get settled again, by Alcatel exemple installs in
Thaïland 10 000 km of optic fibers with SDH facilities.
2) SDH and Sonets are very definite, very robust products and that possess
devices of very sure auto-repair; so an user of SDH is assured of a
guarantee to 99,99% of availability (less than one hour per year of service
stop); all big enterprises use some SDH channels in their important links
and secured.
3) it is necessary to remember that the SDH is a transparent technology to
the protocols that it transports; completely independent of the elated data;
it can transport all sets of bits provided (on condition) that the clocks
are:
or in foreseen toléances; or taken on the SDH equipment (as provides the 114
in V24 or the DB binds 15 in RS 232 or the ST. in RS 449: (clock modem
pprovide to the issuing terminal).
4) it is necessary to know that SDH doesn't possess orders of sorting and
mailing (routage, routers) it resists the piracy (hackers) thus perfectly
because to spy on a lign off SDH it is necessary to work also on the network
of surveillance (monitoring) that is a different network.
The boredom, for the user (and the supplier) it is that 2 interfaces and 2
different protocols are necessary; one of connection demand generally owner
and the other of very very definite transportation.
I think that all protocol of transportation that also transports the
information of sorting and mailing (routage , routers) (among others) is a
fragile protocol; one sees the complexity that arrives in the devices of
cryptages that it is necessary to use now to protect its data in Internet;
with SDH channels it is not useful.
5) the WDM, the DWDM and SWDM are a supplementary layer that widens the
possibilities of the SDH considerably; one can, or one will be able to, to
make pass some packets directly on these optic channels but it will be
necessary, of a manner or the other to take the devices of signaling of the
SDH to achieve all functions of surveillance necessary to the knowledge of
the transportation qualities and to the setting in service of the emergency
devices.
It is besides in progress to the ITU (Geneva) but when one will want smaller
channels (2,048 Mb/ses for example, one will come back in SDH).
SDH assures a transmission regularity without equal, if you send 4 x STM-1
with each 63 VC-12 of 2,048 Mb/s each (of any protocol) you will have, in
receipt 4 x 63 = 252 streams of data that will be presented very
simultaneously; each with its own clock of (emission) broadcast; every clock
of emission (broadcas)t will fully be restored.
The SDH is a little as what is a motor diesel in relation to a motor to gas;
difficult to construct but very robust.
The problem with the other protocols it is that there is interference
between the protocol and its transmission; one says that the SDH, as the WDM
is transparent.
The worse disadvantage of the SDH is its need to work in double sense
(direction) on every channel; so if the data only pass in a sense
(direction) , the other sense is vacant; it cannot be lent to another user,
alas.
Some societies prepare a solution to this defect, as the Dynarc society to
http://www.dynarc.se /
I could tell of it to you more but I would need more of time to translate
because I write in French.
Are not angry at me if you find difficulties of reading.
The networks synchronous extended PDH and SDH G. Bouyer HERMES ISBN
2-86601-644-0
Sonet Walter J. Goralski McGRAW-HILL ISBN 0-07-024563-0
Understanding Sonet/SDH Standards and Applications Ming-Chwan Chow ISBN
0-9650448-2-3
<bey...@my-deja.com> a écrit dans le message :
91vr2d$ah2$1...@nnrp1.deja.com...
Conductor
some providers moving away from SDH toward Lambda net for ATM switches etc.
which of-course still utilise SDH/SONET interfaces. The SDH network is less
complex, simpler to fault diagnose, administer and easily re-routable, I
also believe some customers prefer the additional layered security (leased
STM-N) inherent in SDH.
We will continue to use switched voice/fax calls and RAS connections and it
will take many years for IP based solutions to eliminate this need, we can
look at FDM here in the UK where some customers (very few) still have
Megastream over FDM basically as they state it is working and never failed
so don't fix it.
My guess is SDH will be around for the next 10 years and then begin to
decline with an increase in purely IP solutions (or whatever comes next).
This is how I feel but would be interested in other peoples theories.
Al..
<bey...@my-deja.com> wrote in message news:91vr2d$ah2$1...@nnrp1.deja.com...
Bill Vermillion
>In article <91vr2d$ah2$1...@nnrp1.deja.com>, <mbe...@gnlp.com> wrote:
>>Question: Will SONET/SDH become obsolete in the near future? With
>>technologies like IP over DWDM and Gigabit Ethernet becoming more widely
>>deployed is an interoperable standard like SONET/SDH really necessary?
>>If SONET/SDH is on the way out, when will this happen?
>
>>I'm looking for some views on this subject for publication, so any help
>>you can give will be appreciated.
>Everything is becoming obsolete. Some places are now replacing
>DWDM with Ramman technology. That looks to make the bandwidth
^^^^^^^
>gains seen with DWDM small by comparison.
>
Spelled with only one M - Raman. I had two emails on this.
I first ran across this in Lightwave - www.light-wave.com, and a
search on Google now turns up some sites on Raman.
My apologies for the typo which may have misled some.
Bill