Re: Why doesn't BGP... -Reply

["Larry J. Plato" <ljp () ans net>]

>  
> > > What I don't know, is why is it that SS7, the telephone routing protocol,
> > > can do some of the things that are required, like load sharing across
> > > unequal paths, for example.  Does anyone have any insight into this?
>
> I *believe* one main difference is that telco sig is connection oriented
> whereas IP is pretty much collectionless (interesting comparison
> to netflow switching though); hence telephony switching protocols
> can afford to wait tenths of seconds finding a route whereas this
> would not be an acceptable per packet switching overhead. Another
> is that signalling between switches is carried out-of-band (i.e.
> is not itself affected by line congestion) which is the bane of
> many routing protocols. Also note that esp on intl circuits there
> is still manual preening activity.
>
> (prepares flame-suit for telco interconnect guru attack)
>
> Alex Bligh
> Xara Networks
Alex,

Connectionless and Connection oriented both refer to packet switched 
technologies, whereas the phone company uses circuit switched technology.

Circuit switched means that the same wires/timeslots are dedicated to 
a call from the time it starts until the time it finishes.  If you do
not speak, the wires are idle/wasted.  I am sure you understand packet
switching.  In a packet switched network, connectionless means that each
packet has no state information, and stands alone, in the IP world we call
this UDP.  Connection oriented would be the equivalent of telnet or
some other TCP service.

SS7 (Signalling System 7) is a connectionless packet switched technology
used to control the setup and teardown of circuit switched calls.
Originally is was used as a database query technology to make 800
numbers portable across carriers.  If this did not make sense I can descibe
it in a little mnore detail offline.

Larry Plato
ANS CO+RE Systems
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