As for the data packet flow in DS1s, DS3s, or Fractional pipes, you
have three modes:
1) Circuit Switched - Let's say you call Grandma and once
she answers you two have
exclusive and full use of the circuit that was established
between you. You have that
circuit unti lone of you hang up, at which time it goes idle
until the system of switches
grabs it for another call. The call could be voice, video,
or data The advantage of
circuit swiching is you have it the entire time and it's
full duplex. The disadvantage
is since you have the entire circuit you pay and it is
expensive.
2) Packet Switching - Sending data in packets through a
network to some remote
location. The data to be sent is assembled in the PAD
(Packet Assembler / Disassembler)
into indivisual packets of data, involving a process of
segmentation. Each packet has an
unique ID as well as the destination address. Packet can
take variuos routes to the destination
address and are Reassembled (normally there is a form of
latency due to different paths and lengths).
You have an error checking and correcting occurring through
this process as well since you have
packets arriving at different times and out of order.
3) Message Switching - A technique of receiving a message,
storing it for a while and then
sending it on to the destination. Normally used when the
desired recipinent is not there. The
message will keep attempting delivery, freeing the calling
party to handle other work. No
direct connection is made in message switching between the
incoming and out going
message.
Hopefully this helps you out. I would recommend going to
www.data.com or cisco.com (packet magazine).
JT
From: David Wang <david(_dot_)wang(_at_)metro-optix(_dot_)com> on
03/27/2000 05:23
PM
To: ietf(_at_)ietf(_dot_)org@SMTP(_at_)Exchange
cc:
Subject: How IP Packets are encapsulation in DS1 Signal
Dear Friends,
There are plenty of books describing how IP packets are encapsulated
in
Ethernet frames or ATM cells, or PPP frames. But I have not seen a
book
describe how IP packets be carried in DS1, Fractional DS1, DS3,
Fractional
DS3 signals. These signals are point to point, byte streams. I think
IP
packets should be directly put on those TDM time slots and send from
one end
point to the other. Can somebody answer my question or point out a
book, web
site, or a standard so I can find the answer.
Thanks
David