2-5
Introducing ATM Networking
ATM uses SONET and SHD technology to reduce costs while
achieving high transmission rates. Essentially, ATM combines
multiple STS-1 frames into STS superframes (STS-Nc, where N
stands for some integer value) and likewise for STM-1 frames.
Transmitting 8,000 single STS-1 frames at telephone company in a
second, referred to as STS-1 tr ansmis si on, produces a 51.84 Mbit/sec
transmission rate .
An STS-3C transmission transmits 8,000 STS-3c superframes in a
second, each composed of three concatenated (combined) STS-1
frames. This produces a 155.52 Mbit/sec transmission rate which is
conventionally round e d to 155 Mbits/sec. The ST S - 3 c tr ansmission
rate is identical to the STM-1 transmission rate. ATM supports, or
will eventually support the following:
Adaptec ATM products currently support the STS-3C/STM-1
transmission rate of 155.51 Mbits/sec.
25.6 Mbit/sec ATM
ATM also supports 25.6 Mbit transmission speeds. Adaptec
products providing this transmission speed attach t o switc hes which
can subsequently transport the data at any ATM transmission speed
necessary to reach another switch or node.
Classical TCP/IP
A data communication protocol is a set of conventions that
communicating entities observe to achieve unambiguous data
exchange and the TCP/IP suite of protocol s is the most commonly
used data communication protocol suite. TCP/IP has prevailed
because it is an extensible, effective data communication p rotocol
suite designed from the ground up to integrate disparate networks
with heterogeneous computers. Bec ause of its interconnectivity
origins, TCP/IP is essential to the Internet, w hich itself consists of
■STS-1: 51.84 Mbits/sec
■STS-3c: 155.52 Mbits/sec
■STS-12c: 622.08 Mbits/sec
■STS-24c: 1244.16 Mbits/sec
■STS-48c: 2488.32 Mbits/sec
■STS-192c: 9953.28 Mbits/sec