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T1,T3 are transmission rates that descibe electrical interfaces. A T1 link is 1.5mb ( bits )

T3 = 45mb. OC ( optical carrier ) is a BellCore

description of transmission in SONET networks. ( Synchronous Optical Network ).

The speed of OC-n is derived from the number of interleaved STS streams. STS-1 is 51mb per second

All OC-n rates ( lowest is OC-3 which sts-1×3 ) are derived from a multiple of this.

OC-768 = 768xSTS1 rate = 39168mb per second

OC-48 = 48xSTS-1 rate = 2448mb per second

OC-3 = 3xSTS-1 rate = 153mb per second

OC-n rates can be described as concatenated ( a fat pipe ). or Channelized whereby an OC pipe contains multiple channels ( STS payloads )each

of which can contain different payloads ( packets or atm cells ).

Oc-3c is a concat. fat pipe.

Oc-3 is a channelized pipe.