Example Ring Latency and Token reinsertion

Posted by AJ × 09:26

• Let there be M stations

• b bits delay in stations

• The delay in interface is Mb bits

• typically b=2.5

• d total ring length

• additional delay is d/v or dR/v v-delay in medium

• v=2*108 m/sec

• therefore it is 5microsec to travel 1 kms

• ring latency is defined as the time that it takes for a bit to travel around ring is

given by

• T’=d/v+Mb/R and T’R= dR/v+Mb bits

• Example

• Let R=4Mbps M=20 stations separated by 100m b=2.5

• Latency= 20*100*4*106 /2*108 +20*2.5=90 bits

• IEEE 802.5-After the last bit arrives the token is inserted

• IBM token ring-after the header bit arrives the token is inserted

• IEEE 802.5 and IBM token ring 26Mbps- after last bit transmitted the token is inserted

• Conclusion-improves efficiency in case of the third case.

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