01:198:352 Lecture Notes - Lecture 7: Selective Repeat Arq, Checksum
10 Dec 2017
School
Department
Course
Professor
LECTURE : 7
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Network:
NodalDelay =
+ProcessingDelay: delay in computing on protcol (checksum, figure out who
to relay to, etc...)
+QueuingDelay: delay in sending data out (wait because
media is busy)
+TransmissionDelay delay in getting data on to the medium (because it
is not instantaneous)
+PropagationDelay delay in information to propagate through the medium
(negligable ... or really not)
Transport:
Circuit
C: connection setup time (seconds)
M: message size (bits)
B: bandwidth (bits/second)
C + M/B
Packet
M: message size (bits)
B: bandwidth (bits/second)
h: header size
d: packet data size (payload)
S: stations(hops)
((h+d)/B) * (ceil(M/d) +S )
*Message
M: message size (bits)
B: bandwidth (bits/second)
h: header size
d: packet data size (payload)
S: stations(hops)
((h+M)/B) * (1 + S)
110
Go Back N:
high upstream traffic
minimal work on sender
Selective Repeat:
high downstream traffic
more work on sender
SeqNum:
need to identify each packet
- but -
need to be unique to guard against ambiguity
M
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