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Unformatted text preview: wer services Some
e.g. simple error detection, no ﬂow control, and no retransmission e.g. lightweight transport layer lightweight Transport layer (contd.)
Postal system Postal
doesn t have a transport layer doesn have implemented, if at all, by customers implemented, detect lost letters (how?) and retransmit them detect Internet Internet
two popular protocols are TCP and UDP two TCP provides error control, ﬂow control, multiplexing TCP UDP provides only multiplexing UDP Session layer
Not common in practice Not Provides full-duplex service, expedited data delivery, and session Provides full-duplex and session synchronization Grouping together and Coordinating between Multiple Related Transport Grouping connections of a “Call” :
e.g. For your MSN communication session, you may have: A connection for text messaging A connection for VoIP A connection for Video Conference s picture picture Another data connection for shared Whiteboard Duplex Duplex
if transport layer is simplex, concatenates two transport endpoints together if Expedited data delivery Expedited
allows some messages to skip ahead in end-system queues, by using a separate allows low-delay transport layer endpoint Synchronization Synchronization
allows users to place marks in data stream and to roll back to a pre-speciﬁed allows mark Example
Postal network Postal
suppose a company has separate shipping and receiving clerks suppose chief clerk can manage both to provide abstraction of a duplex chief servi...
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- Spring '10