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Unformatted text preview: tension of the sequence number. Since the
lost segment that reappears at time F has a timestamp of 2, which is less than the most
recent valid timestamp (5 or 6), it is discarded by the PAWS algorithm.
The PAWS algorithm does not require any form of time synchronization between the
sender and receiver. All the receiver needs is for the timestamp values to be monotonically increasing, and to increase by at least one per window. 24.7 T/TCP: A TCP Extension for Transactions file:///D|/Documents%20and%20Settings/bigini/Docu.../homenet2run/tcpip/tcp-ip-illustrated/tcp_fut.htm (15 of 20) [12/09/2001 14.47.34] Chapter 24. TCP Futures and Performance TCP provides a virtual-circuit transport service. There are three distinct phases in the life
of a connection: establishment, data transfer, and termination. Applications such as
remote login and file transfer are well suited to a virtual-circuit service.
Other applications, however, are designed to use a transaction service. A transaction is a
client request followed by a server response with the following characteristics:
1. The overhead of connection establishment and connection termination should be
avoided. When possible, send one request packet and receive one reply packet.
2. The latency should be reduced to RTT plus SPT, where RTT is the round-trip
time and SPT is the server processing time to handle the request.
3. The server should detect duplicate requests and not replay the transaction when a
duplicate request arrives. (Avoiding the replay means the server does not process
the request again. The server sends back the saved reply corresponding to that
One application that we've already seen that uses this type of service is the Domain Name
System (Chapter 14), although the DNS is not concerned with the server replaying
Today the choice an application designer has is TCP or UDP. TCP provides too many
features for transactions, and UDP doesn't provide enough. Usually the application is
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This test prep was uploaded on 04/04/2014 for the course ECE EL5373 taught by Professor Guoyang during the Spring '12 term at NYU Poly.
- Spring '12