ipo001b - Carrier Packet Networks Broadband Systems Support...

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Page 1 of 18 29/01/99 Carrier Packet Networks Broadband Systems Support – Department HF10 Transmission Control Protocol (TCP) Summary Issue B, 29 January, 1999 Name(s) Signature(s) Date(s) Issue Author(s) : Chris Phillips Marino Calierno Approved By : Ashraf Khan Agreed By : Peter Atterton Authorised By : Ken Taylor © Nortel Networks 1999 This document is the property of Nortel Networks who own the copyright therein. The information in this document is given in confidence and without the written consent of Nortel Networks given by contract or otherwise the document must not be copied reprinted or reproduced in any material form either wholly or in part nor must the contents of the document or any method or technique available therefrom be disclosed to any third party. Nortel Networks London Road, Harlow, Essex, CM17 9NA
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IP over Optics Ref: ipo001b.doc Page 2 of 18 29/01/99 1 Overview The Transmission Control Protocol (TCP) provides reliable end-to-end data transmission using full-duplex buffered communication. Reliability is achieved by using a positive acknowledgement retransmission scheme for error recovery. Simple positive acknowledgement protocols provide relatively low performance due to the inability to send data whilst awaiting an acknowledgement for the previous data item. This process is particularly detrimental in a WAN environment. However, TCP uses a sliding window scheme. Sliding window protocols provide improved performance as they allow the transmitter to send multiple data items before an acknowledgement is received. 1.1 TCP Segment Format The fundamental Protocol Data Unit (PDU) used by the TCP protocol is called a segment . Segments comprise both a variable length header and payload as illustrated in Figure 1. The header contains 20 bytes of mandatory fields and scope to extend with various option fields. The size of the payload can be from zero up to (2 16 – 1) 1 . For example, the payload is zero length with a number of TCP control messages. The TCP segment header contains the following fields: Source & destination port: TCP port number of the sender and receiver. TCP ports are essentially the same as UDP ports, but are assigned separately. Thus, TCP port 54 may refer to a different service than UDP port 54. For a client-initiated session between itself and a server, the destination port number is usually set to a well-known value, indicative of the service being requested. The client then typically sets the source port to a value outside the well-known address range that allows this particular TCP connection to be uniquely identified, even when further connections are configured between the same two hosts for additional instances of the same service. Seq. number (32 bits): When a connection is newly established, the sequence number of the SYN segment contains the Initial Sequence Number (ISN) whose value is selected in accordance with Section 2.1. Subsequently, when data is present, its value is incremented by a value equal to the sequence number of the first byte of data in the data portion of the segment. In addition
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This note was uploaded on 08/08/2011 for the course CS 310 taught by Professor Aartisingh during the Spring '11 term at National Institute of Technology, Calicut.

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ipo001b - Carrier Packet Networks Broadband Systems Support...

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