Transmission Control Protocol (TCP)


By Dan DiNicolo, June 2nd, 2006 Posted in CCNA Study Guide Chapter 04. Subscribe to our RSS Feed



Rather Have Fast and Secure Remote Control?

 Securely access PCs and servers worldwide through any firewall. Try it and see for yourself!

As you’ll see shortly, a TCP header carries significantly more information than its UDP counterpart. This is a result of the extra fields that are required as part of making TCP reliable. It is also the reason why you’ll hear it said that TCP as a protocol has higher overhead. The diagram below outlines the fields found in a TCP header.

Figure: TCP header.

The TCP header fields are described below:

  • Source Port. This field specifies the TCP port number of the system sending the segment.
  • Destination Port. This field specifies the TCP port number of the destination system.
  • Sequence Number. The ordered number of the segment that is used to ensure that data can be properly reassembled on the receiving system, since segments may arrive out of order.
  • Acknowledgement Number. The acknowledgement number is used to let the other system know that a segment was received.
  • HLEN. The header length field specifies the total TCP header length, again grouped into 32 bit numbers.
  • Reserved. This field is always set to zero, and is reserved for future use.
  • Code Bits. This field specifies the purpose of the segment. For example, it can be used to denote acknowledgements (ACK), closing a connection (FIN), a synchronization request (SYN), urgent data (URG) and so forth
  • Window. Acts as the window size advertisement, specifying how much data this system is currently willing to receive.
  • Checksum. A computed value that verifies the integrity of the TCP header, similar to a CRC.
  • Urgent Pointer. When the URG code bit is set, this field specifies where within the segment the urgent data can be found.
  • Option. If used, this field specifies the maximum segment size that can be received.
  • Data. The encapsulated data passed down from upper-layer protocols and applications.

Tip: For more information on Transmission Control Protocol, see RFC 793.

Written by Dan DiNicolo - Visit Website

Go To Page: 1 2 3



Print This Post Print This Post













All Tutorials by Category:















Entire site Copyright © 1999-2007 2000Trainers.com, all rights reserved.
Content on this site may not be copied or reproduced in any way without permission.





IT Showcase


Text Link Ads

View all Tutorials by Category: