Ensuring the Reliability of Data Delivery © 2004 Cisco Systems, Inc. All rights reserved. Understanding How UDP and TCP Work INTRO v2.0—6-1.

Ensuring the Reliability of Data Delivery

© 2004 Cisco Systems, Inc. All rights reserved.

Understanding How UDP and TCP Work

INTRO v2.0—6-1

© 2004 Cisco Systems, Inc. All rights reserved. INTRO v2.0—6-2

Outline

• Overview

• Transport Layer Functions

• Reliable vs. Best Effort

• UDP and TCP

• UDP and TCP Port Numbers

• UDP and TCP Header Formats

• Summary

© 2004 Cisco Systems, Inc. All rights reserved. INTRO v2.0—6-3

Transport Layer

• Session multiplexing

• Segmentation

• Flow control (when required)

• Connection-oriented (when required)

• Reliability (when required)

© 2004 Cisco Systems, Inc. All rights reserved. INTRO v2.0—6-4

Reliable vs. Best Effort Comparison

© 2004 Cisco Systems, Inc. All rights reserved. INTRO v2.0—6-5

TCP/IP Protocol Stack

© 2004 Cisco Systems, Inc. All rights reserved. INTRO v2.0—6-6

UDP Characteristics

© 2004 Cisco Systems, Inc. All rights reserved. INTRO v2.0—6-7

TCP Characteristics

© 2004 Cisco Systems, Inc. All rights reserved. INTRO v2.0—6-8

Port Numbers

© 2004 Cisco Systems, Inc. All rights reserved. INTRO v2.0—6-9

UDP Header

© 2004 Cisco Systems, Inc. All rights reserved. INTRO v2.0—6-10

TCP Header

© 2004 Cisco Systems, Inc. All rights reserved. INTRO v2.0—6-11

Summary

• The transport layer operates between the network layer and the application layer and provides communication services directly to the application processes running on different hosts.

• UDP is a best-effort, connectionless protocol used for applications that do not require error checking or sequence numbering, such as voice and video streaming.

• TCP is a reliable, connection-oriented protocol that ensures delivery of packets without error and in correct order.

© 2004 Cisco Systems, Inc. All rights reserved. INTRO v2.0—6-12

Summary (Cont.)

• UDP and TCP use ports to support multiple conversations between different network devices.

• UDP delivers TFTP, SNMP, and RIP.

• TCP delivers FTP, Telnet, and SMTP.

• The UDP header length is always 64 bits.

• The TCP header follows the Internet header, supplying information specific to the TCP protocol. This division allows for the existence of host level protocols other than TCP.