4003-420-01/4005-740-01 Data Communications and Networks I Module 5. Transport Layer -- Lecture Notes Prof. Alan Kaminsky -- Fall Quarter 2012 Rochester Institute of Technology -- Department of Computer Science Key Organizing Principle For This Course What do I need to know about topic X to write network applications? What issues related to topic X affect network application design? Transport Protocols Internet transport protocols User Datagram Protocol (UDP) -- RFC 768 Transmission Control Protocol (TCP) -- RFC 793 A Network Layer protocol transfers data from a source computer to a destination computer Computer address in the Internet: IP address (32 bits) Protocol multiplexing -- protocol numbers Assigned by the Internet Assigned Numbers Authority (IANA) -- http://www.iana.org/ Assigned Internet Protocol numbers -- http://www.iana.org/assignments/protocol-numbers/protocol-numbers.xml A Transport Layer protocol transfers data from a source application to a destination application The same computer can be running multiple applications Application address in the Internet: Port (16 bits) Internet port numbers Assigned by the Internet Assigned Numbers Authority (IANA) -- http://www.iana.org/ Assigned port numbers -- http://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xml Well known ports -- 0 .. 1023 Registered ports -- 1024 .. 49151 Dynamic and private ports -- 49152 .. 65535 Comparison of UDP and TCP Services UDP TCP Connectionless (like postcards) Connection-oriented (like phone calls) Supports one-to-one, one-to-many, many-to-one, and many-to-many communication Supports one-to-one communication only Send and receive messages Send and receive byte streams Limited maximum message size No limit on the amount of data App must do segmentation TCP does segmentation automatically Best-effort delivery -- messages may be lost Reliable delivery -- data is not lost No ordering guarantee -- messages may be delivered out of order Guaranteed order -- data is not reordered No flow control Flow control No congestion control Congestion control Low overhead High overhead Mechanisms for implementing UDP's services   Mechanisms for implementing TCP's services Connection setup Timeouts and retransmissions Buffering out-of-order data Window-based flow control Window-based congestion control   Implications for network application design Neither UDP nor TCP is an ideal transport protocol for network applications Much of the complexity of network application programming stems from the shortcomings of UDP and TCP Data Communications and Networks I • 4003-420-01/4005-740-01 • Fall Quarter 2012 Course Page Alan Kaminsky • Department of Computer Science • Rochester Institute of Technology • 4486 + 2220 = 6706 Home Page Copyright © 2012 Alan Kaminsky. All rights reserved. Last updated 01-Oct-2012. Please send comments to ark­@­cs.rit.edu.