ENVS 1000 Lecture Notes - Lecture 28: Voice Over Ip, Internet Protocol Suite, Connectionless Communication
10 May 2018
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ENVS 1000 Lecture 28 Notes – Network layer (layer 3)
Introduction
• An alternative protocol, UDP, for User Datagram Protocol, is used for some applications
instead of TCP.
• UDP is a connectionless service.
• Unlike TCP, there is no communication between the sender and receiver nodes to set up
a connection in advance.
• UDP packets are known as user datagrams.
• A UDP packet contains the message exactly as delivered from the application, thus it is
the responsibility of the application to divide the message into smaller pieces, if
necessary.
• Every datagram is sent independently.
• UDP is faster and simpler, but does not guarantee delivery.
• There is no acknowledgment of receipt by the receiving node.
• UDP is useful for communications in which the retransmission of a lost, out of order, or
error-containing packet is not practical or in which the loss of a packet is relatively
inconsequential.
• Streaming video is an example of this situation.
• The newest alternative, SCTP, for Stream Control Transmission Protocol, offers features
similar to TCP, with additional features that improve fault tolerance and enable multiple
messages (in the form of byte streams—hence the name) to be transported
simultaneously through the same connection
• Although SCTP could theoretically replace TCP, its current use is limited primarily to new
applications, primarily those used with IP telephony and multimedia applications.
• The network layer is responsible for the addressing and routing of packets to their
proper final destination.
• The TCP/IP network layer is also called the internetworking layer or IP layer.
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