1、Building a Simple Network,Understanding the TCP/IP Transport Layer,Transport Layer,Session multiplexing Segmentation Flow control (when required) Connection-oriented (when required) Reliability (when required),Reliable vs. Best-Effort Comparison,Operates at transport layer of OSI and TCP/IP models P

2、rovides applications with access to the network layer without the overhead of reliability mechanisms Is a connectionless protocol Provides limited error checking Provides best-effort delivery Has no data-recovery features,UDP Characteristics,UDP Header,TCP Characteristics,Transport layer of the TCP/

3、IP stack Access to the network layer for applications Connection-oriented protocol Full-duplex mode operation Error checking Sequencing of data packets Acknowledgement of receipt Data-recovery features,TCP Header,File transfer FTP TFTP Network File System E-mail Simple Mail Transfer Protocol Remote

4、login Telnet rlogin Network management Simple Network Management Protocol Name management Domain Name System,TCP/IP Application Layer Overview,Mapping Layer 3 to Layer 4,Mapping Layer 4 to Applications,Establishing a Connection,Three-Way Handshake,CTL = Which control bits in the TCP header are set t

5、o 1,Flow Control,TCP Acknowledgment,Fixed Windowing,TCP Sliding Windowing,TCP Sequence and Acknowledgment Numbers,Summary,The purpose of the transport layer is to hide the network requirements from the application layer. Connection-oriented transport provides reliable transport; connectionless trans

6、port provides best-effort transport. UDP is a protocol that operates at the transport layer and provides applications with access to the network layer without the overhead of the reliability mechanisms of TCP. UDP is a connectionless, best-effort delivery protocol. TCP is a protocol that operates at

7、 the transport layer and provides applications with access to the network layer. TCP is connection-oriented, provides error checking, delivers data reliably, operates in full-duplex mode, and provides some data recovery functions.,Summary (Cont.),TCP/IP supports a number of applications, including F

8、TP (supports bidirectional binary and ASCII file transfers), TFTP (transfers configuration files and Cisco IOS images), and Telnet (provides capability to remotely access another computer). IP uses a protocol number in the datagram header to identify which protocol to use for a particular datagram.

9、Port numbers are used to map Layer 4 to an application.,Summary (Cont.),Flow control avoids the problem of a transmitting host overflowing the buffers in the receiving host and slowing network performance. TCP provides sequencing of segments with a forward reference acknowledgment. When a single seg

10、ment is sent, receipt is acknowledged and the next segment is then sent.,Summary (Cont.),The TCP window size decreases the transmission rate to a level at which congestion and data loss do not occur. The TCP window size allows a specified number of unacknowledged segments to be sent. A fixed window is a window with an unchanging size that can accommodate a specific flow of segments. A TCP sliding window is a window that can change si