ccna t

ccna t.To complicate matters further, the window size can be different for the same session on the source and target hosts. For example, PC-A has a window size of 3,while PC-B has a window size of 10. In this case, PC-A sends 10 data segments to PC.B before it must wait for an acknowledgment, while PC-B sends 3 data segments to PC-A before it must wait for an acknowledgment.Exam Requirements Transport Layer for TCP/IP After an in-depth discussion of the transport layer basics introduced in Chapter 2, you should be familiar with them o There will not be many exam questions related to the content of this chapter; such exams should be very simple. Be sure to be familiar with common applications that use TCP and UDP and their port numbers; be sure to understand the process of establishing a TCP session using three handshakes and the implementation of TCP windowing techniques; and know the difference between TCP and UDP headers o8.5 Authentication SummaryThe TCP/IP model contains four layers: the application layer, the transport layer, the Internet layer, and the network access layer. This chapter focuses on the transport layer protocols: TCP and UDP. TCP uses sequence numbers and acknowledgments to provide a reliable connection; it also uses three handshakes to establish a connection: SYN, SYN/ACK, and ACK. TCP uses PAR to recover lost data segments: segments are continually retransmitted (with some delay between retransmissions) until an acknowledgment is received. Applications that use TCP include FTP ( 21), HTTP ( 80), SMTP ( 25), SSH ( 22), and Telnet ( 23) o UDP provides unreliable connections, but is more efficient than TCP; applications that use UDP include DNS ( 53), RIP ( 520), SNMP ( 161), and TFTP ( 69) o Note that some protocols (such as DNS and syslog) support both TCP and UDP.8.6 Two-Minute SprintTransport layer functionality . The transport layer provides traffic control through the use of windowing techniques, reliable connectivity through the use of sequence numbers and acknowledgements, session multiplexing through the use of port numbers and IP addresses, and segmentation through the use of data segments. . Transport layer reliability includes handling out-of-sequence arrivals, duplicate packets, and congestion avoidance.Transport Layer Protocols .. TCP provides reliable connection-oriented services using sequence numbering and acknowledgement, windowing techniques, error detection, and correction.. TCP headers are 20 bytes long and contain two port fields, sequence and acknowledgment number fields, code bit fields, window size fields, checksumchecksum field, and so on.