© 2005 Cisco Systems, Inc. All rights reserved.INTRO v2.16-1 Ensuring the Reliability of Data Delivery Establishing a TCP Connection. - презентация

1 © 2005 Cisco Systems, Inc. All rights reserved.INTRO v Ensuring the Reliability of Data Delivery Establishing a TCP Connection

2 © 2005 Cisco Systems, Inc. All rights reserved.INTRO v Outline Overview Establishing a Connection with a Peer System Flow Control Acknowledgment Windowing TCP Sequence Number and Acknowledgment Numbers Summary Lab 6-1: Establishing a Telnet Connection to a Remote Terminal Server

3 © 2005 Cisco Systems, Inc. All rights reserved.INTRO v Establishing a Connection

4 © 2005 Cisco Systems, Inc. All rights reserved.INTRO v Three-Way Handshake ctl = which control bits in the TCP header are set to 1

5 © 2005 Cisco Systems, Inc. All rights reserved.INTRO v Flow Control

6 © 2005 Cisco Systems, Inc. All rights reserved.INTRO v TCP Acknowledgment

7 © 2005 Cisco Systems, Inc. All rights reserved.INTRO v Fixed Windowing

8 © 2005 Cisco Systems, Inc. All rights reserved.INTRO v TCP Sliding Windowing

9 © 2005 Cisco Systems, Inc. All rights reserved.INTRO v TCP Sequence and Acknowledgement Numbers

10 © 2005 Cisco Systems, Inc. All rights reserved.INTRO v Summary Using TCP as the transport layer protocol, before applications can transfer data, both the sending and the receiving applications inform their respective operating systems that a connection will be initiated. Once synchronization has occurred, the two end systems have established a connection and data transfer can begin. 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 segment is sent, receipt is acknowledged and the next segment is then sent.

11 © 2005 Cisco Systems, Inc. All rights reserved.INTRO v 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 for 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 size dynamically to accommodate the flow of segments. TCP provides the sequencing of segments by providing sequence numbers and acknowledgment numbers in the TCP headers.

12 © 2005 Cisco Systems, Inc. All rights reserved.INTRO v