Chapter 4 - OSI Transport Layer CCNA Exploration version 4.0CCNA Exploration version 4.0 Overview • Explain the role of Transport Layer protocols and services in supporting communications across data networks • Analyze the application and operation of TCP mechanisms that support reliability • Học viện mạng Bách khoa - Website: www.bkacad.com 2 • Analyze the application and operation of TCP mechanisms that support reassembly and manage data loss. • Analyze the operation of UDP to support communicate between two processes on end devices Transport Layer Role and Services • Explain the purpose of the Transport layer • Enables multiple applications to communicate over the network at the same time on a single device • Ensures that, if required, all Học viện mạng Bách khoa - Website: www.bkacad.com 3 • Ensures that, if required, all the data is received reliably and in order by the correct application. • Employs error handling mechanisms. Transport Layer Role and Services • Major functions of the transport layer and the role it plays in data networks – Tracking the individual communication between applications on the source and destination hosts. – Segmenting data and managing each piece. – Reassembling the segments into streams of application data. – Identifying the different applications. Học viện mạng Bách khoa - Website: www.bkacad.com 4 – Identifying the different applications. Separating Multiple Communications • Computer connected to a network that is simultaneously receiving and sending e-mail and instant messages, viewing websites, and conducting a VoIP phone call. Each of these applications is Học viện mạng Bách khoa - Website: www.bkacad.com 5 these applications is sending and receiving data over the network at the same time. However, data from the phone call is not directed to the web browser, and text from an instant message does not appear in an e-mail. Segmentation • Without segmentation, only one application, the streaming video for example, would be able to receive data. You could not Học viện mạng Bách khoa - Website: www.bkacad.com 6 You could not receive e-mails, chat on instant messenger, or view web pages while also viewing the video. Controlling the Conversation • Segmentation and Reassembly - Most networks have a limitation on the amount of data that can be included in a single PDU. The Transport layer divides application • Conversation Multiplexing - There may be many applications or services running on each host in the network. Each of these applications or services is assigned an Học viện mạng Bách khoa - Website: www.bkacad.com 7 divides application data into blocks of data that are an appropriate size. At the destination, the Transport layer reassembles the data before sending it to the destination application or service. assigned an address known as a port so that the Transport layer can determine with which application or service the data is identified. Controlling the Conversation Học viện mạng Bách khoa - Website: www.bkacad.com 8 Transport Layer Role and Services Học viện mạng Bách khoa - Website: www.bkacad.com 9 • At the Transport layer the three basic operations of reliability are: – Tracking transmitted data – Acknowledging received data – Retransmitting any unacknowledged data Transport Layer Role and Services • Transmission Control Protocol (TCP) – TCP is a connection-oriented protocol, described in RFC 793. TCP incurs additional overhead to gain functions. Additional functions specified by TCP are the same order delivery, reliable delivery, and Học viện mạng Bách khoa - Website: www.bkacad.com 10 delivery, reliable delivery, and flow control. Each TCP segment has 20 bytes of overhead in the header encapsulating the Application layer data, whereas each UDP segment only has 8 bytes of overhead • UDP is a simple, connectionless protocol, described in RFC 768. It has the advantage of providing for low overhead data delivery, datagrams are sent as "best effort" by this Transport layer protocol. Web, email, file transfer DNS, Video streaming, VoIP [...]... Calculated checksum of the header and data fields • Data – Upper -layer protocol data • The protocols that use UDP include: - TFTP (Trivial File Transfer Protocol) - SNMP (Simple Network Management Protocol) - DHCP (Dynamic Host Control Protocol) - DNS (Domain Name System) H c vi n m ng Bách khoa - Website: www.bkacad.com 18 Transport Layer Role and Services • Identify how a port number is represented... crossing the network at the same time H c vi n m ng Bách khoa - Website: www.bkacad.com 23 Netstat command H c vi n m ng Bách khoa - Website: www.bkacad.com 24 Transport Layer Role and Services • Describe the role of segments in the transport layer and the two principle ways segments can be marked for reassembly H c vi n m ng Bách khoa - Website: www.bkacad.com 25 Application and Operation of TCP Mechanisms... a service using a Dynamic or Private Port H c vi n m ng Bách khoa - Website: www.bkacad.com 20 UDP port H c vi n m ng Bách khoa - Website: www.bkacad.com 21 TCP and UDP Common Port H c vi n m ng Bách khoa - Website: www.bkacad.com 22 TCP and UDP port numbers • Both TCP and UDP use port (socket) numbers to pass information to the upper layers Port numbers are used to keep track of different conversations... Bách khoa - Website: www.bkacad.com 31 Managing TCP Sessions • Trace the steps used by the TCP protocol in which sequence numbers and acknowledgement numbers are used to manage exchanges in a conversation H c vi n m ng Bách khoa - Website: www.bkacad.com 32 Managing TCP Sessions • Describe the retransmission remedy for lost data employed by TCP (refer to 4. 3.3.1) H c vi n m ng Bách khoa - Website:... by TCP (refer to 4. 3.3.1) H c vi n m ng Bách khoa - Website: www.bkacad.com 33 Managing TCP Sessions H c vi n m ng Bách khoa - Website: www.bkacad.com 34 Managing TCP Sessions H c vi n m ng Bách khoa - Website: www.bkacad.com 35 Managing TCP Sessions H c vi n m ng Bách khoa - Website: www.bkacad.com 36 ... accept H c vi n m ng Bách khoa - Website: www.bkacad.com 16 User Datagram Protocol (UDP) • UDP is a simple protocol that exchanges datagrams, without • acknowledgments or guaranteed delivery Error processing and retransmission must be handled by higher layer protocols UDP is designed for applications that do not need to put sequences of segments together H c vi n m ng Bách khoa - Website: www.bkacad.com... reliability mechanism works as part of a session H c vi n m ng Bách khoa - Website: www.bkacad.com 26 Application and Operation of TCP Mechanisms • Describe the role of port numbers in establishing TCP sessions and directing segments to server process H c vi n m ng Bách khoa - Website: www.bkacad.com 27 3 way hand shake H c vi n m ng Bách khoa - Website: www.bkacad.com 28 Application and Operation of TCP Mechanisms... Header format: H c vi n m ng Bách khoa - Website: www.bkacad.com 11 TCP Header format: Port number • Source Port 16 bits • Destination Port 16 bits H c vi n m ng Bách khoa - Website: www.bkacad.com 12 TCP Header format: Sequence • Sequence Number: 32 bits – The sequence number of the first data octet in this segment (except when SYN is present) H c vi n m ng Bách khoa - Website: www.bkacad.com 13 TCP Header... number the sender of the segment is expecting to receive H c vi n m ng Bách khoa - Website: www.bkacad.com 14 TCP Header format: Code bits • Control Bits: 8 bits – – – – ACK: RST: SYN: FIN: Acknowledgment field significant Reset the connection Synchronize sequence numbers No more data from sender H c vi n m ng Bách khoa - Website: www.bkacad.com 15 TCP Header format: Window • Window: 16 bits – The number... port number is represented and describe the role port numbers play in the TCP and UDP protocols H c vi n m ng Bách khoa - Website: www.bkacad.com 19 Port and TCP port • Reserved for services and applications They are commonly used for applications such as HTTP (web server) POP3/SMTP (e-mail server) and Telnet • These port numbers are assigned to user processes or applications When not used for a server . Chapter 4 - OSI Transport Layer CCNA Exploration version 4. 0CCNA Exploration version 4. 0 Overview • Explain the role of Transport Layer protocols. Upper -layer protocol data Học viện mạng Bách khoa - Website: www.bkacad.com 18 • Data – Upper -layer protocol data • The protocols that use UDP include: -