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Transport layer protocols : TCP and UDP
- 1. Transport-Layer Protocols Dr.T.Abirami, Associate Professor, Department of IT , Kongu Engineering College
- 2. USER DATAGRAM PROTOCOL • The User Datagram Protocol (UDP) is a connectionless, unreliable transport protocol. • It does not add anything to the services of IP except for providing process-to-process communication instead of host-to- host communication. • UDP is powerless • UDP packets, called user datagrams, Dr.T.Abirami, Associate Professor, Department of IT , Kongu Engineering College
- 3. Why would a process want to use it? • UDP is a very simple protocol using a minimum of overhead. • If a process wants to send a small message and does not care much about reliability, it can use UDP. • Sending a small message using UDP takes much less interaction between the sender and receiver than using TCP. Dr.T.Abirami, Associate Professor, Department of IT , Kongu Engineering College
- 4. User Datagram • Use fixed-size header of 8 bytes made of four fields, each of 2 bytes (16 bits). Dr.T.Abirami, Associate Professor, Department of IT , Kongu Engineering College
- 5. The following is the content of a UDP header in hexadecimal format. CB84000D001C001C a. What is the source port number? b. What is the destination port number? c. What is the total length of the user datagram? d. What is the length of the data? e. Is the packet directed from a client to a server or vice versa? f. What is the client process? Dr.T.Abirami, Associate Professor, Department of IT , Kongu Engineering College
- 6. Solution a. The source port number is the first four hexadecimal digits (CB84)16, which means that the source port number is 52100. b. The destination port number is the second four hexadecimal digits (000D)16, which means that the destination port number is 13. c. The third four hexadecimal digits (001C)16 define the length of the whole UDP packet as 28 bytes. d. The length of the data is the length of the whole packet minus the length of the header, or 28 − 8 = 20 bytes. e. Since the destination port number is 13 (well-known port), the packet is from the client to the server. f. The client process is the Daytime. Dr.T.Abirami, Associate Professor, Department of IT , Kongu Engineering College
- 7. Hexadecimal Decimal 0 0 1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9 9 A 10 B 11 C 12 D 13 E 14 F 15 Hex to Decimal Formula C = 12 B = 11 8 = 8 4 = 4 (CB84)16 = (12 x 163 + 11 × 162 + 8× 161 + 4 × 160 ) = (52100)10 Dr.T.Abirami, Associate Professor, Department of IT , Kongu Engineering College
- 8. Dr.T.Abirami, Associate Professor, Department of IT , Kongu Engineering College
- 9. UDP Services • UDP provides process-to-process communication using socket addresses, a combination of IP addresses and port numbers • UDP provides a connectionless service • UDP is a very simple protocol. There is no flow control • There is no error control mechanism in UDP except for the checksum • UDP is used for interactive real-time transfer of audio and video. • UDP protocol encapsulates and decapsulates messages. • UDP, queues are associated with ports • UDP multiplexes and demultiplexes. Dr.T.Abirami, Associate Professor, Department of IT , Kongu Engineering College
- 10. UDP Applications • UDP is suitable for a process that requires simple request-response communication with little concern for flow and error control. It is not usually used for a process such as FTP that needs to send bulk data • UDP is suitable for a process with internal flow- and error-control mechanisms. • For example, the Trivial File Transfer Protocol (TFTP) process includes flow and error control. It can easily use UDP. • UDP is a suitable transport protocol for multicasting. Multicasting capability is embedded in the UDP software but not in the TCP software. • UDP is used for management processes such as SNMP . • UDP is used for some route updating protocols such as Routing Information Protocol (RIP). • UDP is normally used for interactive real-time applications that cannot tolerate uneven delay between sections of a received message Dr.T.Abirami, Associate Professor, Department of IT , Kongu Engineering College
- 11. TRANSMISSION CONTROL PROTOCOL • It is a connection-oriented, reliable protocol. • TCP explicitly defines connection establishment, data transfer, and connection teardown phases to provide a connection-oriented service. TCP uses a combination of • GBN and SR protocols to provide reliability • TCP uses checksum (for error detection), retransmission of lost or corrupted packets, cumulative and selective acknowledgments, and timers. • TCP is the most common transport-layer protocol in the Internet Dr.T.Abirami, Associate Professor, Department of IT , Kongu Engineering College
- 12. TRANSMISSION CONTROL PROTOCOL • TCP provides Full Duplex service, i.e., the data flow in both the directions at the same time. • To achieve Full Duplex service, each TCP should have sending and receiving buffers so that the segments can flow in both the directions. • Establish a connection between two TCPs. • Data is exchanged in both the directions. • The Connection is terminated. Dr.T.Abirami, Associate Professor, Department of IT , Kongu Engineering College
- 13. TCP Services • TCP provides process-to-process communication using port numbers • It allows the sending process to deliver data as a stream of bytes and allows the receiving process to obtain data as a stream of bytes Dr.T.Abirami, Associate Professor, Department of IT , Kongu Engineering College
- 14. Segments • TCP groups a number of bytes together into a packet called a segment. • TCP adds a header to each segment (for control purposes) and delivers the segment to the network layer for transmission. • The segments are encapsulated in an IP datagram and transmitted. • segments are not necessarily all the same size Dr.T.Abirami, Associate Professor, Department of IT , Kongu Engineering College
- 15. TCP Services • TCP performs multiplexing at the sender and demultiplexing at the receiver • TCP is a reliable transport protocol. It uses an acknowledgment mechanism to check the safe and sound arrival of data. Dr.T.Abirami, Associate Professor, Department of IT , Kongu Engineering College
- 16. TCP Features • Numbering System • TCP numbers all data bytes (octets) that are transmitted in a connection. Numbering is independent in each direction. • Acknowledgment Number Dr.T.Abirami, Associate Professor, Department of IT , Kongu Engineering College
- 17. Dr.T.Abirami, Associate Professor, Department of IT , Kongu Engineering College
- 18. total six types of flags in control field: •URG: indicates that the data in a segment is urgent. •ACK: it validates the acknowledgement number. •PSH: used to inform the sender that higher throughput is needed so if possible, data must be pushed with higher throughput. •RST: used to reset the TCP connection when there is any confusion occurs in the sequence numbers. •SYN: used to synchronize the sequence numbers in three types of segments: connection request, connection confirmation ( with the ACK bit set ), and confirmation acknowledgement. •FIN: used to inform the receiving TCP module that the sender has finished sending data. It is used in connection termination in three types of segments: termination request, termination confirmation, and acknowledgement of termination confirmation. • Window Size: The window is a 16-bit field that defines the size of the window. • Checksum: The checksum is a 16-bit field used in error detection. • Urgent pointer: is set to 1, then this 16-bit field is an offset from the sequence number indicating that it is a last urgent data byte. • Options and padding: convey the additional information to the receiver. Dr.T.Abirami, Associate Professor, Department of IT , Kongu Engineering College
- 19. A TCP Connection Connection Establishment /three-way handshaking The client sends the first segment, SYN segment The server sends the second segment, a SYN + ACK segment The client sends the third segment. just an ACK segment Dr.T.Abirami, Associate Professor, Department of IT , Kongu Engineering College
- 20. Data Transfer Dr.T.Abirami, Associate Professor, Department of IT , Kongu Engineering College
- 21. Connection Termination The FIN segment consumes one sequence number if it does not carry data. Three-Way Handshaking Dr.T.Abirami, Associate Professor, Department of IT , Kongu Engineering College
- 22. Basis for Comparison TCP UDP Definition TCP establishes a virtual circuit before transmitting the data. UDP transmits the data directly to the destination computer without verifying whether the receiver is ready to receive or not. Connection Type It is a Connection-Oriented protocol It is a Connectionless protocol Speed slow high Reliability It is a reliable protocol. It is an unreliable protocol. Header size 20 bytes 8 bytes acknowledgement It waits for the acknowledgement of data and has the ability to resend the lost packets. It neither takes the acknowledgement, nor it retransmits the damaged frame. Dr.T.Abirami, Associate Professor, Department of IT , Kongu Engineering College