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Transcript of TCP/IP(networking)

  • Copyright 2011 1 Module 5 TCP/IP (The Transport and Internetworking Layer Protocol) By Dr. Percy Dias
  • Copyright 2011 2 History and Future of TCP/IP The U.S. Department of Defense (DoD) created the TCP/IP reference model because it wanted a network that could survive any conditions. Some of the layers in the TCP/IP model have the same name as layers in the OSI model.
  • Copyright 2011 3 Internet Layer The purpose of the Internet layer is to send packets from a network node and have them arrive at the destination node independent of the path taken. Internet Protocol (IP) Internet Control Message Protocol (ICMP) Address Resolution (ARP) Reverse Address Resolution Protocol (RARP) Dynamic Host Configuration Protocol (DHCP)
  • Copyright 2011 4 Internet Layer Protocols IP performs the following operations Defining a packet and an addressing scheme Transferring data between the Internet Layer and the Network Access Layer Routing packets to remote hosts IP is sometimes referred to as an unreliable protocol Provides connectionless, best-effort delivery routing of packets
  • Copyright 2011 Network Layer Protocols and Internet Protocol (IP)
  • Copyright 2011 Network Layer Protocols and Internet Protocol (IP)
  • Copyright 2011 Transport Layer Role and Services Supporting Reliable Communication 7
  • Copyright 2011 8 Transport Layer Perspective
  • Copyright 2011 9 The Transport Layer Functions Five basic services: Segmenting upper-layer application data Establishing end-to-end operations Sending segments from one end host to another end host Ensuring data reliability provided by sequence numbers and acknowledgments Ensuring flow control provided by sliding windows
  • Copyright 2011 10 Reliable Data Transport Ensure that segments delivered will be acknowledged to the sender Provide for retransmission of any segments that are not acknowledged Put segments back into their correct sequence at the destination Provide congestion avoidance and control
  • Copyright 2011 11 Connectionless and Connection- Oriented Protocols Connection-oriented protocol A protocol either that requires an exchange of messages before data transfer begins or that has a required pre-established correlation between two endpoints Connectionless protocol A protocol that does not require an exchange of messages and that does not require a pre- established correlation between two endpoints
  • Copyright 2011 Connectionless Communication
  • Copyright 2011 13 Three-way Handshake TCP is connection-oriented, so it requires connection establishment before data transfer begins For a connection to be established, two hosts must synchronize on each others initial sequence numbers (ISNs) Initial Sequence numbers are actually large random numbers chosen by each host Connection establishment refers to the process of initializing sequence and acknowledgement fields and agreeing to the port numbers used.
  • Copyright 2011 14 Three-Way Handshake
  • Copyright 2011 15 TCP Connection Establishment
  • Copyright 2011 16 Windowing Flow-control mechanism requiring that source device receive an acknowledgment from the destination TCP uses expectational acknowledgments (Forward Acknowledgment) Window size determines the amount of data can transmit at one time before receiving an acknowledgment Larger window sizes increase communication efficiency. Window field implies the maximum number of unacknowledged bytes allowed outstanding at any instance in time.
  • Copyright 2011 17 Window Size Larger window sizes increase communication efficiency.
  • Copyright 2011 18 Window Size TCP window sizes are variable during the lifetime of a connection. The window Slides up and down based on network performance, so it is called sliding window.
  • Copyright 2011 19 Flow Control
  • Copyright 2011 20 TCP Dynamic Sliding Windows
  • Copyright 2011 21 TCP Dynamic Sliding Windows
  • Copyright 2011 22 Acknowledgment Sender keeps a record of each data packet that it sends and expects an acknowledgment. Sender starts a timer when it sends a segment, and it retransmits if the timer expires before an acknowledgment (transmission rate should be slowed) Each Acknowledgement contains a window advertisement that indicates the number of bytes receiver can accept
  • Copyright 2011 23 Segmentation, Reassembly, and In-Order Delivery TCP on the receiving computer reassembles data into its original form The data is put in the correct order If segments of a file are assembled out-of- order, the file is useless TCP provides a guarantee of in-order delivery
  • Copyright 2011 24 Segmentation, Reassembly, and In-Order Delivery Due to IP routing, a TCP receiver can receive data out of order If multiple routes exist between a source and a destination, routers can load-balance over several routes Packets can arrive out of order
  • Copyright 2011 25 TCP Providing In-Order Delivery
  • Copyright 2011 26 Port Numbers
  • Copyright 2011 27 TCP and UDP Port Numbers Internet layer delivers data (packets) from one computer to another, but it does not think about which application sent the data or which application on the receiving computer needs the data. For example, if you have five web-browser windows open, the internet layer delivers the data to the computer, but the transport layer works to ensure that each browser gets the data destined for it and not one of the others. TCP and UDP use port numbers to pass information to the upper layers Port numbers use to keep track of different conversations crossing the network at the same time (Enables the receiving computer to know which application to give the data to).
  • Copyright 2011 28 Using Port Numbers to Identify the Correct Application Process
  • Copyright 2011 29 Identifying Application Processes Using Port Numbers In previous slide, the application was assigned a dynamic port number by the host computer A host typically dynamically allocates port numbers of value 1024 (210 ) through 65,535 (216 - 1). When a host starts a new application process, it allocates a dynamic port number that is not already in use by another process. By each process having its own port number, a PC can have multiple conversations with other PCs (sometimes called multiplexing).
  • Copyright 2011 30 Identifying Application Processes Using Port Numbers Connection to Servers: Well-Known Ports Most TCP/IP applications use a client/server model for communications. Servers cannot use dynamic port numbers because clients must know ahead of time what port numbers servers use. Numbers below 1024 are considered well-known port numbers. well-known port numbers are used by Servers, other port numbers used by clients. Each client on the same host uses a different port number, but a server uses a same port number for all connections. Well-Know Port Numbers are controlled by Internet Assigned Number Authority (IANA).
  • Copyright 2011 31 Client Connecting to Well-Known Port of a Web Server (80)
  • Copyright 2011 32 Popular Well-Known Port Numbers
  • Copyright 2011 33 TCP Sequence and Acknowledgment
  • Copyright 2011 34 TCP Connection Establishment and Termination Reliable (Error recovery consume more bandwidth and use more processing cycles) Divides outgoing messages into segments Reassembles messages at the destination station
  • Copyright 2011 35 TCP Flow control using sliding windows Multiplexing using port numbers TCP relies on IP for end-to-end delivery of data At the receiving station, TCP reassembles the segments into a complete message using sequence numbers. TCP must recover data that is damaged, lost or delivered out of order.
  • Copyright 2011 UDP