5_UDP%26Applications_spring10

5_UDP%26Applications_spring10 - Chapter 5 UDP and Its...

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TCP/IP Essentials A Lab-Based Approach Chapter 5 Chapter 5 UDP and UDP and Its Applications Its Applications Spring 2010
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Polytechnic Institute of NYU Slide 2 zjzhao Orientation The transport layer
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Polytechnic Institute of NYU Slide 3 zjzhao Transport Layer Protocols • Transport layer protocols are end-to-end protocols • They are only implemented at the hosts Application Transport Network HOST Data Link Data Link Data Link Network Application Transport Network HOST Data Link
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Polytechnic Institute of NYU Slide 4 zjzhao UDP and TCP UDP – User Datagram Protocol • Datagram oriented • Unreliable, connectionless •S imp le • Unicast and multicast • Commonly used for network control signaling services - Network management (SNMP), routing (RIP), naming (DNS), etc. • Useful for increasing number of applications, e.g., multimedia applications TCP – Transmission Control Protocol • Stream oriented • Reliable, connection-oriented • Complex • Only unicast • Currently used by most Internet applications: - Web (HTTP), email (SMTP), file
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Polytechnic Institute of NYU Slide 5 zjzhao UDP - User Datagram Protocol UDP supports unreliable transmissions of datagrams UDP merely extends the host-to-to-host delivery service of IP datagram to an application-to-application service The only thing that UDP adds is multiplexing and demultiplexing UDP IP IP IP IP IP UDP Applications Applications
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Polytechnic Institute of NYU Slide 6 zjzhao UDP Format IP header UDP header UDP data (payload) UDP message length Checksum 20 bytes 8 bytes 0 15 16 31 Source Port Number Destination Port Number Port Numbers identify sending and receiving applications (processes). The maximum value for a port number is 2 16 -1= 65,535 Message Length is between 8 bytes (i.e., data field can be empty) and 65,535 bytes (length of UDP header and data in bytes) Checksum is for UDP header and UDP data
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Polytechnic Institute of NYU Slide 7 zjzhao UDP Checksum • Optional – set all 0’s if not calculated – A calculated checksum can never be all 0’s. • Computed using the UDP header, UDP data and a pseudo-header as below. • All fields of pseudo-header are available in UDP layer 16-bit UDP Length 8-bit Protocol (0x17) 0x00 32-bit Destination IP Address 32-bit Source IP Address
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Polytechnic Institute of NYU Slide 8 zjzhao Port Numbers •UDP (and TCP) use port numbers to identify applications •A globally unique flow of host application can be identified by a 5-tuple < Src. IP, Dst IP, Src. Port, Dst. Port, Protocol No.> •There are 65,535 UDP ports available per host – dynamic/private , used by clients, randomly picked, >49,151 (per IANA) – Registered, used by ordinary user processes, 1024 – 49,151 – well-known, used by servers, fixed, 1~1023
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Polytechnic Institute of NYU Slide 9 zjzhao Ephemeral Port Range Ephemeral Port : short-lived port used as transport protocol port
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This note was uploaded on 03/04/2010 for the course EE ee taught by Professor Ee during the Spring '10 term at Istanbul Technical University.

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5_UDP%26Applications_spring10 - Chapter 5 UDP and Its...

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