User Datagram Protocol: Wikis

  
  

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.The User Datagram Protocol (UDP) is one of the core members of the Internet Protocol Suite, the set of network protocols used for the Internet.^ All user datagram protocol Posts .
  • user datagram protocol - Computerworld Blogs 13 January 2010 7:37 UTC blogs.computerworld.com [Source type: General]

^ User Datagram Protocol (783 views) .
  • User Datagram Protocol 13 January 2010 7:37 UTC it.toolbox.com [Source type: FILTERED WITH BAYES]

^ NetDiscover MIB/OID - rfc4113 User Datagram Protocol (UDP).mib .
  • NetDiscover MIB/OID - rfc4113 User Datagram Protocol (UDP).mib 13 January 2010 7:37 UTC www.snmplink.org [Source type: General]

.With UDP, computer applications can send messages, in this case referred to as datagrams, to other hosts on an Internet Protocol (IP) network without requiring prior communications to set up special transmission channels or data paths.^ Internet Protocol (IP) The internetwork datagram delivery protocol that is central to the Internet protocol family.
  • Network Glossary: I 13 January 2010 7:37 UTC www.clock.org [Source type: Reference]

^ A portion of the data of an internet datagram with an internet header.
  • Internet Protocol | Chipkin Automation Systems - BACnet, Modbus 13 January 2010 7:37 UTC www.chipkin.com [Source type: Reference]
  • RFC791 - Internet Protocol(2)_�й�Э�������� 13 January 2010 7:37 UTC www.cnpaf.net [Source type: Reference]

^ On Figure 4 we illustrate the datagram generated on the Internet layer by the IP protocol.
  • How TCP/IP Protocol Works - Part 1 | Hardware Secrets 13 January 2010 7:37 UTC www.hardwaresecrets.com [Source type: Reference]

.UDP is sometimes called the Universal Datagram Protocol.^ Because of this, UDP is sometimes called a "connection-less" protocol.
  • Transport Level - Transmission Control Protocol, User Datagram Protocol 13 January 2010 7:37 UTC www.collocationcenter.eu [Source type: FILTERED WITH BAYES]

^ This protocol is called UDP (User Datagram Protocol).
  • How TCP/IP Protocol Works - Part 1 | Hardware Secrets 13 January 2010 7:37 UTC www.hardwaresecrets.com [Source type: Reference]

^ UDP is sometimes called the Universal Datagram Protocol.

.The protocol was designed by David P. Reed in 1980 and formally defined in RFC 768.^ The protocol was designed by David P. Reed in 1980 and formally defined in RFC 768 .
  • http://udp.at/ 13 January 2010 7:37 UTC udp.at [Source type: Reference]

^ The UDP protocol is defined in RFC 768: User Datagram Protocol .
  • UDP (User Datagram Protocol)-Top Bits 13 January 2010 7:37 UTC www.topbits.com [Source type: Reference]

^ UDP is defined in RFC 768.
  • Glossary 13 January 2010 7:37 UTC www.hifn.com [Source type: General]

[1]
.UDP uses a simple transmission model without implicit hand-shaking dialogues for guaranteeing reliability, ordering, or data integrity.^ UDP does not provide the reliability nor ordering guarantees that TCP does.
  • User Datagram Protocol,Introduction to UDP,User Datagram Protocol - UDP 13 January 2010 7:37 UTC www.roseindia.net [Source type: General]

^ No guarantee that data is delivered reliably or in order .
  • eScience : Networking : 39 / 60 : UDP : User Datagram Protocol (2) 13 January 2010 7:37 UTC escience.anu.edu.au [Source type: FILTERED WITH BAYES]

^ UDP does not provide the reliability and ordering guarantees that TCP does.
  • User Datagram Protocol UDP - Online Training and Tutorials 13 January 2010 7:37 UTC www.tutorial5.com [Source type: General]
  • UDP definition by The Linux Information Project (LINFO) 13 January 2010 7:37 UTC www.linfo.org [Source type: Reference]

.Thus, UDP provides an unreliable service and datagrams may arrive out of order, appear duplicated, or go missing without notice.^ The service provided by UDP is an unreliable service that provides no guarantees for delivery and no protection from duplication (e.g.
  • The User Datagram Protocol (UDP) 13 January 2010 7:37 UTC www.erg.abdn.ac.uk [Source type: Reference]

^ Thus, UDP provides an unreliable service and datagrams may arrive out of order, appear duplicated, or go missing without notice.
  • http://udp.at/ 13 January 2010 7:37 UTC udp.at [Source type: Reference]

^ The User Datagram Protocol provides unreliable, connectionless delivery service.
  • ::::: TCP/IP Protocols ::::: 13 January 2010 7:37 UTC homepages.uel.ac.uk [Source type: FILTERED WITH BAYES]

.UDP assumes that error checking and correction is either not necessary or performed in the application, avoiding the overhead of such processing at the network interface level.^ UDP assumes that error checking and correction is either not necessary or performed in the application, avoiding the overhead of such processing at the network interface level.
  • http://udp.at/ 13 January 2010 7:37 UTC udp.at [Source type: Reference]

^ The iptrace command performs network interface level packet tracing.
  • System Management Guide: Communications and Networks - TCP/IP Protocols 13 January 2010 7:37 UTC www.ncsa.illinois.edu [Source type: Reference]

^ For example, UDP-based data communications applications such as the Simple Network Management Protocol (SNMP) or Sun’s Network File Sharing ( NFS ) implement application level-based acknowledgment and error correction functions.
  • User Datagram Protocol - Hill2dot0 13 January 2010 7:37 UTC www.hill2dot0.com [Source type: Reference]

.Time-sensitive applications often use UDP because dropping packets is preferable to waiting for delayed packets, which may not be an option in a real-time system.^ Time-sensitive applications often use UDP because dropping packets is preferable to using delayed packets.
  • http://udp.at/ 13 January 2010 7:37 UTC udp.at [Source type: Reference]

^ It removes the shortcomings of TCP and UDP for real-time applications...
  • user datagram protocol udp Content at ZDNet UK 13 January 2010 7:37 UTC www.zdnet.co.uk [Source type: General]

^ This may be useful with applications that exchange sensitive data over the open Internet.
  • Internet Core Protocols: The Definitive Guide: Chapter The Internet Protocol 13 January 2010 7:37 UTC oreilly.com [Source type: FILTERED WITH BAYES]

.If error correction facilities are needed at the network interface level, an application may use the Transmission Control Protocol (TCP) or Stream Control Transmission Protocol (SCTP) which are designed for this purpose.^ TCP uses a combination of these techniques, as described in TCP (Transmission Control Protocol)."
  • Microway Working Note 3 13 January 2010 7:37 UTC www.microway.com [Source type: Reference]

^ See also: socket , Transmission Control Protocol (TCP) .
  • Software Carpentry:Glossary (Version 1121) 13 January 2010 7:37 UTC swc.scipy.org [Source type: Reference]

^ Protocols at the level provide application services on the network.

.UDP's stateless nature is also useful for servers that answer small queries from huge numbers of clients.^ Also, its stateless nature is useful for servers that answer small queries from huge numbers of clients.
  • User Datagram Protocol UDP - Online Training and Tutorials 13 January 2010 7:37 UTC www.tutorial5.com [Source type: General]

^ UDP's stateless nature is also useful for servers that answer small queries from huge numbers of clients.
  • http://udp.at/ 13 January 2010 7:37 UTC udp.at [Source type: Reference]

^ An ECHO client and server using TCP .
  • User Datagram Protocol (UDP) 13 January 2010 7:37 UTC www.powerbasic.com [Source type: General]
  • The Internet Protocol (IP) 13 January 2010 7:37 UTC www.powerbasic.com [Source type: General]

.Unlike TCP, UDP is compatible with packet broadcast (sending to all on local network) and multicasting (send to all subscribers).^ So, the request is broadcasted to all the machines on the network.
  • CS425: Computer Networks: Lecture 13 13 January 2010 7:37 UTC www.cse.iitk.ac.in [Source type: FILTERED WITH BAYES]

^ Then, setup the transmitter to send to TCP packets.
  • Transmitting and Tracking Packets of Data Through the TCP and UDPNetwork Protocols - PCATTCPC User Manual 13 January 2010 7:37 UTC www.clarkson.edu [Source type: FILTERED WITH BAYES]

^ Packets that transmit to all hosts on the network.
  • http://www.redhat.com/docs/manuals/linux/RHL-9-Manual/glossary/index.html 13 January 2010 7:37 UTC www.redhat.com [Source type: Reference]

.Common network applications that use UDP include: the Domain Name System (DNS), streaming media applications such as IPTV, Voice over IP (VoIP), Trivial File Transfer Protocol (TFTP) and many online games.^ Common network applications that use UDP include DNS , SNMP , DHCP , RIP, streaming media applications, Voice over IP, TFTP , and online games.
  • SpeedGuide.net :: UDP - User Datagram Protocol 13 January 2010 7:37 UTC www.speedguide.net [Source type: FILTERED WITH BAYES]

^ File Transfer Protocol - Download only .
  • Microsoft Internet Security & Acceleration Server (ISA) 2000 - Configuring protocol definitions 13 January 2010 7:37 UTC www.microsoft.com [Source type: Reference]

^ Streaming media, real-time multiplayer games and voice over IP (VoIP) are examples of applications that often use UDP. Another example is the Simple Network Management Protocol (SNMP) or Routing Information Protocol (RIP).
  • User Datagram Protocol UDP - Online Training and Tutorials 13 January 2010 7:37 UTC www.tutorial5.com [Source type: General]

The Internet Protocol Suite
Application Layer
BGP · DHCP · DNS · FTP · GTP · HTTP · IMAP · IRC · Megaco · MGCP · NNTP · NTP · POP · RIP · RPC · RTP · RTSP · SDP · SIP · SMTP · SNMP · SOAP · SSH · Telnet · TLS/SSL · XMPP · (more)
Transport Layer
TCP · UDP · DCCP · SCTP · RSVP · ECN · (more)
Internet Layer
IP (IPv4, IPv6) · ICMP · ICMPv6 · IGMP · IPsec · (more)
Link Layer
ARP/InARP · NDP · OSPF · Tunnels (L2TP) · PPP · Media Access Control (Ethernet, DSL, ISDN, FDDI) · (more)

Contents

Ports

.UDP applications use datagram sockets to establish host-to-host communications.^ Creating a socket for use with UDP 8.3.
  • The User Datagram Protocol 13 January 2010 7:37 UTC www.scottklement.com [Source type: FILTERED WITH BAYES]

^ Across the network, pvmd processes communicate using UDP datagrams.
  • Citations: Internet Request For Comments RFC - Postel, Protocol (ResearchIndex) 13 January 2010 7:37 UTC citeseer.ist.psu.edu [Source type: Reference]

^ UDP provides datagram oriented communication.
  • EIW Fall 2000 Lecture Notes - Internet Application Protocols 13 January 2010 7:37 UTC www.cs.rpi.edu [Source type: FILTERED WITH BAYES]

.Sockets bind the application to service ports, that function as the endpoints of data transmission.^ Bind the Socket to INADDR_ANY and the specified port .
  • The Micro C++ Library: micro::DatagramSocket Class Reference 13 January 2010 7:37 UTC libmicxx.sourceforge.net [Source type: Reference]

^ Otherwise the socket layer will automatically assign a free local port out of the range defined by net.ipv4.ip_local_port_range and bind the socket to INADDR_ANY .
  • udp(7): User Datagram Protocol for IPv4 - Linux man page 13 January 2010 7:37 UTC linux.die.net [Source type: FILTERED WITH BAYES]

^ A host generally executes application programs on behalf of user(s), employing network and/or Internet communication services in support of this function.

.A port is a software structure that is identified by the port number, a 16 bit integer value, allowing for port numbers between 0 and 65,535. Port 0 is reserved, but is a permissible source port value if the sending process does not expect messages in response.^ Each protocol port is identified by a positive integer.
  • 3.2.10. User Datagram Protocol 13 January 2010 7:37 UTC hq.alert.sk [Source type: Reference]

^ The second 16 bits contain the destination port number and the checksum.
  • System Management Guide: Communications and Networks - TCP/IP Protocols 13 January 2010 7:37 UTC www.ncsa.illinois.edu [Source type: Reference]

^ When you are sending a datagram, this becomes the "source" port number, since you are the source of the datagram.
  • Introduction to TCP/IP 13 January 2010 7:37 UTC www.uic.edu [Source type: FILTERED WITH BAYES]

.Ports 1 through 1023 (hexadecimal 0x3FF) are named "well-known" ports and on Unix-like operating systems, binding to one of these ports requires superuser (root) access.^ Ports 1 through 1023 ( hex 3FF) are named "well-known" ports and on Unix -derived operating systems , binding to one of these ports requires root access.
  • User Datagram Protocol - a knol by Michael Sallander 13 January 2010 7:37 UTC knol.google.com [Source type: Reference]

^ For example, the well-known port for the Domain Name System is 53.
  • User Datagram Protocol - encyclopedia article - Citizendium 13 January 2010 7:37 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]

^ By convention, these ports are maintained in a pool by the network operating system.
  • User Datagram Protocol - a knol by Michael Sallander 13 January 2010 7:37 UTC knol.google.com [Source type: Reference]

.Ports 1024 through 49,151 (0xBFFF) are the registered ports.^ Ports 1024 through 49,151 (hex BFFF) are registered ports .
  • User Datagram Protocol - a knol by Michael Sallander 13 January 2010 7:37 UTC knol.google.com [Source type: Reference]

^ Registered TCP/UDP ports include all port numbers 1024 and greater, up to the maximum possible port number of 65535.
  • User Datagram Protocol - a knol by Michael Sallander 13 January 2010 7:37 UTC knol.google.com [Source type: Reference]

^ Ports 49,152 through 65,535 (hex FFFF) are used as temporary ports primarily by clients when communicating to servers .
  • User Datagram Protocol - a knol by Michael Sallander 13 January 2010 7:37 UTC knol.google.com [Source type: Reference]

.Ports 49,152 through 65,535 (0xFFFF) are used as temporary ports primarily by clients when communicating to servers.^ The client and server communicate using a protocol.
  • IMail Server 7.0 User's Guide - Glossary 13 January 2010 7:37 UTC www.ipswitch.com [Source type: Reference]

^ The client also creates a Socket for communication with the server.
  • Networking Overview 13 January 2010 7:37 UTC java.sun.com [Source type: Reference]

^ Used for internal communications between servers .
  • Microsoft Office Communications Server 2007 R2 ports and protocols (OCS 2007 R2) 13 January 2010 7:37 UTC www.ocspedia.com [Source type: Reference]

Packet structure

.UDP is a minimal message-oriented Transport Layer protocol that is documented in IETF RFC 768.^ Connectionless, unreliable Transport Layer Protocol .
  • User Datagram Protocol - a knol by Michael Sallander 13 January 2010 7:37 UTC knol.google.com [Source type: Reference]

^ Transport layer protocols : .

^ UDP is the simpler of the two transport protocols.

.UDP provides no guarantees to the upper layer protocol for message delivery and the UDP protocol layer retains no state of UDP messages once sent.^ The service provided by UDP is an unreliable service that provides no guarantees for delivery and no protection from duplication (e.g.
  • The User Datagram Protocol (UDP) 13 January 2010 7:37 UTC www.erg.abdn.ac.uk [Source type: Reference]

^ No guarantee that the message will arrive at its destination.
  • |1| 13 January 2010 7:37 UTC www.unc.edu [Source type: Reference]

^ Routing protocols provide the layer 3 network state update.
  • Understanding Routing Protocols - O'Reilly Media 13 January 2010 7:37 UTC www.oreillynet.com [Source type: General]

.For this reason, UDP is sometimes referred to as Unreliable Datagram Protocol.^ UDP is sometimes called the Universal Datagram Protocol.

^ UDP (User Datagram Protocol) is a lightweight, unreliable, datagram-oriented, connectionless protocol.
  • Qt 4.2: QtNetwork Module 13 January 2010 7:37 UTC cep.xor.aps.anl.gov [Source type: Reference]

^ This protocol is called UDP (User Datagram Protocol).
  • How TCP/IP Protocol Works - Part 1 | Hardware Secrets 13 January 2010 7:37 UTC www.hardwaresecrets.com [Source type: Reference]

.UDP provides application multiplexing (via port numbers) and integrity verification (via checksum) of the header and payload.^ This is the port number pertaining to the destination application.
  • The details of Transmission Control Protocol (TCP), User Datagram (UDP) and Raw socket used in Linux Socket or network programming 13 January 2010 7:37 UTC www.tenouk.com [Source type: Reference]

^ UDP introduces the port number concept.
  • Introduction to the Tranmission Control Protocol, Course 202 13 January 2010 7:37 UTC www.industrialethernetu.com [Source type: Reference]

^ It is the checksum of pseudo header, tcp header and payload.
  • The detail explanation of the IP, ICMP, UDP and TCP protocols which include the header datagram and format from RFC which will be used in Linux network or socket programming 13 January 2010 7:37 UTC www.tenouk.com [Source type: Reference]

.If transmission reliability is desired, it must be implemented in the user's application.^ It must enforce any desired transmission control such as reliable delivery.
  • The details of Transmission Control Protocol (TCP), User Datagram (UDP) and Raw socket used in Linux Socket or network programming 13 January 2010 7:37 UTC www.tenouk.com [Source type: Reference]

^ Lacking reliability, UDP applications must generally be willing to accept some loss, errors or duplication.
  • User Datagram Protocol UDP - Online Training and Tutorials 13 January 2010 7:37 UTC www.tutorial5.com [Source type: General]

^ TCP/IP implements FTP in the ftp user command and the ftpd server command and does not provide an applications programming interface (API) to this protocol.
  • System Management Guide: Communications and Networks - TCP/IP Protocols 13 January 2010 7:37 UTC www.ncsa.illinois.edu [Source type: Reference]

bits 0 - 15 16 - 31
0 Source Port Destination Port
32 Length Checksum
64  
Data
 
.The UDP header consists of 4 fields.^ The UDP length field is the length of the UDP header and data.
  • User Datagram Protocol - a knol by Michael Sallander 13 January 2010 7:37 UTC knol.google.com [Source type: Reference]

^ The UDP header consists of only 4 fields.
  • IPv6.com - User Datagram Protocol (UDP) 13 January 2010 7:37 UTC www.ipv6.com [Source type: Reference]
  • User Datagram Protocol - a knol by Michael Sallander 13 January 2010 7:37 UTC knol.google.com [Source type: Reference]

^ The UDP header consists of four fields each of 2 bytes in length: .
  • The User Datagram Protocol (UDP) 13 January 2010 7:37 UTC www.erg.abdn.ac.uk [Source type: Reference]

.The use of two of those is optional in IPv4 (pink background in table).^ The use of two of those is optional (light red background in diagram).
  • UDP (User Datagram Protocol)-Top Bits 13 January 2010 7:37 UTC www.topbits.com [Source type: Reference]

^ The use of two of those is optional (pink background in table).
  • User Datagram Protocol - a knol by Michael Sallander 13 January 2010 7:37 UTC knol.google.com [Source type: Reference]

^ The value cannot be used to compute the shorter of two routes unless those routes are both contained within a single autonomous system.
  • System Management Guide: Communications and Networks - TCP/IP Protocols 13 January 2010 7:37 UTC www.ncsa.illinois.edu [Source type: Reference]

.In IPv6 only the source port is optional (see below).^ Source port is an optional field.
  • Protocol: UDP ( User Datagram Protocol ) 13 January 2010 7:37 UTC www.protocolbase.net [Source type: Reference]

^ To view only the traffic flows for IPv6 DNS packets on UDP port 53 (hex value 0035) , the command show ipv6 flow cache .
  • Cisco Applied Mitigation Bulletin: User Datagram Protocol Delivery Issue For IPv4/IPv6 Dual-stack Routers 13 January 2010 7:37 UTC www.cisco.com [Source type: Reference]

^ Source Port (16 bits): This field is optional and specifies the port number of the application that is originating the user data.
  • Network protocols: Network Layer 13 January 2010 7:37 UTC www.ists.pwr.wroc.pl [Source type: Reference]

Source port 
This field identifies the sending port when meaningful and should be assumed to be the port to reply to if needed. If not used, then it should be zero.
Destination port 
This field identifies the destination port and is required.
Length 
A 16-bit field that specifies the length in bytes of the entire datagram: header and data. The minimum length is 8 bytes since that's the length of the header. The field size sets a theoretical limit of 65,535 bytes (8 byte header + 65527 bytes of data) for a UDP datagram. The practical limit for the data length which is imposed by the underlying .IPv4 protocol is 65,507 bytes.^ The UDP protocol supports representations of port numbers that can be expressed using two bytes of binary information, thereby permitting the identification of ports numbered between 0 and 65,535.
  • PORT ACCESS USING USER DATAGRAM PROTOCOL PACKETS - Patent application 13 January 2010 7:37 UTC www.faqs.org [Source type: Reference]

^ A UDP datagram is carried in a single IP packet and is hence limited to a maximum payload of 65,507 bytes for IPv4 and 65,527 bytes for IPv6.
  • The User Datagram Protocol (UDP) 13 January 2010 7:37 UTC www.erg.abdn.ac.uk [Source type: Reference]

^ The practical limit for the data length which is imposed by the underlying IPv4 protocol is 65,507 bytes.
  • User Datagram Protocol - a knol by Michael Sallander 13 January 2010 7:37 UTC knol.google.com [Source type: Reference]

Checksum 
The 16-bit checksum field is used for error-checking of the header and data. .The algorithm for computing the checksum is different for transport over IPv4 and IPv6. If the checksum is omitted in IPv4, the field uses the value all-zeros.^ The sender can choose to compute a checksum or set the field to zero.

^ The CHECKSUM field is optional and stored as zero if not computed (a computed zero is stored as all ones).

^ The difference is in the data used to make the checksum.
  • User Datagram Protocol - a knol by Michael Sallander 13 January 2010 7:37 UTC knol.google.com [Source type: Reference]

This field is not optional for IPv6.

Checksum computation

The method used to compute the checksum is defined in RFC 768:
Checksum is the 16-bit one's complement of the one's complement sum of a pseudo header of information from the IP header, the UDP header, and the data, padded with zero octets at the end (if necessary) to make a multiple of two octets.
.In other words, all 16-bit words are summed using one's complement arithmetic.^ The values in the sections are added using the one's complement arithmetic.
  • InformIT: TCP/IP: The Internet Layer Protocol > Format of an IP Datagram 13 January 2010 7:37 UTC www.informit.com [Source type: Reference]

^ The checksum field is the 16 bit one's complement of the one's complement sum of all 16 bit words in the header.
  • Internet Protocol | Chipkin Automation Systems - BACnet, Modbus 13 January 2010 7:37 UTC www.chipkin.com [Source type: Reference]

^ The checksum is the 16-bit ones’ complement of the one's complement sum of the ICMP message starting with the ICMP Type.
  • The detail explanation of the IP, ICMP, UDP and TCP protocols which include the header datagram and format from RFC which will be used in Linux network or socket programming 13 January 2010 7:37 UTC www.tenouk.com [Source type: Reference]

.The sum is then one's complemented to yield the value of the UDP checksum field.^ The checksum field is the 16 bit one's complement of the one's complement sum of all 16 bit words in the header.
  • Internet Protocol | Chipkin Automation Systems - BACnet, Modbus 13 January 2010 7:37 UTC www.chipkin.com [Source type: Reference]

^ The 16-bit one's complement of this sum is stored in the checksum field.
  • Chapter 3. IP: Internet Protocol 13 January 2010 7:37 UTC www.goldfish.org [Source type: FILTERED WITH BAYES]

^ Checksum is the 16-bit one's complement of the one's complement sum of a pseudo header of information from the IP header, the UDP header, and the data, padded with zero octets at the end (if necessary) to make a multiple of two octets.
  • User Datagram Protocol - The H Security: News and features 13 January 2010 7:37 UTC www.h-online.com [Source type: FILTERED WITH BAYES]

.If the checksum calculation results in the value zero (all 16 bits 0) it should be sent as the one's complement (all 1's).^ Header Checksum: 16 bits A checksum on the header only.
  • RFC791 - Internet Protocol_�й�Э�������� 13 January 2010 7:37 UTC www.cnpaf.net [Source type: Reference]

^ The transmitted checksum MUST NOT be all zeroes.
  • draft-ietf-tsvwg-udp-lite-00 - The Lightweight User Datagram Protocol (UDP-Lite) 13 January 2010 7:37 UTC tools.ietf.org [Source type: Reference]

^ The checksum field is the 16 bit one's complement of the one's complement sum of all 16 bit words in the header.
  • Internet Protocol | Chipkin Automation Systems - BACnet, Modbus 13 January 2010 7:37 UTC www.chipkin.com [Source type: Reference]

.The difference between IPv4 and IPv6 is in the data used to compute the checksum.^ Note the use of ACE_INET_Addr in the recv method: This helps capture the peer computer from which the data was being transmitted.
  • Learning interprocess communication with the ACE Framework 13 January 2010 7:37 UTC www.ibm.com [Source type: General]

^ Because of this simplicity, RIP protocols have come the closest of any to being an "Open IGP", i.e., a protocol which can be used between different vendors' gateways.

^ A checksum is computed over the pseudo-header , UDP- header , and the data area before sending the user datagram.
  • Lesson 14: User Datagram Protocol (UDP) 13 January 2010 7:37 UTC www.cis.njit.edu [Source type: Reference]

IPv4 PSEUDO-HEADER

.When UDP runs over IPv4, the checksum is computed using a PSEUDO-HEADER that contains some of the same information from the real IPv4 header.^ This checksum procedure is the same as used in TCP. .
  • The detail explanation of the IP, ICMP, UDP and TCP protocols which include the header datagram and format from RFC which will be used in Linux network or socket programming 13 January 2010 7:37 UTC www.tenouk.com [Source type: Reference]

^ It is the checksum of pseudo header, tcp header and payload.
  • The detail explanation of the IP, ICMP, UDP and TCP protocols which include the header datagram and format from RFC which will be used in Linux network or socket programming 13 January 2010 7:37 UTC www.tenouk.com [Source type: Reference]

^ Each of the fragments contains the following header information: .
  • Internet Core Protocols: The Definitive Guide: Chapter The Internet Protocol 13 January 2010 7:37 UTC oreilly.com [Source type: FILTERED WITH BAYES]

.The PSEUDO-HEADER is not the real IPv4 header used to send an IP packet.^ IP packets all have similar headers.

^ If so, it will stick on an Ethernet header, and send the packet.
  • Introduction to TCP/IP 13 January 2010 7:37 UTC www.uic.edu [Source type: FILTERED WITH BAYES]

^ Runs on top of IP and is used as an alternative to TCP. UDP does not, however, provide any error checking for guaranteeing packet delivery.
  • 2-3 Protocols and Standards | StudyNotes.net 13 January 2010 7:37 UTC studynotes.net [Source type: Reference]

.The following table defines the PSEUDO-HEADER used only for the checksum calculation.^ Header Checksum: 16 bits A checksum on the header only.
  • RFC791 - Internet Protocol_�й�Э�������� 13 January 2010 7:37 UTC www.cnpaf.net [Source type: Reference]

^ The Header Checksum at the receiver's end is calculated as: .
  • InformIT: TCP/IP: The Internet Layer Protocol > Format of an IP Datagram 13 January 2010 7:37 UTC www.informit.com [Source type: Reference]

^ (Sum) 1 The Header Checksum calculated by the sender is .
  • InformIT: TCP/IP: The Internet Layer Protocol > Format of an IP Datagram 13 January 2010 7:37 UTC www.informit.com [Source type: Reference]

bits 0 - 7 8 - 15 16 - 23 24 - 31
0 Source address
32 Destination address
64 Zeros Protocol UDP length
96 Source Port Destination Port
128 Length Checksum
160  
Data
 
.The source and destination addresses are those in the IPv4 header.^ The IP header provides the source and destination addresses.
  • Net Surfing With IP Protocol - O'Reilly Media 13 January 2010 7:37 UTC www.oreillynet.com [Source type: FILTERED WITH BAYES]

^ The destination address, an internet header field.
  • Internet Protocol | Chipkin Automation Systems - BACnet, Modbus 13 January 2010 7:37 UTC www.chipkin.com [Source type: Reference]

^ Destination The destination address, an internet header field.
  • RFC791 - Internet Protocol(2)_�й�Э�������� 13 January 2010 7:37 UTC www.cnpaf.net [Source type: Reference]

.The protocol is that for UDP (see List of IP protocol numbers): 17. The UDP length field is the length of the UDP header and data.^ If so, the datagram is delivered to the protocol module specified by the protocol field in the IP header.
  • Chapter 3. IP: Internet Protocol 13 January 2010 7:37 UTC www.goldfish.org [Source type: FILTERED WITH BAYES]

^ The checksum of header and data, see IP checksum.
  • The detail explanation of the IP, ICMP, UDP and TCP protocols which include the header datagram and format from RFC which will be used in Linux network or socket programming 13 January 2010 7:37 UTC www.tenouk.com [Source type: Reference]

^ Indicates the length of the IP header.

.UDP checksum computation is optional for IPv4. If a checksum is not used it should be set to the value zero.^ Set to zero if not used.
  • Lesson 14: User Datagram Protocol (UDP) 13 January 2010 7:37 UTC www.cis.njit.edu [Source type: Reference]
  • Lesson 14: User Datagram Protocol (UDP) 13 January 2010 7:37 UTC www.cis.njit.edu [Source type: Reference]

^ For purposes of computing the checksum, the value of the checksum field is zero.
  • Network protocols: Network Layer 13 January 2010 7:37 UTC www.ists.pwr.wroc.pl [Source type: Reference]
  • RFC791 - Internet Protocol_�й�Э�������� 13 January 2010 7:37 UTC www.cnpaf.net [Source type: Reference]

^ It computes the UDP checksum.
  • Lesson 14: User Datagram Protocol (UDP) 13 January 2010 7:37 UTC www.cis.njit.edu [Source type: Reference]
  • Lesson 14: User Datagram Protocol (UDP) 13 January 2010 7:37 UTC www.cis.njit.edu [Source type: Reference]

IPv6 PSEUDO-HEADER

.When UDP runs over IPv6, the checksum is mandatory.^ However, in the next-generation IP - IPv6 - UDP checksums are mandatory.
  • User Datagram Protocol - a knol by Michael Sallander 13 January 2010 7:37 UTC knol.google.com [Source type: Reference]

^ When UDP runs over IPv6, the checksum is no longer considered optional, and the method used to compute the checksum is changed, as per RFC 246 .
  • User Datagram Protocol - a knol by Michael Sallander 13 January 2010 7:37 UTC knol.google.com [Source type: Reference]

^ TCP checksums are optional but UDP checksums are mandatory UDP checksums are optional but TCP checksums are mandatory TCP checksums are larger than UDP checksums UDP checksums are larger than TCP checksums UDP checksums are optional (for application performance reasons), but TCP checksums are mandatory.
  • User Datagram Protocol - a knol by Michael Sallander 13 January 2010 7:37 UTC knol.google.com [Source type: Reference]

The method used to compute it is changed as documented in RFC 2460:
Any transport or other upper-layer protocol that includes the addresses from the IP header in its checksum computation must be modified for use over IPv6 to include the 128-bit IPv6 addresses.
When computing the checksum, again a PSEUDO-HEADER is used that mimics the real IPv6 header:
bits 0 - 7 8 - 15 16 - 23 24 - 31
0 Source address
32
64
96
128 Destination address
160
192
224
256 UDP length
288 Zeros Next Header
320 Source Port Destination Port
352 Length Checksum
384  
Data
 
.The source address is the one in the IPv6 header.^ The source address, an internet header field.
  • Internet Protocol | Chipkin Automation Systems - BACnet, Modbus 13 January 2010 7:37 UTC www.chipkin.com [Source type: Reference]

^ The source address is the one in the IPv6 header.
  • User Datagram Protocol - a knol by Michael Sallander 13 January 2010 7:37 UTC knol.google.com [Source type: Reference]

^ Source The source address, an internet header field.
  • RFC791 - Internet Protocol(2)_�й�Э�������� 13 January 2010 7:37 UTC www.cnpaf.net [Source type: Reference]

.The destination address is the final destination; if the IPv6 packet doesn't contain a Routing header, that will be the destination address in the IPv6 header; otherwise, at the originating node, it will be the address in the last element of the Routing header, and, at the receiving node, it will be the destination address in the IPv6 header.^ Destination Address field (32 bits) s pecifies the receiving node.

^ IPv6/IPv4 routers can tunnel IPv6 packets to their final destination IPv6 or IPv4 host.
  • System Management Guide: Communications and Networks - TCP/IP Protocols 13 January 2010 7:37 UTC www.ncsa.illinois.edu [Source type: Reference]

^ IP is responsible for routing packets by their IP address.
  • 2-3 Protocols and Standards | StudyNotes.net 13 January 2010 7:37 UTC studynotes.net [Source type: Reference]

.The value of the Next Header field is the protocol value for UDP: 17. The UDP length field is the length of the UDP header and data.^ Length field (16 bits) specifies the length of the header and data.

^ The Next Header value is the protocol value for UDP: 17.
  • User Datagram Protocol - a knol by Michael Sallander 13 January 2010 7:37 UTC knol.google.com [Source type: Reference]

^ Rather, the protocol field in the IP header is set to 17.
  • 152 Network Protocols 13 January 2010 7:37 UTC www.cse.scu.edu [Source type: FILTERED WITH BAYES]

Reliability and congestion control solutions

.Lacking reliability, UDP applications must generally be willing to accept some loss, errors or duplication.^ This is why the PCoIP protocol chose to manage reliability within the application layer while using UDP as a transport layer instead of letting the TCP transport layer manage reliability.
  • How many protocols does it take to deliver a great user experience? » ocb - Citrix Community 13 January 2010 7:37 UTC community.citrix.com [Source type: FILTERED WITH BAYES]

^ This data will generally be both gathered and used by a higher layer protocol, e.g., by TCP, or by an application using UDP. Experiments are currently in progress on caching path properties in this manner.

^ Note, some applications might indeed present the data as a stream when the underlying protocol is UDP. However, this is the layering of an additional protocol on top of UDP, and it is not something inherent in the UDP protocol itself.
  • User Datagram Protocol (UDP) :: UDP I/O Support (xPC Target™) 13 January 2010 7:37 UTC www.mathworks.com [Source type: Reference]

.Some applications such as TFTP may add rudimentary reliability mechanisms into the application layer as needed.^ Host layer protocol that provides a reliable data transport service to the application layer protocols.
  • TCPware V5.7 User's Guide glossary.htm 13 January 2010 7:37 UTC www.process.com [Source type: Reference]

^ This is why the PCoIP protocol chose to manage reliability within the application layer while using UDP as a transport layer instead of letting the TCP transport layer manage reliability.
  • How many protocols does it take to deliver a great user experience? » ocb - Citrix Community 13 January 2010 7:37 UTC community.citrix.com [Source type: FILTERED WITH BAYES]

^ The only other option is to limit the bandwidth provided to the TCP network layer such that you never get into a packet loss situation.
  • How many protocols does it take to deliver a great user experience? » ocb - Citrix Community 13 January 2010 7:37 UTC community.citrix.com [Source type: FILTERED WITH BAYES]

.Most often, UDP applications do not require reliability mechanisms and may even be hindered by them.^ UDP does not provide the reliability and ordering guarantees that TCP does; datagrams may arrive out of order or go missing without notice.

^ Again,UDP is a much simpler protocol than TCP and is useful in situations where the reliability mechanisms of TCP are not necessary.

^ This is why the PCoIP protocol chose to manage reliability within the application layer while using UDP as a transport layer instead of letting the TCP transport layer manage reliability.
  • How many protocols does it take to deliver a great user experience? » ocb - Citrix Community 13 January 2010 7:37 UTC community.citrix.com [Source type: FILTERED WITH BAYES]

.Streaming media, real-time multiplayer games and voice over IP (VoIP) are examples of applications that often use UDP. If an application requires a high degree of reliability, a protocol such as the Transmission Control Protocol or erasure codes may be used instead.^ The Transmission Control Protocol (TCP) manages the reliability of the transmission.
  • Telecommunications and Network Security Concepts for CISSP Exam 13 January 2010 7:37 UTC www.packtpub.com [Source type: Reference]

^ Datagram A datagram is the unit of transmission in the IP protocol.

^ Rfc 0739: Transmission control protocol.
  • Reliable Datagram Protocol 13 January 2010 7:37 UTC gms.freeshell.org [Source type: FILTERED WITH BAYES]

.Lacking any congestion avoidance and control mechanisms, network-based mechanisms are required to minimize potential congestion collapse effects of uncontrolled, high rate UDP traffic loads.^ Priorities for congestion-controlled traffic are: .
  • System Management Guide: Communications and Networks - TCP/IP Protocols 13 January 2010 7:37 UTC www.ncsa.illinois.edu [Source type: Reference]

^ Illustrate the effect of lack of flow control .
  • Transmitting and Tracking Packets of Data Through the TCP and UDPNetwork Protocols - PCATTCPC User Manual 13 January 2010 7:37 UTC www.clarkson.edu [Source type: FILTERED WITH BAYES]

^ Router-based congestion control mechanisms, such as Random Early Detection (RED) [ 7 ] with penalty box [ 6 ], also require intermediate nodes to discriminate between traffic flows.
  • 9th USENIX Security Symposium Paper 13 January 2010 7:37 UTC www.usenix.org [Source type: Reference]

.In other words, since UDP senders cannot detect congestion, network-based elements such as routers using packet queuing and dropping techniques will often be the only tool available to slow down excessive UDP traffic.^ In other words, it is a policy enforcement tool.

^ A connectionless protocol that is used in packet-switched networks such as the Internet.
  • Telecommunications and Network Security Concepts for CISSP Exam 13 January 2010 7:37 UTC www.packtpub.com [Source type: Reference]

^ In other words, routers can now participate in a layer above the IP. Examples of such active networking techniques are:      Internet traffic engineering.
  • 9th USENIX Security Symposium Paper 13 January 2010 7:37 UTC www.usenix.org [Source type: Reference]

.The Datagram Congestion Control Protocol (DCCP) is being designed as a partial solution to this potential problem by adding end host TCP-friendly congestion control behavior to high-rate UDP streams such as streaming media.^ This protocol is called UDP (User Datagram Protocol).
  • How TCP/IP Protocol Works - Part 1 | Hardware Secrets 13 January 2010 7:37 UTC www.hardwaresecrets.com [Source type: Reference]

^ This protocol suit is designed to protect transport layer protocols such as the TCP and UDP .
  • Telecommunications and Network Security Concepts for CISSP Exam 13 January 2010 7:37 UTC www.packtpub.com [Source type: Reference]

^ TCP see transmission control protocol ( TCP ) .
  • http://www.redhat.com/docs/manuals/linux/RHL-9-Manual/glossary/index.html 13 January 2010 7:37 UTC www.redhat.com [Source type: Reference]

Applications

.While the total amount of UDP traffic found on a typical network is often on the order of only a few percent, numerous key Internet applications use UDP, including: the Domain Name System (DNS), where queries must be fast and only consist of a single request followed by a single reply packet, the Simple Network Management Protocol (SNMP), the Dynamic Host Configuration Protocol (DHCP) and the Routing Information Protocol (RIP).^ SNMP Manager An SNMP manager is an application that communicates with SNMP agents.
  • http://www.dart.com/glossary.aspx 13 January 2010 7:37 UTC www.dart.com [Source type: Reference]

^ Some use them only for the local network.
  • Introduction to TCP/IP 13 January 2010 7:37 UTC www.uic.edu [Source type: FILTERED WITH BAYES]

^ Packets that transmit to all hosts on the network.
  • http://www.redhat.com/docs/manuals/linux/RHL-9-Manual/glossary/index.html 13 January 2010 7:37 UTC www.redhat.com [Source type: Reference]

.Voice and video traffic is generally transmitted using UDP. Real-time video and audio streaming protocols are designed to handle occasional lost packets, so only slight degradation in quality occurs, rather than large delays if lost packets were retransmitted.^ This field is not generally used by the Internet at this time.
  • System Management Guide: Communications and Networks - TCP/IP Protocols 13 January 2010 7:37 UTC www.ncsa.illinois.edu [Source type: Reference]

^ Stream Versus Packet — TCP is a stream-oriented protocol, while UDP is a packet-oriented protocol.
  • User Datagram Protocol (UDP) :: UDP I/O Support (xPC Target™) 13 January 2010 7:37 UTC www.mathworks.com [Source type: Reference]

^ Streaming media (audio/video/voice) often use datagrams because it doesn't really matter if a few are lost in transmission.

.Because both TCP and UDP run over the same network, many businesses are finding that a recent increase in UDP traffic from these real-time applications is hindering the performance of applications using TCP, such as point of sale, accounting, and database systems.^ Both TCP and UDP have the following trials that are run: .
  • Transmitting and Tracking Packets of Data Through the TCP and UDPNetwork Protocols - PCATTCPC User Manual 13 January 2010 7:37 UTC www.clarkson.edu [Source type: FILTERED WITH BAYES]

^ The relevant points to running a UDP application such as the following simpleChat are: .
  • User Datagram Protocol Exercise 13 January 2010 7:37 UTC homepages.ius.edu [Source type: Reference]

^ Because of their similarities, many cards support both of these protocols.
  • http://k12linux.mesd.k12.or.us/nag2/x-087-2-intro.tcpip.html 13 January 2010 7:37 UTC k12linux.mesd.k12.or.us [Source type: FILTERED WITH BAYES]

.When TCP detects packet loss, it will throttle back its data rate usage.^ The client who needs to terminate the connection sends a FIN segment to the server that is a TCP Packet with the FIN flag set, indicating that it has finished sending the data.
  • The details of Transmission Control Protocol (TCP), User Datagram (UDP) and Raw socket used in Linux Socket or network programming 13 January 2010 7:37 UTC www.tenouk.com [Source type: Reference]

^ Data is transmitted in packets called TCP segments, which contain TCP headers and data.
  • General Computer Glossary-General Computer Terms-Best Computer Online Store Houston Buy Discount Prices Texas-Directron.com 13 January 2010 7:37 UTC www.directron.com [Source type: Reference]

^ Key point: This bit is set in every packet but the first one, because every TCP packet acknowledges the last data it received.

.Since both real-time and business applications are important to businesses, developing quality of service solutions is seen as crucial by some.^ Another important point to be noted is that the TOS bits will be meaningful only if the network devices through which a datagram is routed are programmed to support and provide a quality of service.
  • InformIT: TCP/IP: The Internet Layer Protocol > Format of an IP Datagram 13 January 2010 7:37 UTC www.informit.com [Source type: Reference]

^ This means that every incoming packet is received by both adapters, so every request is seen multiple times, and responded to multiple times.

^ Cisco Wide Area Application Services (WAAS) is a solution designed to bridge the divide between application performance and infrastructure consolidation in WAN environments.
  • Chapter 1: Introduction to Cisco Wide Area Application Services (WAAS) - Network World 13 January 2010 7:37 UTC www.networkworld.com [Source type: Reference]

[2]

Comparison of UDP and TCP

.Transmission Control Protocol is a connection-oriented protocol, which means that it requires handshaking to set up end-to-end communications.^ TCP is a connection-oriented protocol that is widely used in Internet communications.
  • Telecommunications and Network Security Concepts for CISSP Exam 13 January 2010 7:37 UTC www.packtpub.com [Source type: Reference]

^ Rfc 0739: Transmission control protocol.
  • Reliable Datagram Protocol 13 January 2010 7:37 UTC gms.freeshell.org [Source type: FILTERED WITH BAYES]

^ Transmission Control Protocol security considerations.
  • Infos about (Unicast) Transport Protocols, especially TCP 13 January 2010 7:37 UTC mark.doll.name [Source type: Reference]

.Once a connection is set up user data may be sent bi-directionally over the connection.^ Once a connection is established this is always sent.
  • The detail explanation of the IP, ICMP, UDP and TCP protocols which include the header datagram and format from RFC which will be used in Linux network or socket programming 13 January 2010 7:37 UTC www.tenouk.com [Source type: Reference]

^ The client who needs to terminate the connection sends a FIN segment to the server that is a TCP Packet with the FIN flag set, indicating that it has finished sending the data.
  • The details of Transmission Control Protocol (TCP), User Datagram (UDP) and Raw socket used in Linux Socket or network programming 13 January 2010 7:37 UTC www.tenouk.com [Source type: Reference]

^ LAN to Road Runner We sent data from a computer connected to a LAN to a computer connected by a Road Runner service.
  • Transmitting and Tracking Packets of Data Through the TCP and UDPNetwork Protocols - PCATTCPC User Manual 13 January 2010 7:37 UTC www.clarkson.edu [Source type: FILTERED WITH BAYES]

.
  • Reliable – TCP manages message acknowledgment, retransmission and timeout.^ This is why the PCoIP protocol chose to manage reliability within the application layer while using UDP as a transport layer instead of letting the TCP transport layer manage reliability.
    • How many protocols does it take to deliver a great user experience? » ocb - Citrix Community 13 January 2010 7:37 UTC community.citrix.com [Source type: FILTERED WITH BAYES]

    ^ TCP achieves this reliability by assigning a sequence number to each octet it transmits and requiring a positive acknowledgment (ACK) from the receiving TCP .
    • System Management Guide: Communications and Networks - TCP/IP Protocols 13 January 2010 7:37 UTC www.ncsa.illinois.edu [Source type: Reference]

    ^ In an implementation with a segment retransmission queue, TCP performance may be enhanced by repacketizing the segments awaiting acknowledgment when the first retransmission timeout occurs.

    .Many attempts to reliably deliver the message are made.^ That is, ICMP does not guarantee that an IP packet is delivered reliably or that an ICMP message is returned to the source host when an IP packet is not delivered or is incorrectly delivered.
    • System Management Guide: Communications and Networks - TCP/IP Protocols 13 January 2010 7:37 UTC www.ncsa.illinois.edu [Source type: Reference]

    ^ Packets may be delivered zero, one or many times, and no guarantees on delivery are made.
    • SDP - Secure Datagram Protocol #1 13 January 2010 7:37 UTC www.webfunds.org [Source type: Reference]

    ^ The uncontrolled messages tend to be less reliably delivered and suffer less delay.
    • RFC791 - Internet Protocol(2)_�й�Э�������� 13 January 2010 7:37 UTC www.cnpaf.net [Source type: Reference]

    .If it gets lost along the way, the server will re-request the lost part.^ Most application protocols support write requests that are asynchronous, that is, the acknowledgement of that request by the server has no impact on the way the client sending the data handles that data.
    • Chapter 1: Introduction to Cisco Wide Area Application Services (WAAS) - Network World 13 January 2010 7:37 UTC www.networkworld.com [Source type: Reference]

    ^ If a packet is lost along the way, either the sender or the receiver must detect the loss and recover from it.
    • Microway Working Note 3 13 January 2010 7:37 UTC www.microway.com [Source type: Reference]

    ^ For stream oriented transports the connection MAY be lost if the connection is not accepted before the server end of the connection request timeouts.
    • PushRegistry (MID Profile) 13 January 2010 7:37 UTC java.sun.com [Source type: Reference]

    .In TCP, there's either no missing data, or, in case of multiple timeouts, the connection is dropped.
  • Ordered – if two messages are sent over a connection in sequence, the first message will reach the receiving application first.^ ACK - acknowledgment of a data message received .
    • EIW Fall 2000 Lecture Notes - Internet Application Protocols 13 January 2010 7:37 UTC www.cs.rpi.edu [Source type: FILTERED WITH BAYES]

    ^ There is no privacy for the receiver, though.
    • Reliable Datagram Protocol 13 January 2010 7:37 UTC gms.freeshell.org [Source type: FILTERED WITH BAYES]

    ^ Messages passing in either direction go over the same TCP connection.
    • Reliable Datagram Protocol 13 January 2010 7:37 UTC gms.freeshell.org [Source type: FILTERED WITH BAYES]

    .When data segments arrive in the wrong order, TCP buffers the out-of-order data until all data can be properly re-ordered and delivered to the application.
  • Heavyweight – TCP requires three packets to set up a socket connection, before any user data can be sent.^ P Packet Data that is sent across a network.
    • http://www.dart.com/glossary.aspx 13 January 2010 7:37 UTC www.dart.com [Source type: Reference]

    ^ Data is transmitted in packets called TCP segments, which contain TCP headers and data.
    • General Computer Glossary-General Computer Terms-Best Computer Online Store Houston Buy Discount Prices Texas-Directron.com 13 January 2010 7:37 UTC www.directron.com [Source type: Reference]

    ^ A segment consists of a TCP header followed by application data.

    TCP handles reliability and congestion control.
  • Streaming – Data is read as a byte stream, no distinguishing indications are transmitted to signal message (segment) boundaries.
.UDP is a simpler message-based connectionless protocol.^ UDP is a connectionless transport protocol.
  • 2-3 Protocols and Standards | StudyNotes.net 13 January 2010 7:37 UTC studynotes.net [Source type: Reference]

^ UDP also differs from TCP in that it is a connectionless protocol.
  • PORT ACCESS USING USER DATAGRAM PROTOCOL PACKETS - Patent application 13 January 2010 7:37 UTC www.faqs.org [Source type: Reference]

^ The User Datagram Protocol (UDP) is based on a connectionless-oriented service .
  • Transmitting and Tracking Packets of Data Through the TCP and UDPNetwork Protocols - PCATTCPC User Manual 13 January 2010 7:37 UTC www.clarkson.edu [Source type: FILTERED WITH BAYES]

.Connectionless protocols do not set up a dedicated end-to-end connection.^ At that point, Mark's stack automatically picks up the connection and continues the protocol.

^ FIG. 4 is a flow chart of logic operations performed at a control point in a node in setting up a connection or in processing datagrams to be sent to a given partner.
  • Compensation for mismatched transport protocols in a data communications network - Patent 5224098 13 January 2010 7:37 UTC www.freepatentsonline.com [Source type: Reference]

^ The network layer IP protocol is a connectionless service while the transport layer provides reliable connection-oriented services, in some cases over highly unreliable networks.
  • Microway Working Note 3 13 January 2010 7:37 UTC www.microway.com [Source type: Reference]

.Communication is achieved by transmitting information in one direction from source to destination without verifying the readiness or state of the receiver.^ Upon receiving the datagram transmitted by the application hosted on the server 310, the communication server 340 can determine the associated addressing information, including the source port and the destination port.
  • PORT ACCESS USING USER DATAGRAM PROTOCOL PACKETS - Patent application 13 January 2010 7:37 UTC www.faqs.org [Source type: Reference]

^ This way, no one in the public Internet other than the source, the destination and the trusted intermediate nodes has access to TCP header or TCP data, and no one other than source and destination (not even the trusted intermediate node) has access to TCP data.
  • 9th USENIX Security Symposium Paper 13 January 2010 7:37 UTC www.usenix.org [Source type: Reference]

^ Data communications is all about transmitting information from one device to another.
  • Microway Working Note 3 13 January 2010 7:37 UTC www.microway.com [Source type: Reference]

.
  • Unreliable – When a message is sent, it cannot be known if it will reach its destination; it could get lost along the way.^ When a gateway cannot route a datagram (e.g., it doesn't have an appropriate route in its local table), it discards the message and returns an ICMP destination unreachable message to the sending host.
    • Internet Protocol 13 January 2010 7:37 UTC web.cs.wpi.edu [Source type: Reference]

    ^ This value is usually sent along with the message when it is transmitted.
    • DEFINITIONS AND TERMS 13 January 2010 7:37 UTC www.columbia.edu [Source type: Reference]

    ^ This message type is sent with the network portion of IP destination address set to a value of 0.
    • System Management Guide: Communications and Networks - TCP/IP Protocols 13 January 2010 7:37 UTC www.ncsa.illinois.edu [Source type: Reference]

    .There is no concept of acknowledgment, retransmission and timeout.
  • Not ordered – If two messages are sent to the same recipient, the order in which they arrive cannot be predicted.
  • Lightweight – There is no ordering of messages, no tracking connections, etc.^ No guarantee that the message will arrive at its destination.
    • |1| 13 January 2010 7:37 UTC www.unc.edu [Source type: Reference]

    ^ There are no retransmissions.
    • Internet Protocol | Chipkin Automation Systems - BACnet, Modbus 13 January 2010 7:37 UTC www.chipkin.com [Source type: Reference]
    • RFC791 - Internet Protocol_�й�Э�������� 13 January 2010 7:37 UTC www.cnpaf.net [Source type: Reference]

    ^ If it is available, it responds with a connection acknowledgment message.
    • Microway Working Note 3 13 January 2010 7:37 UTC www.microway.com [Source type: Reference]

    .It is a small transport layer designed on top of IP.
  • Datagrams – Packets are sent individually and are checked for integrity only if they arrive.^ SDP1 is designed for small numbers of small datagrams.
    • SDP - Secure Datagram Protocol #1 13 January 2010 7:37 UTC www.webfunds.org [Source type: Reference]

    ^ The IP address of who sent the packet.

    ^ This requires only delivery of individual packets.

    Packets have definite boundaries which are honored upon receipt, meaning a read operation at the receiver socket will yield an entire message as it was originally sent.

See also

References

  1. ^ RFC 768, User Datagram Protocol, J. Postel, The Internet Society (August 1980)
  2. ^ The impact of UDP on Data Applications

External links


Citable sentences

Up to date as of November 30, 2010

Here are sentences from other pages on User Datagram Protocol, which are similar to those in the above article.








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