Internet Protocol (IP) Internet Protocol (IP) TCP versus UDP TCP - PDF document

Special Course on Networked Virtual January 30, 2004 Environments Internet Protocol (IP) Internet Protocol (IP) TCP versus UDP TCP versus UDP � Low Low- -level protocols used by hosts and routers level protocols used by hosts and routers � Transmission Control Protocol Transmission Control Protocol User User Datagram Datagram Protocol Protocol (TCP/IP) (UDP/IP) � Guides the packets from source to destination host Guides the packets from source to destination host (TCP/IP) (UDP/IP) � � Point Point- -to to- -point connection point connection � Lightweight data transmission Lightweight data transmission � � � Hides the transmission path Hides the transmission path � � Reliable transmission using Reliable transmission using � Differs from TCP Differs from TCP � � � phone lines, LANs, WANs, wireless radios, satellite links, carri phone lines, LANs, WANs, wireless radios, satellite links, carrier er � acknowledgement and acknowledgement and � connectionless transmission connectionless transmission � pigeons,… pigeons,… retransmission retransmission � ‘best ‘best- -efforts’ efforts’ delivery delivery � � Applications rarely use the IP directly but the protocols that a Applications rarely use the IP directly but the protocols that are re � � Stream Stream- -based data semantics based data semantics � packet packet- -based data semantics based data semantics � � written on top of IP written on top of IP � Big Big overhead overhead � Packets are easy to process Packets are easy to process � � � Transmission Control Protocol (TCP/IP) Transmission Control Protocol (TCP/IP) � � data checksums data checksums � Transmission and receiving Transmission and receiving � � � User Datagram Protocol (UDP/IP) User Datagram Protocol (UDP/IP) � � Hard to Hard to ‘skip ‘skip ahead’ ahead’ immediate immediate � � No connection information for No connection information for � each host in the operating system each host in the operating system � Packet loss can be Packet loss can be handled handled � UDP and Datagrams in Java UDP and Datagrams in Java Datagram Example Datagram Example Socket can both send and receive packets can both send and receive packets � Dat agr am � Dat agr am Socket t r y t r y t r y t r y { { � no server sockets because there is no need to establish a connec no server sockets because there is no need to establish a connection tion � socket = new new Dat agr am new Dat agr am Socket ( PO ( PO RT) ; socket = new Socket RT) ; Packet includes all the data to be sent/received includes all the data to be sent/received � Dat agr am � Dat agr am Packet socket . r ecei ve( dp1) ; socket . r ecei ve( dp1) ; � maximum size 64 kB maximum size 64 kB � � Constructing a receiving packet: Constructing a receiving packet: socket . send( dp2) ; socket . send( dp2) ; � byt e byt e byt e byt e[ ] buf f er = [ ] buf f er = ne ne new byt e new byt e[ CAPACI TY] ; byt e byt e [ CAPACI TY] ; } cat ch cat ch ( cat ch ( Socket Except i on Socket Except i on e) { e) { } cat ch Dat agr am Packet dp1 = Dat agr am Packet dp1 = / / Coul d not open t he socket . / / Coul d not open t he socket . new new new Dat agr am new Dat agr am Packet Packet ( buf f er , CAPACI TY) ; ( buf f er , CAPACI TY) ; � Constructing a packet to send: Constructing a packet to send: � } cat ch } cat ch cat ch cat ch ( ( I O I O Except i on Except i on e) { e) { byt e byt e byt e byt e[ ] m [ ] m essage; essage; / / The byt es t o send. / / The byt es t o send. / / Pr obl em / / Pr obl em s wi t h com s wi t h com m m uni cat i on. uni cat i on. Dat agr am Packet dp2 = Dat agr am Packet dp2 = } f i nal f i nal f i nal l y l y { { new new new new Dat agr am Dat agr am Packet Packet ( m ( m essage, m essage, m essage. l engt h, essage. l engt h, } f i nal l y l y addr ess, por t ) ; addr ess, por t ) ; socket . cl ose( ) ; socket . cl ose( ) ; } } Datagram Contents IP Broadcasting Datagram Contents IP Broadcasting � Using a single UDP/IP socket, the Using a single UDP/IP socket, the � With UDP/IP, the data is only With UDP/IP, the data is only � Sender’s address: Sender’s address: � � � same packet can be sent to same packet can be sent to delivered to the applications delivered to the applications that that I net Addr ess addr = dp. get Addr ess( ) ; I net Addr ess addr = dp. get Addr ess( ) ; multiple destinations by repeating multiple destinations by repeating are receiving on a designated port are receiving on a designated port the send call call � Sender’s port: Sender’s port: the send � Broadcast Broadcast is expensive is expensive � � � ‘unicasting’ ‘unicasting’ � � each host has to receive and each host has to receive and � i nt i nt i nt i nt por t = dp. get Por t ( ) ; por t = dp. get Por t ( ) ; � great bandwidth is required great bandwidth is required process every broadcast packet process every broadcast packet � � Packet payload size: Packet payload size: � each host has to maintain a list of each host has to maintain a list of � Only recommended (and only Only recommended (and only � � � other hosts other hosts guaranteed) on the local LAN guaranteed) on the local LAN i nt i nt i nt i nt si ze si ze = dp. get Lengt h( ) ; = dp. get Lengt h( ) ; � Not suitable for Internet Not suitable for Internet- -based based � � Packet payload data: Packet payload data: � � IP broadcasting allows a single IP broadcasting allows a single applications applications � transmission to be delivered to all transmission to be delivered to all byt e byt e[ ] [ ] dat a dat a = = dp. get Dat a( ) ; dp. get Dat a( ) ; byt e byt e hosts on the network hosts on the network � a a special bit mask of receiving special bit mask of receiving � hosts is used as a address hosts is used as a address Jouni Smed 1