网络带宽报告

Design and Analysis of Computer Networks

COMP5/6320

Project#1

UDP transmission Performance Report

Liang Tang

Chih-Jye Wang(Jeff)

1.Background for UDP

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. UDP uses a simple transmission model without implicit handshaking dialogues for providing reliability,ordering,or data integrity.Thus,UDP provides an unreliable service and datagrams may arrive out of order, appear duplicated,or go missing without notice.Thus,UDP offers only a minimal transport service--non-guaranteed datagram delivery--and gives applications direct access to the datagram service of the IP layer. UDP is used by applications that do not require high reliability and keeping connection which are available in TCP.UDP is almost a null protocol;the only services it provides over IP are checksumming of data and multiplexing by port number.Therefore,an application program running over UDP must deal directly with end-to-end communication problems that a connection-oriented protocol would have handled,when these are required.UDP's stateless nature is also useful for servers answering small queries from huge numbers of clients.Unlike TCP,UDP supports packet broadcast(sending to all on local network)and multicasting(send to all subscribers).

2.Program Description

We implement a UDP program,but it could supply a reliable data transimission service between a UDP client and a UDP server.The UDP server starts,"./udpserv ".Then UDP client stars"./udpclient serverIP128".the client sends a data request containing IP address of server and data size in terms of MB,There are two types of packets:data_packet contains32KB of effective data and sequence number, control_packet which is ACK,NACK or data_request.The programs use sliding window,ACK,NACK and retransmission to insure reliable transmission.The default window size is50.As loss of packets is not usual,simulation of packet loss is enabled.The transmission IO throughput is calculated by packet_number/MAXDATA/time,with unit of e make to install and gcc all C files.

3.Experiment results

We test the Bandwidth for different request size(1MB,2MB,4MB,8MB,16MB, 32MB,64MB,128MB,256MB,512MB).It varied from the packet size.the packet size vary from1kb to32kb,and the throughput changes.we find that transmitting in 32kb per packet has the best performance.When it transmit8MB,it has the best speed:800Mb/s.

We use syslab39to be the server machine,while client end was installed in the syslab38to fulfill the process.And then the communication will begin,and the program use clock to document the time about transmission time.Finally,it calculated the throughput statistics.

Table1

Table1illustrated when UDP packet size is32KB.Since we set the constant window size is50.That means that when the sender send50packets,it will wait the ACK of them.And then,it will continue sending another50more packets.Thus,the most fascinating situation is that the packet is large,which will not waste the bandwidth much.To speed up the transmission efficiency,we neglect the whole process of data manipulating.The sender and receiver just operate ACK,NACK,and data.