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Objectives

Objectives. Understand time division multiplexing and statistical multiplexing Why is the delay*bandwidth product important? Basic Socket Programming Threads Intro to Lab 2. Mannet. What is bandwidth? How do you increase the bandwidth of a connection? How does latency effect Bandwidth?

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Objectives

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  1. Objectives • Understand time division multiplexing and statistical multiplexing • Why is the delay*bandwidth product important? • Basic Socket Programming • Threads • Intro to Lab 2

  2. Mannet • What is bandwidth? • How do you increase the bandwidth of a connection? • How does latency effect Bandwidth? • What is Time division Multiplexing? • What is Statistical Multiplexing?

  3. Cost-Effective Resource Sharing Must share (multiplex) network resources (nodes and links) among multiple users.

  4. Time Division Multiplexing . . .

  5. Statistical Multiplexing • Time-division, but on demand rather than fixed • Reschedule link on a per-packet basis • Packets from different sources interleaved on the link • Buffer packets that are contending for the link • Packet queue may be processed FIFO • Buffer overflow is called congestion . . .

  6. Addressing and Routing • address: byte-string that identifies a node; usually unique • routing: process of determining how to forward messages towards the destination node based on its address • types of addresses • unicast: node-specific • broadcast: all nodes on the network • multicast: some subset of nodes on the network

  7. Physical Layer Lab

  8. Socket Operations • Creating a socket • int socket(int domain, int type, int protocol) • domain=PF_INET, PF_UNIX • type=SOCK_STREAM, SOCK_DGRAM • Passive open on server • int bind(int socket, struct sockaddr *address, int addr_len) • int listen(int socket, int backlog) • int accept(int socket, struct sockaddr *address, int *addr_len) • Active open on client • int connect(int socket, struct sockaddr *address, int addr_len) • Sending and receiving messages • int write(int socket, char *message, • int msg_len, int flags) • int read(int socket, char *buffer, int buf_len, • int flags)

  9. Pthreads • int pthread_create(pthread_t *thread, pthread_attr_t * attr, void * (*start_routine)(void *), void * arg); • static void *readloop(void *arg) • pthread_t mythread; • pthread_create (&mythread, NULL, physical::readloop, (void *)this);

  10. Layering • Use abstractions to hide complexity • Abstraction naturally leads to layering • Can have alternative abstractions at each layer

  11. Protocols • Building blocks of a network architecture • Each protocol object has two different interfaces • service interface: defines operations on this protocol • peer-to-peer interface: defines messages exchanged with peer Host2 High Level Object Protocol Host1 High Level Object Protocol Service Interface Peer to peer

  12. Protocol Graph • collection of protocols and their dependencies • most peer-to-peer communication is indirect • peer-to-peer is direct only at hardware level Telnet FTP Video Telnet FTP Video RRP MSP RRP MSP HHP HHP

  13. Communication • Multiplexing and Demultiplexing (demux key) • Encapsulation (header/body) Application Application data data RRP RRP RRP data RRP data HHP HHP HHP RRP data

  14. Standard Architectures • Open Systems Interconnect (OSI) Architecture • International Standards Organization (ISO) • International Telecommunications Union (ITU); formerly CCITT • “X dot” series: X.25, X.400, X.500 • Reference Model

  15. Wired Washers Here’s one more reason for college students to quit lugging their laundry home on weekends. Two companies will roll out technology today that lets college students pay for their laundry using their cell phone or a debit card tied to their student ID. Even better, students can visit a Web site to find out when Internet-wired washers in their dorm’s laundry room are available, and receive a cell phone call or an e-mail when their loads are done. ‘‘Doing laundry is always one of those real nuisances for anybody,’’ said Dean Douglas, a vice president at IBM Corp., which teamed with USA Technologies Inc. on the new systems. Along with making dorm life easier, Douglas said jokingly, ‘‘this is going to help mother-child relations.’’

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