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Introduction, Continued

Introduction, Continued. COS 461. Mechanics. Forgot to cite worm text – ZDNet Books (should be) on reserve in eng library Peterson/Davie text TCP/IP Illustrated (vol 1 & 2) New room Web page mostly up Notify me with errors/questions Reading assignments shown (2.1-2.5 for next time).

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Introduction, Continued

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  1. Introduction, Continued COS 461 CS 461

  2. Mechanics • Forgot to cite worm text – ZDNet • Books (should be) on reserve in eng library • Peterson/Davie text • TCP/IP Illustrated (vol 1 & 2) • New room • Web page mostly up • Notify me with errors/questions • Reading assignments shown (2.1-2.5 for next time) CS 461

  3. Computer Lab • Friend 010 (Fishbowl) • Machines will be reformatted • You’ll have “root” access – superuser • Currently, very few info e-mails • Send them now • This is how your accounts get established CS 461

  4. Grading • Grade breakdown • 65% projects • 35% exams (in-class midterm, final format?) • Audit • Audit credit = take exams, skip projects • Projects • First one solo, rest in pairs • Builds system progressively CS 461

  5. Layering • Use abstractions to hide complexity • Abstraction naturally lead to layering • Alternative abstractions at each layer Application programs Request/reply Message stream channel channel Host-to-host connectivity Hardware CS 461

  6. Protocols • Building blocks of a network architecture • Each protocol object has two different interfaces • service interface: operations on this protocol • peer-to-peer interface: messages exchanged with peer • Term “protocol” is overloaded • specification of peer-to-peer interface • module that implements this interface CS 461

  7. Interfaces Host1 Host2 Service High-level High-level interface object object Protocol Protocol Peer-to-peer interface CS 461

  8. Protocol Machinery • Protocol Graph • most peer-to-peer communication is indirect • peer-to-peer is direct only at hardware level Host 2 Host 1 Digital Digital Video Video File File library library application application application application application application RRP MSP RRP MSP HHP HHP CS 461

  9. Machinery (cont) • Multiplexing and Demultiplexing (demux key) • Encapsulation (header/body) Host 1 Host 2 Application Application program program Data Data RRP RRP RRP Data RRP Data HHP HHP HHP RRP Data CS 461

  10. FTP HTTP NV TFTP UDP TCP IP … NET NET NET 2 1 n Internet Architecture • Defined by Internet Engineering Task Force (IETF) • Hourglass Design • Application vs Application Protocol (FTP, HTTP) CS 461

  11. ISO Architecture End host End host Application Application Presentation Presentation Session Session Transport Transport Network Network Network Network Data link Data link Data link Data link Physical Physical Physical Physical One or more nodes within the network CS 461

  12. Performance Metrics • Bandwidth (throughput) • data transmitted per time unit • link versus end-to-end • notation • KB = 210 bytes • Mbps = 106 bits per second • Latency (delay) • time to send message from point A to point B • one-way versus round-trip time (RTT) • components Latency = Propagation + Transmit + Queue Propagation = Distance / c Transmit = Size / Bandwidth CS 461

  13. Bandwidth versus Latency • Relative importance • 1-byte: 1ms vs 100ms dominates 1Mbps vs 100Mbps • 25MB: 1Mbps vs 100Mbps dominates 1ms vs 100ms • Infinite bandwidth • RTT dominates • Throughput = TransferSize / TransferTime • TransferTime = RTT + 1/Bandwidth x TransferSize • 1-MB file to 1-Gbps link as 1-KB packet to 1-Mbps link CS 461

  14. Delay x Bandwidth Product • Amount of data “in flight” or “in the pipe” • Usually relative to RTT • Example: 100ms x 45Mbps = 560KB CS 461

  15. Socket API • Creating a socket int socket(int domain, int type, int protocol) • domain =PF_INET, PF_UNIX • type = SOCK_STREAM, SOCK_DGRAM, SOCK_RAW • Passive Open (on server) int bind(int socket, struct sockaddr *addr, int addr_len) int listen(int socket, int backlog) int accept(int socket, struct sockaddr *addr, int addr_len) CS 461

  16. Sockets (cont) • Active Open (on client) int connect(int socket, struct sockaddr *addr, int addr_len) • Sending/Receiving Messages int send(int socket, char *msg, int mlen, int flags) int recv(int socket, char *buf, int blen, int flags) CS 461

  17. Protocol-to-Protocol Interface • Configure multiple layers • static versus extensible • Process Model • avoid context switches • Buffer Model • avoid data copies CS 461

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