1 / 33

Network Core and Network Edge

Network Core and Network Edge. By Muhammad Hanif To BS IT 4 th Semester. Now back to work ☺. Ninety-nine percent of the failures come from people who have the habit of making excuses. George Washington. Network Core and Edge. Network Devices and Components Internet overview

pekelo
Télécharger la présentation

Network Core and Network Edge

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Network Core and Network Edge By Muhammad Hanif To BS IT 4th Semester

  2. Now back to work ☺ • Ninety-nine percent of the failures come from people who have the habit of making excuses. • George Washington

  3. Network Core and Edge • Network Devices and Components • Internet overview • what’s a protocol? • network edge, core, access network • performance: loss, delay • layering and service models • backbones, NAPs, ISPs

  4. A Simple Network

  5. Network Devices and Components • Four major components • End Points • PCs, Servers, Printers, Smart Phones, etc • Interconnections • NIC cards, Media, Connectors • Switches • Connects endpoints to the Local Area Network (LAN) • Router • Connect multiple LANs to form Internetworks • Chooses best path between LAN and Wider Area Networks (WAN)

  6. millions of connected computing devices: hosts, end-systems pc’s workstations, servers PDA’s, phones, running network apps communication links fiber, copper, radio, satellite routers: forward packets (chunks) of data thru network router workstation server mobile local ISP regional ISP company network What’s the Internet: “nuts and bolts” view

  7. protocols: control sending, receiving of msgs e.g., TCP, IP, HTTP, FTP, PPP Internet: “network of networks” loosely hierarchical public Internet versus private intranet Internet standards RFC: Request for comments IETF: Internet Engineering Task Force What’s the Internet: “nuts and bolts” view router workstation server mobile local ISP regional ISP company network

  8. communication infrastructure enables distributed applications: WWW, email, games, e-commerce, database, more? communication services provided: connectionless connection-oriented What’s the Internet: a service view

  9. … specific msgs sent … specific actions taken when msgs received, or other events all communication activity in Internet governed by protocols protocols define format, order of msgs sent and received among network entities, and actions taken on msg transmission, receipt What’s a network protocol?

  10. a human protocol and a computer network protocol: TCP connection reply. Get http://gaia.cs.umass.edu/index.htm Got the time? 2:00 <file> time What’s a protocol? Hi TCP connection req. Hi

  11. network edge: applications and hosts network core: routers network of networks access networks residential institutional mobile physical media wire (digital / analog) wireless (radio / cellular) A closer look at network structure:

  12. end systems (hosts): run application programs e.g., WWW, email at “edge of network” client/server model client host requests, receives service from server e.g., WWW client (browser)/ server; email client/server peer-peer model: host interaction symmetric e.g.: teleconferencing The network edge:

  13. Goal: data transfer between end sys. handshaking: setup (prepare for) data transfer ahead of time set up “state” in two communicating hosts TCP - Transmission Control Protocol Internet’s de-facto connection-oriented service TCP service[RFC 793] reliable, in-order byte-stream data transfer dealing with loss: acknowledgements and retransmissions flow control: sender won’t overcome receiver congestion control: senders “slow down sending rate” when network congestion detected Network edge: connection-oriented service

  14. Goal: data transfer between end systems same as before! UDP - User Datagram Protocol [RFC 768]: Internet’s connectionless service unreliable data transfer no flow control no congestion control App’s using TCP: HTTP (WWW), FTP (file transfer), Telnet (remote login), SMTP (email) App’s using UDP: streaming media, teleconferencing, Internet telephony Network edge: connectionless service

  15. mesh of interconnected routers the fundamental question: how is data transferred through net? circuit switching: dedicated circuit per call: telephone net packet-switching: data sent thru net in discrete “chunks” The Network Core

  16. End-end resources reserved for “call” link bandwidth, switch capacity dedicated resources: no sharing circuit-like (guaranteed) performance call setup required Network Core: Circuit Switching

  17. network resources (e.g., bandwidth) divided into “pieces” pieces allocated to calls resource piece idle if not used by owning call (no sharing) dividing link bandwidth into “pieces” frequency division time division code division Network Core: Circuit Switching

  18. each end-end data stream divided into packets user A, B packets share network resources each packet uses full link bandwidth resources used as needed, Bandwidth division into “pieces” Dedicated allocation Resource reservation Network Core: Packet Switching resource contention: • aggregate resource demand can exceed amount available • congestion: packets queue, wait for link use • store and forward: packets move one hop at a time • transmit over link • wait turn at next link

  19. D E Network Core: Packet Switching 10 Mbs Ethernet C A statistical multiplexing 1.5 Mbs B queue of packets waiting for output link 45 Mbs

  20. Goal: move packets among routers from source to destination we’ll study several path selection algorithms datagram network: destination address determines next hop routes may change during session Packet-switched networks: routing

  21. Q: How to connect end systems to edge router? residential access nets institutional access networks (school, company) mobile access networks Keep in mind: bandwidth (bits per second) of access network? shared (e.g. cable, ethernet) or dedicated (e.g., DSL)? Access networks and physical media

  22. Dialup via modem up to 56Kbps direct access to router (conceptually) DSL: digital subscriber line up to 1 Mbps home-to-router up to 8 Mbps router-to-home Residential access: point to point access

  23. company/univ local area network (LAN) connects end system to edge router Ethernet: shared or dedicated cable connects end system and router 10 Mbs, 100Mbps, Gigabit Ethernet Institutional access: local area networks

  24. shared wireless access network connects end system to router wireless LANs: radio spectrum replaces wire e.g., Wavelan 10 Mbps wider-area wireless access wireless access to ISP router via cellular network router base station mobile hosts Wireless access networks

  25. packets experience delay on end-to-end path four sources of delay at each hop nodal processing: check bit errors determine output link queueing time waiting at output link for transmission depends on congestion level of router transmission A propagation B nodal processing queueing Delay in packet-switched networks

  26. Transmission delay: R=link bandwidth (bps) L=packet length (bits) time to send bits into link = L/R Propagation delay: d = length of physical link s = propagation speed in medium (~2x108 m/sec) propagation delay = d/s transmission A propagation B nodal processing queueing Delay in packet-switched networks Note: s and R are very different quantitites!

  27. Networks are complex! many “pieces”: hosts routers links of various media applications protocols hardware, software Question: Is there any hope of organizing structure of network? Or at least our discussion of networks? Protocol “Layers”

  28. Why layering? Dealing with complex systems: • explicit structure allows identification, relationship of complex system’s pieces • layered reference model for discussion • layering considered harmful?

  29. application: supporting network applications ftp, smtp, http transport: host-host data transfer tcp, udp (reliable delivery, rate regulation) network: routing of datagrams from source to destination ip, routing protocols link: data transfer between neighboring network elements ppp, ethernet, wireless, multiple access protocols physical: bits “on the wire” application transport network link physical Internet protocol stack

  30. M M H H H H H H H H H H H H t t t t l n l t n n t n M M M M application transport network link physical application transport network link physical M M Protocol layering and data Each layer takes data from above • adds header information to create new data unit • passes new data unit to layer below source destination message segment datagram frame

  31. roughly hierarchical national/international backbone providers (NBPs) interconnect (peer) with each other privately, or at public Network Access Point (NAPs) regional ISPs connect into NBPs local ISP, company connect into regional ISPs local ISP local ISP NAP NAP Internet structure: network of networks regional ISP NBP B NBP A regional ISP

  32. Covered a “ton” of material! Internet overview what’s a protocol? network edge, core, access network performance: loss, delay layering and service models backbones, NAPs, ISPs You now hopefully have: context, overview, “feel” of networking more depth, detail later in course Intro: Summary

More Related