Documents
Resources
Learning Center
Upload
Plans & pricing Sign in
Sign Out

CMPT 371 Chapter 1 - PowerPoint

VIEWS: 17 PAGES: 67

									       School of Computing Science
         Simon Fraser University




CMPT 371: Data Communications and
           Networking

 Instructor: Dr. Mohamed Hefeeda




                                     1-1
Course Objectives
 Understand principles of designing and
  operating computer networks,

 Understand the structure and protocols of
  the largest network of networks (Internet),

 Know how to implement network protocols
  and networked applications, and …

 Have fun!
                                                1-2
Course Info
 Textbook
      Kurose and Rose, Computer Networking: A top-
      down Approach Featuring the Internet, 3rd
      edition, 2005

 Course web page


  http://nsl.cs.surrey.sfu.ca/teaching/06/371/

  Or access it from my web page:
     www.cs.sfu.ca/~mhefeeda
                                                      1-3
Grading
 Homework:           30%
   Six assignments, each may have programming
    AND non-programming questions


 Midterm exam:         20%

 Final exam:           45%

 Class participation: 5%
    Asking and answering questions, few quizzes


                                                   1-4
Topics
 Introduction
   Overview; Network types; Protocol layering;
    History of the Internet; Signals and Physical
    media
 Network Applications
   Principles of network applications and protocols;
    Sample applications: HTTP, DNS; Socket
    programming
 Transport Layer
   Transport-layer services; Flow and congestion
    control; Internet transport protocols: UDP and
    TCP

                                                        1-5
Topics (cont’d)
 Network Layer
      Routing algorithms (e.g., OSPF, RIP, BGP);
       Forwarding and addressing in the Internet (IP);
       Router design
 Link Layer and Local Area Networks
    Contention resolution and multiple access
     protocols; Error detection and correction;
     Ethernet; Bridges and switches
 Wireless Networks (time permits)
      Characteristics of wireless channels; Wireless
       LANs; Cellular Networks
                                                         1-6
Chapter 1: Overview

 Goal: Get a “feel” of the computer
 networking area

 Approach: we use the Internet as
 example




                                       1-7
Chapter 1: roadmap
 1.1 What is the Internet?
 1.2 Network edge
 1.3 Network core
 1.4 Network access and physical media
 1.5 Internet structure and ISPs
 1.6 Delay & loss in packet-switched networks
 1.7 Protocol layers, service models



                                                1-8
What’s the Internet: “nuts and bolts” view
  millions of connected            router
                                               workstation
     computing devices: hosts
   = end systems                      server
                                                  mobile
  running network apps          local ISP
  communication links
        fiber, copper, radio,
         satellite                             regional ISP
        transmission rate =
         bandwidth
    routers: forward packets
     (chunks of data)
                                 company
                                 network

                                                              1-9
“Cool” Internet appliances

                                              Web-enabled toaster +
                                              weather forecaster

     IP picture frame
     http://www.ceiva.com/




World’s smallest web server
http://www-ccs.cs.umass.edu/~shri/iPic.html      Internet phones

                                                                      1-10
What’s the Internet: “nuts and bolts” view
   protocols control sending,             router     workstation
    receiving of msgs                        server
       e.g., TCP, IP, HTTP, FTP, PPP                    mobile
   Internet: “network of               local ISP
    networks”
       loosely hierarchical
       public Internet versus                        regional ISP
        private intranet
 Internet standards
    RFC: Request for comments
    IETF: Internet Engineering
     Task Force                         company
                                        network

                                                                     1-11
What’s the Internet: A service view
  communication
   infrastructure enables
   distributed applications:
       Web, email, games, e-
        commerce, file sharing
  communication services
   provided to apps:
       Connectionless unreliable
       connection-oriented
        reliable




                                      1-12
What’s a protocol?
human protocols:           network protocols:
 “what’s the time?”        machines rather than
 “I have a question”        humans
 introductions             all communication
                             activity in Internet
… specific msgs sent         governed by protocols
… specific actions taken   protocols define format,
  when msgs received,        order of msgs sent and
  or other events           received among network
                              entities, and actions
                                  taken on msg
                              transmission, receipt
                                                      1-13
What’s a protocol?
a human protocol and a computer network protocol:


       Hi
                               TCP connection
                               request
       Hi
                               TCP connection
     Got the                   response
      time?                    Get http://www.awl.com/kurose-ross
      2:00
                                     <file>
                     time


                                                                    1-14
Chapter 1: roadmap
 1.1 What is the Internet?
 1.2 Network edge
 1.3 Network core
 1.4 Network access and physical media
 1.5 Internet structure and ISPs
 1.6 Delay & loss in packet-switched networks
 1.7 Protocol layers, service models



                                                1-15
A closer look at network structure

 network edge:
  applications and
  hosts
 network core:
   routers
   network of
    networks
 access networks,
  physical media:
  communication links
                                     1-16
 The network edge
 End systems (hosts):
     run application programs
      (e.g., email) at “edge of network”
 Two models
   client/server model
       • client requests, receives service
         from server, e.g. web browser/server
     peer-to-peer model
       • minimal (or no) use of dedicated servers
       • e.g. Gnutella, KaZaA, …

 Two services from network
     Connection-oriented
     Connectionless
                                                    1-17
Network edge: Services from Network
Goal: Transfer data between end systems
 Connection-oriented          Connectionless
    Prepare for data             No connection set up,
     transfer ahead of time        simply send
    i.e., establish a            Faster, less overhead
     connection  set up          No reliability, flow
     “state” in the two            control, or congestion
     communicating hosts           control
    Usually comes with:
     reliability, flow and
                                    Internet: UDP—User
     congestion control
                                     Datagram Protocol
    Internet: TCP—
     Transmission Control
     Protocol


                                                            1-18
Internet Transport Services: TCP, UDP
  TCP [RFC 793]                       UDP [RFC 768]
      reliable, in-order                connectionless
       byte-stream
        • loss: acknowledgements         unreliable data
          and retransmissions             transfer
      flow control                      no flow control
        • sender won’t overwhelm
          receiver                       no congestion
      congestion control                 control
        • senders “slow down” when       App’s using UDP
          network congested
                                            • streaming media,
      App’s using TCP                        teleconferencing,
        • HTTP (Web), FTP (file               DNS, Internet
          transfer), Telnet (remote           telephony
          login), SMTP (email)

                                                                  1-19
Chapter 1: roadmap
 1.1 What is the Internet?
 1.2 Network edge
 1.3 Network core
 1.4 Network access and physical media
 1.5 Internet structure and ISPs
 1.6 Delay & loss in packet-switched networks
 1.7 Protocol layers, service models



                                                1-20
The Network Core
 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”

                              1-21
Network Core: Circuit Switching

End-end resources
  reserved for “call”
 link bandwidth, switch
  capacity
 dedicated resources: no
  sharing
 circuit-like (guaranteed)
  performance
 call setup required




                                  1-22
Network Core: Circuit Switching
 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



                                                     1-23
Circuit Switching: FDM and TDM
                         Example:
FDM
                         4 users

      frequency

                  time
TDM


      frequency

                  time
                                    1-24
Numerical example
 How long does it take to send a file of
  640,000 bits from host A to host B over a
  circuit-switched network?
   All links are 1.536 Mbps
   Each link uses TDM with 24 slots/sec
   500 msec to establish end-to-end circuit


Let’s work it out!

 NOTE: 1 Kb = 1000 bits, not 210 bits!

                                               1-25
Network Core: Packet Switching
each end-end data stream           resource contention:
  divided into packets              aggregate resource
 packets from different             demand can exceed
  users share network                amount available
  resources                         congestion: packets
 each packet uses full link         queue, wait for link use
  bandwidth                         store and forward:
 resources used as needed           packets move one hop
                                     at a time
                                         Node receives complete
Bandwidth division into “pieces”          packet before forwarding
     Dedicated allocation
    Resource reservation
                                                                 1-26
Packet Switching: Statistical Multiplexing
        10 Mb/s
A       Ethernet     statistical multiplexing   C

                          1.5 Mb/s
    B
          queue of packets
          waiting for output
                 link


                          D                     E

Sequence of A & B packets does not have fixed pattern,
  shared on demand  statistical multiplexing.
TDM: each host gets same slot in revolving TDM frame.
                                                    1-27
Packet switching versus circuit switching
Packet switching allows more users to use network!
 1 Mb/s link
 each user:
    100 kb/s when “active”
    active 10% of time

 circuit-switching:           N users
    10 users
                                                       1 Mbps link
 packet switching:
    with 35 users,
     probability > 10 active
     less than .0004
                                  Q: how did we get value 0.0004?

                                                                    1-28
Packet switching versus circuit switching

 Advantages
   no call setup  simpler
   resource sharing (statistical multiplexing) 
       • better resource utilization
       • more users or faster transfer (a single user can use
         entire bw)
       • Well suited for bursty traffic (typical)
 Disadvantages
     Congestion may occur 
       • packet delay and loss
       • need protocols to control congestion and ensure
         reliable data transfer

                                                                1-29
Packet-switched networks: forwarding
   Goal: move packets through routers from source to
    destination
       we’ll study several path selection (i.e. routing) algorithms
        (chapter 4)
 datagram network:
    destination address in packet determines next hop
    routes may change during session
    analogy: driving, asking directions

 virtual circuit network:
    each packet carries tag (virtual circuit ID), tag
     determines next hop
    fixed path determined at call setup time, remains fixed
     thru call
    routers maintain per-call state
                                                                       1-30
Network Taxonomy
                   Telecommunication
                       networks



     Circuit-switched                   Packet-switched
         networks                          networks



 FDM                                Networks         Datagram
                  TDM
                                    with VCs         Networks


 • Datagram network is neither connection-oriented
 nor connectionless.
 • Internet provides both connection-oriented (TCP) and
 connectionless services (UDP) to apps.
                                                            1-31
Chapter 1: roadmap
 1.1 What is the Internet?
 1.2 Network edge
 1.3 Network core
 1.4 Network access and physical media
 1.5 Internet structure and ISPs
 1.6 Delay & loss in packet-switched networks
 1.7 Protocol layers, service models



                                                1-32
Access networks and physical media
 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 or dedicated?



                                     1-33
Residential access: point to point access

 Dialup via modem
    up to 56Kbps direct access to
     router (often less)
    Can’t surf and phone at same
     time: can’t be “always on”

 ADSL: asymmetric digital subscriber line
    up to 1 Mbps upstream (today typically < 256 kbps)
    up to 8 Mbps downstream (today typically < 1 Mbps)
    FDM: 50 kHz - 1 MHz for downstream
          4 kHz - 50 kHz for upstream
          0 kHz - 4 kHz for ordinary telephone
                                                          1-34
Residential access: cable modems

  HFC: hybrid fiber coax
     asymmetric: up to 30Mbps downstream, 2 Mbps
      upstream
  network of cable and fiber attaches homes to ISP
   router
     homes share access to router
  deployment: available via cable TV companies




                                                      1-35
Residential access: cable modems




 Diagram: http://www.cabledatacomnews.com/cmic/diagram.html   1-36
Cable Network Architecture: Overview

           FDM:
                                                                       C
                                                                       O
                                      V    V   V   V   V   V           N
                                      I    I   I   I   I   I   D   D   T
                                      D    D   D   D   D   D   A   A   R
                                      E    E   E   E   E   E   T   T   O
                                      O    O   O   O   O   O   A   A   L

                                      1    2   3   4   5   6   7   8   9

                                               Channels




   cable headend

                                    home
              cable distribution
                  network
                                   Typically 500 to 5,000 homes
                                                                           1-37
Institutional access: local area
networks
 company/univ local area network
  (LAN) connects end system to
  edge router
 Ethernet:
    shared or dedicated link
     connects end system and
     router
    10 Mbs, 100Mbps, Gigabit
     Ethernet
 LANs: chapter 5




                                    1-38
Wireless access networks
 shared    wireless access network
  connects end system to router
      via base station aka “access point”   router
 wireless LANs:
    802.11b (WiFi): 11 Mbps                   base
 wider-area wireless access                 station
    provided by telco operator
    3G ~ 384 kbps
      • Will it happen??
    WAP/GPRS in Europe                                mobile
                                                        hosts


                                                           1-39
Home networks
Typical home network components:
 ADSL or cable modem
 router/firewall/NAT
 Ethernet
 wireless access point


                                                 wireless
   to/from                                       laptops
              cable   router/
    cable
             modem    firewall
   headend
                                      wireless
                                      access
                           Ethernet    point

                                                            1-40
Physical Media

 Bit: propagates between           Twisted Pair (TP)
  transmitter/rcvr pairs             two insulated copper
 physical link: what lies            wires
  between transmitter &                   Category 3: traditional
                                           phone wires, 10 Mbps
  receiver
                                           Ethernet
 guided media:                           Category 5:
      signals propagate in solid          100Mbps Ethernet
       media: copper, fiber, coax
 unguided media:
    signals propagate freely,
     e.g., radio


                                                                     1-41
Physical Media: coax, fiber
 Coaxial cable:                   Fiber optic cable:
  two concentric copper           glass fiber carrying light
   conductors                       pulses, each pulse a bit
  bidirectional                   high-speed operation:
                                         high-speed point-to-point
  baseband:
                                     
                                         transmission (e.g., 10’s-
       single channel on cable          100’s Gps)
        legacy Ethernet
                                   low error rate: repeaters
    

  broadband:                       spaced far apart; immune
     multiple channels on          to electromagnetic noise
      cable
     HFC




                                                                 1-42
Physical media: radio
  signal carried in             Radio link types:
   electromagnetic                terrestrial microwave
   spectrum                          e.g. up to 45 Mbps channels

  no physical “wire”             LAN (e.g., Wifi)
  bidirectional                     2Mbps, 11Mbps, 54 Mbps

  propagation &                  wide-area (e.g., cellular)
   environment effects:              e.g. 3G: hundreds of kbps

       reflection                satellite
       obstruction by objects       Kbps to 45Mbps channel (or
       Interference                  multiple smaller channels)
       fading                       270 msec end-end delay
                                     geosynchronous versus low
                                      altitude
                                                                  1-43
Chapter 1: roadmap
 1.1 What is the Internet?
 1.2 Network edge
 1.3 Network core
 1.4 Network access and physical media
 1.5 Internet structure and ISPs
 1.6 Delay & loss in packet-switched networks
 1.7 Protocol layers, service models



                                                1-44
 Internet structure: network of networks

 roughly hierarchical
 at center: “tier-1” ISPs (e.g., MCI, Sprint, AT&T, Cable
  and Wireless), national/international coverage
    treat each other as equals

                                              Tier-1 providers
                                              also interconnect
  Tier-1                                      at public network
  providers
                         Tier 1 ISP
                                      NAP     access points
  interconnect                                (NAPs)
  (peer)
  privately
                 Tier 1 ISP      Tier 1 ISP



                                                           1-45
Tier-1 ISP: e.g., Sprint
Sprint US backbone network
                                                                          DS3 (45 Mbps)
                                                                          OC3 (155 Mbps)
                                                                          OC12 (622 Mbps)
                                                                          OC48 (2.4 Gbps)
              Seattle
             Tacoma
                        POP: point-of-presence

                            to/from backbone
                                                                                     New York
   Stockton                         Cheyenne         Chicago
                                        peering                                     Pennsauken

  San Jose
                        …                …                                         Relay
                                                                                   Wash. DC
                                                         Roachdale
                                       Kansas City
                                         .
        Anaheim
                                      …
                        …

                               …




                                                               Atlanta
                           to/from customers
                                        Fort Worth


                                                                         Orlando
                                                                                                 1-46
   Internet structure: Tier-2 ISPs
  “Tier-2” ISPs: smaller (often regional) ISPs
     Connect to one or more tier-1 ISPs, possibly other tier-2 ISPs




                                                            Tier-2 ISPs
Tier-2 ISP pays         Tier-2 ISP                          also peer
                                          Tier-2 ISP        privately with
tier-1 ISP for
connectivity to                 Tier 1 ISP                  each other,
rest of Internet                                  NAP       interconnect
                                                            at NAP
Tier-2 ISP is
customer of           Tier 1 ISP        Tier 1 ISP      Tier-2 ISP
tier-1 provider
                   Tier-2 ISP        Tier-2 ISP


                                                                       1-47
   Internet structure: Tier-3 ISPs
  “Tier-3” ISPs and local ISPs
     last hop (“access”) network (closest to end systems)


                  local
                   ISP     Tier 3                   local
                                         local            local
                            ISP                      ISP
                                          ISP              ISP
Local and tier-            Tier-2 ISP            Tier-2 ISP
3 ISPs are
customers of                        Tier 1 ISP
higher tier                                           NAP
ISPs
connecting
them to rest
                          Tier 1 ISP             Tier 1 ISP       Tier-2 ISP
of Internet
                                                                        local
                    Tier-2 ISP           Tier-2 ISP
                                                                         ISP
              local         local          local
               ISP           ISP            ISP                                 1-48
 Internet structure: packet journey
 a packet passes through many networks!


           local
            ISP     Tier 3                    local
                                   local            local
                     ISP                       ISP
                                    ISP              ISP
                    Tier-2 ISP             Tier-2 ISP

                              Tier 1 ISP
                                                NAP


                   Tier 1 ISP              Tier 1 ISP       Tier-2 ISP
                                                                  local
              Tier-2 ISP           Tier-2 ISP
                                                                   ISP
        local         local          local
         ISP           ISP            ISP                                 1-49
A snapshot of the Internet in 1999 showing major ISPs




                                                        1-50
Chapter 1: roadmap
 1.1 What is the Internet?
 1.2 Network edge
 1.3 Network core
 1.4 Network access and physical media
 1.5 Internet structure and ISPs
 1.6 Delay & loss in packet-switched networks
 1.7 Protocol layers, service models



                                                1-51
 How do loss and delay occur?
packets queue in router buffers
 packet arrival rate to link exceeds output link capacity
 packets queue, wait for turn


                               packet being transmitted (delay)



  A


      B
                              packet queueing (delay)
                free (available) buffers: arriving packets
                dropped (loss) if no free buffers
                                                                  1-52
Four sources of packet delay
1. nodal processing:                2. queueing
     check bit errors                      time waiting at output
     determine output link                  link for transmission
                                            depends on congestion
                                             level of router



  A


      B
                  nodal
                processing    queueing


                                                                      1-53
Delay in packet-switched networks
3. Transmission delay:           4. Propagation delay:
 Time to “push” the entire       Time for last bit of packet to
   packet on link                   propagate from src to dst
 R=link bandwidth (bps)          d = length of physical link
 L=packet length (bits)          s = propagation speed in
 Transmission delay = L/R          medium (~2x108 m/sec)
                                  propagation delay = d/s

                                     Note: s and R are very
           transmission                different quantities!
A                           propagation


    B
              nodal
            processing    queueing
                                                                    1-54
 Transmission vs. propagation: Caravan analogy

                              100 km             100 km
      ten-car          toll              toll
      caravan         booth             booth
 car~bit; caravan ~ packet         Time to “push” entire
 Cars “propagate” at                caravan through toll
  100 km/hr                          booth onto highway =
 Toll booth takes 12 sec to
                                     12*10 = 120 sec
  service a car                     Time for last car to
  (transmission time)                propagate from 1st to
 Q: How long until caravan
                                     2nd toll both:
  is lined up before 2nd toll        100km/(100km/hr)= 1 hr
  booth?                            A: 62 minutes

                   See applet at textbook web site          1-55
Total nodal delay
           d nodal  d proc  d queue  d trans  d prop

 dproc = processing delay
    typically a few microsecs or less

 dqueue = queuing delay
    depends on congestion

 dtrans = transmission delay
    = L/R, significant for low-speed links

 dprop = propagation delay
    a few microsecs to hundreds of msecs



                                                           1-56
Queueing delay (revisited)

 R=link bandwidth (bps)
 L=packet length (bits)
 a=average packet
  arrival rate

 traffic intensity = La/R

 La/R ~ 0: average queueing delay small
 La/R -> 1: delays become large
 La/R > 1: more “work” arriving than can be
  serviced, average delay infinite!
                                               1-57
“Real” Internet delays and routes

 What do “real” Internet delay & loss look like?
 Traceroute program: provides delay
  measurement from source to router along end-end
  Internet path towards destination. For all i:
      sends three packets that will reach router i on path
       towards destination
      router i will return packets to sender
      sender times interval between transmission and reply.


       3 probes        3 probes

            3 probes


                                                               1-58
“Real” Internet delays and routes
traceroute: gaia.cs.umass.edu to www.eurecom.fr
                                    Three delay measurements from
                                    gaia.cs.umass.edu to cs-gw.cs.umass.edu
1 cs-gw (128.119.240.254) 1 ms 1 ms 2 ms
2 border1-rt-fa5-1-0.gw.umass.edu (128.119.3.145) 1 ms 1 ms 2 ms
3 cht-vbns.gw.umass.edu (128.119.3.130) 6 ms 5 ms 5 ms
4 jn1-at1-0-0-19.wor.vbns.net (204.147.132.129) 16 ms 11 ms 13 ms
5 jn1-so7-0-0-0.wae.vbns.net (204.147.136.136) 21 ms 18 ms 18 ms
6 abilene-vbns.abilene.ucaid.edu (198.32.11.9) 22 ms 18 ms 22 ms
7 nycm-wash.abilene.ucaid.edu (198.32.8.46) 22 ms 22 ms 22 ms trans-oceanic
                                                                   link
8 62.40.103.253 (62.40.103.253) 104 ms 109 ms 106 ms
9 de2-1.de1.de.geant.net (62.40.96.129) 109 ms 102 ms 104 ms
10 de.fr1.fr.geant.net (62.40.96.50) 113 ms 121 ms 114 ms
11 renater-gw.fr1.fr.geant.net (62.40.103.54) 112 ms 114 ms 112 ms
12 nio-n2.cssi.renater.fr (193.51.206.13) 111 ms 114 ms 116 ms
13 nice.cssi.renater.fr (195.220.98.102) 123 ms 125 ms 124 ms
14 r3t2-nice.cssi.renater.fr (195.220.98.110) 126 ms 126 ms 124 ms
15 eurecom-valbonne.r3t2.ft.net (193.48.50.54) 135 ms 128 ms 133 ms
16 194.214.211.25 (194.214.211.25) 126 ms 128 ms 126 ms
17 * * *
18 * * *              * means no response (probe lost, router not replying)
19 fantasia.eurecom.fr (193.55.113.142) 132 ms 128 ms 136 ms

                                                                       1-59
Packet loss
 queue (aka buffer) preceding link in buffer
  has finite capacity
 when packet arrives to full queue, packet is
  dropped (aka lost)
 lost packet may be retransmitted by
  previous node, by source end system, or
  not retransmitted at all




                                                 1-60
Chapter 1: roadmap
 1.1 What is the Internet?
 1.2 Network edge
 1.3 Network core
 1.4 Network access and physical media
 1.5 Internet structure and ISPs
 1.6 Delay & loss in packet-switched networks
 1.7 Protocol layers, service models



                                                1-61
Protocol “Layers”
Networks are complex!
 many “pieces”:
   hosts                      Question:
   routers               Is there any hope of
   links of various      organizing structure of
    media                        network?
   applications
   protocols           Or at least our discussion
   hardware,                   of networks?
    software


                                                     1-62
Layering of airline functionality

ticket (purchase)                                            ticket (complain)   ticket

baggage (check)                                              baggage (claim      baggage

  gates (load)                                                gates (unload)     gate

runway (takeoff)                                              runway (land)      takeoff/landing

airplane routing    airplane routing      airplane routing   airplane routing    airplane routing

   departure                intermediate air-traffic              arrival
    airport                     control centers                   airport



Layers: each layer implements a service
    via its own internal-layer actions
    relying on services provided by layer below



                                                                                             1-63
Why layering?
Dealing with complex systems:
 explicit structure allows identification,
  relationship of complex system’s pieces
 modularization eases maintenance, updating of
  system
    change of implementation of layer’s service
     transparent to rest of system
    e.g., change in gate procedure doesn’t affect
     rest of system
 What is the downside of layering?



                                                     1-64
Internet protocol stack
 application: supporting network
  applications                         application
      FTP, SMTP, HTTP
 transport: host-host data transfer   transport
    TCP, UDP

 network: routing of datagrams from    network
  source to destination
      IP, routing protocols              link
 link: data transfer between
  neighboring network elements          physical
      PPP, Ethernet
 physical: bits “on the wire”

                                                     1-65
      message         M
                           source
                          application
                                                   Encapsulation
    segment Ht        M   transport
 datagram Hn Ht       M    network
frame      Hl Hn Ht   M      link
                           physical
                                         Hl Hn Ht       M      link       Hl Hn Ht     M
                                                             physical

                                                                                   switch



                destination                Hn Ht    M       network        Hn Ht   M
           M     application            Hl Hn Ht    M         link      Hl Hn Ht   M
     Ht    M     transport                                  physical
   Hn Ht    M     network
Hl Hn Ht    M       link                                                           router
                  physical

                                                                                           1-66
Introduction: Summary
Covered a “ton” of material!    You now have:
 Internet overview              context, overview,
 what’s a protocol?              “feel” of networking
 network edge, core, access     more depth, detail to
  network                         follow!
    packet-switching versus
     circuit-switching
 Internet/ISP structure
 performance: loss, delay
 layering and service models
 History (self reading)

                                                     1-67

								
To top