networks by wuyunqing



   Overview ( Lei You )
   Overview of Local Network Topology
    ( Ryan McKenzie )
   Internetworking Protocol ( Benjamin A
    Pullen )
   Mobile IP ( Hui Tan )
         What is a Network?
   Two or more computers are connected together
    by a medium and are sharing resources. These
    resources can be files, printers, hard-drives, or
    CPU number-crunching power.
   A network can consist of two computers
    connected together on a desk, or it can consist
    of many Local Area Networks (LANs) connected
    together to form a Wide Area Network (WAN)
    across a continent.
                 The Big Picture
   Many individuals have asked to see the
    "Big Picture" of networking: How does
    everything . Where does Microsoft NT fit
    in with routers and the OSI layers? What
    about UNIX, Linux and Novell?

   The big picture in the following slide
    attempts to show all areas of networking
    and how they tie into each other.
Graphical Symbols Used in the Big

    Circles - Network Operating Systems
    Squares - Communication & cabling protocols (OSI
     Transport to Physical Layer)
    Storm Clouds - Telecommunications media or
     Information Providers that connect to the Internet
    Machine symbol - Network "linker" can be a bridge,
     router, brouter or gateway
    Jagged haphazard dotted line - the Internet
Telecommunications Components of
The Big Picture

   ISDN - Integrated Services Digital Network
   Private Branch Exchanges - PBXs, Key Systems
   Telcos - AT&T, Bell Telephone, Sprint, Telus
   DataPac & DataRoute - Packet switching and analog
    switching WAN protocols
   Cell Relay - Digital packet switching WAN protocol
   Frame Relay - Digital packet switching WAN protocol
   X.25 - Analog packet switching WAN protocol
   ATM - Asynchronous Transfer Mode WAN protocol
   World Wide Web - Hypertext-based multimedia system
   ADSL - Asymmetrical Digital Subscriber Line
              ISO/OSI Model
   The International Standards Organization (ISO) Open
    Systems Interconnect (OSI) is a standard set of rules
    describing the transfer of data between each layer in a
    network operating system. Each layer has a specific
    function. For example, the physical layer deals with the
    electrical and cable specifications.

   The OSI Model clearly defines the interfaces between
    each layer. This allows different network operating
    systems and protocols to work together by having each
    manufacturer adhere to the standard interfaces. The
    application of the ISO OSI model has allowed the
    modern multi-protocol networks that exist today.
Seven Layers in the OSI Model
   7.   Application Layer (Top Layer)
   6.   Presentation Layer
   5.   Session Layer
   4.   Transport Layer
   3.   Network Layer
   2.   Data Link Layer
   1.   Physical Layer (Bottom Layer)
      ISO/OSI Model …
The OSI model provides the basic rules
that allow multi protocol networks to
operate. Understanding the OSI model
is instrumental in understanding how
the many different protocols fit into the
networking jigsaw puzzle.
The Big Picture can be broken up according to its
protocols into the following four areas:

                  Local Loops
                  LANs
                  MANs
                  WANs
        The Local Loop
The Local Loop is often called "the last
mile", and it refers to the last mile of
analog phone line that goes from the
telephone company's central office (CO)
to your house.
The Local Loop …
       Typical Local Loop Protocols
   Voice Lines
   Modem Connections – 56 kbps
   ISDN (Integrated Services Digital Network)
    - 2 x 64 kbps digital lines
   ADSL (Asymmetrical Digital Subscriber
    Line) - up to 8 Mbps
   * Cable Modems - up to 30 Mbps
Cable modems are not part of the local
loop but do fall into the category of the last
mile, or how high speed digital
communication gets to the premises
(home). It would incredibly expensive to
replace the existing cabling structure. And
because this cabling was designed for voice
communications rather than digital, all of
these protocols are needed to overcome
the existing cabling limitations in the local
loop and provide high speed digital data
Local Area Networks
 A Local Area Network is a system of
 computers that share resources such as disk
 drives, printers, data, CPU power,
 fax/modem, applications, etc. They usually
 have distributed processing, which means
 that there are many desktop computers
 distributed around the network and that there
 is no central processor machine (mainframe).
Local Area Networks (LANS) …
Components Used by LANs
    Cabling standards

    Hardware

    Protocols
    LANS: Cabling Standards
   Cat 3, 4 and 5 cables
   IBM Type 1-9 cabling standards
   EIA568A and 568B
   Ethernet cabling standards: IEEE 802.3
    (10Base5), IEEE 802.3a (10Base2), IEEE 802.3i
   Unshielded Twisted Pair (UTP)
   Shielded Twisted Pair (STP)
   Connectors: RJ45, RJ11, Hermaphroditic
    connectors, RS-232, DB-25, BNC, TEE
        LANS: Hardware Devices
   Network Interface Cards (NICs)
   Repeaters
   Ethernet Hubs or multi port repeaters
   Token Ring Multi Station Access Units
    (MSAUs), Control Access Units (CAUs) and
    Lobe Access Modules (LAMs)
   Bridges
LANS: Hardware Devices …
   Brouters
   Routers
   Gateways
   Print servers
   File servers
   Switches
    LANS: Examples of Protocols
   Ethernet frame types: Ethernet_II,
    Ethernet_SNAP, Ethernet_802.2,
   Media Access Control layer (MAC layer)
   Token Ring: IBM and IEEE 802.5
   Logical Link Control Layer (LLC) IEEE 802.2
   TCP/IP
   Asynchronous Transfer Mode (ATM)
 Metropolitan Area Networks
A Metropolitan Area Network is a system of LANs
connected throughout a city or metropolitan
area. MANs have the requirement of using
telecommunication media such as voice channels
or data channels. Branch offices are connected
to head offices through MANs. Examples of
organizations that use MANs are universities and
colleges, grocery chains, and banks.
Metropolitan Area Networks
 Metropolitan Area Networks

The main criterion for a MAN is that the
connection between LANs is through a local
exchange carrier (the local phone company).
The protocols that are used for MANs are quite
different from those used for LANs (except for
ATM, which can be used for both under certain
          Examples of MAN Protocols
   RS-232, V-35
   X.25 (56kbps), PADs
   Frame Relay (up to 45 Mbps), FRADs
   Asynchronous Transfer Mode (ATM)
   ISDN (Integrated Services Digital Network) PRI and BRI
   Dedicated T-1 lines (1.544 Mbps) and Fractional T-1
   T-3 (45 Mbps) and OC-3 lines (155 Mbps)
   ADSL (Asymmetrical Digital Subscriber Line) - up to 8
   XDSL (many different types of Digital Subscriber Lines)
        Wide Area Networks

WANs connect LANs together between cities
    Wide Area Networks
         (WANS) …

The main difference between a MAN
and a WAN is that the WAN uses Long
Distance Carriers. Otherwise the same
protocols and equipment are used as a

1. Introduction to Networking and Data Communications
   Eugene Blanchard
   Edited by Joshua Drake, Bill Randolph and Phuong Ma
2. Computer Networking: A Top-Down Approach Featuring the
  Jim Kurose & Keith Ross
3. Internetworking Technology Overview
   Cisco Systems
4. Internetworking Case Studies
   Cisco Systems
Network Topology

  Overview of Network Topology
 Case Study of Flat Neighborhoods
Goals in Topology Design
   Reliable and Robust
   Fast and Efficient
   Simple and Scalable

Examples of well known designs follow this
  slide, we shall assume all topologies are using
  100 Mbit Ethernet as the medium and rate
  them on design categories.
Bus Topology
                  Robustness

                  Efficiency

                  Simplicity

                  Scalability
Bus Topology
                  Robustness
                  Efficiency
                  Simplicity
                  Scalability
Ring Topology
                   Robustness

                   Efficiency

                   Simplicity

                   Scalability
Ring Topology
                   Robustness
                   Efficiency
                   Simplicity
                        Very Good
                   Scalability
Star Topology
                   Robustness

                   Efficiency

                   Simplicity

                   Scalability
Star Topology
                   Robustness
                        Very Good
                   Efficiency
                        Very Good
                   Simplicity
                   Scalability
A New Topology is Born

In the past, it has been standard to come
  up with a topology first, and then adapt
  it to certain tasks. Modern design
  philosophy has changed this practice.
  Now a subset of problems or needs
  gives rise to special task network
  designs. One such design has been
  conceived right here at UK.
The Flat Neighborhood Network
   Brought about by the need to build a
    large cluster supercomputer from
    common networking components.
   Driven to evolve from the need for
    (more) efficient communication
    between cluster nodes.
The Basics of FNN‟s
               This example shows how
                 one could construct a
                 FNN for 6 PCs using just
                 two NICs/PC and three
                 4-port switches. Note
                 that every PC has at
                 least one single-switch
                 latency path to every
                 other PC; some PC pairs
                 have more than one
                 such path.
   Some NEW Design Problems
Multiple small, interleaved subnets link each
machine by a number of one-switch latency paths.
Any machine can belong to as many subnets as it
has network cards onboard. Sounds simple, but
several problems arise from the design.

      Design of Subnets      Wiring Scheme
      Routing and            Efficient use of
       Addressing              Bandwidth
The Solutions:
Subnets and Wiring
      The wiring scheme and subnets can now be
       designed by a piece of software developed in
       the KAOS lab. This problem appears to be NP
       Complete (Very Bad) and must be solved
       using a genetic search algorithm. A simplified
       version allows you to design your own FNN
       on the web.
The Solutions:
Genetic Search Algorithm
      Generate 256 random networks.
      Evaluate and rate each based on…
          Latency, Bandwidth Balance, Comm. Patterns
      Throw out bottom 2/3 results and
       replace with mutations thereof.
      Merge Subnets of pairs in top 1/3
      Re-Evaluate and rate accordingly
The Solutions:
Basic Routing

      Each machine in the cluster swaps
       unique identifiers with all of its
       neighbors at boot up. Address
       resolution is done locally using the table
       that this swap generates.
      Non-Dynamic Solution
The Implementation: KLAT2
   Assembled on April 11, 2000 in the KAOS lab by Dr. Dietz and
    Mr. Mattox
   Fully Functional on April 16
   The first working implementation of an FNN
The Main Event:
KLAT2 vs. Superdome
KLAT2 vs. Superdome
Round 1: Cost
          KLAT2
              Total Value: $41,205
              Peak Performance:
               64 GFlops
              $643.83 / GF
          Superdome
              Total Value: $1.5M / yr
              Peak Performance:
               672 GFlops
              $2,232.14 / GF / yr
          Advantage
              KLAT2
KLAT2 vs. Superdome
Round 2: Upgrading
          KLAT2
              Purchase new Nodes
              Upgrade the Old Nodes
              Recompute Scheme
              Rewire EVERYTHING
          Superdome
              Purchase a new Cabinet
              Plug and Play
          Advantage
              Superdome
The Lowdown
   FNN‟s provide wonderful cost efficiency,
    but are plagued by limitations.
       Number if NIC‟s in each node
       PCI Bus Speed
       Increased Physical Distance
       Complexity of Design
Use of KLAT2
   KLAT2 is mainly a lab experiment, thus its
    practical uses are limited :
       Insufficient Non-Volatile Storage
       Weak Back-Up System
       Slow Internet Connection to the WAN
       Limited Application Compatability
   With further R+D, the FNN cluster may
    evetually bring about a “supercomputer in
    every home” movement.
   Topology Development Philosophy has
   Special Purpose Topologies use
    Networks to Solve Specific Problems
   Network Topologies are Always
       More Topologies Being Concieved
       Faster, More Advanced Media
The Credits
   Dr. Hank Dietz, (859) 257-4701
   Mr. Tim Mattox at the KAOS Lab, (859) 257-9695
   KAOS Lab Documentation and Publications on FNN‟s
   Dr. Craig Douglas, (859) 257-2326
   Mr. John Connolly at the UK Center for Computational Sciences
   UK SDX Home Page
Internetworking Protocol
Version 4

   Why?
   What?
   How?
Why IP?
   Why do we build networks?
   Why do we need inter-networks?
What is IP?
   Protocol suit defining an interface
    between lower level hardware
    functionality and higher level application
    oriented protocols.
   Provides a “least common denominator”
    for all network hardware.
   Provides best effort service for
    datagram delivery from host to host.
Version(4 bits) – 4
Header Length(4 bits) – Size of the
  header in 4 byte words.
Type of Service(8 bits) – Mostly unused.
Length(16 bits) – Total length of IP
  datagram in bytes.
Fields continued
   Identification(16 bits) – „unique‟
   Flags(3 bits) – 0, Don‟t fragment, More
   Fragment Offset(13 bits) – Offset of
    fragment in 8 byte words.
Fields continued, again
   Time To Live (8 bits) – Hop count.
   Protocol(8 bits) – Higher level protocol
   Header Checksum – One‟s compliment
    sum of all 16 bit words in IP header.
Fields, more?
   Source Address(32 bits) – Where it
    came from.
   Destination Address(32 bits) – Ummm,
    you know.
Fields, will it ever end!?
   Options – options.
   Padding – even out to 32 bit words.
   IP only requires ~500 byte MTU from
    hardware layer but allows for packet
    sizes up to 65535 bytes.
   IP datagrams can be fragmented into
    smaller packets to travel over various
    networks then reassembled at the
   Fragments from the same datagram
    carry the same identifier field.
   All fragments except the last have the
    More Fragments bit set.
   The Offset Field is an index into the
    original datagram payload.
IP Addressing
   Hierarchical (cuz that‟s what CS people do)
   32 Bits long.
   Globally unique (most of the time.)
   Assigned to network adapter, not host.
   Composed of network part and host part.
   Hosts on the same physical network have the
    same network address.
IP Addressing
   Class A - [0][7 Bit Network][24 Bit
   Class B - [10][14 Bit Network][16 Bit
   Class C - [110][21 Bit Network][8 Bit
IP Addressing
   Classless IP addressing (the way it
    really is.)
   Arbitrarily long network portion followed
    by host portion.
   Can not tell dividing line from IP
   A netmask is used to divide the
IP Forwarding
   Each host has a table with tuples of network
    addresses, address length, next hop
    information, and interface information.
   To forward an IP packet, find the longest
    network address that matches destination
   Send the packet out the corresponding
    interface to the next hop (may be local.)
     IP Forwarding
Interface0 =
Interface1 =

Address/Length       Next Hop        Interface     Local           Interface0   Interface0      Local           Interface1      Interface1
What‟s Next?
   IPv6
   128 bit addressing (more people can
    play quake.)
   Fewer fields for simplicity
   Mobility in the Internet
   Basic Mobile IP Protocol
   IMHP : Route Optimization in Mobile IP
   Other Issues
Mobile Computers’ Characteristics
   May change point of network
    connection frequently
   May be in use as point of network
    connection changes
   Usually have less powerful CPU, less
    memory and disk space
   Less secure physically
   Limited battery power
Current State of Mobile
   Mobile computers are one of the fastest growing
    segments of the PC market
   Short-range wireless networks (Bluetooth)
    available from IBM, Toshiba, Dell, HP…
   High-speed (11 Mbps) wireless LAN products are
    now easily and cheaply available (IEEE 802.11a,
    IEEE 802.11b)
   Low speed (currently 128 Kbps) Metropolitan Area
    Wireless Network services are available in some
    cities and spreading (Metricom’s Ricochet)
     Mobility in the Internet
   Problem with current IP
    .It assumes that a node‟s IP address uniquely
    identifies its point of attachment to the
   Mobility alternatives without Mobile IP
     .On moving, change IP address
   Use host-specific routes(using LSR) to
    reach mobile hosts
     .Mobility vs. Portability
     Functional Entities in Mobile
   Functional Entities in Mobile IP :
    -Mobile Node
    -Home Agent
    -Foreign Agent
   Each mobile node is assigned a unique
    home address within its home network
   When away from home network, it is
    assigned a care-of address either by :
    -Registering with a Foreign Agent
    -Obtaining a temporary IP address
Basic Mobile IP


Protocol Overview
   Agent Discovery
   Registration
   Tunneling
     Agent Discovery
   Extension of ICMP Router Discovery
   Used by mobile nodes to discover
    Foreign Agents and to detect movement
    from one subnet to another
   Mobility Agents (H.A.s and F.A.s)
    periodically broadcast agent
     Agent Discovery (...contd.)
   Mobile node expects to receive periodic
   If it doesn‟t receive them, it deduces
    that either
    -it has moved OR
    -its agent has failed
   Mobile node can also broadcast Agent
    Solicitation messages
   Mechanism by which M.H.
    communicates reachability info to its
   Registration messages create or modify
    a mobility binding at a H.A., which is
    then valid for a certain lifetime period
   Uses 2 control messages sent over UDP
    -Registration Request
    -Registration Reply
Registration Authentication

   Replay Protection : Needed to ensure
    that registration messages are not
    replayed by a malicious host. Done
    using :
    -Nonces OR
Registration Authentication
   Concern : Forged registrations permit
    malicious hosts to remotely redirect
    packets destined for the mobile host
   Default authentication between M.H.
    and H.A. uses MD-5 with a shared
    secret key
   No authentication between M.H. and
Delivering Datagrams :
   When the mobile host is away, H.A.
    intercepts packets addressed to
    the M.H. and tunnels them to the
    M.H.s care-of address
   The tunneling scheme could use
    either of :
    - IP-in-IP Encapsulation
    -„Minimal‟ Encapsulation
Delivering Datagrams
   Broadcast Datagrams
     -A H.A. forwards a broadcast datagram only
    if the M.H. requested forwarding of
    broadcast datagrams (in the registration
   Multicast Datagrams
     -M.H. can use a local multicast router
     -M.H. can use a bidirectional tunnel to its H.A.
   Extension to the basic Mobile IP
    protocol that features :
    -Route Optimization
    -Authentication of Management packets
   Defines four entities :
    -Mobile Hosts
    -Local Agents
    -Cache Agents
    -Home Agents
Route Optimization (IMHP)
   Triangle Routing in basic Mobile IP
    -Limits performance transparency
    -Creates bottleneck at Home Agent



Route Optimization
   Eliminates triangle routing                M.H.
   Any correspondent node
    can maintain a binding cache
   Correspondent node tunnels
    datagrams directly to the
    care-off address of the                     F.A.
    mobile host                Correspondent

    Binding Management
   Four message types :
    -Binding Warning
    -Binding Request
    -Binding Update
    -Binding Acknowledge
   Lazy notifications are used (except
    MH to HA and previous FA)
Foreign Agent Smooth
   As part of registration, M.H. requests its new
    F.A. to notify its previous F.A.
   New F.A. sends binding update to prev F.A.
   Previous F.A. updates its binding cache entry
    for the M.H. and sends a binding ack.
   Authentication of binding update is based on
    a shared registration key
Special Tunnels
   When a F.A. receives a tunneled
    datagram for a M.H. for which it has no
    entry, it is tunneled back to the H.A. in
    a special tunnel
   Gives the datagram one more chance of
    successful delivery
   Avoids possible routing loops
Authentication in IMHP
   IMHP
   has simple authentication procedures
    which preserve the level of security in
    today‟s Internet
   is defined to make use of strong
Authentication in IMHP
   M.H. to H.A. authentication
    -strong authentication based on a
    shared secret
   General Authentication
    -a random number specified in binding
    request is echoed in the reply by the

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