Networks

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Networks

• Overview ( Lei You )
• Overview of Local Network Topology
• ( Ryan McKenzie )
• Internetworking Protocol ( Benjamin A Pullen
  )
• Mobile IP ( Hui Tan )

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Overview
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What is a Network?

• Two or more computers are connected together by a
  medium and are sharing resources. These resources
  can be files, printers, harddrives, 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.

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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.

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Graphical Symbols Used in the Big Picture

• 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

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Telecommunications Components of The Big Picture

• ISDN Integrated Services Digital Network
• Private Branch Exchanges PBXs, Key Systems
• Telcos ATT, 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

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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 multiprotocol
  networks that exist today.

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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)

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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.

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The Big Picture can be broken up according to its
protocols into the following four areas

• Local Loops
• LANs
• MANs
• WANs

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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.

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The Local Loop
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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

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• 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 transmission.

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Local Area Networks (LANS)

• 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).

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Local Area Networks (LANS)
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Components Used by LANs

• Cabling standards
• Hardware
• Protocols

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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 (10BaseT)
• Unshielded Twisted Pair (UTP)
• Shielded Twisted Pair (STP)
• Connectors RJ45, RJ11, Hermaphroditic
  connectors, RS-232, DB-25, BNC, TEE

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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

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LANS Hardware Devices

• Brouters
• Routers
• Gateways
• Print servers
• File servers
• Switches

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LANS Examples of Protocols

• Ethernet frame types Ethernet_II, Ethernet_SNAP,
  Ethernet_802.2, Ethernet_802.3
• Media Access Control layer (MAC layer)
• Token Ring IBM and IEEE 802.5
• Logical Link Control Layer (LLC) IEEE 802.2
• TCP/IP
• IPX/SPX
• Asynchronous Transfer Mode (ATM)

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Metropolitan Area Networks
(MANs)

• 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.

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Metropolitan Area Networks
(MANs)
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Metropolitan Area Networks
(MANs)

• 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
  conditions).

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Examples of MAN Protocols

• RS232, V35
• X.25 (56kbps), PADs
• Frame Relay (up to 45 Mbps), FRADs
• Asynchronous Transfer Mode (ATM)
• ISDN (Integrated Services Digital Network) PRI
  and BRI
• Dedicated T1 lines (1.544 Mbps) and Fractional
  T1
• T3 (45 Mbps) and OC3 lines (155 Mbps)
• ADSL (Asymmetrical Digital Subscriber Line) up
  to 8 Mbps
• XDSL (many different types of Digital Subscriber
  Lines)

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Wide Area Networks
(WANS)

• WANs connect LANs together between cities

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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 MAN.

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References

• 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 Internet
• Jim Kurose Keith Ross
• 3. Internetworking Technology Overview
• Cisco Systems
• 4. Internetworking Case Studies
• Cisco Systems

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Network Topology

• Overview of Network Topology
• and
• Case Study of Flat Neighborhoods

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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.

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Bus Topology

• Robustness
• Efficiency
• Simplicity
• Scalability

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Bus Topology

• Robustness
• Good
• Efficiency
• Good
• Simplicity
• Excellent
• Scalability
• Fair

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Ring Topology

• Robustness
• Efficiency
• Simplicity
• Scalability

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Ring Topology

• Robustness
• Poor
• Efficiency
• Good
• Simplicity
• Very Good
• Scalability
• Poor

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Star Topology

• Robustness
• Efficiency
• Simplicity
• Scalability

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Star Topology

• Robustness
• Very Good
• Efficiency
• Very Good
• Simplicity
• Poor
• Scalability
• Excellent

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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.

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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.

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The Basics of FNNs

• 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.

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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
• Routing and Addressing

• Wiring Scheme
• Efficient use of Bandwidth

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The SolutionsSubnets 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.
• http//aggregate.org/FNN/

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The SolutionsGenetic 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 results.
• Re-Evaluate and rate accordingly

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The SolutionsBasic 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

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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

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The Main EventKLAT2 vs. Superdome
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KLAT2 vs. SuperdomeRound 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

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KLAT2 vs. SuperdomeRound 2 Upgrading

• KLAT2
• Purchase new Nodes
• Upgrade the Old Nodes
• Recompute Scheme
• Rewire EVERYTHING
• Superdome
• Purchase a new Cabinet
• Plug and Play
• Advantage
• Superdome

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The Lowdown

• FNNs provide wonderful cost efficiency, but are
  plagued by limitations.
• Number if NICs in each node
• PCI Bus Speed
• Increased Physical Distance
• Complexity of Design

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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 RD, the FNN cluster may evetually
  bring about a supercomputer in every home
  movement.

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Summary

• Topology Development Philosophy has Evolved
• Special Purpose Topologies use Networks to Solve
  Specific Problems
• Network Topologies are Always Expanding
• More Topologies Being Concieved
• Faster, More Advanced Media

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The Credits

• Dr. Hank Dietz, [phone]
• http//www.engr.uky.edu/ece/faculty/dietz/index.ht
  ml
• Mr. Tim Mattox at the KAOS Lab, [phone]
• http//aggregate.org/KAOS/
• KAOS Lab Documentation and Publications on FNNs
• http//aggregate.org/FNN/
• Dr. Craig Douglas, [phone]
• http//www.ccs.uky.edu/douglas/
• Mr. John Connolly at the UK Center for
  Computational Sciences
• http//www.ccs.uky.edu/connolly/
• UK SDX Home Page
• http//sdx.uky.edu/

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Internetworking Protocol Version 4

• (IPv4)

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Topics

• Why?
• What?
• How?

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Why IP?

• Why do we build networks?
• Why do we need inter-networks?

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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.

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How?
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How?
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Fields

• 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.

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Fields continued

• Identification(16 bits) unique identifier
• Flags(3 bits) 0, Dont fragment, More
  fragments.
• Fragment Offset(13 bits) Offset of fragment in
  8 byte words.

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Fields continued, again

• Time To Live (8 bits) Hop count.
• Protocol(8 bits) Higher level protocol address.
• Header Checksum Ones compliment sum of all 16
  bit words in IP header.

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Fields, more?

• Source Address(32 bits) Where it came from.
• Destination Address(32 bits) Ummm, you know.

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Fields, will it ever end!?

• Options options.
• Padding even out to 32 bit words.

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Fragmentation

• 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 destination.

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Fragmentation

• 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.

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IP Addressing

• Hierarchical (cuz thats 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.

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IP Addressing

• Class A - 07 Bit Network24 Bit Host
• Class B - 1014 Bit Network16 Bit Host
• Class C - 11021 Bit Network8 Bit Host

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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 address.
• A netmask is used to divide the address.

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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 address.
• Send the packet out the corresponding interface
  to the next hop (may be local.)

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IP Forwarding
Example Interface0 128.163.125.2/24 Interface1
24.249.125.187/24 Address/Length Next
Hop Interface 128.163.125.0/24 Local Interface0
128.168.0.0/16 128.163.125.1 Interface0 24.249.1
25.0/24 Local Interface1 0.0.0.0/0 24.249.125.1
Interface1
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Whats Next?

• IPv6
• 128 bit addressing (more people can play quake.)
• Fewer fields for simplicity

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Overview

• Mobility in the Internet
• Basic Mobile IP Protocol
• IMHP Route Optimization in Mobile IP
• Other Issues

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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

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Current State of Mobile Computing

• 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 (Metricoms Ricochet)

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Mobility in the Internet

• Problem with current IP
• .It assumes that a nodes IP address uniquely
  identifies its point of attachment to the
  Internet
• Mobility alternatives without Mobile IP
• .On moving, change IP address
• Use host-specific routes(using LSR) to reach
  mobile hosts
• .Mobility vs. Portability

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Functional Entities in Mobile IP

• 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

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Basic Mobile IP
H.A.
Correspondent node
F.A.
M.H.
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Protocol Overview

• Agent Discovery
• Registration
• Tunneling

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Agent Discovery

• Extension of ICMP Router Discovery protocol
• 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 advertisements

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Agent Discovery (...contd.)

• Mobile node expects to receive periodic
  advertisements
• If it doesnt receive them, it deduces that
  either
• -it has moved OR
• -its agent has failed
• Mobile node can also broadcast Agent Solicitation
  messages

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Registration

• Mechanism by which M.H. communicates reachability
  info to its H.A.
• 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

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Registration Authentication (..contd.)

• Replay Protection Needed to ensure that
  registration messages are not replayed by a
  malicious host. Done using
• -Nonces OR
• -Timestamps

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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 F.A.

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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

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Delivering Datagrams (..contd.)

• Broadcast Datagrams
• -A H.A. forwards a broadcast datagram only if
  the M.H. requested forwarding of broadcast
  datagrams (in the registration request)
• Multicast Datagrams
• -M.H. can use a local multicast router
• -M.H. can use a bidirectional tunnel to its
  H.A.

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IMHP

• 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

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Route Optimization (IMHP)

• Triangle Routing in basic Mobile IP
• -Limits performance transparency
• -Creates bottleneck at Home Agent

H.A.
Correspondent Node
F.A.
M.H.
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Route Optimization

• Eliminates triangle routing
• Any correspondent node
• can maintain a binding cache
• Correspondent node tunnels
• datagrams directly to the
• care-off address of the
• mobile host

M.H.
F.A.
Correspondent Node
H.A.
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Binding Management

• Four message types
• -Binding Warning
• -Binding Request
• -Binding Update
• -Binding Acknowledge
• Lazy notifications are used (except MH to HA and
  previous FA)

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Foreign Agent Smooth Handoff

• 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

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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

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Authentication in IMHP

• IMHP
• has simple authentication procedures which
  preserve the level of security in todays
  Internet
• is defined to make use of strong authentication

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Authentication in IMHP (..contd.)

• 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 H.A.