Goals

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Goals

• Identify common media connectors
• Identify common network components
• Identify features of 802 project network
  standards (hardware protocols)
• 802.2 (LLC)
• 802.3 (CSMA/CD) ethernet)
• 802.5 (token ring)
• 802.11 (wireless)
• FIDDI

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Terminology Common to all Networks

• Clients computer that requests resources from
  another computer
• Server computer on the network that manages
  shared resources
• Workstation desktop computer, most clients are
  workstations
• Network interface card ( NIC) device that
  connects a computer to the network media
• Network operating system (NOS) software that
  runs on a server to manage network functions
• Host computer that enables resource sharing
• Node client, server or device that can
  communicate over a network and is identified by a
  unique network address
• Shared resource data or hardware provided to
  the client by the server
• Topology physical or logical layout of a
  computer network
• Connectivity device special devices which allow
  2 or more networks or network segments to
  communicate
• Protocol predetermined method or format for
  exchanging data between computers. Data packets
  distinct units of data transmitted from one
  computer to another
• Addressing scheme for assigning unique
  identifier to each node
• Transmission media means of transmitting data,
  physical connection wired or wireless

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Basic Network Hardware

• Transceivers a device that interfaces another
  device to a network, broadcasts and receives
  signals to and from the surrounding computers.
• NIC card
• Access point for wireless network
• Repeaters simplest connectivity device used to
  regenerate a signal
• 2 ports
• Hubs multi-port repeater. Concentrator
• Common wiring point for networks based on a star
  topology.
• Takes input through one port and redistributes
  through all other ports
• Each hub is a separate collision domain
• Connects 2 LAN segments of the same type to
  expand collision domains
• Type of Hubs
• Passive no power required, passes signal does
  not regenerate signal
• Active regenerates and cleans signal , power
  required (repeater)

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Network Hardware continued

• Switch physically like a hub, but
  electronically more sophisticated.
• Can determine proper port for packet destination
  using MAC address reducing network traffic.
• Preserves bandwidth on the network using
  segmentation
• Bridges- connects 2 network segments together,
  forwards frames based on the MAC address
• Protocol independent
• Extend collision domains
• Segment networks using non-routing protocols
• All broadcast data is passed

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Network Hardware cont

• Router
• multi-port device that directs data between
  networks and nodes using logical addressing,
• switches devices that connect to LANs where
  multiple paths exist, determining best path.
• Used to interconnect LANs and WANs
• Each port can be configured for a unique network
  address
• Can connect different types of network
  architecture together
• Brouter
• perform the function of bridge and router in one
  device
• Can forward outside subnet
• CSU/DSU channel service unit/data service unit
  
• connects networks to a communications carrier
• Gateway
• Enables communication between 2 completely
  different computing environments or architectures
  that do not use the same protocols

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Basics Concepts of Networking Media ( chapter 3)

• Media is the physical connection on which signals
  move from one device to another. (Including
  wireless media)
• Media types are bounded or unbounded
• Unbounded
• Radio waves
• Infrared Light pulses
• Laser beams
• Microwave
• Bounded
• Copper
• Fiber optic

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Topologies

• Physical or logical layout of the network, (how
  the signal is carried)
• 4 major topologies
• Bus
• Star
• Ring
• Mesh
• Most networks are hybrid of the basic
  topologies.
• Institute of Electrical and Electronic Engineers
  (IEEE) defined the topologies in 1980 along with
  some hardware protocols.
• Known as the 802 Project(for Feb 1980)

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Bus Networks

• Bus devices are connected on a common linear
  cable (coaxial cable)
• Both ends of the network must be terminated
• All computers listen to the cable only one
  computer transmits at a time
• Signal is seen by all, but processed only by the
  computer whose address matches the destination
  address in the packet
• Factors affecting performance
• Break in the cable or loss of termination will
  stop network traffic
• More computers the longer the wait the slower the
  network
• Simple to install, difficult to troubleshoot

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Ring Network

• Connects computers on a single circle of cable
• Foundation for token ring architecture and FIDDI
• Logical rings interconnected by multi-station
  access units (MAU) devices
• Can reconfigure the ring when a computer goes
  down
• Similar to a hub, internal wiring is a ring with
  ring-in ring-out ports for extending ring

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Star Network

• Most common network
• Star network several computers or devices
  interconnect to one another over a hub
• Modular, centralized administration, easy to
  troubleshoot
• Complex cabling schemes document!!!!

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Hardware protocols

• Hardware protocols define how the devices put
  data on and take data off the network cable
• also called channel access method
• Closely associated with topologies but not the
  same
• Defined in the 802 Project standards (combination
  of the physical topologies and hardware
  protocols)
• 802.2
• 802.3 CSMA/CD
• 802.4
• 802.5 Token Passing
• 802.11
• 802.12 Demand Priority
• Methods to access the wire
• Contention or Probabilistic
• CSMA/CD and CSMA/CA
• Deterministic or Token Passing
• Token Ring
• FIDDI

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CSMA/CD CSMA/CA

• IEEE 802.3 standard (often called Ethernet
  standard)
• Defined specifications for moving data across
  twisted pair and coaxial cables and the
  terminators used
• Star or Bus networks
• Carrier sense multiple access collision detect
• Each computer listens for traffic on the wire
  (carrier sense)
• If a computer senses the cable is free it sends
  frame
• Often referred to as a packet
• All computers can see the signal (multiple
  access)
• No other computer can send until the cable is
  free again
• If a collision occurs the sending computers wait
  a random time and resend (collision detect)
• Collision frames collide with frames from
  another computer blending the signals making both
  frames useless

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Packet

• Packet- a unit of information transmitted as a
  whole for one device to another on a network.
  Large data is broken into manageable packets
  which are the basic unit of network data
  communication.
• Data is broken into packets to
• Avoid flooding the cable speeding up
  transmissions
• Lower the impact of retransmissions
• Common packet components ( common to all
  protocol packets) include
• Header
• Alert signal and or clocking information
• source address
• destination address
• instructions for reassembling
• Data
• Varies from 512bytes to 4 KB depending on the
  network
• Trailer
• Error checking
• CRC (cyclical redundancy checkmathematical
  calculation performed on the packet at the source
  and again at the destination)

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FIDDI

• Fiber Distributed Data Interface uses token
  passing protocol
• Uses fiber optic media
• CDDI uses copper media
• Dual Ring topology
• Secondary ring is backup only
• Stations can be single or dual attached
• A port attaches to primary ring
• B port attaches to secondary ring
• M port attaches single attached station to
  primary ring

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Features of peer to peer network

• No dedicated server
• Share level security
• no central administration
• When to use
• Security is not an issue,
• 10 or less computers
• Simple to configure, low cost
• Expansion is not an issue

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Client/Server Network

• Client/server- A network in which one or more
  master computers keeps a database of users and is
  responsible for responding to network requests
• Features of client/server network
• Dedicated server running NOS software
• Centralized administration
• Backups made easy
• Redundancy
• Security
• Permissions access rights to network resources
• Authentication
• User ID
• Password
• Privileges actions a user can perform on a
  network
• User accounts with rights to change the system
• MS administrator
• Novell Netware Supervisor
• Unix or Linux root (Superuser)

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Trust Relationships

• One-way explicit trusts (Windows NT)
• Two-way transitive trusts (Windows 2000)

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Directory Service

• Organizes and simplifies access to resources
• Identifies users and resources
• Provides a way to organize and access users and
  resources
• Allows you to perform a number of functions
• Acts as administration tool and end-user tool

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Components of Directory Service

• Objects distinct named set of attributes that
  represents a network resource and its properties
• Objects are assigned attributes
• Each object must have, at minimum, an object
  class field and if a user a UID field
• 3 types of objects
• Root represents the beginning of the hierarchy
• Container- (called OU by MS)
• exists off the root or other container used to
  organize objects into logical groups
• Country
• optional
• Organization-
• Represents a country or organization
• Organizational unit (OU)divide leaf objects into
  workgroups
• Leaf
• Represents network entities such as users,
  groups, printers, servers
• Distinguished name objects name along with the
  completer context starting from root.
• .psprinter.accounting.microsoft.us.

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Organizational Unit (OU)

• Subsection under domain
• A container that can hold users and computers
• Administrative control of an OU can be given to a
  user
• OUs can be assigned policies that apply to their
  contained objects
• Locations where you can create OUs are
• Under a domain
• Under another OU

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Media terminology

• Carrier wave the constant voltage of electrical
  current that carries the data what the signal
  wave rides on.
• Encoding the representation of the computers
  digital zeroes and ones as a physical signal such
  as electrical current or light pulses
• A one bit may be a 5 volt signal and a 0 bit a 2
  volt signal
• Frequency or amplitude of the signal wave is
  altered to encode data

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Analog signal vs digital

• Data can be transmitted via one of 2 signaling
  methods
• Analog
• Digital
• Both are electrical current measured in volts
• voltage -- strength of the signal
• Digital is more reliable than analog transmission
• Digital is less affected by noise than analog
  transmissions

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Digital signal

• Digital is an on off state
• positive voltage 1
• no voltage 0
• 1s and 0s are used to encode data
• Pulse bit
• 8 bits byte
• One byte carries one piece of information
• Most data transmission is digital

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Analog signal

• Data sent on the wire is usually some form of
  analog signal
• Electrical signals
• Radio waves
• Microwaves
• Analog signals vary in frequency and amplitude

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Frequency modulation

• The data travels along a particular frequency
• The carrier signal is modified by the application
  of the data signal
• Signal strength is constant , frequency of the
  signal changes

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Amplitude modulation

• The amplitude of the carrier signal is modified
  by the data signal
• Frequency of the signal is constant, strength of
  the signal changes

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Baseband Transmission
3

• Bi directional using digital encoding
• Single fixed frequency
• Entire bandwidth for each signal
• All devices use one channel
• Signal decreases with length (attenuation)

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Baseband Transmission (cont.)
3

• Baseband systems like Ethernet
• Use repeaters to amplify signals
• Restores strength quality
• Sends signal out on another cable
• Increases span of network

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Broadband Transmission
3

• Uses analog techniques to encode
• Continuous electrical or optic waves
• Multiple channels on a single cable
• Amplifiers are used to
• Strengthen rebroadcast signal

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Broadband Transmission(cont.)
3

• To support two-way communication
• Mid-split uses a single cable
• Different frequencies for each channel
• Dual cable uses two cables
• One each for receive transmit

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Transmission Direction

• Simplex
• Simplest
• One direction only ( sending or receiving)
• Half duplex
• Both directions
• One direction at a time
• Full duplex
• Both directions
• Same time
• Separate transmit and receives buffers maintained
  by the transceivers

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Fiber Optics

• Glass or plastic strand core
• 2 modes
• Single mode fiber
• Faster
• Longer distance 4000m
• More expensive
• Multimode fiber
• 2000 m
• Thicker glass fiber core
• Both have limited bend radius
• Uses separate lines for send and receive
• GB/s transmissions

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Fiber Optics cont

• 2 methods to translate digital stream to light
  pulses
• LED (light emitting diode)
• Short distances
• LD (laser diode)
• Long distances
• Connectors used
• Straight tip (ST)
• MTRJ
• Subminiature assembly (SMA)(SC)

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Advantages and disadvantages of Fiber Optics

• Advantages
• Faster data transmission
• Longer distance
• 150 to 40000 meters segments
• Immune to interference
• Immune to corrosion
• Secure from eavesdropping
• Disadvantages
• Cost
• Hard to install

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Infrared

• Encodes data into pulses of infrared light
• Transmission methods include
• Line of sight
• Reflective
• Uses central access point
• Scatter infrared (slowest)
• Bounces the signal
• Needs reflective surfaces
• Reflected light may interfere
• Broadband optical telepoint (fastest)
• Multiple signals at once on different frequency
  channels
• Infrared is one of the slower technologies
• Distance is limited

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Laser

• Overcomes the limits of speed and distance of
  infrared
• 155Mbps 622Mbps
• 4KM
• Speed and distance are inversely proportional
• More expensive
• Harder to install
• Line of sight
• Affected by physical obstruction
• Protocol transparent

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Radio

• Medium of choice for SOHO
• 3 categories
• Short wave
• Very high frequency (VHF)
• Ultra high frequency (UHF)
• FCC regulates usage of frequencies
• License are required except for public bands
• 902-928MHz
• 5.72-5.85 GHz
• Broadcasting power is limited to avoid bleedover
• Transmissions are
• Single frequency
• Spread spectrum

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The 7 Layers of OSI

• Divide and conquer
• Breaks networking concepts into easy to
  understand functions and their devices
• Makes troubleshooting easier by isolating the
  functions layer and focusing on the protocols
  and devices responsible
• Allows development of new technologies without
  restructuring the entire network

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Seven-Layer OSI Model
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Application Layer (7)

• Topmost layer
• Represents services that directly support user
  applications
• Window to network services
• Handles network access, flow control, and error
  recovery

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Presentation Layer (6)

• Network translator
• On sending end, determines formatting used to
  exchange data among computers and adds formatting
  so data can be understood by network
• On receiving end, translates data from
  application format to a common intermediate
  format
• Manages data compression, translation, encryption
• I/O redirectors work to redirect resources to a
  server

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Session Layer (5)

• Allows two applications on different computers to
  open, use, and close connections
• Performs name recognition and provides security
• Provides synchronization by placing checkpoints
  in the data stream
• Implements dialog control between communication
  processes

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Transport Layer (4)

• Sending end repackages message, divides long
  messages to ship properly over determined route
  and arrive error-free
• Receiving end unpacks message, reassembles it,
  and acknowledges receipt
• Provides flow control, error handling, and solves
  transmission problems

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Network Layer (3)

• Addresses the package using network address
  scheme
• Determines the best route on the network based on
  network conditions, priority of service
• Performs packet switching, routing, traffic
  management, and controls congestion of data

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Data-Link Layer (2)

• Sending end sends data frames from network layer
  to physical layer
• Receiving end packages raw bits from physical
  layer into data frames
• Parts of data frame Destination ID, Sender ID,
  Control Data
• Acknowledges data frames, error checking, and
  verification

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Physical Layer (1)

• Bottommost Layer
• Hardware-oriented, establishes and maintains
  physical link between communication computers
• Defines how the cable is attached to the NIC
• Packet sent as an unstructured raw bit stream
  over physical medium
• Referred to as the hardware layer

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802 Specifications

• Set Standards for
• Network Interface Cards (NICs)
• Wide area network (WAN) components
• Components used to create twisted-pair and
  coaxial cable networks

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802 Specification Categories

• 802.1 Internetworking
• 802.2 Logical Link Control (LLC)
• 802.3 MAC layer, Carrier Sense Multiple Access
  with Collision Detection (CSMA/CD) LAN
  (Ethernet)
• 802.4 MAC layer, Token Bus LAN
• 802.5 MAC layer, Token Ring LAN
• 802.6 Metropolitan area Network (MAN)
• 802.7 Broadband Technical Advisory Group
• 802.8 Fiber-Optic Technical Advisory Group
• 802.9 Integrated Voice/Data Networks
• 802.10 Network Security
• 802.11 Wireless Network
• 802.12 Demand Priority Access LAN,
  100BaseVG-AnyLAN
• 802.13 Unused
• 802.14 Cable modem standards
• 802.15 Wireless personal area networks (WPAN)
• 802.16 Broadband wireless standards

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Project 802 LLC and MAC Sublayers
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Function of the Physical Layer

• Hardware Layer
• Defines the electrical and mechanical aspects of
  the network media
• Voltages
• Cables
• Connectors
• NICs, hubs and repeaters
• Converts the bit stream furnished by the
  data-link layer into electrical, radio or optical
  signals and sends it across the media
• Frame the smallest unit of information that is
  sent after the Data-Link layer adds its header

Layer Network device Unit of information
Media Access control NIC drivers /MAC address Frames
Physical Connectors, cables, NICs, hubs, repeaters Bits and voltages
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Three Components of the Physical Layer

• Physical Signaling (PLS)
• Physical Medium Attachment (PMA)
• Medium Dependent Interface (MDI)

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CRC

• Performs a mathematical algorithm on the frame
• Adds result to trailer of packet
• Receiving end does the same
• ACk is sent if the same
• NACK if different

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Types of Fiber

• Cable types
• Loose-tube
• Multi-strand, single cable
• Tight-buffered
• Single strand
• Kevlar sheath
• Cable of choice for interior installation
• Single-mode fiber
• One signal per strand
• Faster rates longer distances
• Multi-mode
• Wavelength division multiplexing several light
  beams per cable
• Shorter distances due to modal dispersion

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Signaling

• Optical transmitter
• Light emitting diode
• Laser diode
• Light on light off logic
• Speed is direct corollary of the pulse rate
• LED is slower MHz
• LD GHz
• Pulse width modulation
• Streaming light short separators
• Pulse rate modulation
• Duration of separator is changed

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Unbounded Signaling

• Optical
• Infrared
• laser
• Radio
• Microwave

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Optical

• Infrared
• Works like fiber light pulses
• Line of sight
• Scatter infrared
• Reflective
• Broadband optical telepoint
• Laser
• Requires line of sight

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Radio

• AlohaNet first radio-based network
• 802.11 standard
• 2.4GHz frequency range
• 1-2 Mbps
• 802.11a
• 5GHz range
• 5Mbps, 11Mbps and 54Mbps speeds
• 802.11b
• 2.4GHz at higher speeds

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Functions of the Data Link Layer (Layer 2)

• Physical Addressing
• Network Topology
• Error Notification
• Access to the physical media
• Flow Control

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Data Link Sub Layers

• Data Link is divided into 2 sub-layers
• Logical Link Control (LLC)
• Defines the rules that govern the establishment
  of logical interface points (SAPs) between
  devices and layers
• Media Access Control (MAC)
• Defines physical addressing and medium
• Channel Access methods

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Physical Address (MAC sublayer)

• MAC address 48 bit fixed physical address
  burned into the network interface by the
  manufacturer
• Displayed in 6 part hexadecimal notation
• 0060B6A17817
• First 24 bits Organizational Unique Identifier
  (OUI)
• Assigned and administered by IEEE Registration
  Authority
• Last 24 bits manufacturer assigned interface
  serial number
• Used to uniquely identify all network interfaces
• Each addressable port of a device must have a
  unique MAC address

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Network Topologiesphysical or logical layout of
the network

• Bus
• Ring
• Star
• Mesh
• Hybrid

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Bus

• Devices are on a common linear cable (backbone,
  trunk or segment)
• Cable requires termination on both ends
• Break in the cable will bring the network to a
  halt
• Uses contention to access the wire

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Star

• Cable segments from each computer are connected
  through a central component called a hub
• Centralized management
• Requires more cable than a bus
• Failure of a cable or computer affects only that
  computer
• Failure of a hub affects the whole segment

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Ring

• Connects computers on a single circle of cable
• Uses a token to move data
• Data is passed by each computer in one direction
• Failure of a computer can stop the network

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Baseband signaling

• Used by most LAN technologies
• Digital communication
• Full bandwidth
• Bi-directional

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IEEE

• IEEE developed the 802 standards for design and
  compatibility for hardware components operating
  in the data-link and physical layers of the OSI
• Common 802 standards
• 802.3 Ethernet (CSMA/CD)
• 802.12 Demand Priority Access
• 802.11 CSMA/CA
• 802.5 Token Ring
• FDDI (ANSI X3T9.1 standard)

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CSMA/CD (ETHERNET)

• Follows the 802.2 and 802.3 standards
• Star or Bus Topology
• Baseband Transmission
• Contention based, probabilistic
• Carrier Sense Multiple Access
• All devices listen for traffic on the wire
• A device sends only if the wire is clear
• Collision Detect
• If a collision occurs the systems back-off and
  after a random time resend
• More traffic more collisions
• Segmenting the network can reduce collisions
• Use a switch to create separate collision domains

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10BaseT

• 10Mbps Baseband over Twisted Pair (cat 3,4,5,or
  6)
• Star pattern, internal bus signal
• Hub is a multi-port repeater
• Maximum segment length 100 meters
• Maximum computers on a network 1024
• Minimum distance between computers is 2.5 meters
• RJ-45 connections, transceivers on the NIC

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10BASE-2
7

• 200 meters (185) maximum segment
• Thinnet,
• easy to manipulate
• not TV coax (75 OHM cable RG58U)
• RG-58A/U and RG58C/U 50ohm coaxial(IEEE spec)
• minimum length is .5 meters or 20 inches
• Transceiver built into NIC
• BNC connector, terminators (50 ohm)
• Bus topology, 5-4-3 rule

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10BASE-5
7

• Standard Ethernet-- used when ethernet was
  introduced
• Transceivers,attached to thicknet via vampire
  taps, drop cables less than 50 meter max to NICs
  connect with AUI or DIX port 2.5 meters apart
• 500 meter maximum segment length
• 2500 meter maximum network length
• 5 segments using repeaters (5-4-3 rule)

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5-4-3 rule

• Max 5 segments
• 4 repeaters
• 3 populated segments

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10BASE-F
7

• Fiber-optic cable
• 3 subcategories
• 10BASE-FL fiber to the desktop (LAN)
• 10BASE-FP passive hubs (rather than repeaters)
  maximum cable length 500 meters per segment
• 10BASEFB Fiber backbone between hubs
• All use star topology

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10BASE-F cont

• Used for long runs between buildings 2000meter
  max segment length
• 1023 max number of segments
• Max device per segment 2
• CSMA/CD channel access method
• High cost
• reserved for connections between hubs or for
  connections requiring security from EMI
• difficult to install

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Token Ring
7

• Developed by IBM
• IEEE 802.5 standard
• Star-wired topology
• Star cabled, operate as logical ring
• Token passing channel access method
• Wired in a star from the hub logical ring in the
  hub
• NICs are either 4Mbps or 16Mbps baseband
  transmission
• Used with fiber and switches for high speed and
  distance

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Beaconing
7

• Active monitor sends beacon announcement every 7
  seconds
• If computer does not receive the beacon puts a
  message on the ring
• Source address
• Address of upstream computer
• Continues to send until it receives beacon from
  upstream number
• Finally the only machine beaconing is the one
  directly downstream from the fault
• Hub reconfigures ring dropping the non-responsive
  device

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FDDI

• Fiber optic cable
• Token passing channel access
• Uses dual ring topology for redundancy
• Data flows in opposite directions
• NICS are
• Dual attachment stations (A port stations can
  reconfigure the ring)
• Single attachment stations

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FDDI

• Key difference in frame transmission from token
  passing
• FDDI computer can transmit as many frames as it
  can produce in a predetermined period of time
  before releasing the token

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Error Detection

• Lost Frames
• Checksum or CRC
• Frame Size
• Buffer Overflow
• Interference
• Data Link notifies Transport Layer. Error
  correction is done in the Transport layer.

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Network Layer

• Allows internetworking-- Services of the network
  layer allow different networks to find each other
• Services may be used by LANs but WANs cannot
  exist without them
• Supports both connection-oriented and
  connectionless service from upper layer protocols
• Protocols are typically routing protocols

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Routable Protocols

• Protocols that support multipath LAN to LAN
  communication
• TCP/IP
• IPX/SPX

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Non-routable

• Work only in local LAN
• Use physical addressing

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Connection-Oriented Protocols

• Connection is established
• Data is sent in orderly,slower fashion
• Packet receipt is acknowledged
• Resends error packets
• Connection is terminated

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Connectionless Protocols

• Place the data on the network and assume it will
  arrive
• Faster than connection oriented
• Does not establish, maintain or tear down a
  session
• Packet sequencing and sorting is handled in the
  higher layers
• Not as reliable as connection oriented
• PDU is a datagram

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Functions of the Network Layer

• Manage Logical Addressing
• Translate logical to physical address
• Route messages between networks
• Determine best path
• Controls congestion
• Uses priority and network conditions
• Does switching and routing of packets
• PDU is a packet or datagram at this layer

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Protocols of the Network Layer

• Internet Packet Exchange(IPX) logical
  addressing protocol used by Novell NetWare
• Internet Protocol (IP) logical addressing
  protocol used by TCP/IP networks
• Internet Control Message Protocol (ICMP) used
  to send control, confirmation and error messages
• Border Gateway Protocol (BGP)internet
  inter-domain routing protocol
• Open Shortest Path First- (OSPF) a link state ,
  interior gateway protocol used in TCP/IP networks
• Routing Information Protocol (RIP) an Internet
  routing protocol that uses hop count metric
• Address Resolution Protocol-(ARP) resolves
  logical to physical address
• Reverse Address Resolution Protocol (RARP)
  resolves physical to logical address

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IP

• Provides source and destination addressing and
  routing
• Connectionless datagram protocol assumes other
  protocols will ensure reliable delivery

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Classes

• There are 5 Classes
• Class A(1-126),B(128-191),C (192-223) unicast
  addresses used by networks
• Class D multicast address (224-239)
• Class E is experimental, future use (240-255)

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Routing in TCP/IP

• Subnet mask is used to identify the network
  portion of the IP address
• Only devices on the same network can see each
  other
• Default gateway is an address of a multi-homed
  device (router)
• Maintains a table of all known networks
• Forwards the packet via the port connected to the
  network of the destination IP

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Netmask

• Signifies the part of the address used for the
  network and the part used for the host
• Default mask for each Class
• A 255.0.0.0
• B 255.255.0.0
• C 255.255.255
• 1 network 0hosts

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Routing Tables

• Static
• Administrator manually configures route tables
  (reconfigure for changes)
• More secure
• Dynamic
• Routers use routing protocols to configure
  routing tables
• Routing tables must contain a minimum of 2
  fields
• IP address prefix (netmask)
• Next hop (gateway)
• Most include the metric of a route

92
Distance Vector

• Simple
• Router knows only of directly connected devices
• Maintains a table of next hop on interface
• Uses metric to determine hop count and routes
  accordingly
• Not very secure
• Not scalable (15 hop limit)
• RIP protocol

93
Link State

• Monitor condition of each connected link
• Advertise conditions to neighboring routers
• Link speed
• Latency
• Status of routers on the network
• OSPF protocol

94
Internet Control Message Protocol

• ICMP- RFC792- defined
• Integral part of IP part of Internet Layer
• Uses IP datagram delivery facility to send
  messages
• ICMP messages function(used by routers)
• Flow Control destination host sends
• ICMP Source Quench Message to sender
• Temporarily stops transmission
• Detectiong unreachable destination
• System which detected problems sends destinatin
  unreachable to datagrams source
• If destination is network or host intermediate
• System sends
• If port is unreachable
• Destination host sends message
• Redirecting routes
• Gateway sends ICMP Redirect Message
• Better route to tell the host to use a
  different gateway

95
ARP

• Address resolution protocol
• Determines hardware address for IP
• If address is not cached then broadcasts request
• RARP
• Reverse address resolution protocol
• Maintains a database of machine numbers, (created
  by system administrator)
• Provides IP number to hardware address

96
Transport Protocols

• Facilitate communication sessions between
  computers
• Ensure reliable movement of data
• Monitor flow control
• End to end error detection recovery
• Responsible for end-to-end integrity of data
• Congestion control
• solves transmission problems
• Breaks data into chunks (segments data) and and
  sequences segments begins encapsulation

97
Transport Layer (4)

• Sending end repackages message, divides long
  messages to ship properly over determined route
  and arrive error-free
• Receiving end unpacks message, reassembles it,
  and acknowledges receipt
• Provides flow control, error handling, and
  transmission.

9
98
Transport Protocols
6

• Ensure reliable data delivery
• TCP (Transmission Control Protocol)
• SPX (Sequenced Packet eXchange)
• Novells connection-oriented protocol
• NWLink (MS implementation of SPX)
• NetBEUI-MS standard transport layer non-routable
  (NetBEUI/NetBIOS)

99
Connectionless Protocols
6

• Place the data on the network and assume it will
  arrive
• Faster, doesnt waste time establishing,
  maintaining, and tearing down connections.
• Packet sequencing and sorting are handled at
  higher layers
• Not as reliable as connection-oriented
• Connectionless packets referred to as datagrams

100
Connection-Oriented Protocols
6

• Connection is established
• Data sent in orderly, slower fashion
• Packet receipt is acknowledged
• Resends error packets
• Connection is terminated

101
Port Numbers

• Logical address that points to a specific
  protocol
• Identifies application to transport layer
• Up to 65,536 ports
• 2 port addresses
• Well known ports (0-1023)
• Controlled and assigned by IANA
• Destination port
• Ephemeral ports
• Used by client to establish connections
• source and destination
• Registered ports (1024-4951)
• Accessible to network users and processes with no
  special administrative privileges
• Must be registered with IANA
• Dynamic or private ports (49152-65535)
• Open for use without restriction

102
Well Known Ports

• 20 FTP data
• 21 FTP control
• 23 Telnet
• 25 SMTP
• 53 DNS
• 80 HTTP
• 444 HTTPS
• 109 POP v2
• 110 POP v3
• 2049 NFS

103
Flow Control

• Buffer overflow
• Do nothing potential for large number of
  retransmissions
• Stop and Wait
• Ack packet for each frame
• Static Window
• Set number of frames to transmit before waiting
  for ack
• Agreed on during the handshake
• Sliding Window
• Receiving device sends a hold packet . 2 types
• Selectively repeat---Only nack generates resends
• Go back n--- cumulative ack
• Packets arrive in sequence
• Resends bad packet and any that followed it

104
Error Control

• Types of error
• Packet loss
• Packet corruption
• Packet duplication

105
DNS (Domain Name System)

• Transport layer, name-to-address resolution
  protocol
• DNS server keeps a list of systems names and
  their IP addresses.
• Can use a systems logical name (microsoft.com)
  rather than its numerical address when
  communicating

106

• Session --Virtual connection for the purpose of
  transferring data
• Dialogue series of sessions used for a complex
  process or transfer of a large quantity of data.

107
Session Layer Functions

• Allows applications on different computers to
  open, use and close a connection
• Structured dialog
• Security
• name recognition
• Synchronization
• check points in data

108
Steps for establishing a session

• Logon on authentication
• Establish connection ID number
• Agree on services and duration
• Determine who initiates transfer
• Coordinate ack and retransmission procedures
• Session layer relies on support from lower layers
  to create sessions. In TCP/IP the transport and
  session functions are combined in the transport
  layer.

109
Logon Authentication

• Connection oriented --required before session
  building can begin
• credentials user information required by a
  system to permit access to network resources
• Username and password
• Cached and checked each time a resource is
  accessed
• Client/server model authentication is done by the
  security database of the server running the
  service
• Peer to peer model the password is compared to
  the password assigned to the resource

110
Presentation

• Network Translator
• On sending end determines format used to exchange
  data among networked computers and adds
  formatting so data can be understood
• Uses a commonly recognized intermediary format,
  receiving computer translates back to own format
• Managers data compression, translation, and
  encryption
• Redirector operates here

111
Presentation Layer Protocols

• Presentation layer implementations are not
  typically associated with a particular protocol
  stack.
• Some examples of presentation layer coding and
  conversion schemes include
• ASCII.
• EBCDIC
• Motion Picture Experts Group (MPEG)
• QuickTime
• Tagged Image File Format (TIFF)
• Joint Photographic Experts Group (JPEG)
• Graphics Interchange Format (GIF),

112
Compression

• Choice of file format dictates compression scheme
• Source encoding compression at file level
• Lossless
• Maintains quality
• tif and bmp
• Lossy-
• Trade quality for size
• gif and jpg
• Data compression compression at transfer
• Finite set of symbols
• Run length encoding

113
Encryption

• Data security
• sending device scrambles the bit order before
  transmitting
• Receiving device has key to unscramble
• 3 common methods
• Substitution cipher
• Substitute one letter for another
• Transposition cipher
• Reorders characters
• Data encryption standard (DES)
• Most secure
• 64 bit key exchanged at beginning of the session
  determines bit order
• May use Exclusive Or-Gate in data stream to
  change the key

114
Application (7)

• Services that directly support the users
  applications
• Application processes communicate between
  applications and lower layer services
• Allow software programs to negotiate formatting,
  procedure, security and synchronization
• File transferData base accessE-mail
• Window for application to access network services

115
Hardware

• Gateway

116
TCP/IP Protocol Stack

• 4 layers
• Process/Application app/pres/sess
• Host to Host transport
• Internet network
• Network Access datalink/physical

117
IP

• IP V4 uses a 32 bit address in 4byte divisions
• Each byte has 256 possibilities
• 0 and 255 reserved for network broadcast
• 127 is a loop back
• 1-254 are used to denote networks or hosts

118
IP Addressing

• Logical Address assigned to each host
• IP locates the network of a device
• Once the network is located the network will find
  the device by the host portion of the address

119
Subnet Mask

• Used to denote which part of the address Is the
  network and which is the node
• 1 masks the network

120
IP Addressing (Ver. 4)
6

• First octet denotes class A, B, C, D, E
• Class A,B,C are network classes
• Class D is multicast addresses
• Class E is experimental
• Class A 1-126 16,387,064 hosts
• (254254254 hosts)
• Class B 128-191 64,512 hosts
• (254254 hosts)
• Class C 192-223
• 254 hosts per network

121
Fully Qualified Domain Name

• Unique computer name within a DNS namespace
• Examplesales.www.emcp.com
• Read from left to right
• More specific information is on the left

122
Network layer protocols of TCP/IP suite

• IP
• BootP
• DHCP
• ICMP
• ARP
• RARP

123
DHCP

• Places available IP addresses into a pool and
  leases to clients
• 50 maturity client request renewal from leasing
  server
• 75 maturity client requests reassignment from
  any server
• Can hand out most TCP/IP configuration parameters

124
ICMP (Internet Control Message Protocol)

• RFC 792
• TCP/IP best troubleshooting aid
• Network layer protocol used to send control
  messages (errors and confirmations)
• Out of band messages separate from the data

125
ARP Address Resolution Protocol

• Network layer protocol used to resolve a logical
  (IP) address to a physical (MAC) address
• When a system begins a conversation with a host
  that it does not have a physical address for, it
  sends and ARP broadcast packet requesting the
  physical address that corresponds to the logical
  address. Then, the Data Link layer can correctly
  send the packet through the network.
• RARP- assign IP address to MAC address

126
WINS

• NETBIOS to IP
• Requires WINS server
• WINS database is dynamic
• system broadcasts when it boots to the network
• Server extracts information

127
Hosts and LMHosts

• Statically resolve IP addresses
• Hosts
• DNS to IP
• LMHosts
• NETBIOS to IP

128
TCP/IP Protocol Suite
6

• RIP (Routing Information Protocol)
• Network layer protocol
• Distance-vector routing protocol used for route
  discovery (hops)
• OSPF (Open Shortest Path First)
• Network layer protocol
• Link-state routing protocol used by routers
  running TCP/IP to determine the best path through
  a network.

129
Transmission Control Protocol (TCP/IP)

• Three-Way Handshake
• Requestor sends a packet specifying the port
  number and its initial sequence number (ISN) to
  server
• Server acknowledges with its ISN, which consists
  of the requestors ISN, plus 1
• The requester replies with the servers ISN, plus
  1

12
130
Configuring TCP/IP

• TCP/IP protocol can be configured one of two ways
• Dynamic via DHCP (automatic IP)
• Static IP set
• IP address
• Subnet mask
• Gateway IP for forwarding packets beyond the LAN

131
Gateway

• A gateway in TCP/IP is a doorway to other
  networks
• Usually an internal port of a router
• Can be a 2nd ethernet card on a dual homed system
• If multiple gateways are listed in the routing
  table, they will be queried in the order listed
• Default gateway defines where to send a packet
  if the network or node is not recognized

132
Subnetting

• Borrowing host bits of a IP network address
• More networks fewer hosts per network
• Reduce congestion
• Security

133
CIDR (Supernetting)

• Classless Interdomain Routing (classless IP)
• Response to the depleted supply of IPv4 addresses
• Borrow bits from the network portion of the
  address to allow for more hosts
• Used for networks that require more than 254
  hosts
• Network addresses must be contiguous or fall
  within the range of the subnet mask
• To combine class C the 3rd octet of the first
  address must be divisible by the range of
  addresses
• If public addressing must be contiguous range
• Network Address uses an IP prefix/CIDR block
• 192.168.16.0/20

134
TCP/IP Utilities

• Troubleshooting utilities that are part of the
  TCP/IP suite
• Tracert
• Ping
• IPconfig
• Nbtstat
• Route
• Netstat

135
IPX/SPX

• Developed by Xerox in early 1980s
• Default network protocol for Novell NetWare
  versions prior to 5.0
• Protocol provides transport services for data
  over the network
• IPX is connectionless protocol
• SPX is connection oriented protocol

136
NetBEUI

• IBM NetBIOS Enhanced User Interface (1985) for
  LAN Manager server application
• Default protocol for WNT3.51
• NetBEUI is a non routable protocol
• Operates mostly in the Data Link Layer
• Modeled after the LLC of the OSI
• Requires a bridge or switch to segment the
  network
• Fastest of all protocols currently in use
• Discontinued as of XP

137
AppleTalk Addressing

• Name Binding Protocol (NBP) dynamically assigns a
  unique node ID to each host and binds the NBP
  name to the ID
• Datagram Delivery Protocol (DDP) provides point
  to point delivery functions
• Uses a 16 bit network number
• DDP packet contains source and destination
  address, hop count and checksum
• Hop count over 16 is discarded
• Connectionless protocol

138
WAN Overview

• Most are combinations of LANS and communication
  components connected by WAN Links
• Packet-switching networks
• Fiber-optic cable
• Microwave transmitters
• Satellite links
• Cable television coaxial systems
• Usually leased from service provider due to cost
• Use the following transmission technologies
• Analog digital---packet-switching

139
Remote Access (WAN) Protocols

• Point to Point Protocol (PPP)
• Point to Point Tunneling Protocol (PPTP)
• Used on Virtual Private Network (VPN)
• Remote Desktop Protocol (RDP)
• Citrix Independent Computing Architecture
  protocol (ICA)

140
PPTP (tunneling for VPN)

• More secure connection
• Uses encryption keys Supports multiprotocol VPN
• Can connect via the internet to network
• Connect to the RAS server
• PPTP routes IP, IPX, or NetBEUI PPP protocol
  packets over TCP/IP network
• Uses encapsulation

141
Circuit Switching

• Used in telephone communication
• Established connection from point A to point B
  maintained for duration of the session
• Packets arrive in order
• Used by Public Switched Telephone Network (PSTN)
  (POTS)
• And Integrated Services Digital Network (ISDN)

142
Packet Switching Networks

• Switches direct packets over pathways.For short
  and long distance
• Fast efficient , reliable
• Internet is packet switching network
• Data handling
• Original data is segmented into packets
• Each packet is labeled with sequence and
  destination
• Each packet sent individually onto the network
• By fastest, shortest route
• Reconstructs data at destination end
• Does not depend on any single pathway
• Use Virtual circuits for temporary dedicated
  pathways
• Switched Virtual Circuit ppp established when
  needed
• Permanent Virtual Circuit established as
  permanent logical connection

143
T1

• Most widely used digital line type
• PPP 2 wire pairs
• Send and receive
• Full duplex rate of 1.544Mbps
• Transmits digital voice and data and video
• Most costly of WAN links
• Can subscribe to a channel in 64Kbps (fractional
  T-1)

144
CSU/DSU

• Channel service unit/data service unit
• Provides network interface for the T1 connection
  and your computer equipment
• CSU provides filtering of noise and intercepts
  loopback signals
• DSU provides synchronization and timing

145
Sonet/SDH

• Synchronous Optical Network and Synchronous Data
  Hierarchy are competing technologies
• SONET
• Physical Layer protocol uses fiber optics for
  transmission
• Can be configured in dual ring or bus topology
• 155Mbps-2.5Gbps transmission
• Deliver voice data and video
• Sonet uses Time Division Multiplexing to mix
  signals of different speeds into a single high
  speed transmission

146
SONET cont

• SONET networks are divided into 3 separate
  regions
• Local collector ring individual access
• Regional network collates signals into a single
  pipeline
• Broadband backbone moves data over the highspeed
  pipeline

147
VPN

• Uses the Internet for remote connection
• Uses PPTN protocol, encrypting data and securing
  the connection

148
RAID (tab 16.4)

• Redundant array of independent disks
• Levels
• Level 0 striping
• 64k blocks divided equally across disk no
  redundancy
• 2-32 drives
• Large logical disk
• Level 1 Disk Mirroring
• Two drives single controller
• Disk duplexing
• Two drives , two controllers
• Level 2 Striping with ecc
• Block is distributed across stripes
• Level 50 RAID1 and RAID5

149
Security in the NOS

• Security patches
• Security features
• Share level access
• User level access
• Authentication
• File system security
• Printer security
• Directory services
• IP Security
• Kerberos

150
Share level

• Owner is responsible for security
• Restrictions are set on the share (passwords are
  optional)
• Read only (read and copy)
• Full control ( anything including modify
  permissions and ownership)
• Change ( read edit delete)

151
User Level

• User ID and password are the key to the netwo