Transcript Slide 1

Goals
• Identify common media connectors
• Identify common network components
• Identify features of 802 project network
standards (hardware protocols)
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802.2 (LLC)
802.3 (CSMA/CD) *ethernet)
802.5 (token ring)
802.11 (wireless)
FIDDI
Terminology Common to all Networks
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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
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)
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
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Protocol independent
Extend collision domains
Segment networks using non-routing protocols
All broadcast data is passed
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
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
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Radio waves
Infrared Light pulses
Laser beams
Microwave
– Bounded
• Copper
• Fiber optic
Topologies
• Physical or logical layout of the network, (how the signal is
carried)
• 4 major topologies
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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)
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
Ring Network
• Connects computers on a single circle of
cable
• Foundation for token ring architecture and
FIDDI
• Logical rings interconnected by multistation 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
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!!!!
Hardware protocols
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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
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Defined in the 802 Project standards (combination of the physical topologies and
hardware protocols)
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802.2
802.3 CSMA/CD
802.4
802.5 Token Passing
802.11
802.12 Demand Priority
Methods to access the wire
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Contention or Probabilistic
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CSMA/CD and CSMA/CA
Deterministic or Token Passing
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Token Ring
FIDDI
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
Packet
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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
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Common packet components ( * common to all protocol packets) include:
– Header
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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 check—mathematical calculation performed on the packet at the
source and again at the destination)
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
Features of peer to peer network
– No dedicated server
– Share level security
– no central administration
• When to use
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Security is not an issue,
10 or less computers
Simple to configure, low cost
Expansion is not an issue
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
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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)
Trust Relationships
• One-way explicit trusts
(Windows NT)
• Two-way transitive trusts
(Windows 2000)
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
Components of Directory Service
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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
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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
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Distinguished name – objects name along with the completer context
starting from root.
– .psprinter.accounting.microsoft.us.
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
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
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
Digital signal
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Digital is an on off state
positive voltage = 1
no voltage = 0
1’s and 0’s are used to encode data
– Pulse = bit
– 8 bits = byte
– One byte carries one piece of information
• Most data transmission is digital
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
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
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
• 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
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• 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
• Uses analog techniques to
encode
• Continuous electrical or optic
waves
• Multiple channels on a single
cable
• Amplifiers are used to:
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Broadband
Transmission(cont.)
• 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
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
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
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)
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
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
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
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
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
function’s layer and focusing on the protocols
and devices responsible
– Allows development of new technologies
without restructuring the entire network
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
802.2
802.3
802.4
802.5
802.6
802.7
802.8
802.9
802.10
802.11
802.12
802.13
802.14
802.15
802.16
Internetworking
Logical Link Control (LLC)
MAC layer, Carrier Sense Multiple Access with Collision Detection
(CSMA/CD) LAN (Ethernet)
MAC layer, Token Bus LAN
MAC layer, Token Ring LAN
Metropolitan area Network (MAN)
Broadband Technical Advisory Group
Fiber-Optic Technical Advisory Group
Integrated Voice/Data Networks
Network Security
Wireless Network
Demand Priority Access LAN, 100BaseVG-AnyLAN
Unused
Cable modem standards
Wireless personal area networks (WPAN)
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
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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 Bits and
, cables,
voltages
NICs, hubs,
repeaters
Three Components of the Physical
Layer
• Physical Signaling (PLS)
• Physical Medium Attachment (PMA)
• Medium Dependent Interface (MDI)
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
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
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
Unbounded Signaling
• Optical
– Infrared
– laser
• Radio
• Microwave
Optical
• Infrared
• Works like fiber light pulses
– Line of sight
– Scatter infrared
– Reflective
– Broadband optical telepoint
• Laser
– Requires line of sight
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
Functions of the Data Link Layer
(Layer 2)
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Physical Addressing
Network Topology
Error Notification
Access to the physical media
Flow Control
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
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
• 00:60:B6:A1:78:17
– 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
Network Topologies—physical
or logical layout of the network
• Bus
• Ring
• Star
• Mesh
• Hybrid
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
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
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
Baseband signaling
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Used by most LAN technologies
Digital communication
Full bandwidth
Bi-directional
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
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802.3 – Ethernet (CSMA/CD)
802.12 – Demand Priority Access
802.11 – CSMA/CA
802.5 – Token Ring
• FDDI (ANSI X3T9.1 standard)
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
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
•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
•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)
5-4-3 rule
– Max 5 segments
– 4 repeaters
– 3 populated segments
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10BASE-F
•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
•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
• 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
•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
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
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
Error Detection
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Lost Frames
Checksum or CRC
Frame Size
Buffer Overflow
Interference
Data Link notifies Transport Layer. Error
correction is done in the Transport layer.
Network Layer
• Allows internetworking-- Services of the
network layer allow different networks to
find each other
• Services may be used by LAN’s but
WAN’s cannot exist without them
• Supports both connection-oriented and
connectionless service from upper layer
protocols
• Protocols are typically routing protocols
Routable Protocols
• Protocols that support multipath LAN to
LAN communication
• TCP/IP
• IPX/SPX
Non-routable
• Work only in local LAN
• Use physical addressing
Connection-Oriented Protocols
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Connection is established
Data is sent in orderly,slower fashion
Packet receipt is acknowledged
Resends error packets
Connection is terminated
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
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
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
IP
• Provides source and destination
addressing and routing
• Connectionless datagram protocol –
assumes other protocols will ensure
reliable delivery
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 (240255)
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 multihomed device (router)
– Maintains a table of all known networks
– Forwards the packet via the port connected
to the network of the destination IP
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 0=hosts
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
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
Link State
• Monitor condition of each
connected link
• Advertise conditions to
neighboring routers
–Link speed
–Latency
–Status of routers on the network
• OSPF protocol
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
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
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
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
6
Transport Protocols
•Ensure reliable data delivery
•TCP (Transmission Control Protocol)
•SPX (Sequenced Packet eXchange)
– Novell’s connection-oriented protocol
•NWLink (MS implementation of SPX)
•NetBEUI-MS standard transport layer
non-routable (NetBEUI/NetBIOS)
6
Connectionless Protocols
•Place the data on the network and assume
it will arrive
•Faster, doesn’t 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
6
Connection-Oriented Protocols
•Connection is established
•Data sent in orderly, slower fashion
•Packet receipt is acknowledged
•Resends error packets
•Connection is terminated
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
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
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
Error Control
• Types of error
– Packet loss
– Packet corruption
– Packet duplication
DNS (Domain Name System)
– Transport layer, name-to-address
resolution protocol
– DNS server keeps a list of system’s
names and their IP addresses.
• Can use a system’s logical name
(microsoft.com) rather than its numerical
address when communicating
• 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.
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
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.
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
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
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),
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
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
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 transfer
Data base access
E-mail
• Window for application to access network services
Hardware
• Gateway
TCP/IP Protocol Stack
•
•
•
•
•
4 layers
Process/Application
Host to Host
Internet
Network Access
app/pres/sess
transport
network
datalink/physical
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
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
Subnet Mask
• Used to denote which part of the address
Is the network and which is the node
• 1 masks the network
6
IP Addressing (Ver. 4)
•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
•(254*254*254 hosts)
– Class B 128-191 64,512 hosts
•(254*254 hosts)
– Class C 192-223
•254 hosts per network
Fully Qualified Domain Name
• Unique computer name within a DNS
namespace
– Example—sales.www.emcp.com
• Read from left to right
• More specific information is on the left
Network layer protocols of
TCP/IP suite
– IP
– BootP
– DHCP
– ICMP
– ARP
– RARP
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
•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
–
•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
WINS
NETBIOS to IP
Requires WINS server
WINS database is dynamic–
system broadcasts when it boots to the
network
Server extracts information
Hosts and LMHosts
Statically resolve IP addresses
Hosts
DNS to IP
LMHosts
NETBIOS to IP
6
TCP/IP Protocol Suite
•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.
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
requestor’s ISN, plus 1
• The requester replies with the server’s ISN, plus 1
12
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
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
Subnetting
• Borrowing host bits of a IP network
address
– More networks fewer hosts per network
• Reduce congestion
• Security
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
TCP/IP Utilities
• Troubleshooting utilities that are part of the
TCP/IP suite
– Tracert
– Ping
– IPconfig
– Nbtstat
– Route
– Netstat
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
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
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
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
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)
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
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)
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
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)
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
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
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
VPN
• Uses the Internet for remote connection
• Uses PPTN protocol, encrypting data and
securing the connection
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
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
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)
User Level
– User ID and password are the key to the network resources
(Credentials)
• Association of permissions and rights are through the Security
Identification (SID) number in Windows
– Kept in the Security Accounts Management database (SAM)
• Novell the user is an object and permissions are properties of that
object
– Directory Services tracks UID and GID against the object properties
– Credentials are checked each time a resource is accessed
Building Barriers
• Firewalls
– Circuit gateway– session layer of OSI
– directs all traffic to the gateway IP port
– Substitutes sending machines IP address with
gateway address
– Intercepts incoming traffic, filters and passes it
on
– Application gateway– control traffic primarily
by opening and closing ports
Firewalls continued
• Direct traffic via:
– Packet filtering
– Stateful inspection
– Proxy service
Proxy service
• Similar to proxy servers
• Intercepts packets from the outside and
forwards to host
• Replaces outgoing IP address with
gateway (circuit gateway)
SSL and TLS
• Secure Socket Layer (SSL) Connection security
protocol that provides secured point to point
connection between 2 devices
– SSL Handshake protocol--Requires secure
connection and credential exchange (encryption and
key exchange)
– SSL Record Protocol– encapsulates network data
and allows encryption and transmission
• Transport Layer Security (TLS) – recent
implementation of SSL focuses on transport
layer