Ch. 9 : Network Organization Concepts

1
Ch. 9 Network Organization Concepts

• Basic Terminology
• Network Topologies
• Network Types
• Software Design Issues
• Circuit Switching
• Packet Switching
• Access Control Techniques
• Medium Access Control Procedures
• Transport Protocol Standards

• Hardware Software
• Connections Design
• Many Network Designs
• Transport Protocol Standards

2
Networks

• When computer facilities are connected together
  by data-communication components, form network of
  automated resources.
• Support many functions of business, education,
  healthcare, government, other organizations.
• Provide essential infrastructure to process,
  manipulate, and distribute data information.
• Common goal to provide a convenient way to share
  resources while controlling users access to
  them.
• Resources include hardware (CPU, memory,
  printers, modems, disk drives) and software
  (application programs, data files).

3
General Configurations for Operating Systems for
Networks

• Network operating system -- networking capability
  added to single-user operating system.
• Users aware of specific computers and resources
  in the network.
• Access via logon to/data transfer from remote
  host.
• Distributed operating system -- users can access
  remote resources as if local resources.
• Good control for distributed computing systems.
• Represents total view across multiple computer
  systems for controlling managing resources
  without local dependencies.
• Management is cooperative -- encompasses every
  resource involves every site.

4
Distributed Operating System

• At minimum, must provide
• Process or object management.
• Memory management.
• I/O management.
• Device management.
• Network management.
• Easy and reliable resource sharing.
• Improved computation performance.
• Adequate load balancing.
• Good reliability.
• Dependable communications among network users.

5
Basic Terminology Network Processors

• Network -- collection of loosely coupled
  processors, interconnected by communication
  network.
• In distributed system each processor classifies
  other processors resources as remote and
  considers its own resources local.
• Size, type, and identification of processors
  varies. Depending on context in which theyre
  mentioned, referred to as
• Site -- indicates specific location in network
  with 1 computers.
• Host -- specific computer system found at site
  whose services resources can be used from
  remote locations.
• Node -- name assigned computer system connected
  to network to identify it to other computers in
  network..

6
Basic Terminology Client/Server

• Host at one site (server) has resources that host
  at another site (client) wants to use.
• Assignments arent static.
• Actual role of client and server can alternate
  between 2 networked hosts depending on
  application and network configuration.

7
Network Topologies

• Sites in any networked system can be physically
  or logically connected to one another in variety
  of topologies.
• Most common geometric arrangements star, ring,
  bus, tree, hybrid.
• Tradeoffs between need for fast communication
  among all sites, tolerance of failure at site or
  communication link, cost of long communication
  lines, and difficulty of connecting a site to
  large number of other sites.
• Key to choosing best design is to understand
  available technology customers business
  requirements budget.

8
Criteria for Selection of a Topology

• Basic costexpense required to link various sites
  in system.
• Communications costtime required to send a
  message from one site to another.
• Reliabilityassurance that many sites can
  communicate with each other even if link or site
  in system fails.
• Users environmentcritical parameters that
  network must meet to be a successful business
  investment.

9
Star Topology (Hub, Centralized Topology)

• All transmitted data must pass through central
  controller when going from sender to receiver.
• Easy routing since central station knows path to
  all other sites.
• Easily controlled access to network due to
  central control point.
• Priority status given to selected sites.
• Centralization of control requires that central
  site be extremely reliable able to handle all
  network traffic.

10
Ring Topology

• All sites connected in closed loop.
• Data transmitted in packets with source
  destination addresses.
• Each packet is passed in one direction only.
• Destination station copies data into local
  buffer.
• Packet continues to circulate until it returns to
  source station, where its removed from ring.
• Every node must be functional for network to
  perform.
• Rings can allow failed nodes to be bypassed.

11
Double loop computer network using ring topology.
Packets of data flow in both directions. Network
can be connected to other networks via bridge or
gateway.
12
Multi-rings bridged together. Three rings
connected to each other by two bridges. This
variation of ring topology allows several
networks with same protocol to be linked
together.
13
Bus Topology

• All sites are connected to single communication
  line running length of network.
• Hosts are connected to one another in a linear
  fashion.
• Data flows in both directions from host to host
  and is turned around when it reaches an end point
  controller.
• All sites share a common communication line, so
  only one of them can successfully send messages
  at any one time .

14
Control Mechanism Is Needed to Prevent Collisions
in Bus Topology

• Data may pass directly from one device to
  another.
• Messages sent directly to target node without
  reaching end point controller.
• Data may be routed to end point controller at end
  of line.
• If data reaches end point controller without
  being accepted by host, controller turns it
  around sends it back so message can be accepted
  by appropriate node on way back.
• With some busses each message must always go to
  end of line before going back down communication
  line to node to which its addressed.

15
Tree Topology
Data flows up and down branches of trees and is
absorbed by controllers at end points.
16
Tree Topology

• A collection of busses.
• Communication line is branching cable with no
  closed loops.
• Tree layout begins at head end, where 1 cables
  start.
• Each cable may have branches with additional
  branches.
• Can use bridges between busses with same protocol
  and as translators to busses with different
  protocols
• Networks can operate at speeds responsive to
  hosts in network.

17
Messages in Tree Topologies

• Message from any site circulates through
  communication line.
• Can be received by all other sites.
• If message reaches end point controller without
  being accepted by host, controller absorbs it.
• One advantage of bus and tree topologies is that
  even if single node fails, message traffic can
  still flow through network.

18
Hybrid Topology

• Some combination of any of 4 topologies.
• E.g., replace single host in star with ring
  (shown below).
• E.g., star with bus topology as communication
  line feeding hub.
• Select strong points of each topology combine
  to effectively meet systems communications
  requirements.

19
Network Types

• Useful to group networks according to physical
  distances they cover.
• Defining characteristics becoming increasingly
  blurred as communications technology advances.
• Generally divided into
• Local area networks (LAN).
• Metropolitan area networks (MAN).
• Wide area networks (WAN).

20
Local Area Network (LAN)

• Configuration found within office building,
  warehouse, campus, or similarly enclosed
  computing environment.
• E.g., cluster of personal computers located in
  same general area.
• Usually owned, used, and operated by single
  organization.
• Allows computers to communicate directly through
  common communication line.
• Physically confined to well-defined local area,
  but communications arent limited to that area.
• LAN can be a component of larger communication
  network.
• Provide easy access to outside through bridge or
  gateway.

21
Bridges and Gateways

• Bridge device and software that connects 2
  geographically distant LANs with same protocols.
• E.g., simple bridge used to connect 2 Ethernet
  LANs.
• Gateway more complex device and software used
  to connect 2 LANs or systems that use different
  protocols.
• Translate 1 networks protocol into another,
  resolving hardware and software
  incompatibilities.
• E.g., systems network architecture (SNA) gateway
  can connect microcomputer network to mainframe
  host.

22
Data Rates and Media for LANs

• Data rate of high-speed LANs varies from 100 mbps
  to 1 gbps.
• Bandwidths can support very high-speed
  transmission for fully animated, full-color
  graphics video, digital voice transmission,
  other high data-rate analog or digital signals.
• Star, ring, bus, tree, hybrid topologies
  construct LANs.
• Transmission medium vary among topologies.
• Baseband coaxial cable and optical fiber are
  common to all.

23
Factors to Consider When Selecting Transmission
Medium

• Cost.
• Data rate.
• Reliability.
• Number of devices that can be supported.
• Distance between units.
• Technical limitations.

24
Metropolitan Area Network (MAN)

• Configuration spanning area larger than LAN.
• Ranges from several blocks of buildings to entire
  city but not exceeding circumference of 100
  kilometers.
• Owned operated by a single organization.
• Usually used by many individuals organizations.
  
• May be owned operated as public utilities,
  providing means for internetworking several LANs.
  
• High-speed network.

25
MAN Typically Configured As a Logical Ring

• Depending on protocol used, messages are either
• Transmitted in 1 direction using only 1 ring.
• Transmitted in both directions using 2
  counter-rotating rings,
• One always carrying messages in one direction and
  other always carrying messages in opposite
  direction.

26
Wide Area Network (WAN)

• Configuration that interconnects communication
  facilities in different parts of a country or
  world, or thats operated as part of public
  utility.
• Uses communications lines of common carriers
  (government-regulated private companies such as
  telephone companies).
• Uses broad range of communication media (e.g.,
  satellite, microwaves).
• WANs are generally slower than LANs.

27
ARPAnet

• First WAN developed by Advanced Research Projects
  Agency (ARPA) in 1969.
• Defense Communications Agency in 1975.
• Successor, Internet, is most widely recognized
  WAN.
• Other commercial WANs exist (e.g Telenet).

28
Software Design Issues

• How do sites use addresses to locate other sites?
• How are messages routed and how are they sent?
• How do processes communicate with each other?
• How are conflicting demands for resources
  resolved?

29
Addressing Conventions

• Network sites need to uniquely identify users so
  can communicate access each others resources.
• Names, addresses, routes required because sites
  arent directly connected except over
  point-to-point links.
• Addressing protocols are closely related to
  network topology geographic location of each
  site.
• Local name -- name by which a unit is known
  within its own system.
• Global name -- name by which a unit is known
  outside its own system.

30
Domain Name Service (DNS) Protocol

• Distributed data query service used to resolve
  Internet addresses.
• Follows hierarchical organization (left to
  right) from logical user to host machine, from
  host machine to net machine, from net machine to
  cluster, and from cluster to network.
• someone_at_icarus.lis.pitt.edu
• someone logical user
• icarus host for user called someone
• lis net machine for icarus
• pitt cluster for lis
• edu network for University of Pittsburgh.  

31
Router

• Router -- internetworking device, primarily
  software driven, which directs traffic between 2
  different types of LANs or 2 network segments
  with different protocol addresses.
• Operates at Network Layer.
• Role of routers changes as network designs
  change.
• Used extensively for connecting sites to each
  other to Internet.
• Used for a variety of functions including
• Securing info generated in predefined areas.
• Choosing the fastest route from 1 point to
  another.
• Providing redundant network connections.

32
Routing Strategy

• Routing protocols must consider
• Addressing.
• Address resolution.
• Message format.
• Error reporting.
• Two of most widely used routing protocols in
  Internet
• Routing information protocol.
• Open shortest path first.

33
Routing Protocols

• Most routing protocols are based on addressing
  format using network node number to identify
  each node.
• When network is powered on, each router records
  addresses of networks that are directly
  connected.
• At specified intervals each router in
  inter-network broadcasts copy of its entire
  routing table.
• Eventually all routers know how to get to each of
  different destination networks.

34
Address Resolution

• Addresses allow routers to send data from network
  to network .
• Cant be used to get from one point in network to
  another point in same network.
• Address resolution allows router to map original
  address to hardware address store mapping in
  table used for future transmissions.

35
Message Formats Defined by Routing Protocols

• Messages allow protocol to perform its functions.
• Finding new nodes on a network.
• Testing to determine whether theyre working.
• Reporting error conditions.
• Exchanging routing information.
• Establishing connections.
• Transmitting data.

36
Problems with Data Transmission

• Conditions may arise that cause errors such as
  inability to reach destination due to
  malfunctioning node or network.
• Routers routing protocols report error
  condition.
• Error correction is left to protocols at other
  levels of networks architecture.

37
Routing Information Protocol (RIP)

• Path selection for transfer data between networks
  is based on number of intermediate nodes (hops)
  between source destination.
• Path with smallest number of hops is always
  chosen.
• Distance vector algorithm that is easy to
  implement.
• Doesnt consider bandwidth, data priority, or
  type of network.
• Can exclude faster or more reliable paths from
  being selected just because they have more hops.

38
More Problems with RIP

• Another limitation relates to routing tables.
• Entire table updated reissued every 30 seconds,
  whether or not changes have occurred.
• Increases internetwork traffic negatively
  affects delivery of messages.
• Tables propagate from one router to another.
• Because not all routers have same info about
  internetwork, failure at any one hop can create
  unstable environment for all message traffic.

39
Open Shortest Path First (OSPF)

• Selection of transmission path made after state
  of network determined.
• If intermediate hop is malfunctioning its
  eliminated immediately from consideration until
  its services have been restored.
• Routing update messages sent only when changes in
  routing environment occur.
• Reduces number of messages in internetwork.
• Reduces size of messages by not sending entire
  routing table.

40
Problems with OSPF

• Memory usage is increased because OSPF tracks
  more info than RIP.
• Savings in bandwidth consumption are offset by
  higher CPU usage needed for calculation of the
  shortest path.
• Dijkstras algorithmfind shortest paths from
  given source to all other destinations by
  proceeding in stages developing path in
  increasing lengths.
• Computes all different paths to each destination
  in internetwork.
• Creates topological database that is maintained
  by OSPF and is updated whenever failures occur.

41
Connection Models

• Communication network concerned with moving data
  from one point to another.
• Nodes are connected to communication network
  designed to minimize transmission costs provide
  full connectivity among all attached devices.
• Data entering network at one point is routed to
  destination by being switched from node to node.
• Circuit switching.
• Packet switching.

42
Circuit Switching

• Communication model in which dedicated
  communication path is established between two
  hosts.
• Path is connected sequence of links connection
  between 2 points exists until one of them is
  disconnected.
• E.g., Telephone system
• Connection path must be set up before data
  transmission begin.
• If entire path becomes unavailable, messages
  cant be transmitted because circuit would not be
  complete.
• Delay before signal transfer begins while
  connection is set up.
• Once circuit completed, network is transparent to
  users.
• Info transmitted at fixed rate of speed with
  insignificant delays at intermediate nodes.

43
Packet Switching

• Store-and-forward technique.
• Message divided into multiple equal-sized units
  (packets).
• Packets sent through network to their
  destination.
• Reassembled into their original long format.
• Does not require a dedicated connection.

44
Packet Switching Is a 3-step Procedure

• Divide data into addressed packets.
• Send each packet toward its destination.
• At destination, confirm receipt of all packets,
  place them in order, reassemble data, and deliver
  it to recipient.

45
Pros Cons of Packet Switching

• Effective for long-distance data transmission.
• More flexible than circuit switching -- data
  transmission between devices that
  receive/transmit data at different rates.
• No guarantee that packets all travel along same
  path or arrive in physical sequential order.
• Packets from one message may be interspersed with
  those from other messages as travel toward
  destinations.
• Attach header with pertinent info about packet
  before it's transmitted.
• Info varies according to routing method used by
  network.

46
Packet Switching vs. Circuit Switching
47
Method of Selecting Path Datagrams

• Destination sequence number of packet added to
  info uniquely identifying message to which packet
  belongs.
• Each packet handled independently route is
  selected as each packet is accepted into network.
• At destination, all packets of same message
  reassembled by sequence number into continuous
  message delivered.
• Message cant be delivered until all packets
  accounted for.
• Receiving node requests retransmission of lost or
  damaged packets.

48
Advantages of Datagram Routing

• Helps diminish congestion by sending incoming
  packets through less heavily used paths.
• Provides more reliability, because alternate
  paths may be set up when one node fails.

49
Method of Selecting Path Virtual Circuit
Approach

• Complete path from sender to receiver established
  before transmission starts.
• All packets belonging to that message use same
  route.
• Destination packet sequence number arent
  necessary.
• Different from dedicated path used in circuit
  switching because any node can have several
  virtual circuits to any other node.
• Routing decision made once for all packets
  belonging to same message.
• If node fails, all virtual circuits using that
  node become unavailable.
• When circuit experiences heavy traffic,
  congestion is more difficult to resolve.

50
Conflict Resolution

• Some method to control access is necessary to
  facilitate equal and fair access to network
• Round robin.
• Reservation. Access control techniques
• Contention.
• Carrier sense multiple access.
• Token passing. Medium access
• Distributed-queue. control protocols
• Dual bus.

51
Access Control Techniques Round Robin

• Allows each node on network to use communication
  medium.
• If node has data to send, its given certain
  amount of time to complete transmission, at end
  of which opportunity is passed to next node.
• If node has no data to send or completes
  transmission before time is up, then next node
  begins its turn.
• Efficient technique with many nodes transmitting
  over long periods.
• When few nodes transmit over long periods of
  time, substantial overhead to pass turns from
  node to node.
• Other techniques preferable depending on whether
  transmissions are short intermittent (e.g.,
  interactive terminal-host sessions), or lengthy
  continuous (e.g., massive file transfer
  sessions).

52
Access Control Techniques Reservation

• Well suited for lengthy continuous traffic.
• Access time on medium is divided into slots
  node can reserve future time slots for its use.
• Similar to synchronous time-division multiplexing
  (used for multiplexing digitized voice streams)
  where time slots are fixed in length
  preassigned to each node.
• Good for configuration with several terminals
  connected to host computer through single I/O
  port.

53
Access Control Techniques Contention

• Better for short and intermittent traffic.
• No attempt is made to determine whose turn it is
  to transmit so nodes compete for access to
  medium.
• Works well under light to moderate traffic.
• Performance tends to break down under heavy
  loads.
• Major advantage -- easy to implement.

54
Medium Access Control Procedures Carrier Sense
Multiple Access (CSMA)

• Contention-based protocol thats easy to
  implement.
• Network node listens to (tests) communication
  medium before transmitting any messages.
• Prevents collision with another node thats
  currently transmitting.
• Multiple access -- several nodes connected to
  same communication line as peers, on same level,
  and with equal privileges.

55
Collisions In CSMA

• 2 nodes could transmit at same instant,
  creating collision.
• Data from all transmissions damaged line
  remains unusable while damaged messages are
  dissipated.
• When receiving nodes fail to acknowledge
  transmission, senders know it didnt reach
  destinations.
• Both retransmit.
• Probability of collisions increases if nodes
  farther apart.
• CSMA less appealing access protocol for large or
  complex networks.

56
Carrier Sense Multiple Access With Collision
Detection (CSMA/CD).

• CSMA algorithm was modified to include collision
  detection.
• E.g., Ethernet.
• Collision detection does not eliminate collisions
  but it does reduce them.
• When collision occurs, jamming signal sent
  immediately to both senders, which wait random
  period before retrying.
• With this protocol amount of wasted transmission
  capacity is reduced to time it takes to detect
  collision.

57
Collision Avoidance (CSMA/CA).

• Collision avoidance -- access method prevents
  multiple nodes from colliding during
  transmission.
• Efficiency is questionable.
• Implemented in LocalTalk, Apples cabling system,
  which uses a protocol called LocalTalk link
  access protocol.
• If collisions occur, involve only 3-byte packets,
  not actual data.
• Protocol does not guarantee data will reach its
  destination, but it ensures that any data thats
  delivered will be error free.

58
Token-Passing Networks

• Special electronic message (token) is generated
  when network is turned on and passed along from
  node to node.
• Only node with the token allowed to transmit, and
  after it has done so, it must pass token on to
  another node.
• Popular because access is fast and collisions are
  nonexistent.
• Typical topologies bus or ring.

59
Token-Bus Network

• Token is passed to each node in turn.
• Upon receipt of token, node attaches data to it
  and sends packet with token data to its
  destination.
• Receiving node copies data, adds acknowledgment,
  returns packet to sending node.
• Sending node passes token on to next node in
  logical sequence.
• Initial node order determined by cooperative
  decentralized algorithm.
• Once network is running, turns determined by
  priority based on node activity.
• Higher overhead at each node than CSMA/CD.
• Nodes may have long waits under certain
  conditions before receiving token.

60
Token Ring

• Most widely used protocol for ring topology.
• Based on use of free/busy token that moves
  between nodes in turn one direction only.
• If node wants to send message,waits free token
  to come by.
• Changes token from free to busy sends its
  message immediately following busy token.
• All other nodes must wait for free token to come
  to them again.
• Receiving node copies message in packet sets
  copied bit to indicate it was successfully
  received.
• Packet continues, making complete round trip back
  to sender.
• Sending node releases new free token on network..

61
Distributed-Queue, Dual Bus (DQDB) Protocol

• Intended for use with dual-bus configuration.
• Where each bus transports data in only one
  direction.
• Standardized by IEEE as part of MAN standards.
• Transmission on each bus consists of steady
  stream of fixed-size slots.
• Slots generated at end of each bus marked free
  sent downstream, where theyre marked busy
  written to by nodes ready to transmit.
• Nodes read and copy data from slots, which then
  continue to travel toward end of bus, where they
  dissipate.

62
Transport Protocol Standards

• Network usage quickly grew in 1980s along with
  need to integrate dissimilar network devices from
  different vendors.
• Increasingly difficult as number complexity of
  network devices increased.
• Users pressured industry to create single
  universally adopted network architecture for true
  multi-vendor interoperability.
• Two competing standards
• OSI.
• TCP/IP.

63
Open Systems Interconnection (OSI) Reference
Model from ISO

• International Standards Organization (ISO)
  created open systems interconnection reference
  model.
• Serves as framework for defining services that
  network should provide to its users.
• Provides basis for connecting open systems for
  distributed applications processing.
• Open means that any 2 systems that conform to
  reference model related standards can be
  connected, regardless of vendor.

64
OSI Layers and Protocols

• Similar functions collected together into 7
  logical clusters (layers).
• Group easily localized functions so each layer
  could be redesigned its protocols changed
  without changing services expected from/provided
  to, adjacent layers.
• Boundaries between layers were selected at points
  that past experience had revealed to be
  effective.
• Software handles data transmission from one
  terminal or application program to another.

65
Layer 1The Physical Layer

• Bottom of model where mechanical, electrical,
  functional specifications for connecting device
  to particular network described.
• Primarily concerned with transmitting bits over
  communication lines.
• Voltages of electricity timing factors
  important.
• Only layer concerned with hardware.
• All data must be passed down to it for actual
  data transfer between units to occur.
• E.g., 10Base-T, RS449, and CCITT V.35.

66
Layer 2The Data Link Layer

• Software is needed to implement Layer 2 is
  stored in some type of programmable device (e.g.,
  front end processor, network node).
• Bridging between 2 homogeneous networks occurs
  here.
• On one side, DLL establishes controls physical
  path of communications before sending data to
  physical layer below it.
• Takes data packets assembles it for
  transmission by completing its frame.
• Frames contain data combined with control error
  detection characters.
• On other side, DLL checks for transmission errors
  resolves problems caused by damaged, lost, or
  duplicate message frames.
• E.g., High-Level Data Link Control (HDLC) and
  Synchronous Data Link Control (SDLC).

67
Layer 3The Network Layer

• Provides services such as addressing routing
  that move data through network to its
  destination.
• Software at this level accepts blocks of data
  from Layer 4, resizes them into shorter packets,
  routes them to proper destination.
• Addressing methods that allow a node and its
  network to be identified, algorithms to handle
  address resolution are specified here.
• Database of routing tables keeps track of all
  possible routes a packet may take determines
  how many different circuits exist between any 2
  packet switching nodes.

68
Layer 4The Transport Layer

• Host-to-host or end-to-end layer -- maintains
  reliable data transmission between end users.
• Program at source computer can send virtual
  communication to similar program at destination
  via message headers control messages.
• Physical path goes to Layer 1 across to
  destination computer.
• Software handles user addressing ensures that
  all packets of data received none lost.
• Stored in front end processors, packet switching
  nodes, or host computers.
• Has mechanism to regulate info flow so fast host
  cant overrun slower terminal or overloaded host.
  
• E.g., Transmission Control Protocol (TCP).

69

• Layer 5The Session Layer
• Layer 5 is responsible for providing a
  user-oriented connection service and transferring
  data over the communication lines. The transport
  layer is responsible for creating and maintaining
  a logical connection between end points. The
  session layer provides a user interface that adds
  value to the transport layer in the form of
  dialogue management and error recovery. Sometimes
  the session layer is known as the data flow
  control layer because it establishes the
  connection between two applications or processes,
  enforces the regulations for carrying on the
  session, controls the flow of data, and resets
  the connection if it fails. This layer may also
  perform some accounting functions to ensure that
  users receive their bills. The functions of the
  transport layer and session layer are very
  similar, and because the operating system of the
  host computer generally handles the session
  layer, it would be natural to combine both layers
  into one, as does TCP/IP.

70
Layer 6The Presentation Layer

• Responsible for data manipulation functions
  common to many applications.
• E.g., formatting, compression, encryption, data
  conversion, syntax conversion, protocol
  conversion.
• Gateways connecting networks with different
  protocols are presentation layer devices.
• Accommodate totally different interfaces as seen
  by terminal in one node expected by application
  program at host computer.
• E.g., IBM's Customer Information Control System
  (CICS) teleprocessing monitor is presentation
  layer service located in host mainframe.

71
Layer 7The Application Layer

• Application program's, terminals, and computers
  access network.
• Provides interface to users
• Responsible for formatting user data before
  passing it to lower layers for transmission to a
  remote host.
• Contains network management functions tools to
  support distributed applications.
• E.g., File transfer and electronic mail.
• Once OSI model is assembled, it allows nodes to
  communicate with each other.
• Each layer provides completely different array of
  functions to network.
• All layers work in unison to ensure that network
  provides reliable transparent service to users.

72
Transmission Control Protocol/ Internet Protocol
(TCP/IP)

• Oldest transport protocol standard.
• Basis for Internet communications..
• Developed for U.S. Department of Defenses
  ARPAnet.
• Provides reasonably efficient error-free
  transmission between different systems.
• Large info files can be sent across sometimes
  unreliable networks with high probability that
  data will arrive error free.
• TCP/IP emphasizes internetworking and providing
  connectionless services.

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TCP/IP

• Organizes a communication system with 3 main
  components
• Processes
• Hosts.
• Networks.
• Processes execute on hosts, which can support
  multiple simultaneous processes that are defined
  as primary units that need to communicate.
• Processes communicate across networks where hosts
  connected.
• Based on hierarchy, model roughly partitioned
  into 2 major tasks
• Manages transfer of info to host in which process
  resides.
• Ensures it gets to correct process within host.
• Network needs to be concerned only with routing
  data between hosts, as long as hosts can then
  direct data to appropriate processes.

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Network Access Layer

• Equivalent to physical, data link, and part of
  network layers of OSI model.
• Protocols at this layer provide access to
  communication network.
• Some functions performed here
• Flow control.
• Error control between hosts.
• Security.
• Priority implementation.

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Internet Layer

• Equivalent to portion of network layer of OSI
  model that isnt already included in previous
  layer.
• Specifically mechanism that performs routing
  functions.
• Protocol is usually implemented within gateways
  hosts.
• Example of a standard set by DoD is Internet
  Protocol (IP).
• Provides connectionless service for end systems
  to communicate across 1 networks.

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Host-Host Layer

• Equivalent to transport and session layers of the
  OSI model.
• Supports mechanisms to transfer data between 2
  processes on different host computers.
• Services provided include
• Error checking.
• Flow control.
• Ability to manipulate connection control signals.
  
• Example of a standard set by DoD is Transmission
  Control Protocol (TCP).
• Provides a reliable end-to-end data transfer
  service.

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Process/Application Layer

• Equivalent to presentation application layers
  of OSI model.
• Protocols for computer-to-computer resource
  sharing terminal-to-computer remote access.
• Specific examples of standards set by the DoD
• File Transfer Protocol (FTP)-- simple application
  for transfer of ASCII, EBCDIC, binary files.
• Simple Mail Transfer Protocol (SMTP) -- simple
  electronic mail facility.
• TELNET -- simple asynchronous terminal capability
  that provides remote log-on capabilities to users
  working at terminal or PC.

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Terminology

• ARPAnet
• bridge
• bus topology
• distance vector algorithm
• distributed operating system (DOS)
• Domain Name Service (DNS)
• Ethernet
• gateway
• hosts
• hybrid topology
• Internet

• ISO
• local
• local area network (LAN)
• metropolitan area network (MAN)
• network operating system (NOS)
• nodes
• open shortest path first (OSPF)
• OSI reference model
• packets
• protocol

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Terminology -2

• remote
• ring topology
• router
• routing information protocol (RIP)
• sites
• star topology
• TCP/IP model
• token ring
• token-bus

• topological database
• tree topology
• wide area network (WAN)