Chapter 1 Introduction to Computers and C Programming

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CS 56

• Networking Essentials

Chapter 6 Defining Network Protocols
Sonny Huang
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Chapter 6 Defining Network Protocols

• Outline
• Introduction to Protocols
• TCP/IP
• NetWare Protocols
• Other Common Protocols

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Introduction to Protocols

• Function of Protocols
• A. Protocols are rules and technical procedures
  governing network communication and interaction.
• 1. Many different protocols for different
  functions.
• 2. Work at various OSI layers.
• 3. Can work together in a protocol stack or
  suite.
• B. How Protocols Work.
• 1. Data transmission is a step-by-step process.
• 2. Each step has its own protocol, or rules it
  is important that every computer plays by the
  rules at each step of the OSI layer.

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Introduction to Protocols

• 3. Sending computers protocol breaks data into
  packets that the protocol can handle, adds
  addressing information, and prepares and sends
  data out onto the network cable.
• 4. Receiving computer must use same protocol to
  take packet off the cable, bring data packets
  into computer through the NIC, strip off the
  transmission data, copy data to buffers, rebuild
  the packets into data, and pass data to
  application.
• 5. Both computers must process packets following
  exactly the same procedures.

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Introduction to Protocols

• C. Routable Protocols.
• 1. Data sent from one LAN to another along any
  of several available paths is said to be routed.
• 2. Protocols that support multipath LAN-to-LAN
  communications are known as routable protocols.
• 3. Routable protocols can be used to tie several
  LANs together and create new wide-area
  environment.
•  
• A routable protocol is needed to allow data to
  travel between networks. Nonroutable protocols
  can work only on a single network. TCP/IP
  protocol is a suite or stack. TCP performs
  one function, IP another, and the other
  components of the suite have their own roles to
  play.

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Introduction to Protocols

• Protocols in a Layered Architecture
• A. Protocols have to work together to ensure data
  is prepared, transferred, received, and acted
  upon.
• 1. Must be coordinated.
• 2. Results of this coordination effort are known
  as layering.
• B. Protocol Stacks.
• 1. Each OSI layer has its own protocol (rules).
• 2. Combination of protocols is called a protocol
  stack.
• 3. Lower layers determine how vendors design
  hardware.

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Introduction to Protocols
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Introduction to Protocols

• 4. Upper layers define rules for communication
  and interpretation of applications.
• 5. Higher the layer is in the stack, the more
  complex its tasks and their associated protocols.
• C. Binding Process.
• 1. Allows network protocols and cards to be
  mixed.
• 2. Two or more protocols (TCP/IP and IPX) can be
  bound to one card.
• 3. OS will attempt to use the protocols in the
  order they are bound.
• 4. Protocol stacks need to be bound to the
  components above and below them.

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Introduction to Protocols

• If three transport protocols are bound to a NIC
  on a Windows NT computer, each packet that is
  sent from the computer is sent on all three
  protocols. Only the protocols that are really
  needed should be bound.
•  
• D. Standard Stacks
• 1. ISO/OSI Protocol Suite
• 2. IBM Systems Network Architecture (SNA)
• 3. Digital DECnet
• 4. Novell NetWare
• 5. Apple AppleTalk
• 6. Internet Protocol Suite, TCP/IP

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Introduction to Protocols

• Protocols exist at each layer of these stacks,
  performing the tasks specified by that layer.
  However, the communication tasks that networks
  need to perform are grouped into one of three
  protocol types. Each type is comprised of one
  or more layers of the OSI.

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Introduction to Protocols

• SNA, DECnet, and IPX/SPX are proprietary
  protocols, while OSI and TCP/IP are open
  standards.
• E. Application protocols work at the upper layer
  of the OSI model and provide application-to-applic
  ation data exchange.
• 1. APPC (Advanced Program-to-Program
  Communication) IBMs peer-to-peer SNA protocol.
• 2. FTAM (File Transfer Access and Management)
  OSI file access protocol.
• 3. X.400 CCITT protocol for international
  e-mail transmission.
• 4. X.500 CCITT protocol for file and directory
  services across several systems.

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Introduction to Protocols

• 5. SMTP (Simple Mail Transfer Protocol)
  Internet protocol for transferring e-mail.
• 6. FTP (File Transfer Protocol) Internet file
  transfer protocol.
• 7. SNMP (Simple Network Management Protocol)
  Internet protocol for monitoring networks and
  network components.
• 8. Telnet Internet protocol for logging on to
  remote hosts and processing data locally.
• 9. Microsoft SMBs (Server Message Blocks) and
  client shells or redirectors.
• 10. NCP (Novell NetWare Core Protocol) and
  Novell client shells or redirectors.

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Introduction to Protocols

• 11. AppleTalk and Apple Shares Apples
  networking protocol suite.
• 12. AFP (AppleTalk Filing Protocol) Apples
  protocol for remote file access.
• 13. DAP (Data Access Protocol) A DECnet file
  access protocol.

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Introduction to Protocols

• F. Transport protocols provide communication
  sessions between computers and ensure data is
  able to move reliably between computers.
• 1. TCP (Transmission Control Protocol) TCP/IP
  protocol guarantees delivery of sequenced data.
• 2. SPX Novells IPX/SPX protocol suite for
  sequenced data.
• 3. NWLink Microsofts implementation of
  IPX/SPX.
• 4. NetBEUI/NetBIOS Establishes communication
  sessions between computers (NetBIOS) and provides
  the underlying data transport services (NetBEUI).
• 5. ATP (AppleTalk Transaction Protocol) and NBP
  (Name Binding Protocol) Apples
  communication-session and data-transport
  protocols.

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Introduction to Protocols

• G. Network protocols provide link services that
  handle addressing and routing, error checking,
  and retransmission requests.
• 1. IP (Internet Protocol) TCP/IP protocol for
  packet forwarding and routing.
• 2. IPX (Internetwork Packet Exchange) NetWares
  protocol for packet forwarding and routing.
• 3. NWLink Microsoft implementation of IPX/SPX.
• 4. NetBEUI Transport protocol that provides
  data transport services for NetBIOS sessions and
  applications.
• 5. DDP (Datagram Delivery Protocol) AppleTalks
  data transport protocol.

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Introduction to Protocols

• H. Protocol Standards.
•   The OSI reference model is used to define which
  protocols should be used at each layer.

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Introduction to Protocols

• 1. All have common physical layer, which is very
  important, since all stacks must agree.
• 2. The NICs driver is just above the physical
  layer.
• 3. IEEE Protocols at physical layer.
• a. 802.3 (Ethernet)
• (1). A logical bus network can transmit data
  at 10 Mbps.
• (2). Data is transmitted on the network to
  every computer.
• (3).Only computers meant to receive the data
  acknowledge the transmission.
• (4). CSMA/CD protocol regulates network
  traffic.

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Introduction to Protocols

• b. 802.4 (Token passing)
• (1). A bus layout uses a token-passing
  scheme.
• (2). All computers receive data, but only
  the computers that are addressed
  respond.
• (3). A token that travels the network
  determines which computer is able to
  broadcast.
• c. 802.5 (Token Ring)
• (1). This is a logical ring network that
  transmits at either 4 Mbps or 16 Mbps.
  
• (2). Although this is called a ring, it more
  resembles a star.
• (3). The ring is actually inside the hub.
• (4). A token traveling around the ring
  determines which computer can send
  data.

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Introduction to Protocols

• 4. IEEE Protocols at data-link layer.
• a. Logical Link Control (LLC)
• b. Media Access Control (MAC)

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Introduction to Protocols

• MAC Driver.
• A MAC driver is located at the Media Access
  Control sublayer this device driver is also
  known as the NIC driver. It provides low-level
  access to network adapters by providing
  data-transmission support and some basic adapter
  management functions.
• a. Detects network traffic and collisions.
• b. Waits, then retransmits (Ethernet).
• c. Waits for another token (Token Ring).

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Introduction to Protocols

• Implementing and Removing Protocols
• A. Protocols are implemented and removed in much
  the same way that drivers are added and removed.
• B. Essential protocols are installed
  automatically at the same time the initial
  operating system is installed on the computer.

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TCP/IP

• Overview
• A. TCP/IP is an industry-standard suite of
  protocols that provide communications in a
  heterogeneous environment.
• B. Provides a routable, enterprise networking
  protocol and access to the Internet and its
  resources.
• C. Now the de facto standard for what is known as
  internetworking, the intercommunication in a
  network that is composed of smaller networks.
• D. Developed by the U.S. Department of Defense as
  a set of WAN protocols to maintain communication
  links between sites in the event of a nuclear war.

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TCP/IP

• The TCP/IP Class is denoted by the first octet
  in the TCP/IP address. The range for the first
  octet of a Class A address is 1-126, Class B is
  128-191, Class C is 192-223. Example
  192.150.64.12 is considered a Class C address.
•  
• Introduction To TCP/IP
• A. Protocols written specifically for the TCP/IP
  suite
• 1. SMTP (Simple Mail Transfer Protocol)
• 2. FTP (File Transfer Protocol)
• 3. SNMP (Simple Network Management Protocol)

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TCP/IP

• B. Advantages
• 1. An open protocol not controlled by a single
  company and less subject to compatibility issues.
• 2. Contains a set of utilities for connecting
  dissimilar operating systems.
• 3. Uses scalable, cross-platform client server
  architecture.
• C. Disadvantages
• 1. Two primary disadvantages size and speed.
• 2. Is a relatively large protocol stack that can
  cause problems for MS-DOS clients.

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TCP/IP

• Standards
• A. Standards are published in a series of
  documents called Requests for Comment (RFC).
• 1. Primary purpose is to provide information or
  to describe work in progress.
• 2. Not originally intended to serve as
  standards, many RFCs are accepted as true
  standards.
• 3. Internet Architecture Board (IAB) is the
  committee responsible for managing and publishing
  RFCs for the Internet.
• 4. Anyone or any company can submit or evaluate
  an RFC.

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TCP/IP

• B. InterNIC Directory and Database provided by
  ATT is a service that furnishes sources of
  information about the Internet to the public.
• 1. Directory and Database that includes the RFCs
• 2. On the Web at www.internic.net

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TCP/IP

• TCP/IP and OSI
• A. TCP/IP and OSI Comparison
• Instead of seven layers, TCP/IP only has four.
• Network interface layer
• Internet layer
• Transport layer
• Application layer
• 2. Commonly referred to as the Internet Protocol
  Suite.

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TCP/IP

• B. Network Interface Layer
• 1. Corresponds to the physical and data-link
  layers of the OSI model.
• 2. Communicates directly with the network.
• 3. Provides interface between the network
  architecture (token ring, Ethernet) and the
  Internet layer.

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TCP/IP

• C. Internet Layer
• 1. Overview
• a. Corresponds to the network layer of the OSI
  model.
• b. Uses several protocols for routing and
  delivering packets.
• c. Routers function at this layer and are used
  to forward packets from one network or segment to
  another.

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TCP/IP

• 2. Internet Protocol (IP)
• a. Packet-switched protocol that performs
  addressing and route selection.
• b. Connectionless protocol that sends packets
  without expecting the receiving host to
  acknowledge receipt.
• c. Responsible for packet assembly and
  disassembly as required by the physical and
  data-link layers of the OSI model.
• d. Each IP packet is made up of a source and
  destination address, protocol identifier,
  checksum (a calculated value), and a TTL (time to
  live).

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TCP/IP

• e. TTL tells each router on the network between
  the source and destination how long the packet
  has to remain on the network.
• f. Each router subtracts one from the TTL until
  it reaches zero and the packet is discarded or
  eliminated from the network.
• g. TTL prevents lost or damaged data packets
  from endlessly wandering the network.
• h. IP ANDs the current address with the
  destination address to determine if the
  destination is on a local or remote network.

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TCP/IP

• An AND is a logical operation combining the
  values of two bits (0, 1) or two Boolean values
  (false, true) that returns a value of 1 (true) if
  both input values are 1 (true) and returns a 0
  (false) otherwise.
•  
• 3. Address Resolution Protocol (ARP)
• a. Determines the hardware address (MAC address)
  that corresponds to an IP address.
• b. If ARP does not contain the address in its
  own cache, it broadcasts a request for the
  address.
• c. All hosts on the network process the request
  and, if they contain the MAC address for the
  specific IP address, pass the address back to the
  requestor.
• d. Cache is updated with this new address.

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TCP/IP

• 4. Reverse Address Resolution Protocol (RARP)
• a. System administrator creates a database of
  machine numbers on RARP server.
• b. Provides an IP number to a requesting
  hardware address.
• 5. Internet Control Message Protocol (ICMP)
• a. Used by IP and higher level protocols to send
  and receive status reports about information
  being transmitted.
• b. Routers commonly use ICMP to control the
  flow, or speed, of data between themselves.
• c. Two basic categories of ICMP messages are
  reporting errors and sending queries.

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TCP/IP

• D. Transport Layer
• 1. Overview
• a. Corresponds to the transport layer of the OSI
  model.
• b. Responsible for establishing and maintaining
  end-to-end communication between two hosts.
• c. Provides acknowledgment of receipt, flow
  control, and sequencing of packets.
• d. Handles retransmission of packets.
• e. Can use either TCP or User Datagram Protocol
  (UDP).

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TCP/IP

• 2. Transmission Control Protocol (TCP)
• a. Overview.
• (1) Responsible for the reliable transmission of
  data from one node to another.
• (2) Connection protocol that establishes a
  connection between two machines before any data
  is transferred.
• b. Uses a three-way handshake that establishes
  the port number and beginning sequence numbers
  from both sides of the transmission.
• (1) The requestor sends a packet specifying the
  port number it plans to use and its initial
  sequence number (ISN) to the server.

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TCP/IP

• (2) The server acknowledges with its ISN, which
  consists of the requestors ISN, plus 1.
• (3) The requestor in turn acknowledges with the
  servers ISN, plus 1.
• c. To maintain a reliable connection, each packet
  must contain
• (1) A source and destination TCP port number.
• (2) A sequence number for messages that must be
  broken into smaller pieces.
• (3) Checksum to ensure that information is sent
  without error.

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TCP/IP

• (4) An acknowledgement number that tells the
  sending machine which pieces of the message have
  arrived.
• (5) TCP Sliding Windows.

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TCP/IP

• 3. Ports, Sockets, and Sliding Windows
• a. Ports
• (1) Are used to reference the location of a
  particular application or process on each
  machine.
• (2) Port address identifies the application to
  the transport layer.
• (3) Applications and services can configure up
  to 65,535 (216) ports.
• (4) TCP/IP applications and services typically
  use the first 1023 ports.
• (5) Internet Assigned Numbers Authority (IANA)
  has assigned these ports as standard or default
  ports.

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TCP/IP

•  Some of the default port assignments IANA has
  assigned include FTP 21, Telnet 23, SMTP 25,
  HTTP 80
•  b. Sockets
• (1) Services and applications use sockets to
  establish connections with another host.
• (2) Uses TCP if the application needs to
  guarantee the delivery of data.
• (3) Uses User Datagram Protocol (UDP) if the
  application chooses the connectionless service.
•  

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TCP/IP

• A socket is an identifier for a particular
  service on a particular node on a network. The
  socket consists of a node address and a port
  number that identifies the service.
•  
• c. Sliding Windows
• (1) Used by TCP for transferring data between
  hosts.
• (2) Regulate how much information can be passed
  over a TCP connection before the receiving host
  must send an acknowledgement.
• (3) Send and receive window is used to buffer
  data and make the communication process more
  efficient.
• (4) Sending window tracks data that has been
  sent if an acknowledgment is not received within
  a given amount of time, the packets are re-sent.

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TCP/IP

• 4. User Datagram Protocol (UDP)
• a. Connectionless protocol.
• b. Responsible for end-to-end transmission of
  data.
• c. Does not establish a connection.
• d. Used to send small amounts of data for which
  guaranteed delivery is not required.
• e. Uses ports that are different from TCP ports
  therefore, they can use the same numbers without
  interference.

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TCP/IP

• E. Application Layer
• 1. Overview
• a. Corresponds to the session, presentation, and
  application layers of the OSI model.
• b. Connects applications to the network.
• c. Two APIs provide access to the TCP/IP
  transport protocols (Windows Sockets and
  NetBIOS).
• 2. Windows Sockets (Winsock) Interface
• a. Networking API designed to facilitate
  communication among different TCP/IP applications
  and protocol stacks.

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TCP/IP

• b. Established so that applications using TCP/IP
  could write to a standard interface.
• c. Winsock is derived from the original Sockets
  created for the BSD Unix operating system.
• d. Any program or application written using the
  Winsock API can communicate with any TCP/IP
  protocol and vice versa.

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NetWare Protocols

• Introduction
• A. Overview
• 1. Defined well before the finalization of the
  OSI model.
• 2. No direct correlation to the layer boundaries
  exists between the two architectures.
• 3. Follow an enveloping pattern.
•  
• The upper-level protocols (NCP, SAP, and RIP)
  are enveloped by IPX/SPX. A Media Access Protocol
  header and trailer then envelop IPX/SPX.

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NetWare Protocols

• B. Five main protocols used by NetWare
• 1. Media Access Protocol
• 2. Internetwork Packet Exchange/Sequenced Packet
  Exchange (IPX/SPX)
• 3. Routing Information Protocol (RIP)
• 4. Service Advertising Protocol (SAP)
• 5. NetWare Core Protocol (NCP)
• These protocols were defined well before the
  finalization of the OSI reference model, they do
  not exactly match OSI.

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NetWare Protocols

• No direct correlation to the layer boundaries of
  the two architectures exists.
• The upper-lever protocols (NCP, SAP, and RIP) are
  enveloped by IPX/SPX.
• A Media Access Protocol header and trailer then
  envelop IPX/SPX.

47
NetWare Protocols

• Media Access Protocols
• A. Overview
• 1. Define the addressing that distinguishes each
  node on a NetWare network.
• 2. Addressing is implemented on the hardware or
  NIC.
• 3. Responsible for placing the header on the
  packet.
• 4. Header includes the source and destination
  code.
• 5. Each receiving NIC checks the address if
  their address matches the destination address on
  the packet or if the packet is a broadcast
  message, the NIC copies the packet and sends it
  up the protocol stack.
• 6. Also provides bit-level error checking in the
  form of a cyclical redundancy check (CRC).

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NetWare Protocols

• CRC error checking uses a complex calculation to
  generate a number based on the data transmitted.
  The sending device performs the calculation
  before transmission and includes it in the packet
  that it sends to the receiving device. The
  receiving device repeats the same calculation
  after transmission. If both devices obtain the
  same result, it is assumed that the transmission
  was error free. The procedure is known as a
  redundancy check because each transmission
  includes not only data, but also extra
  (redundant) error checking values.

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NetWare Protocols

• B. Most Common Implementations
• 1. 802.5 Token Ring
• 2. 802.3 Ethernet
• 3. Ethernet 2.0
• Internetwork Packet Exchange and Sequenced Packet
  Exchange (IPX/SPX)
• A. IPX
• 1. Defines the addressing schemes used on a
  NetWare network.
• 2. Datagram based, connectionless, unreliable,
  network layer protocol that is equivalent to IP.
• 3. Does not require an acknowledgment for each
  packet sent.

50
NetWare Protocols

• Novell developed IPX based on the Xerox Network
  System (XNS) Internet Datagram Protocol.
•  
• B. IPX Addressing
• 1. Internetwork addressing The address of a
  segment on the network, identified by the network
  number assigned during installation.
• 2. Intranode addressing The address of a process
  within a node that is identified by a socket
  number.

51
NetWare Protocols

• C. SPX
• 1. Provides security and reliability to the IPX
  protocol.
• 2. Connection oriented, reliable services at the
  transport layer.
•  
• NetWare is moving toward using TCP/IP as a
  standard.

52
NetWare Protocols

• Routing Information Protocol (RIP)
• A. Overview
• 1. Designed to facilitate the exchange of
  routing information on a NetWare network.
• 2. Also developed from XNS.
• 3. Includes an extra field to the packet to
  improve the decision criteria for selecting the
  fastest route to a destination.
• B. Broadcast of a RIP packet allows several
  things to occur
• 1. Workstations can locate the fastest route to
  a network number.

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NetWare Protocols

• 2. Routers can request routing information from
  other routers to update their own internal
  tables.
• 3. Routers can respond to route requests from
  workstations and other routers.
• 4. Routers can make sure that all other routers
  are aware of the internetwork configuration.
• 5. Routers can detect a change in the
  internetwork configuration.

54
NetWare Protocols

• Service Advertising Protocol (SAP)
• A. Overview
• 1. Allows service providing nodes to advertise
  their services and addresses.
• 2. Clients are able to obtain the internetwork
  address of any servers they can access.
• 3. Adding and removing resources from the
  network becomes dynamic.
• 4. SAP server broadcasts its presence every 60
  seconds.

55
NetWare Protocols

• B. SAP Packet Contains
• 1. Operating Information
• 2. Service Type
• 3. Server Name
• 4. Network Address
• 5. Node Address
• 6. Socket Address
• 7. Total Hops to Server
• 8. Operational Field
• 9. Additional Information

56
NetWare Protocols

• NetWare Core Protocol (NCP)
• A. Defines the connection control and service
  request encoding that make it possible for
  clients and servers to interact.
• B. Provides transport and session services.
• C. Also provides NetWare security.

57
Other Common Protocols

• Network Basic Input/Output System (NetBIOS)
• A. Overview
• 1. Most services and applications that run within
  the Windows operating system use either NetBIOS
  interface or interprocess communication (IPC).
• 2. Standard interface for applications to use to
  access networking protocols in the transport
  layer for both connection-oriented and
  nonconnection-oriented communications.
• 3. Interfaces exist for NetBEUI, NWLink, and
  TCP/IP.
• 4. Requires an IP address and a NetBIOS name to
  uniquely identify a computer.

58
Other Common Protocols

• B. Performs Four Primary Functions
• 1. Name Resolution
• a. Each workstation has one or more names.
• b. Maintains a table of names and aliases.
• c. First name in the table is the unique name of
  the NIC.
• d. Optional user names can be added to provide a
  user-friendly identification system.
• e. Cross references the names as required.

59
Other Common Protocols

• 2. Datagram Service
• a. Allows a message to be sent to any name,
  group of names, or to all users on the network.
• b. No guarantee that the message will arrive at
  its destination(does not use point-to-point
  connections).
• 3. Session Service
• a. Opens a point-to-point connection between two
  workstations on the network one workstation
  initiates a call to another and opens the
  connection.
• b. Both workstations are peers.
• c. Can send and receive data concurrently.

60
Other Common Protocols

• 4. NIC/Session Status
• a. Makes information about the local NIC and
  other NICs available to any application software
  using NetBIOS.
• b. Makes information about the currently active
  sessions available to any application software
  using NetBIOS.
•  
• Originally, IBM offered NetBIOS as a separate
  product, implemented as a terminate-and-stay-resid
  ent (TSR) program. This TSR program is now
  obsolete and should be replaced with the Windows
  NetBIOS interface.
•  

61
Other Common Protocols

• NetBEUI
• A. Overview
• 1. Acronym for NetBIOS Enhanced User Interface.
• 2. Originally closely tied together with NetBIOS.
• 3. NetBIOS separated so that it could be used
  with other routable transport protocols.
• B. Advantages
• 1. Small size
• 2. Speed of data transfer on the network medium
• 3. Compatibility with all Microsoft networks

62
Other Common Protocols

• C. Disadvantages
• 1. Does not support routing
• 2. Limited to Microsoft networks
• X.25 Packet Switching
• A. Overview
• 1. A set of WAN protocols.
• 2. Packet-switching network made up of switching
  services.
• 3. Originally established to connect remote
  terminals to mainframe host systems.

63
Other Common Protocols

• 4. Network breaks up each transmission into
  multiple packets and places them on the network.
• 5. Pathway between nodes is a virtual circuit
  that looks like a single, continuous, logical
  connection to the upper layers.
• 6. Each packet can take different routes from the
  source to the destination.
•  
• The network transmitting an X.25 packet is often
  drawn as a cloud, signifying that the transport
  service is a purchased service which only the
  sender and receiver need to know how to connect.

64
Other Common Protocols

• B. Typical X.25 Packet
• 1. Includes 128 bytes of data.
• 2. Source and destination can negotiate a
  different packet size.
• 3. Support a theoretical maximum of 4095
  concurrent virtual circuits across a physical
  link.
• 4. Typical data transmission speed is 64 Kbps.
• 5. Works in the physical, data-link layer of the
  OSI model.

65
Other Common Protocols

• C. Two Shortcomings
• 1. Store-and-forward mechanism causes delays.
• 2. Large amount of buffering is required to
  support the store-and-forward data transfer.
•  
• A flip-flop is a circuit that alternates
  between two possible states when a pulse is
  received at the input. For example, if the output
  of a flip-flop is high and a pulse is received at
  the input, the output flips to low a second
  input pulse flops the output back to high, and
  so forth.

66
Other Common Protocols

• D. Differences between X.25 and TCP/IP
• 1. TCP/IP has only end-to-end error checking and
  flow control X.25 has error checking from node
  to node.
• 2. TCP/IP is passive and has a more complicated
  flow control and window mechanism.
• 3. X.25 has tightly specified the electrical and
  link levels TCP/IP is designed to travel over
  many different kinds of media, with many
  different types of link service.

67
Other Common Protocols

• Xerox Network System (XNS)
• A. Developed for Ethernet LANs.
• B. Widely used in the 1980s.
• C. Slowly replaced by TCP/IP.
• Large, slow protocol.
• Advanced Program-to-Program Communication (APPC)
• A. IBMs transport protocol developed as part of
  its Systems Network Architecture (SNA).
• B. Designed to enable application programs
  running on different computers to communicate and
  exchange data directly.

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Other Common Protocols

• 6. AppleTalk
• A. Overview
• 1. Designed to enable Apple Macintosh computers
  to share files and printers.
• 2. Introduced in 1984 as a self-configuring LAN
  technology.
• 3. Also available on UNIX systems.
• B. Protocols
• 1. AppleTalk A collection of protocols that
  correspond to the OSI reference model. It
  supports LocalTalk, EtherTalk, and TokenTalk.

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Other Common Protocols

• 2. LocalTalk Describes the simple, shielded,
  twisted-pair cable used to connect Macintoshes to
  other Macintoshes or printers. A LocalTalk
  segment supports a maximum of 32 devices and
  operates at a speed of 230 Kbps.
• 3. EtherTalk AppleTalk over Ethernet. It
  operates at a speed of 10 Mbps. Fast EtherTalk
  operates at a speed of 100 Mbps.
• 4. TokenTalk AppleTalk over Token-Ring.
  Depending on its hardware, TokenTalk operates at
  either 4 Mbps or 16 Mbps.

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Other Common Protocols
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Other Common Protocols

• OSI Protocol Suite
• A. Complete protocol stack.
• B. Each protocol maps directly to a single layer
  of the OSI model.
• Includes routing and transport protocols, IEEE
  802 series protocols, a session layer protocol, a
  presentation layer protocol, and several
  application layer protocols designed to provide
  full networking functionality.

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Other Common Protocols

• DECnet
• A. Digital Equipment Corporations proprietary
  protocol stack.
• B. Set of hardware and software products that
  implement the Digital Network Architecture (DNA).
• C. Defines communication networks over Ethernet
  LANs, Fiber Distributed Data Interface
  metropolitan area networks (FDDI MANs), and WANs
  that use private or public data-transmission
  facilities.
• D. Can use TCP/IP and OSI protocols as well as
  its own.
• E. Routable Protocol.
• F. Each update is called a phase, current
  revision is DECnet Phase V.