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					              Chapter 3
Using Network Communication Protocols




             Spring 2009
       Objectives
     Explain network protocols, including IPX/SPX, NetBEUI,
      AppleTalk, and TCP/IP
     Discuss how IP addressing works
     Understand the promise of IPv6
     Explain and use application protocols in the TCP/IP suite




2
      Objectives (continued)
     Compare TCP/IP to the OSI model
     Discuss WAN protocols used for remote communications
     Understand how to design a network to use TCP/IP and
     application protocols




3
     An Overview of Network Protocols
     Protocols enable interchange
     Analogize protocols to dialects
       Computer communication requires common protocol
       Human communication requires common dialect
     LANs may transport multiple protocols
       Network device (such as router) makes distinctions




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       Properties of a LAN Protocol
     LAN protocol capabilities
       Communicate at relatively high speeds
       Handle source and destination node addressing
       Follow standards, particularly the IEEE 802 standards
     Protocols have different strengths and drawbacks
       Example 1: some (not all) protocols are routable
       Example 2: some protocols have poor error checking
     Protocols typically used on LANs
       IPX/SPX, NetBEUI, AppleTalk, and TCP/IP
       TCP is most widely used due to relation to Internet



6
        Understanding IPX/SPX
     Internetwork Packet Exchange (IPX)
       Developed by Novell for NetWare operating system
         NetWare used with Ethernet bus, token ring, ARCnet

     Sequenced Packet Exchange (SPX)
       Companion protocol to IPX
       Developed for use with applications, such as databases
     IPX/SPX used on NetWare servers through version 4
     TCP/IP is preferred protocol for NetWare 6 and above
     New NetWare versions can still implement IPX/SPX



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       Understanding NetBEUI
     NetBEUI (NetBIOS Extended User Interface)
       Developed for LAN Manager and LAN Server
       Predates Windows NT
     NetBEUI used in early versions of Windows NT
     NetBEUI not supported in Windows XP or Windows Server
      2003 (or higher)
     Disadvantages of NetBEUI
       Cannot be routed
       Causes unnecessary traffic


8
        Understanding Apple Talk
     AppleTalk protocol networks Macintosh computers
     AppleTalk is a peer-to-peer network protocol
       Enables Macs to communicate without server
     Windows Server 2003 and Novell use AppleTalk
       Enables communication with Mac computers
     AppleTalk Phase II
       Handles more networked computers than Phase I
       Interoperable with heterogeneous networks hosting multiple
        protocols


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        The History and Role of TCP/IP
      Advanced Research Projects Agency (ARPA)
        Networking goal: enable university, research, and Defense
         Department to communicate
      ARPANET WAN: prototype for modern networks
      An early protocol: Network Control Protocol (NCP)
        Enabled DEC, IBM, and other hosts to communicate
        Did not provide wholly reliable communication
      TCP/IP combination: an improvement over NCP
        TCP (Transmission Control Protocol)
        IP (Internet Protocol)
      TCP/IP has become most widely used protocol suite

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     The History and Role of TCP/IP
     (continued)
      Five advantages of TCP/IP
        Used worldwide on most networks and the Internet
        Influences design of wide range of network devices
        Main protocol of many computer operating systems
        Subject to many troubleshooting and network analysis tools
        Understood by large body of network professionals
      TCP/IP associated with a suite of protocols and applications
      Vast range of communications capabilities



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      Understanding TCP/IP
  TCP specified in RFC 793
      Designed for point-to-point communications
  IP specified in RFC 791
      Developed to link nodes in different networks or WANs
  TCP and IP first combined for use with UNIX
  TCP/IP layers may be roughly mapped to OSI layers
  Core components of TCP/IP protocol suite
      Transmission Control Protocol (TCP)
      User Datagram Protocol (UDP)
      Internet Protocol (IP)


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     Transmission Control Protocol
      TCP is a transport protocol (Layer 4 in OSI model)
        Establishes sessions between network nodes
        Sequences and acknowledges frames
          Provides for reliable end-to-end delivery




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     Transmission Control Protocol
     (continued)
  Main TCP functions (similar in OSI Transport layer)
    Monitor for session requests
    Establish sessions with other TCP nodes
    Transmit and receive data
    Close transmission sessions
  TCP ports:
    Used to form virtual circuit between nodes
    Enable multiple processes to communicate in session




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     Complete list of port assignment

     http://www.iana.org/assignments/port-numbers


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       How the Internet Protocol (IP) Works
  Communications enabled by Internet Protocol (IP)
      Between different subnetworks on a LAN
      Between different networks on a WAN
  Network transport options should be compatible with TCP/IP
      Transport options include: Ethernet, token ring, X.25, FDDI, ISDN,
       DSL, frame relay, ATM




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     How the Internet Protocol (IP) Works
     (continued)
  Basic IP Functions: data transfer, packet addressing, packet
   routing, fragmentation, detection of errors
  Addressing essential for data transfer and routing
      32-bit network node address used with 48-bit MAC address
  Connectionless protocol
      Provides network-to-network addressing and routing information
      Changes packet size when size varies with network
  Datagram: TCP segment formatted with IP header
  IP packet header consists of thirteen fields



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        How IP Addressing Works
      IP addressing used to identify two entities
        Specific node
        Network on which node resides
      Unique IP address enables accurate packet delivery
      Two nodes with same IP address create error
      IP addressing concepts fundamental in networking




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     Basic IP Addressing
 Dotted decimal notation: IP address format
      Four fields totaling 32 bits
        Fields are decimal values representing 8-bit binary octets
      Part of address is network ID, part is host ID
      Example in decimal format: 129.5.10.100
 Five IP address classes, Class A through Class E
      Address reflects network size and transmission type
 Three types of transmission
      Unicast: packet sent to each requesting client
      Multicast: packet sent to group of requesting clients
      Broadcast: communication sent to all network nodes

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       The Role of the Subnet Mask
      TCP/IP requires configured subnet mask
      Subnet mask used for two purposes
        Show class of addressing used
        Divide networks into subnetworks to control traffic
      Example of a subnet mask:
        11111111.00000000.00000000.00000000 (255.0.0.0)
        Indicates Class A network
        Ones represent network/subnet identification bits
        Zeroes represent host identification bits



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     Creating Subnetworks
  Ex: On a Class B network; the first two octets represent the network ID; the
   last two octets represent host ID
  11111111.11111111. 00000000.00000000
  If using (255.255.255.0) as the subnet mask; the third octet is used as the
   subnet ID
      255.255.255.0 = 11111111.11111111.11111111.00000000
  Classless Inter-domain Routing (CIDR) addressing
      Puts a slash ( / ) after the dotted decimal notation
         Number after slash represents bits in network ID
      Example (decimal): 165.100.18.44/18
         18 bits needed for network ID, 14 for host ID (32 -18)



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        IP Address Rules
      Network number 127.0.0.0 cannot be assigned
        Address used for diagnostic purposes
      Certain IP network numbers reserved as private
      No one can use private addresses on the Internet
        Designed for use behind NAT device; e.g., firewall
        May be used on private network with NAT device
      Network ID cannot be assigned to a host
      Highest number on a network cannot be assigned
        Address interpreted as broadcast message for subnet
        Example: cannot assign 198.92.4.255


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     Private IP
      10.x.x.x
      172.16.x.x - 172.31.x.x
      192.168.x.x




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        The Promise of IPv6
      IPv6 developed through IETF initiative
      IPv6 overcomes limitations of IPv4
      Networks are beginning to transition to IPv6
      Five prominent features of IPv6
        128-bit address capability
        Single address associated with multiple interfaces
        Address autoconfiguration and CIDR addressing
        40-byte header instead of IPv4’s 20-byte header
        New IP extension headers for special needs
          Includes more routing and security options


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     The Promise of IPv6 (continued)
  Three IPv6 packet types: unicast, anycast, multicast
  DES (Data Encryption Standard)
      Network symmetric-key encryption standard
  IPv6 supports DES compatible encryption techniques
  Benefits of IPv6 encryption capability
      Security over Internet
      Security over other types of LANs and WANs
  Disadvantage of IPv6 encryption capability
      Increases latency of network communications
         Latency: travel time from sending node to receiving node


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     TCP/IP Application Protocols
      Useful protocols and applications in TCP/IP suite
        Telnet
        Secure Shell (SSH)
        FileTransfer Protocol (FTP), Trivial FileTransfer Protocol (TFTP),
         and Network File System (NFS)
        Simple Mail Transfer Protocol (SMTP)
        Domain Name System (DNS)
        Dynamic Host Configuration Protocol (DHCP)
        Address Resolution Protocol (ARP)
        Simple Network Management Protocol (SNMP)
        Hypertext Transfer Protocol (HTTP), Secure Hypertext Transfer
         Protocol (S-HTTP), HTTP Secure (HTTPS)

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     File Transfer Protocol (FTP), Trivial File Transfer
     Protocol (TFTP), and Network File System
     (NFS)
 FTP: allows transfer of data between remote devices
      Transmissions may be binary or ASCII formatted files
      Transmissions ensured by connection-oriented service
 Limitation of FTP: cannot transfer portion of file
 TFTP: intended for transfer of small files
      Use for non-critical and non-secure transmissions
      Connectionless protocol running UDP instead of TCP
 NFS: Sun Microsystem's alternative to FTP
      Uses connection-oriented protocol running in TCP

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       Simple Mail Transfer Protocol (SMTP)
  Designed for exchange of electronic mail
  Two implementations
      For e-mail exchange between networked systems
      In local e-mail systems for Internet transport
  Provides alternative to FTP for file transfer
      Limited to sending text files
      Requires e-mail address on receiving end
      Does not require logon ID and password
  Two part message: address header and message text
  Supported in TCP by connection-oriented service

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      Domain Name System (DNS)
  Domain: logical grouping of network resources
  Domains given unique names; e.g., Microsoft.com
  DNS resolves domain names
      Resolution: converts domain name to IP address
  Internet host domain names have two to three parts
      Top-level domain name (TLD): organization or country
      Optional subdomain name: university/business name
      Host name: name of computer
      Example: myname@myorganization.com
  ICANN coordinates and registers root domain names

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     http://www.icann.org/tlds/
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Domain Name System (DNS) (continued)
 Namespace: logical area with list of named objects
 Zones: partitions in DNS server with resource records
      Forward lookup zone links computer name to IP address
      Reverse lookup zone links IP address to computer name
 Three servers related to DNS
      Primary DNS server: authoritative server for zone
      Secondary DNS server: backup servers
      Root servers: find TLDs on the Internet
 Two DNS standards
      Service resource record (SRV RR)
      DNS dynamic update protocol

34
     Dynamic Host Configuration Protocol
     (DHCP)
  Enables automatic assignment of IP address
  Process of assigning address by DHCP server
       Newly configured computer contacts DHCP server
       DHCP server leases an IP address to new computer
       Lease length set on DHCP server by network admin
       Server or host may be given lease that does not expire
         IP address will never change with permanent lease




35
     Address Resolution Protocol (ARP)
      Enables sender to retrieve MAC address
      Process of obtaining MAC address
        Sending node sends ARP broadcast frame
          Frame has MAC address, IP address of recipient
        Receiving node sends back its MAC address
      Reverse Address Resolution Protocol (RARP)
        Used by network node to determine its IP address
        Used by applications to determine IP address of workstation or
         server



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     Simple Network Management
     Protocol (SNMP)
  Enables steady monitoring of network activity
  Advantages
      Operates independently on the network
      Management functions carried out on special node
      Has low memory overhead
  Node types: network management station (NMS) and network
   agents
  SNMPv2 offers better security, error handling, multiprotocol
   support, transmissions
  SNMP and SNMPv2 monitor LANs and WANS

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     HTTP, S-HTTP, and HTTPS
      Hypertext Transfer Protocol (HTTP)
        Enables establishment of a Web connection
        Provides for exchange of resources
          Example: displaying Web page in browser

      Secure Hypertext Transfer Protocol (S-HTTP)
        Used primarily in native HTTP communications
        Does not encrypt data in IP-level communications
      Hypertext Transfer Protocol Secure (HTTPS)
        Uses Secure Sockets Layer to implement security
        More common than S-HTTP


39
     TCP and the OSI Reference Model
     Compared
  Portions of TCP moving closer to OSI model
      Physical layer: TCP supports coaxial, twisted-pair, fiber-optic,
       wireless communication
      Data Link layer: TCP compatible with IEEE 802.2 LLC and MAC
       addressing
      Network layer: TCP/IP equivalent is IP
      Transport layer: both TCP and UDP operate here
      Upper layers of OSI correspond to TCP/IP applications




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     Transporting LAN Protocols Over
     WANs
  WAN protocols enable transport from LANs to WANs
  Serial Line Internet Protocol (SLIP)
      Encapsulates TCP/IP during connection session
      TCP/IP removed from SLIP after data payload received
  Compressed Serial Line Internet Protocol (CSLIP)
      Newly developed extension of SLIP
      Compresses header in each packet sent across link
  SLIP and CSLIP do not support
      Network connection authentication
      Setup of connections at multiple layers
      Synchronous connections
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     Transporting LAN Protocols Over
     WANs (continued)
  Point-to-Point Protocol (PPP)
      Supports more network protocols than SLIP
      Automatically sets up connections with several layers
      Supports connection authentication and encryption
  Point-to-Point Tunneling Protocol (PPTP)
      Supplements PPP
      Enables remote communications via the Internet
  PPTP and PPP support synchronous communication
  PPTP and PPP support Password Authentication Protocol (PAP)


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     Transporting LAN Protocols Over
     WANs (continued)
  Layer Two Tunneling Protocol (L2TP)
      Similar to PPTP, and like PPTP used on VPNs
      Like PPTP, L2TP encapsulates PPP
      Creates special tunnels over public network (Internet)
      Uses Layer Two Forwarding (based on MAC addresses)
  Signaling System 7 (SS7)
      For fast communications between different type WANS
      Supports call roaming, voicemail, redirection of 800 calls
      Adapted for T-carrier and other WAN communications


44
     Designing A Network To Use TCP/IP
     And Application Protocols
  Scenario: network personnel in medical office
  Seven major components in network design
      Workstations and servers configured for TCP/IP
        Automatic (DHCP-based) IP addressing used
      DHCP used to lease IP addresses to workstations
        All servers given permanent IP addresses
      SNMP used in certain stations for network monitoring
      Network browsers set up to use PPP for Internet links
      Workstations set up to use FTP/HTTP through firewalls
      E-mail system configured to employ SMTP
      Primary DNS server and secondary DNS server set up

45
     Summary
  Protocols are the language of networks
  IPX/SPX and NetBEUI used on some older networks
  AppleTalk used by Macintosh systems
  ARPANET WAN was a network prototype
  TCP establishes links and ensures reliability




46
     Summary (continued)
      IP enables data transfer and routing with packet addressing
      TCP/IP combination universal used on networks and
       Internet
      UDP used with IP in certain non-critical situations
      Dotted decimal notation address: IP address format
      Five IP address classes (A through E)




47
     Summary (continued)
      Networks subdivided using subnet mask or CIDR
      IPv6 is newest version of IP
      TCP/IP steadily aligning with layers of OSI model
      Supported by TCP/IP : Telnet, SSH, FTP, SMTP, DNS,
       DHCP, ARP, SNMP, and HTTP
      Basic WAN protocols: SLIP, PPP, PPTP, L2TP




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