Network

1

• Network
• Protocols

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Introduction to Protocols

• Protocol
• Rules network uses to transfer data
• Protocols that can span more than one LAN segment
  are routable
• Multiprotocol network
• Network using more than one protocol

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TCP/IP
OSI Model
TCP/IP

• Transmission Control Protocol/Internet Protocol
  (TCP/IP)
• Suite of small, specialized protocols called
  subprotocols

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TCP/IP model

• File Transfer Protocol (FTP)
• Hypertext Transfer Protocol (HTTP)
• Simple Mail Transfer Protocol (SMTP)
• Domain Name System (DNS)
• Trivial File Transfer Protocol (TFTP)
• The common transport layer
• protocols include
• Transport Control Protocol (TCP)
• User Datagram Protocol (UDP)
• The primary protocol of the
• Internet layer is
• Internet Protocol (IP)

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TCP/IP model
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TCP/IP Compared to theOSI Model

• Application layer roughly corresponds to Session,
  Application, and Presentation layers of OSI Model
• Transport layer roughly corresponds to Transport
  and session layers of OSI Model
• Internet layer is equivalent to Network layer of
  OSI Model
• Network Interface layer roughly corresponds to
  Data Link and Physical layers of OSI Model

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The TCP/IP Core Protocols

• Certain subprotocols of TCP/IP suite
• Operate in Transport or Network layers of OSI
  Model
• Provide basic services to protocols in other
  layers of TCP/IP
• TCP and IP are most significant core protocols in
  TCP/IP suite

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Internet Protocol (IP)

• Provides information about how and where data
  should be delivered
• Subprotocol that enables TCP/IP to internetwork
• To internetwork is to traverse more than one LAN
  segment and more than one type of network through
  a router
• In an internetwork, the individual networks that
  are joined together are called subnetworks

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Internet Protocol (IP)

• IP datagram
• IP portion of TCP/IP frame that acts as an
  envelope for data
• Contains information necessary for routers to
  transfer data between subnets

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IP header format
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IP header format Version

• 4 bits.
• Indicates the version of IP currently used.
• IPv4 0100
• IPv6 0110

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IP header format Header length

• 4 bits.
• IP header length Indicates the datagram header
  length in 32 bit words (4 bits), and thus points
  to the beginning of the data.

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IP header format Service type

• 8 bits.
• Specifies the level of importance that has been
  assigned by a particular upper-layer protocol.
• Precedence.
• Reliability.
• Speed.

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IP header format Total length

• 16 bits.
• Specifies the length of the entire IP packet,
  including data and header, in bytes.

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IP header format Identification

• 16 bits.
• Identification contains an integer that
  identifies the current datagram.
• Assigned by the sender to aid in assembling the
  fragments of a datagram.

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IP header format Flags

• 3 bits.
• The second bit specifying whether the packet can
  be fragmented .
• The last bit specifying whether the packet is the
  last fragment in a series of fragmented packets.

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IP header format Fragment offset

• 13 bits.
• The field that is used to help piece together
  datagram fragments.
• The fragment offset is measured in units of 8
  octets (64 bits).
• The first fragment has offset zero.

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IP header format Time to Live

• 8 bits.
• Time-to-Live maintains a counter that gradually
  decreases to zero, at which point the datagram is
  discarded, keeping the packets from looping
  endlessly.

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IP header format Protocol

• 8 bits.
• Indicates which upper-layer protocol receives
  incoming packets after IP processing has been
  completed
• 06 TCP
• 17 UDP

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IP header format Header checksum

• 16 bits.
• A checksum on the header only, helps ensure IP
  header integrity.

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IP header format Addresses

• 32 bits each.
• Source IP Address
• Destination IP Address

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IP header format Options

• Variable length.
• Allows IP to support various options, such as
  security, route, error report ...

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IP header format Padding

• The header padding is used to ensure that the
  internet header ends on a 32 bit boundary.

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Ethereal Lab (Analyzing the IP Header)

• Use Ethereal to capture some frames. Open one of
  the frames and look at the IP header. Based on
  what you see, try to answer the following
• What is the IP version?
• What is the IP header length?
• What is the type of Service?
• What is the time to live?
• What is the protocol?
• What is the source IP address?
• What is the destination IP address?

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Internet Protocol (IP)

• IP is an unreliable, connectionless protocol,
  which means it does not guarantee delivery of
  data
• Connectionless
• Allows protocol to service a request without
  requesting verified session and without
  guaranteeing delivery of data

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Transport Control Protocol (TCP)

• TCP
• Provides reliable data delivery services
• Connection-oriented subprotocol
• Requires establishment of connection between
  communicating nodes before protocol will transmit
  data
• TCP segment
• Holds TCP data fields
• Becomes encapsulated by IP datagram

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Transport Control Protocol (TCP)

• Port
• Address on host where application makes itself
  available to incoming data

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Ethereal Lab (Analyzing the TCP Header)

• Use Ethereal to capture some frames. Open one of
  the frames and look at the TCP header. Based on
  what you see, try to answer the following
• What is the source Port?
• What is the destination Port?
• What is the sequence Number?
• What Is the Acknowledgement Number?
• What is the header Length?

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Additional Core Protocols of the TCP/IP Suite

• User Datagram Protocol (UDP)
• Connectionless transport service
• Internet Control Message Protocol (ICMP)
• Notifies sender of an error in transmission
  process and that packets were not delivered
• Address Resolution Protocol (ARP)
• Obtains MAC address of host or node
• Creates local database mapping MAC address to
  hosts IP address

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• ?ARP Lab

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TCP/IP Application Layer Protocols

• Telnet
• Used to log on to remote hosts using TCP/IP
  protocol suite
• File Transfer Protocol (FTP)
• Used to send and receive files via TCP/IP
• Simple Mail Transfer Protocol (SMTP)
• Responsible for moving messages from one e-mail
  server to another, using the Internet and other
  TCP/IP-based networks
• Simple Network Management Protocol (SNMP)
• Manages devices on a TCP/IP network

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Labs

• FTP Lab
• Telnet Lab

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Addressing in TCP/IP

• IP Address
• Logical address used in TCP/IP networking
• Unique 32-bit number
• Divided into four groups of octets (8-bit bytes)
  that are separated by periods
• IP addresses are assigned and used according to
  very specific parameters

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Addressing in TCP/IP

• Though 8 bits have 256 possible combinations,
  only the numbers 1 through 254 are used to
  identify networks and hosts
• Number 255 is reserved for broadcasts
• Broadcast are transmissions to all stations on a
  network

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Addressing in TCP/IP

• Loopback address
• IP address reserved for communicating from a node
  to itself
• Value of the loopback address is always 127.0.0.1
• Internet Corporation for Assigned Names and
  Numbers (ICANN)
• Non-profit organization currently designated by
  U.S. government to maintain and assign IP
  addresses

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Addressing in TCP/IP

• Firewall
• Specialized device (typically a router)
• Selectively filters or blocks traffic between
  networks
• May be strictly hardware-based or may involve a
  combination of hardware and software
• Host
• Computer connected to a network using the TCP/IP
  protocol

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Addressing in TCP/IP

• In IP address 131.127.3.22, to convert the first
  octet (131) to a binary number
• On Windows 2000, click Start, point to Programs,
  point to Accessories, then click Calculator
• Click View, then click Scientific (make sure Dec
  option button is selected)
• Type 131, then click Bin option button
• The binary equivalent of number 131, 10000011,
  appears in the display window

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Addressing in TCP/IP

• Static IP address
• IP address manually assigned to a device
• Dynamic Host Configuration Protocol (DHCP)
• Application layer protocol
• Manages dynamic distribution of IP addresses on a
  network

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Viewing Current IP Information
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Viewing Current IP Information
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Addresses and Names

• In addition to using IP addresses, TCP/IP
  networks use names for networks and hosts
• Each host requires a host name
• Each network requires a network name, also called
  a domain name
• Together, host name and domain name constitute
  the fully qualified domain name (FQDN)

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NetBIOS and NetBEUI

• Network Basic Input Output System (NetBIOS)
• Originally designed by IBM to provide Transport
  and Session layer services
• Adopted by Microsoft as its foundation protocol
• Microsoft added Application layer component
  called NetBEUI

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NetBIOS and NetBEUI

• NetBIOS Enhanced User Interface
• Fast and efficient protocol
• Consumes few network resources
• Provides excellent error correction
• Requires little configuration
• Can handle only 254 connections
• Does not allow for good security

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NetBIOS Addressing
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Installing Protocols

• After installing protocols, they must be binded
  to NICs and services they run on or with
• Binding
• Process of assigning one network component to
  work with another

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Chapter Summary

• Protocols define standards for communication
  between nodes on a network
• Protocols vary in speed, transmission efficiency,
  utilization of resources, ease of setup,
  compatibility, and ability to travel between one
  LAN segments
• TCP/IP is the most popular network protocol

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Chapter Summary

• TCP/IP suite of protocols can be divided into
  four layers roughly corresponding to seven layers
  of OSI Model
• Operating in Transport or Network layers of OSI
  Model, TCP/IP core protocols provide
  communications between hosts on a network
• Each IP address is a unique 32-bit number,
  divided into four groups of octets separated by
  periods

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Chapter Summary

• Every host on a network must have a unique number
• Internetworking Packet Exchange/Sequenced Packet
  Exchange (IPX/SPX) is a protocol originally
  developed by Xerox then modified and adopted by
  Novell in the 1980s for its NetWare network
  operating system
• Core protocols of IPX/SPX provide services at
  Transport and Network layers of OSI Model

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Chapter Summary

• Addresses on an IPX/SPX network are called IPX
  addresses
• Network Basic Input Output System (NetBIOS) was
  originally developed by IBM to provide Transport
  and Session layer services
• Microsoft adopted NetBIOS as its foundation
  protocol, then added an Application layer
  component called NetBIOS Enhanced User Interface
  (NetBEUI)

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Chapter Summary

• To transmit data between network nodes, NetBIOS
  needs to know how to reach each workstation
• Each workstation must have a NetBIOS name
• AppleTalk is the the protocol suite used to
  interconnect Macintosh computers
• An AppleTalk network is separated into logical
  groups of computers called AppleTalk zones

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Chapter Summary

• Though Apple has improved AppleTalks ability to
  use different network models and span network
  segments, it remains unsuited to large LANs or
  WANs
• In addition to zone names, AppleTalk uses node
  IDs and network numbers to identify computers on
  a network
• Though some protocols (such as NetBIOS) require
  no configuration after installation, others (such
  as TCP/IP) do require configuration