Chapter Three

1
Chapter Three

• Network
• Protocols

2
Agenda

• Attendance, and Ch.2 Quiz questions
• TCP/IP Model
• IP Header (Using Ethereal to analyze the IP
  header)
• TCP Header (using Ethereal to analyze the TCP
  Header)
• Address Resolution Protocol Lab

3
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

4
TCP/IP
OSI Model
TCP/IP

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

5
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)

6
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

8
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

11
IP header format
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IP header format Version

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

13
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.

15
IP header format Total length

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

16
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.

17
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.

22
IP header format Addresses

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

23
IP header format Options

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

24
IP header format Padding

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

25
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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Agenda

• Attendance and questions about last weeks
  material.
• TCP/IP Application Layers
• FTP Lab
• Telnet Lab
• Break
• Binary and hexadecimal conversion

33
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

36
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

38
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

39
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
42
Viewing Current IP Information
43
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)

44
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

45
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

46
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

48
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

49
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

50
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

51
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)

52
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

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Next Week

• Make sure that you have taken chapter 3 Quiz
  online
• Make sure that you have read chapter 11
• Download packet tracer from my web site and
  install it at home. Try to read the tutorial to
  gain some understanding on how it works. You
  will use this program in your project