SAAM 2

• Computer Network


  A collection of computers and computing resources connected together to facilitate communication between resources
• Establishing network access


  1. Have a network interface that connects to your network access point

  2. Run your network services

  3. Have access to a network-broadcast device
• Network interface


  • Ethernet device (Ethernet card or wireless card)
• Network-broadcast devices

  • Hub
  • Switch
  • Router
  • Gateway
• Hub


  Broadcasts the message it receives to all devices on the subnet where it operates
• Switch


  Broadcasts the message it receives to a single device on the subnetwork using a MAC address for addressing
• Router


  Examines a message's destination IP address and routes the message onto the proper network or subnetwork as the next link in the chain of the communication
• Gateway


  Connects local area networks of different types together
• TCP/IP layers


  • Network Interface Layer
  • Internet Layer
  • Transport Layer
  • Application Layer
• Network Interface Layer


  • Responsible for placing TCP/IP packets on the network medium and receiving TCP/IP packets off the network medium
• Internet Layer protocols

  • responsible for addressing, packaging, and routing functions
• Internet Protocol (IP)


  Responsible for IP addressing, routing, and the fragmentation and reassembly of packets
• Address Resolution Protocol (ARP)


  Responsible for the resolution of the Internet layer address to the Network Interface layer such as a hardware address
• Internet Control Message Protocol (ICMP)


  Responsible for providing diagnostic functions and reporting errors due to the unsuccessful delivery of IP packets
• Internet Group Management Protocol (IGMP)


  Responsible for the management of IP multicast groups
• Transport Layer protocols

  • responsible for providing the Application layer with session and datagram communication services
  • Transmission Control Protocol (TCP)
  • User Datagram Protocol (UDP)
• Transmission Control Protocol (TCP)


  Responsible for establishment of a TCP connection, the sequencing and acknowledging of packets sent, and the recovery of packets lost during transmission
• User Datagram Protocol (UDP)


  Used when the amount of data to be transferred is small, when the overhead of establishing a TCP connection is not desired, or when the applications or upper layer protocols provide reliable delivery
• Application Layer protocols


  • allows applications to access the services of the other layers and defines the protocols that applications use to exchange data.
  • Hypertext Transfer Protocol (HTTP)
  • File Transfer Protocol (FTP)
  • Simple Mail Transfer Protocol (SMTP)
  • Telnet
• Hypertext Transfer Protocol (HTTP)


  Used to transfer files that make up the Web pages of the World Wide Web
• File Transfer Protocol (FTP)


  Used for interactive file transfer
• Simple Mail Transfer Protocol (SMTP)


  Used for the transfer of mail messages and attachments
• Telnet


  A terminal emulation protocol used for logging on remotely to network hosts
• Other TCP/IP protocols


  • Domain Name System (DNS)
  • Routing Information Protocol (RIP)
  • Simple Network Management Protocol (SNMP)
• Domain Name System (DNS)


  Used to resolve a host name to an IP address
• Routing Information Protocol (RIP)


  Used by routers to exchange routing information on an IP internetwork
• Simple Network Management Protocol (SNMP)


  Used to collect and exchange network management information between a network management console and network devices
• Networking commands

  • ping
  • traceroute/tracepath
  • ip
  • netstat
  • ftp
  • wget
  • ssh
• ping


  Sends a special network packet called an ICMP ECHO_REQUEST to network hosts
• traceroute/tracepath


  Prints the route packets trace to a network host
• ip

  Shows/manipulates routing, devices, policy routing, and tunnels
• netstat


  Prints network connections, routing tables, interface statistics, masquerade connections, and multicast memberships
• ftp


  Internet file transfer program
• wget


  Non-interactive network downloader
• ssh


  OpenSSH SSH client (remote login program)
• ping linuxcommand.org


  Sample usage of ping
• tracepath sti.edu

  Sample usage of tracepath
• ip a


  Sample usage of ip a
• netstat-ie


  Sample usage of netstat
• netstat-r


  Sample usage of netstat-r