Pre-Finals 2

• Computer Network


  It is a collection of computers and computing resources connected together to facilitate communication between resources.
• The most common network interface

  Ethernet device
• An ethernet device can be

  1. Ethernet card, which is a wired connection
  2. Wireless card
• Card that connects your computer to a LAN

  Ethernet card
• The most important service


  Network
• Type of Network Services

  1. Firewall service
  2. Interface device services
  3. network authentication services
  4. network file systems services
• 4 Categories of 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.
• What is TCP?


  Transmission Control Protocol
• 4 Layers of TCP/IP

  1. Network Interface Layer (Network Access Layer)
  2. Internet Layer
  3. Transport Layer
  4. Application Layer
• Network Interface Layer (Network Access Layer)


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


  responsible for addressing, packaging, and routing functions.
• What layer in TCP/IP has 4 core protocols.

  Internet Layer
• 4 Core Protocols of Internet Layer

  1. Internet Protocol (IP)
  2. Address Resolution Protocol (ARP)
  3. Internet Control Message Protocol (ICMP)
  4. Internet Group Management Protocol (IGMP)
• 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 


  responsible for providing the Application layer with session and datagram communication services
• 2 Core Protocols of Transport Layer

  • 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:

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


  allows applications to access the services of the other layers and defines the protocols that applications use to exchange data.
• The most widely known application layer protocols are.

  • Hypertext Transfer Protocol (HTTP)
  • File Transfer Protocol (FTP)
  • Simple Mail Transfer Protocol (SMTP)
  • Telnet
• Telnet


  a terminal emulation protocol used for logging on remotely to network hosts.
• Hypertext Transfer Protocol (HTTP) 


  used to transfer files that make up the Web pages of the World Wide Web.
• Simple Mail Transfer Protocol (SMTP) 


  used for the transfer of mail messages and attachments.
• File Transfer Protocol (FTP) 


  used for interactive file transfer.
• 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