Network Technology

• Encapsulation


  A process wherein a new string of information is added to an existing unit to form a new unit of information
• Decapsulation


  The reverse process of encapsulation wherein the header and tail of a packet are removed to obtain the data payload
• Packet


  A data unit that is exchanged and transmitted on a network, in the format of header+data payload+tail
• Header


  Information segment added before the data payload during packet assembly to facilitate information transmission
• Tail


  Information segment added after the payload to facilitate information transmission
• Protocol Data Units (PDUs)

  • Physical layer - raw bits
  • Data Link layer - a frame
  • Network layer - a packet
  • Transport layer - a segment
  • Session layer - the data passed to the network connection
  • Presentation layer - the data formatted for presentation
  • Application layer - the data received or transmitted by a software application
• Internet Protocol (IP)


  • Defines a packet and an addressing scheme
  • Transfers data between the Internet layer and network access layers
  • Routes packets to remote hosts
• Internet Control Message Protocol (ICMP)


  • Handles errors and controls the process of sending data between computers
  • Includes an echo request/reply that is used to test whether a destination is reachable and responding
• Internet Group Management Protocol (IGMP)


  • Handles multicasting
  • Hosts use IGMP to keep local routers apprised of their membership in multicast groups
• Address Resolution Protocol (ARP)


  • Obtains the physical address of a node from a specific IP number
  • Used to dynamically bind a high-level IP address to a low-level physical hardware address
• Reverse Address Resolution Protocol (RARP)


  • Allows a host with no local permanent data storage media to find its Internet address given its physical address
• Common Network Access Layer Protocols


  • Ethernet
  • Point-to-Point Protocol (PPP)
  • Fiber distributed data interface (FDDI)
  • Asynchronous Transfer Mode (ATM)
  • Frame Relay
  • Proxy ARP
• Routing


  The process of selecting paths on a network along which packets are sent from a source to a destination
• Path determination


  • Enables a router to compare the destination address to the available routes in its routing table and to select the best path
• Route


  The path information used to guide packet forwarding
• Routing device (Router)


  A network device that forwards packets to a destination subnet based on routes, maintaining an IP routing table that stores routing information
• Packet forwarding


  The passing or moving of information between interfaces according to the "directions"
• Packet Delivery


  Direct Delivery - when the IP node forwards a packet to its final destination

  Indirect Delivery - when the IP node forwards a packet to an intermediate node because the final destination is not on a directly attached network
• Routing Table


  A database that contains information about which router network interface or port to place information to send it to a particular network segment
• Routing Table Fields


  • Destination/Mask
  • Protocol (Proto)
  • Preference (Pre)
  • Cost
  • Next Hop
  • Interface
• The table lists the preferences of some common routing protocols
• Route Preference


  When a router obtains routes to the same destination subnet from different routing protocols, the router compares the preferences of these routes and prefers the route with the lowest preference value
• Types of Routing


  • Direct routes
  • Static routes
  • Dynamic routes
• it is a database that contains information about which network interface or port to place information to send it to a particular netwoork segment.

  Routing Table (Huawei)
• occurs when the IP node forwards a packet to its final destination in the network


  Direct Delivery
• occurs when the IP node (host) forwards a packet to an intermediate node (IP router) because the final destination is not on a directly attached network


  Indirect delivery
• indicates the destination network address and mask of a specific route


  Destination/Mask
• indicates the protocol type of the route, that is, the protocol through which a router learns the route


  Protocol (proto)
• indicates the routing protocol preference of the route. it is used to compare routes from different routing protocols


  Preference (Pre)
• indicates the cost of the routes. it is also known as the metric.

  Cost
• indicates the local router's next-hop address of the route to the destination network.


  Next Hop
• indicated the outbound interface of the route


  Interface
• Command to check the IP routing table


  display ip routing-table
• are automatically generated by devices and point to local directly connected networks. These are the routes destined for the subnets ti which directly connected interface belong

  Direct routes
• are manually configured by network administrator. This can be an effective method for networks with small and simple structures and reduce the effect of bandwidth and CPU resource consumption that occurs when other protocols are implemented


  Static routes
• are learned by dynamic routing protocols running on routers. This route uses routing protocols to talk to other routers and find out what networks they are attached to

  Dynamic routes