Chapter 8: Network Layer

What are the 4 basic operations network layer PTCs perform? Explain in detail.

1) Addressing end devices - End devices must be configured with a unique IP address for identification on the network. 2) Encapsulation - The network layer encapsulates the protocol data unit (PDU) from the transport layer into a packet. The encapsulation process adds IP header information, such as the IP address of the source (sending) and destination (receiving) hosts. The encapsulation process is performed by the source of the IP packet. 3) Routing - The network layer provides services to direct the packets to a destination host on another network. To travel to other networks, the packet must be processed by a router. The role of the router is to select the best path and direct packets toward the destination host in a process known as routing. A packet may cross many routers before reaching the destination host. Each router a packet crosses to reach the destination host is called a hop. 4) De-encapsulation - When the packet arrives at the network layer of the destination host, the host checks the IP header of the packet. If the destination IP address within the header matches its own IP address, the IP header is removed from the packet. After the packet is de-encapsulated by the network layer, the resulting Layer 4 PDU is passed up to the appropriate service at the transport layer. The de-encapsulation process is performed by the destination host of the IP packet.

ID which range of IPs are for which class

A - 0-127 B - 128-191 C - 192-223 D - 224-239 E - 240-255

Which delivery method does not guarantee that the packet will be delivered fully without errors? connectionless, best effort, or media independent?

Best effort

If a computer has to send a packet to a destination host on the same LAN, how will the packet be sent?

Directly to the dest host.

What is the term for splitting up an IP packet when forwarding it from one medium to another medium with a smaller MTU?

Fragmentation

Go over the fields in IPv4 and IPv6 fields in the header.

IPv4 - version, DS, TTL, PTC, header checksum source IP address dest IP address IPv6 - version, traffic class, FC, payl length, next header, hop limit srce IP address, dest IP address

Which layer is responsible for taking an IP packet and preparing it for transmission over the communications medium?

L2 - data link layer

What info is added during encaps at OSI Layer 3?

L3, network layer, the source and destination IP address.

Which OSI layer sends segments to be encapsulated in an IPv4 or IPv6 packet?

L4 - transport layer

What is MTU and its relation the network layer?

Maximum Transmission Unit - L2, data link layer, sends the MTU to the L3 (network layer), L3 then uses that information to determine how large the packet can be when sending.

Describe one of the characteristics IPv6 enhancement over IPv4?

The IPv6 header is simpler than IPv4, which improves packet handling.

When a connectionless protocol is in use at a lower layer of the OSI model, how is missing data detected and retransmitted if necessary?

Upper-layer conn-oriented PTCs keep track of the data received and can request transmission from the upper level PTCs on the sending host.

What are the basic characteristics of IP?

best effort delivery - packets are sent without confirmation or retransmission regardless if data is missing when sent to destination host. more in chapter...

via Windows Host, what command is used to display the routing table? command used to display a router's routing table?

command used can either be: netstat -r route print to display a router's routing table, the command is show ip route

An IPv4 header has fewer fields than an IPv6 header has, true or false?

false, IPv4 has more fields.