Topic #11: The Network Layer Flashcards
It is the layer that provides services to exchange data over the network between end devices
Network Layer
Differences between the Network and Transport Layer
Transport layer connects processes while Network Layer enables devices to reach each other
4 Processes in the Network Layer
Addressing
Encapsulation
Routing
Decapsulation
Functions of the Network Layer
- receives segments of data from the transport layer
- uses protocols to add addressing information and other information and send it along the best path
Function of Network Layer Protocols
- shares upper-layer information between hosts
- specifies the addressing and packaging of a transport layer and describe how the PDU is to be carried with minimum overhead
Network Layer tasks to be performed
- Addressing packets with an IP address
- Encapsulation of Packets
- Routing of Packets
- Decapsulation of Packets
Devices in IP networks that have IP addresses
Hosts
IP address of the sending host
source IP address
IP address of the receiving host
destination IP address
This contains the address information and some other bits that identify the PDU as a network layer PDU
IP headeer
The process of adding the address information to the data
Encapsulation
When a level 4 PDU has been encapsulated what is it referred to?
Packet
It is the process routers perform when receiving packets, analyze address information, use the address information to select a path for the packet and forward it to the next router
Routing
Each route that a packet takes to reach the next device
Hop
It is the process of removing encapsulation data at different layers
Decapsulation
Where does the IP packet decapsulated
at the Final destination
Network Layer protocols
IPv4
IPv6
Novell IPX
AppleTalk
Connectionless Network Service
It is the most widely used network protocol
Internet Protocol version 4
It is an network layer protocol that will work with IPv4 and will likely to replace it
IPv6
A Widely popular internetworking protocol in the 1980s and 1990s
Novell IPX
Apple Computer’s proprietary networking protocol
AppleTalk
it is a common networking protocol used in telecommunication networks that does not require established circuits
Connectionless Network Service
Characteristics of IPv4
- Connectionless - receiving host is NOT contacted before the message is sent
- Best Effort - IP does not have the capability to manage and recover, missing and corrupt packets
- Independent - operates independently of the medium carrying the data
Key fields in an IPv4 Header
IP Source Address
IP Destination Address
Time to Live
Type of Service
Protocol
Flag and Fragment Offset
This IPv4 key field contains the host that will send the packet
IP Source Address
This IPv4 key field contains the host that will receive the packet
IP Destination Address
This IPv4 field describes the maximum hops a packet can take before it is considered “lost” or undeliverable
Time to Live
This IPv4 field describes the level of throughput priority a router should use in processing a packet
Type of Service
This IPv4 field describes upper-layer protocol
Protocol
This IPv4 field describes whether to fragment a packet when forwarding it from one medium to another
Flag and Fragment Offset
This IPv4 field describes whether it is version 4 or 6
Version
This IPv4 field describes how long the header is
Internet Header Length
This IPv4 field helps reassemble any fragments
Identification
This IPv4 field describes the length of the header
Header Checksum
This IPv4 field used rarely to provide special routing services
Options
This IPv4 field is used when header does not end on a 32-bit boundary
Padding
Basis to divide networks
*Purpose - users with similar software and bandwidth needs are grouped together
*Ownership - users that help in controlling access, administration and security are grouped together
Geographic Location - users that are in the same location are grouped together
Reasons to Separate Hosts in a Network
- Increase performance
- Better Security
- Better address management
