UNIT-III
CONNECTING LANs-CONNECTING DEVICES
Layer-3 in the OSI model is called Network layer. Network layer manages options
pertaining to host and network addressing, managing sub-networks, and
internetworking.
Network layer takes the responsibility for routing packets from source to destination
within or outside a subnet. Two different subnet may have different addressing
schemes or non-compatible addressing types. Same with protocols, two different
subnet may be operating on different protocols which are not compatible with each
other. Network layer has the responsibility to route the packets from source to
destination, mapping different addressing schemes and protocols.
Layer-3 Functionalities
Devices which work on Network Layer mainly focus on routing. Routing may include
various tasks aimed to achieve a single goal. These can be:
Addressing devices and networks.
Populating routing tables or static routes.
Queuing incoming and outgoing data and then forwarding them according to
quality of service constraints set for those packets.
Internetworking between two different subnets.
Delivering packets to destination with best efforts.
Provides connection oriented and connection less mechanism.
Network Layer Features
With its standard functionalities, Layer 3 can provide various features as:
Quality of service management
Load balancing and link management
Security
Interrelation of different protocols and subnets with different schema.
Different logical network design over the physical network design.
L3 VPN and tunnels can be used to provide end to end dedicated connectivity.
, Internet protocol is widely respected and deployed Network Layer protocol which helps
to communicate end to end devices over the internet. It comes in two flavors. IPv4
which has ruled the world for decades but now is running out of address space. IPv6 is
created to replace IPv4 and hopefully mitigates limitations of IPv4 too.
Layer 3 network addressing is one of the major tasks of Network Layer. Network
Addresses are always logical i.e. these are software based addresses which can be
changed by appropriate configurations.
A network address always points to host / node / server or it can represent a whole
network. Network address is always configured on network interface card and is
generally mapped by system with the MAC address (hardware address or layer-2
address) of the machine for Layer-2 communication.
There are different kinds of network addresses in existence:
IP
IPX
AppleTalk
We are discussing IP here as it is the only one we use in practice these days.
IP addressing provides mechanism to differentiate between hosts and network.
Because IP addresses are assigned in hierarchical manner, a host always resides under
a specific network.The host which needs to communicate outside its subnet, needs to
CONNECTING LANs-CONNECTING DEVICES
Layer-3 in the OSI model is called Network layer. Network layer manages options
pertaining to host and network addressing, managing sub-networks, and
internetworking.
Network layer takes the responsibility for routing packets from source to destination
within or outside a subnet. Two different subnet may have different addressing
schemes or non-compatible addressing types. Same with protocols, two different
subnet may be operating on different protocols which are not compatible with each
other. Network layer has the responsibility to route the packets from source to
destination, mapping different addressing schemes and protocols.
Layer-3 Functionalities
Devices which work on Network Layer mainly focus on routing. Routing may include
various tasks aimed to achieve a single goal. These can be:
Addressing devices and networks.
Populating routing tables or static routes.
Queuing incoming and outgoing data and then forwarding them according to
quality of service constraints set for those packets.
Internetworking between two different subnets.
Delivering packets to destination with best efforts.
Provides connection oriented and connection less mechanism.
Network Layer Features
With its standard functionalities, Layer 3 can provide various features as:
Quality of service management
Load balancing and link management
Security
Interrelation of different protocols and subnets with different schema.
Different logical network design over the physical network design.
L3 VPN and tunnels can be used to provide end to end dedicated connectivity.
, Internet protocol is widely respected and deployed Network Layer protocol which helps
to communicate end to end devices over the internet. It comes in two flavors. IPv4
which has ruled the world for decades but now is running out of address space. IPv6 is
created to replace IPv4 and hopefully mitigates limitations of IPv4 too.
Layer 3 network addressing is one of the major tasks of Network Layer. Network
Addresses are always logical i.e. these are software based addresses which can be
changed by appropriate configurations.
A network address always points to host / node / server or it can represent a whole
network. Network address is always configured on network interface card and is
generally mapped by system with the MAC address (hardware address or layer-2
address) of the machine for Layer-2 communication.
There are different kinds of network addresses in existence:
IP
IPX
AppleTalk
We are discussing IP here as it is the only one we use in practice these days.
IP addressing provides mechanism to differentiate between hosts and network.
Because IP addresses are assigned in hierarchical manner, a host always resides under
a specific network.The host which needs to communicate outside its subnet, needs to
