Network Layer
Routing
Networks: Routing 1
, Network Layer
• Concerned with getting packets from source to
destination.
• The network layer must know the topology of the
subnet and choose appropriate paths through it.
• When source and destination are in different
networks, the network layer (IP) must deal with
these differences.
* Key issue: what service does the network layer
provide to the transport layer (connection-
oriented or connectionless).
Networks: Routing 2
, Network Layer Design Goals
1. The services provided by the network layer
should be independent of the subnet topology.
2. The Transport Layer should be shielded from the
number, type and topology of the subnets
present.
3. The network addresses available to the
Transport Layer should use a uniform
numbering plan (even across LANs and WANs).
Networks: Routing 3
Routing
Networks: Routing 1
, Network Layer
• Concerned with getting packets from source to
destination.
• The network layer must know the topology of the
subnet and choose appropriate paths through it.
• When source and destination are in different
networks, the network layer (IP) must deal with
these differences.
* Key issue: what service does the network layer
provide to the transport layer (connection-
oriented or connectionless).
Networks: Routing 2
, Network Layer Design Goals
1. The services provided by the network layer
should be independent of the subnet topology.
2. The Transport Layer should be shielded from the
number, type and topology of the subnets
present.
3. The network addresses available to the
Transport Layer should use a uniform
numbering plan (even across LANs and WANs).
Networks: Routing 3
