2. INTRODUCTION
• The Network Access Layer is the lowest layer of the TCP/IP
protocol suite.It is the most mysterious and least uniform of
TCP/IP's layers.
• The Network Access layer manages all the services and
functions necessary to prepare the data for the physical
network .The protocols in this layer provide the means for the
system to deliver data to the other devices on a directly
attached network. It defines how to use the network to
transmit an IP datagram.
• A network interface device, usually a line card, adaptor or
port is used to connect the physical wires or fibers to the
computer so that it can communicate with other computers.
This network interface is assigned an address from the
Internet Layer so that it can communicate with devices on
other networks.
4. INTRODUCTION
• Unlike higher-level protocols, Network Access Layer
protocols must know the details of the underlying network
(its packet structure, addressing, etc.) to correctly format
the data being transmitted to comply with the network
constraints.
• The TCP/IP Network Access Layer can encompass the
functions of all three lower layers of the OSI reference
Model (Data Link, and Physical).
• As new hardware technologies appear, new Network
Access protocols must be developed so that TCP/IP
networks can use the new hardware. Consequently, there
are many access protocols - one for each physical network
standard.
5. FUNCTIONS OF THE NETWORK
LAYER
•
•
•
•
Functions performed at this level include encapsulation of IP datagrams(a unit of
information in the Internet Protocol containing both data and address information)
into the frames transmitted by the network.
Mapping of IP addresses to the physical addresses used by the network. One of
TCP/IP's strengths is its universal addressing scheme. The IP address must be
converted into an address that is appropriate for the physical network over which
the datagram is transmitted.
It defines how to use the the network to transmit an IP datagram
It formats the data being transmitted to comply with the network constraints
6. EXAMPLES OF
PROTOCOLS IN THE
NETWORK ACCESS LAYER
• Address Resolution Protocol(ARP)-obtains the MAC
•
•
•
•
•
address/pysical address a unique address assigned to a
Network Interface Card(NIC)
Internetwork Packet Exchange(IPX)-provides
internetworking services as well as logical addressing
Point to Point Protocol(PPP)-connects multiple users
on a LAN to a remote location
Internet Protocol(IP)-gives info on how & where data
should be delivered
Open Short Path First Protocol(OSPF)
Media Access Protocols
