Networking Notes 4 - Network support group

Network Layer

Network layer is concerned with getting packets from source all the way to destinations.

It is the lowest layer that deals with end-to-end transmission, and may make many hops at intermediate nodes.

Physical and data link layers only operate locally.

Hop - is one portion of the path between source and destination.

Network-Layer Function

• Connect heterogeneous networks together to look like a single network (Internetworking)
• Uniquely identify each device (addressing)
• Make decision to deliver data (routing)
• Fit data to size used by the lower layer protocol (fragmentation)

Jobs for sending side: encapsulates segments into datagrams

Jobs for receiving side: delivers segments to transport layer

Address in TCP

Physical address

Logical address

Port address

Physical Address

Address of a node as defined by its LAN or WAN

In a data link level, frame transfer only contains Physical addresses in the header.

Most LAN use a 48-bit(6bytes) physical address written as 12 hexadecimal digits with every digits separated by a colon.

Physical Address also called Media Access Control (MAC) address

MAC address is performed via the Address Resolution Protocol (ARP)

Logical Address

Universal address that can pass through the LAN boundaries.

Address of a LAN. Logical Address + Physical Address needed to send data to another LAN network.

Port Address

Computer can run multiple processes at the same time, but need to label different processes by using port address

Port address is 16-bit address. (2^16) 0 - 65535, 65536 in total.

DNS

Domain Name System

Translation of a hostname into an IP address.