CS601 Final Term Notes by Mohsin Chinioti

A TEAM BY VU SQUAD · CS-601 FINAL TERM NOTCE BY MOHSIN CHINIOTI · Chptr(9 to 16) · Note: M means MCQs & Q means Question Chapter 09 · Data-Link Layer

The Internet is a combination of networks joined together by connecting devices (routers or switches). M If a packet is to travel from a host to another host, it needs to pass through these networks. M Data Link layer controls node-to-node communication. M

Nodes and Links

Communication at the data-link layer is node-to-node. M A data unit from one point in the Internet needs to pass through many networks (LANs and WANs) to reach another point. We refer to the two routers as a node and the networks in between as a links. M

Services provided by Data-Link Layer

Data Link Layers Located between the physical and the network layers. M Data Link Layers Provides services to Network Layer and receives services from Physical layer. M

• Framing
• Flow Control
• Error Control
• Blocking Control

Two Categories of Links

We can have the following two types of links: M &Q

•  Point-to-point link or a
•  Broadcast link

Two nodes are physically connected by a transmission medium such as cable or air. M Data-link layer controls how the medium is used

•  Data-link layer can use whole capacity
•  Data-link layer can use only part of the capacity

Two Sub layers of Data-Link Layer M

• Data Link Control (DLC)
• Media Access Control (MAC)

DLC is both Broadcast and point to point links. M MAC is Only Broadcast link. M

Why LINK-LAYER ADDRESSING?

IP addresses are the identifiers at the network layer. M In Internet we cannot make a packet reach its destination using only IP addresses. Source end and destination end, IP addresses define the both ends but cannot define which links the packet will take.

Three Types of addresses

Some link-layer defines three types of addresses: M

• Unicast
• Multicast
• Broadcast

Even numbers show the multicast Address. M