Computer Networks · M2 · read

Device, link, frame, packet and router

Only the basics you need

Prerequisites for CN M2

Definition. A computer network is a collection of interconnected devices that exchange data using agreed communication rules called protocols.

Simple meaning. Device number bhejta hai; link usko carry karta hai; protocol batata hai kaise bhejna hai.

Swipe across the diagram to read its labels ↔

Diagram: One packet travels through several local links. Labels: One packet travels through several local links | One packet travels through several local links | 1. Host creates an IP packet | Destination IP identifies where the packet is going. | 2. Local frame carries it to the next hop | The next-hop MAC address is used on the current Ethernet link. | 3. Router selects another next hop | It uses the destination prefix and its forwarding table. | 4. A new local frame carries the packet onward | The link-layer addresses belong to the new link.

Understand it step by step

1. A host is an end device such as a laptop. A link is the wired or wireless connection over which data travels.
2. A bit is 0 or 1. A frame is the data-link unit carried over one link. A packet is the network-layer unit, such as an IP packet. A packet is normally carried inside a frame.
3. A switch forwards Ethernet frames within a local network using MAC addresses. A router forwards IP packets between networks using destination IP addresses.
4. An IP address identifies an interface logically. An Ethernet MAC address is used for delivery on the current local link. The local next-hop MAC can change at each routed hop.

Yaad rakho: Frame = ek link; packet = networks ke paar.