Network Layer Concepts and Routing Overview

IP Datagram Format

Fields: Version, Header Length, Total Length, TTL, Protocol, Checksum, Source/Destination Address, etc.

Data Plane

Responsible for forwarding data packets.

Control Plane

Determines the path packets take.

Forwarding

One of the two key functions of the network layer.

Routing

One of the two key functions of the network layer.

Router Architecture

Input ports, switching fabric, output ports, and routing processor.

Longest Prefix Matching

Used in routing tables to determine the best match for a destination IP.

Switching Fabrics

Types: Memory, Bus, and Crossbar.

Input/output port queuing

Occurs when packets arrive faster than can be processed.

Scheduling mechanisms

FIFO, priority, round-robin, weighted fair queuing (WFQ).

Subnetting

Divide IP networks into smaller segments.

DHCP

Dynamically assigns IP addresses to devices.

NAT (Network Address Translation)

Allows multiple devices to share one public IP address.

IPv6

New version of IP with a 128-bit address space.

Tunneling

Encapsulating IPv6 packets in IPv4 packets for transport.

SDN (Software-Defined Networking)

SDN separates control and data planes.

OpenFlow

Protocol enables communication between the SDN controller and switches.

Link-State (LS)

Uses global information about the network.

Distance-Vector (DV)

Uses local information from neighbors.

Intra-AS Routing

Routing within an autonomous system (e.g., OSPF).

Inter-AS Routing

Routing between autonomous systems (e.g., BGP).

OSPF (Open Shortest Path First)

A link-state routing protocol used in intra-AS routing.

BGP (Border Gateway Protocol)

Used for inter-AS routing and policy-based routing.

ICMP (Internet Control Message Protocol)

Used for diagnostic purposes (e.g., ping, traceroute).

SNMP (Simple Network Management Protocol)

Protocol for monitoring and managing network devices.

Link Layer Services

Framing, error detection/correction, and medium access control.

Link Layer Implementation

Typically in the network interface card (NIC).

Cyclic Redundancy Check (CRC)

Used to detect errors in data transmission.

Multiple Access Protocols

TDMA/FDMA: Divide access by time or frequency.

ALOHA Protocol

Random access method with high collision probability.

CSMA (Carrier Sense Multiple Access)

Listens before transmitting to avoid collisions.

Cable Access Networks

Use frequency division multiplexing for shared access.

ARP (Address Resolution Protocol)

Maps IP addresses to MAC addresses.

Ethernet

A widely used link-layer technology with broadcast and unicast frames.

Switches

Forward frames based on MAC addresses.

VLANs

Allow logical segmentation of networks.

Data Center Networking

Scalable networking techniques for high-density environments.

What are the two key functions of the network layer?

Forwarding and routing.

How does NAT work?

NAT allows multiple devices to share a single public IP by translating private IPs to a public IP.

What protocol is used for inter-AS routing?

BGP (Border Gateway Protocol).

What is the purpose of VLANs?

VLANs enable logical segmentation of networks, improving security and performance.

What is the maximum address size for IPv6?

128 bits.

What does the Cyclic Redundancy Check (CRC) detect?

Errors in data transmission.