Overview of the Network Core

Key Concepts

Network Core: Comprises a set of routers interconnected by communication links.
Packet Switching: Core operation of the internet where data is divided into packets and transmitted.
Circuit Switching: An alternative to packet switching, involves reserving network resources for a specific call.

Forwarding: Moving a packet from the router's input link to the output link. Controlled by a forwarding table.
Routing: Global action determining source to destination paths for packets. Involves routing algorithms to compute paths and forwarding tables.
Store-and-Forward: A packet's bits are transmitted, stored, and forwarded to the next link once fully received.

Forwarding Table: Used to find the destination address and determine the packet's path.
Queuing: Occurs when packets arrive faster than they can be forwarded, leading to delays and potential packet loss.
- Example: Home networks with varying transmission rates can lead to queuing.

Call Setup: Resources are allocated before the call starts, ensuring no queuing or data loss.
Sharing Methods:
- Frequency Division Multiplexing (FDM): Divides spectrum into frequency bands.
- Time Division Multiplexing (TDM): Divides time into slots.

Packet Switching Advantages:
- Efficient for bursty data.
- No call setup, simple operation.
- Can support more users due to statistical multiplexing.

Internet Structure: Described as a network of networks with multiple levels:
- Tier 1 ISPs: Large networks with national/international coverage.
- Regional Networks: Connect access networks closer to home.
- Access Networks: At the edge, connecting users.
- Content Provider Networks: Private networks for services like Google, Facebook.
Peering and Interconnection: Networks peer with each other at points like Internet Exchange Points.