Network Basics 2: Components

Here's some info on network components (OSI-model interpretation).

General:

Collision Domain:

- Layer 1 : amplified by hubs and repeaters (both being layer 1 devices)
- A group of network nodes (interfaces) with similar caracteristics concerning network performance, i.c. all network nodes that compete for bandwith.
- All devices on the same hub are in the same collision domain. Demarcated by layer 2 devices.

Broadcast Domain:

- Layer 2 : amplified by bridges and switches (both being layer 2 devices)
- A group of network nodes (interfaces) with similar caracteristics concerning network performance, i.c. network nodes that receive the same broadcasts.
- Ethernet broadcast: within 1 domain.
- ARP request can reach different networks over routers.

Components:

Repeater:

- Layer 1: Signal amplifier with 2 ports (no buffer).

Hub:

- Layer 1: multi-port repeater (typical for UTP).

Bridge:

- Layer 2: can read MAC-adresses (physical adresses): the bridge uses source and destination MAC adresses to build a table of nodes on its right- and leftside.
- Broadcasts and packets with unidentified destination pass through.

Switch:

- Layer 2: a hubbed bridge: can buffer several frames.

Router:

- Layer 3: demarcates the frontiers of a LAN (--> blocks (ethernet- and IP)broadcasts.)
- Sends packets to the correct interface. Routers are protocol-specific (--> IP-networks require IP-router). Multi-Protocol Routers can manage them all.
- Builds tables using network adresses.

Gateway:

- Layer 4: binds networks with different protocols.

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