Network topology
Local area networks
- Local Area Network (LAN): A number of computing devices on a single site or in a single building, connected together by cables
- May consist of a number of PCs, other devices (like printers and scanners), and a central server.
- Users on the network can:
- Communicate with each other
- Share data
- Share hardware devices (e.g. printers and scanners)
- Can transmit data very fast, but only over a short distance
Bus vs star topology
- LANs can use different layouts, or topologies
- Network topology: The arrangement of the elements of a communication network
| Bus topology | Star topology |
|---|---|
| All computers connected to a single cable, the ends of which are plugged into a terminator | All computers connected to a central node, which may be a switch or computer acting as a router to transmit messages |
| }}Inexpensive to install - requires less cable and no additional hardware}} | [[Costly to install - a lot more cable required[[ |
| [[If the main cable fails, network data can no longer be transmitted to any of the nodes[[ | }}If one cable fails, only one station is affected - simple to isolate faults}}[[But, if the central device fails, network data can no longer be transmitted to any node[[ |
| [[Performance degrades with heavy traffic[[ | }}Consistent performance even when the network is being heavily used}} |
| }}Low security - all computers on the network can see all data transmissions}} | }}System is more secure - messages sent directly to the central computer and cannot be intercepted by other stations}} |
| }}No problems with data ‘collisions’}} | |
| }}Higher transmission speeds - can give better performance}} | |
| }}Easy to add stations without disrupting the network}} |
Operation of a star network
- Switch keeps a record of the unique MAC address of each device on the network and can identify which particular computer on the network it should send the data to.
Operation of a logical bus network
- Network signals are sent through the main cable to reach all connected devices (or station)
- Traffic generated by each station has equal priority
- Each message contains a destination address that identifies its intended recipient
- Only the intended recipient actually accepts and processes the message
Physical vs logical topology
- Physical topology: The actual design layout of a network
- Logical topology: The shape of the path the data travels in a network, describing how components communicate across the physical topology
- They are independent of each other
- A network physically wired as a star topology can behave logically as a bus network by using a bus protocol and appropriate physical switching
- Any variety of Ethernet uses a logical bus topology when components communicate, regardless of the physical cable layout
MAC addresses
- MAC address: Media Access Control address
- Media Access Control (MAC) address: The unique address that identifies a NIC, which is assigned and hard-coded by the manufacturer
- 48 bits long
- Written as 12 hex digits
- E.g. 00-09-5D-E3-F7-62
- Unique → can be used to track devices
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