Network Architecture Overview
The architecture on which you choose to base your network is the single most important decision you make when setting up a LAN. The architecture defines the speed of the network, the medium access control mechanism it uses (for example, collision detection, token passing, and so on), the types of cables you can use, the network interface adapters you must buy, and the adapter drivers you install.
The Institute of Electrical and Electronic Engineers (IEEE) has defined and documented a set of standards for the physical characteristics of both collision-detection and token-passing networks. These standards are known as IEEE 802.3 (Ethernet) and IEEE 802.5 (Token-Ring), respectively. IEEE 802.11 (Wi-Fi) defines wireless versions of Ethernet.
Note: Be aware, however, that the colloquial names Ethernet and Token-Ring actually refer to earlier versions of these architectures, on which the IEEE standards were based. Minor differences exist between the frame definitions for true Ethernet and true IEEE 802.3. In terms of the standards, IBM’s 16 Mb/s Token-Ring products are an extension of the IEEE 802.5 standard.
New Token-Ring installations are rare today and are not covered here.
The most common choice today for new networks is Ethernet (both wired and wireless). In rare cases, you may encounter a Token-Ring or ARCnet network. Network data-link architectures you might encounter are summarized in the following table. The abbreviations used for the cable types are explained in the following sections.
|LAN Architecture Summary|
|Network Type||Speed||Maximum Number of Stations||Transmission Types||Notes|
|Ethernet||10 Mb/s||1024||Category 3 UTP or better (10BASE-T), Thinnet RG-58 coax (10BASE-2), Thicknet coax (10BASE-5), fiber-optic (10BASE-F)||Replaced by Fast Ethernet; backward compatible with Fast or Gigabit Ethernet when using UTP.|
|Fast Ethernet||100 Mb/s||1024||Category 5 UTP or better||The most popular wired networking standard, rapidly being replaced by gigabit Ethernet.|
|Gigabit Ethernet||1000 Mb/s||1024||Category 5 UTP or better||Recommended for new installations; uses all four signal pairs in the cable.|
|10 Gigabit Ethernet||10 000 Mb/s||1024||Category 6a UTP or better||Uses all four signal pairs in the cable.|
|802.11a Wireless Ethernet||Up to 54 Mb/s||1024||RF 5 GHz band with dual-band 802.11n||Short range; interoperable with dual-band 802.11n.|
|802.11b Wireless Ethernet||Up to 11 Mb/s||1024||RF 2.4 GHz band||Interoperable with 802.11g/n.|
|802.11g Wireless Ethernet||Up to 54 Mb/s||1024||RF 2.4 GHz band||Interoperable with 802.11b/n.|
|802.11n Wireless Ethernet||Up to 600 Mb/s||1,024||RF 2.4/5 GHz bands||Longest range; interoperable with 802.11a/b/g; dual-band hardware needed to interoperate with 802.11a; recommended for new installations.|
|Token-Ring||4/16/100 Mb/s||72 on UTP; 250–260 on Type 1 STP||UTP, Type 1 STP, and fiber-optic||Replaced by Ethernet; obsolete for new installations.|
|ARCnet||2.5 Mb/s||255||RG-62 coax UTP, Type 1 STP||Replaced by Ethernet; obsolete for new installations; uses the same coax cable as IBM 3270 terminals.|
|UTP = unshielded twisted pair, STP = shielded twisted pair, RF = Radio Frequency|