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  1. Introduction
  2. Network Model
  3. Topology
  4. Physical Media
  5. Wireless Media
  6. Network Card
  7. Modems
  8. Outside Connections
  9. Wide Area Network Connections
  10. Repeaters, Bridges, Routers
  11. Network Types
  12. Ethernet
  13. Token Ring
  14. ARCnet
  15. AppleTalk
  16. FDDI
  17. Architecture Comparisons
  18. Categories
  19. TCP/IP
  20. IPX/SPX
  21. NetBEUI
  22. AppleTalk
  23. SNA
  24. Others
  25. Suites and Network Layers
  26. Installing Drivers
  27. DNS
  28. Network Operating Systems
  29. Applications, mail, groupware, DBMS
  30. Backing up the network
  31. Troubleshooting
  32. Web, SNMP, admin, firewalls
  33. Networking Terms and Definitions
  34. Credits

Ethernet

The IEEE 802.3 standard defines ethernet at the physical and data link layers of the OSI network model. Most ethernet systems use the following:

  • Carrier-sense multiple-access with collision detection (CSMA/CD) for controlling access to the network media.
  • Use baseband broadcasts
  • A method for packing data into data packets called frames
  • Transmit at 10Mbps, 100Mbps, and 1Gbps.

Types of Ethernet

  • 10Base5 - Uses Thicknet coaxial cable which requires a transceiver with a vampire tap to connect each computer. There is a drop cable from the transceiver to the Attachment Unit Interface (AIU). The AIU may be a DIX port on the network card. There is a transceiver for each network card on the network. This type of ethernet is subject to the 5-4-3 rule meaning there can be 5 network segments with 4 repeaters, and three of the segments can be connected to computers.
    • Uses terminators.
    • Vampire tap is used to connect stations and drip cables may be up to 50 meters.
    • It uses bus topology.
    • Maximum segment length is 500 Meters with the maximum overall length at 2500 meters.
    • Minimum length between nodes is 2.5 meters.
    • Maximum nodes per segment is 100.
  • 10Base2 - Uses Thinnet coaxial cable. Uses a BNC connector and bus topology requiring a terminator at each end of the cable. The cable used is RG-58A/U or RG-58C/U with an impedance of 50 ohms. RG-58U is not acceptable. Uses the 5-4-3 rule meaning there can be 5 network segments with 4 repeaters, and three of the segments can be connected to computers. Barrel connectors can be used to link smaller pieces of cable on each segment, but each barrel connector reduces signal quality. To troubleshoot, the center of the T to the shield should be around 25 ohms. Terminators should be 50 ohms. One end of each cable should be grounded.
    • Uses terminators.
    • It uses bus topology.
    • The maximum length of one segment is 185 meters.
    • Minimum length between nodes is 0.5 meters.
  • 10BaseT - Uses Unshielded twisted pair (UTP) cable. Uses star topology. Shielded twisted pair (STP) is not part of the 10BaseT specification. Not subject to the 5-4-3 rule. They can use category 3, 4, or 5 cable, but perform best with category 5 cable. Category 3 is the minimum. Require only 2 pairs of wire. Cables in ceilings and walls must be plenum rated. Maximum segment length is 100 meters. Minimum length between nodes is 2.5 meters. Maximum number of connected segments is 1024. Maximum number of nodes per segment is 1 (star topology). Uses RJ-45 connectors.
  • 10BaseF - Uses Fiber Optic cable. Can have up to 1024 network nodes. Maximum segment length is 2000 meters. Uses specialized connectors for fiber optic. Includes three categories:
    • 10BaseFL - Used to link computers in a LAN environment, which is not commonly done due to high cost. Speed is 10Mbps.
    • 10BaseFP - Used to link computers with passive hubs to get cable distances up to 500 meters.
    • 10BaseFB - Used as a backbone between hubs.
  • 100BaseT - Also known as fast ethernet. Uses RJ-45 connectors. Topology is star. Uses CSMA/CD media access. Minimum length between nodes is 2.5 meters. Maximum number of connected segments is 1024. Maximum number of nodes per segment is 1 (star topology). IEEE802.3 specification.
    • 100BaseTX - Requires category 5 two pair cable. Maximum distance is 100 meters.
    • 100BaseT4 - Requires category 3, 4, or 5 cable with 4 pair. Maximum distance is 100 meters.
    • 100BaseFX - Can use fiber optic to transmit up to 2000 meters. Requires two strands of fiber optic cable.
    A media converter can be used to adapt from one cable type to another. Full duplex simultaneously transmits and receives data effectivly doubling the 100 Mbps speed. It also extends the distance of 100BaseFX to 2000 meters from 400 meters.
  • 100VG-AnyLAN - Requires category 3 cable with 4 pair. Maximum distance is 100 meters with cat 3 or 4 cable. Can reach 150 meters with cat 5 cable. Two segment lengths combined cannot exceed 250 meters. Can use fiber optic to transmit up to 2000 meters. This ethernet type supports transmission of Token-Ring network packets in addition to ethernet packets. IEEE 802.12 specification. Speed is 100Mbps. Uses demand-priority media access control. The topology is star. It uses a series of interlinked cascading hubs. Uses RJ-45 connectors.
  • 10BaseX - Uses UTP and CSMA/CD.
  • 10Broad36 - Uses a coax cable with maximum segment length of 3600 meters. It uses broadband transmission.

The IEEE naming convention is as follows:

  1. The transmission speed in Mbps
  2. Baseband (base) or Broadband data transmission
  3. The maximum distance a network segment could cover in hundreds of meters.

10Base2 and fiber ethernet networks may mix using a fiber/thinnet repeater. If thinnet has repeaters, the signal quality error (SQE) must be off or the SQE signal will look like collissions on the network.

Ethernet Comparisons

EthernetCableSpeedTopologyNodes/NetMax SegmentsMax Seg Length
10Base5Thicknet10MbpsBus1005500 meters
10Base2Thinnet10MbpsBus5-4-35185 meters
10BaseT4UTP Cat 3, 4 pair10MbpsStar10244 hubs in a row100 meters
10BaseT5UTP Cat 3, 5 pair10MbpsStar10244 hubs in a row100 meters
10BaseTXUTP Cat 5, 2 pair10MbpsStar10244 hubs in a row100 meters
10BaseFFiber10Mbps10242000 meters
100VG-AnyLANUTP Cat 3,4100MbpsStar1024100 meters
UTP Cat 5100MbpsStar1024150 meters
Fiber100MbpsStar10242000 meters

Types of ethernet frames

  • Ethernet 802.2 - These frames contain fields similar to the ethernet 802.3 frames with the addition of three Logical Link Control (LLC) fields. Novell NetWare 4.x networks use it.
  • Ethernet 802.3 - It is mainly used in Novell NetWare 2.x and 3.x networks. The frame type was developed prior to completion of the IEEE 802.3 specification and may not work in all ethernet environments.
  • Ethernet II - This frame type combines the 802.3 preamble and SFD fields and include a protocol type field where the 802.3 frame contained a length field. TCP/IP networks and networks that use multiple protocols normally use this type of frames.
  • Ethernet SNAP - This frame type builds on the 802.2 frame type by adding a type field indicating what network protocol is being used to send data. This frame type is mainly used in AppleTalk networks.

The packet size of all the above frame types is between 64 and 1,518 bytes.