The Institution of Electrical and Electronics Engineers (IEEE) has defined standards for local area networks, metropolitan area networks, and wireless LANs as the IEEE 802 standards. The IEEE 802 standards describe the operation of networking protocols, services, devices, and media at the two lowermost layers of the seven-layer OSI reference model: the Data Link and Physical layers. (The OSI model is discussed later in this section.) The Data Link layer is further divided into two layers: the Logical Link Control (LLC) layer and the MAC layer. Table 1 lists various standards in the IEEE 802 family.
1. IEEE 802.2
The 802.2 standard describes how the upper-layer protocols access the Logical Link Control (LLC), which is the upper layer of the two Data Linklayers in the OSI model. This standard defines how different protocols manage the error control and data flow control. Error control refers to detection and retransmission of dropped packets, if requested. Flow control refers to management of data flow between network devices so that they can efficiently handle flow of information.
The 802.2 standard describes how the upper-layer protocols access the Logical Link Control (LLC), which is the upper layer of the two Data Linklayers in the OSI model. This standard defines how different protocols manage the error control and data flow control. Error control refers to detection and retransmission of dropped packets, if requested. Flow control refers to management of data flow between network devices so that they can efficiently handle flow of information.
2. IEEE 802.3
The IEEE 802.3 standard describes characteristics for Ethernet networks at the Physical layer and at the MAC sub layer of the Data Link layer. This is a whole family of standards that define Ethernet networks with a variety of speeds and cabling. The IEEE 802.3 family of standards is collectively known as 802.3x standards.
Speed
The original IEEE 802.3 standard defined a speed of 10 Mbps over thin coaxial cable in Ethernet networks. With the Fast Ethernet standard 802.3u, the speed can go up to 100 Mbps. The 802.3z standard defines Gigabit Ethernet with a speed of up to 1000 Mbps.
Access method
The access method defines the process for network devices to access network media. Ethernet networks use the Carrier Sense Multiple Access/Collision Detection (CSMA/CD) method. Devices on the network continuously monitor the network media. If two devices start the transmission simultaneously, data collision occurs. If a collision occurs, the sending device is required to wait for a specified time before it can retransmit.
Topology
Original Ethernet networks could be wired using either the star or the bus topology using coaxial or twisted pair cables. IEEE 802.3u and 802.3z use only star topology with twisted pair cables.
Media
Media refers to the physical cabling of the network. A variety of cables types can be used with IEEE 802.3x standards including coaxial, twisted pair, and fiber optic. The choice of cables mainly depends on the specific standard used in the network.
The IEEE 802.3 standard describes characteristics for Ethernet networks at the Physical layer and at the MAC sub layer of the Data Link layer. This is a whole family of standards that define Ethernet networks with a variety of speeds and cabling. The IEEE 802.3 family of standards is collectively known as 802.3x standards.
Speed
The original IEEE 802.3 standard defined a speed of 10 Mbps over thin coaxial cable in Ethernet networks. With the Fast Ethernet standard 802.3u, the speed can go up to 100 Mbps. The 802.3z standard defines Gigabit Ethernet with a speed of up to 1000 Mbps.
Access method
The access method defines the process for network devices to access network media. Ethernet networks use the Carrier Sense Multiple Access/Collision Detection (CSMA/CD) method. Devices on the network continuously monitor the network media. If two devices start the transmission simultaneously, data collision occurs. If a collision occurs, the sending device is required to wait for a specified time before it can retransmit.
Topology
Original Ethernet networks could be wired using either the star or the bus topology using coaxial or twisted pair cables. IEEE 802.3u and 802.3z use only star topology with twisted pair cables.
Media
Media refers to the physical cabling of the network. A variety of cables types can be used with IEEE 802.3x standards including coaxial, twisted pair, and fiber optic. The choice of cables mainly depends on the specific standard used in the network.
3. IEEE 802.5
The IEEE 802.5 standard defines characteristics for Token Ring networks, originally developed by IBM. Token Ring is a LAN protocol that works at the Data Link layer of the OSI model. The Token Ring technology is rarely used these days because of the popularity of Ethernet networks. Even IBM no longer supports networks based on Token Ring technology. The characteristics of the IEEE 802.5 standard are as follows:
Speed
The transfer speed of IEEE 802.5 Token Ring networks is 4 Mbps and 16 Mbps.
Access method
Token Ring networks use the Token Passing access method. This uses a special three-byte frame known as a token that travels around the ring. The token keeps looking for a device on the ring that needs to transmit data. The device must acquire the token before it can transmit data on the network. Only one device can possess the token and transmit data at a time. The token travels with the data to the destination device where it is detached from the data and becomes free.
Topology
The physical setup of a Token Ring network is a star, while the logical setup is in a ring topology. A central device known as Multi-Station Access Unit (MSAU or MAU) is used to create a physical star topology.
The IEEE 802.5 standard defines characteristics for Token Ring networks, originally developed by IBM. Token Ring is a LAN protocol that works at the Data Link layer of the OSI model. The Token Ring technology is rarely used these days because of the popularity of Ethernet networks. Even IBM no longer supports networks based on Token Ring technology. The characteristics of the IEEE 802.5 standard are as follows:
Speed
The transfer speed of IEEE 802.5 Token Ring networks is 4 Mbps and 16 Mbps.
Access method
Token Ring networks use the Token Passing access method. This uses a special three-byte frame known as a token that travels around the ring. The token keeps looking for a device on the ring that needs to transmit data. The device must acquire the token before it can transmit data on the network. Only one device can possess the token and transmit data at a time. The token travels with the data to the destination device where it is detached from the data and becomes free.
Topology
The physical setup of a Token Ring network is a star, while the logical setup is in a ring topology. A central device known as Multi-Station Access Unit (MSAU or MAU) is used to create a physical star topology.
Media
The IEEE 802.5 standard defines the use of unshielded twisted pair (UTP) and shielded twisted pair (STP) cables.
4. IEEE 802.11
The IEEE 802.11 family of standards defines several protocols used for wireless communications. This standard defines all aspects of wireless communications from the frequency range specifications to physical layouts to authentication mechanisms. The original IEEE 802.11 standard is known as legacy 802.11. The characteristics of the IEEE 802.11 standard are as follows:
Speed
The data transfer speed defined in the legacy 802.11 standard was limited to 1 or 2 Mbps within the frequency range of 2.4 GHz. Speeds for other 802.11 standards are discussed later in this section.
Access method
Wireless networks use Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA), which is a variation of the CSMA/CD access method. The devices on the wireless network “listen” to the network for “silence” before they start transmission. This helps avoid collisions on the network media.
Topology
Wireless networks defined in IEEE 802.11 standards can be implemented in either Ad-hoc or Infrastructure topology as discussed earlier in this section.
Wireless networks defined in IEEE 802.11 standards use radio frequencies with spread spectrum technology: frequency-hopping spread spectrum (FHSS) or direct- sequence spread spectrum (DSSS). Spread spectrum technologies are discussed later in this section. The most popular of the IEEE 802.11 wireless network standards are 802.11b, 802.11a, and 802.11g. Security standards for these protocols are defined in the 802.11i standard.
IEEE 801.11b. The IEEE 802.11b standard defines DSSS-based network devices that use a 2.4 GHz frequency range and can communicate at speeds of 1,2, 5.5, or 11 Mbps. This standard is compatible with the legacy 802.11 standard. 802.11b is designed for a point-to-multipoint wireless communication setup. Usually a wireless access point (AP) is used with an omni-directional transmission antenna and can communicate with wireless clients located in the coverage area around the AP. The indoor range of a 802.11b wireless AP is about 100 feet (30 meters) at 11 Mbps speed When used with 1 Mbps speed, the range can be as high as 300 feet (90 meters).
IEEE 802.11a. The IEEE 802.11a standard uses a 5GHz frequency range with up to 54 Mbps data transmission speed. This standard defines the use of 52-subcarrier Orthogonal Frequency-Division Multiplexing (OFMD), which is a modulation technique. (Modulation techniques are covered later in this section.) If required, the data speed can be reduced to 48, 36, 24, 18, 16, 12, 9, and 6 Mbps. The IEEE 802. 11a standard is not backward-compatible with the 802.11b standard. The range for 802.11a-based devices is also about 100 feet (30 meters) when used indoors.
IEEE 802.11g. The IEEE 802.11g standard defines a frequency range of 2.4 GHz (same as 802.11b) but with much higher data transfer speeds of up to 54 Mbps. The data speed can fall back to lower values. IEEE 802.11g is backward-compatible with 802.11b standard devices. The devices normally use the OFDM modulation technique but can switch back to Quadrature Phase-Shift Keying (QPSK) modulation when the data speed falls back to 5.5 or 11 Mbps. Since it operates in the already crowded frequency range of 2.4 GHz, the 802.11g device is also susceptible to interferences such as the 802.11b devices.
The IEEE 802.5 standard defines the use of unshielded twisted pair (UTP) and shielded twisted pair (STP) cables.
4. IEEE 802.11
The IEEE 802.11 family of standards defines several protocols used for wireless communications. This standard defines all aspects of wireless communications from the frequency range specifications to physical layouts to authentication mechanisms. The original IEEE 802.11 standard is known as legacy 802.11. The characteristics of the IEEE 802.11 standard are as follows:
Speed
The data transfer speed defined in the legacy 802.11 standard was limited to 1 or 2 Mbps within the frequency range of 2.4 GHz. Speeds for other 802.11 standards are discussed later in this section.
Access method
Wireless networks use Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA), which is a variation of the CSMA/CD access method. The devices on the wireless network “listen” to the network for “silence” before they start transmission. This helps avoid collisions on the network media.
Topology
Wireless networks defined in IEEE 802.11 standards can be implemented in either Ad-hoc or Infrastructure topology as discussed earlier in this section.
Wireless networks defined in IEEE 802.11 standards use radio frequencies with spread spectrum technology: frequency-hopping spread spectrum (FHSS) or direct- sequence spread spectrum (DSSS). Spread spectrum technologies are discussed later in this section. The most popular of the IEEE 802.11 wireless network standards are 802.11b, 802.11a, and 802.11g. Security standards for these protocols are defined in the 802.11i standard.
IEEE 801.11b. The IEEE 802.11b standard defines DSSS-based network devices that use a 2.4 GHz frequency range and can communicate at speeds of 1,2, 5.5, or 11 Mbps. This standard is compatible with the legacy 802.11 standard. 802.11b is designed for a point-to-multipoint wireless communication setup. Usually a wireless access point (AP) is used with an omni-directional transmission antenna and can communicate with wireless clients located in the coverage area around the AP. The indoor range of a 802.11b wireless AP is about 100 feet (30 meters) at 11 Mbps speed When used with 1 Mbps speed, the range can be as high as 300 feet (90 meters).
IEEE 802.11a. The IEEE 802.11a standard uses a 5GHz frequency range with up to 54 Mbps data transmission speed. This standard defines the use of 52-subcarrier Orthogonal Frequency-Division Multiplexing (OFMD), which is a modulation technique. (Modulation techniques are covered later in this section.) If required, the data speed can be reduced to 48, 36, 24, 18, 16, 12, 9, and 6 Mbps. The IEEE 802. 11a standard is not backward-compatible with the 802.11b standard. The range for 802.11a-based devices is also about 100 feet (30 meters) when used indoors.
IEEE 802.11g. The IEEE 802.11g standard defines a frequency range of 2.4 GHz (same as 802.11b) but with much higher data transfer speeds of up to 54 Mbps. The data speed can fall back to lower values. IEEE 802.11g is backward-compatible with 802.11b standard devices. The devices normally use the OFDM modulation technique but can switch back to Quadrature Phase-Shift Keying (QPSK) modulation when the data speed falls back to 5.5 or 11 Mbps. Since it operates in the already crowded frequency range of 2.4 GHz, the 802.11g device is also susceptible to interferences such as the 802.11b devices.
5. Fiber Distributed Data Interface (FDDI)
The FDDI networking standard is based on Token Ring topology and describes the use of dual rings in order to provide fault tolerance to the network. It uses fiber optic cables, and the length of a single cable segment can be more than 200 Km. A variation of FDDI exists that uses copper wires and is called the Copper Distributed Data Interface (CDDI). CDDI uses the same protocols as FDDI. The characteristics of the FDDI standard are as follows:
Speed
FDDI networks can achieve a maximum data transfer speed of up to 100 Mbps.
Access method
Since this topology is based on Token Ring, the devices use the token passing method to access network media
Topology
FDDI is based on dual ring topology that provides fault tolerance.
Media
As the name suggests, FDDI uses fiber optic cables.
The FDDI networking standard is based on Token Ring topology and describes the use of dual rings in order to provide fault tolerance to the network. It uses fiber optic cables, and the length of a single cable segment can be more than 200 Km. A variation of FDDI exists that uses copper wires and is called the Copper Distributed Data Interface (CDDI). CDDI uses the same protocols as FDDI. The characteristics of the FDDI standard are as follows:
Speed
FDDI networks can achieve a maximum data transfer speed of up to 100 Mbps.
Access method
Since this topology is based on Token Ring, the devices use the token passing method to access network media
Topology
FDDI is based on dual ring topology that provides fault tolerance.
Media
As the name suggests, FDDI uses fiber optic cables.
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