PinoyBIX Engineering Problem Solving and Reference

Lesson Objectives - the students should be able to:

Lecture on Network Models PPT

List of Data Communications Course Outline and Lectures

Definition of Terms

• The International Standards Organization created a model called the Open Systems Interconnection, which allows diverse systems to communicate.
• The seven-layer OSI model provides guidelines for the development of universally compatible networking protocols.
• ISO is the organization. OSI is the model.
• The physical layer coordinates the functions required to transmit a bit stream over a physical medium.
• The data link layer is responsible for delivering data units from one station to the next without errors.
• The network layer is responsible for the source-to-destination delivery of a packet across multiple network links.
• The transport layer is responsible for the process-to-process delivery of the entire message.
• The session layer establishes, maintains, and synchronizes the interactions between communicating devices.
• The presentation layer ensures interoperability between communicating devices through transformation of data into a mutually agreed upon format.
• TCP/IP is a five-layer hierarchical protocol suite developed before the OSI model.
• The TCP/IP application layer is equivalent to the combined session, presentation,
  and application layers of the OSI model.

Lesson Objectives - the students should be able to:

Lecture on Introduction to Datacommunication and Networking PPT

List of Data Communications Course Outline and Lectures

Definition of Terms

• Data communication is the transfer of data from one device to another via some form of transmission medium.
• A data communications system must transmit data to the correct destination in an accurate and timely manner.
• A network is a set of communication devices connected by media links.
• Topology refers to the physical or logical arrangement of a network. Devices may be arranged in a mesh, star, bus, or ring topology.
• An internet is a network of networks.
• The Internet is a collection of many separate networks.
• TCP/IP is the protocol suite for the Internet.
• A protocol is a set of rules that governs data communication; the key elements of a protocol are syntax, semantics, and timing.
• Standards are necessary to ensure that products from different manufacturers can work together as expected.
• Forums are special-interest groups that quickly evaluate and standardize new technologies.
• A Request for Comment (RFC) is an idea or concept that is a precursor to an Internet standard.

Definition of Terms

• At the network layer, a global identification system that uniquely identifies every host and router is necessary for delivery of a packet from host to host (network to network).
• An IPv4 address is 32 bits long and uniquely and universally defines a host or router on the Internet. 
• The IPv4 addresses are unique and universal.
• The address space of  IPv4 is 2³² or 4,294,967,296.
• An address space is the total number of addresses used by the protocol. If a protocol uses N bits to define an address, the address space is 2N because each bit can have two different values (0 or 1) and N bits can have 2N values.
• In binary notation, the IPv4 address is displayed as 32 bits. Each octet is often referred to as a byte. So it is common to hear an IPv4 address referred to as a 32-bit address or a 4-byte address.
• Dotted-Decimal Notation - to make the IPv4 address more compact and easier to read, Internet addresses are usually written in decimal form with a decimal point (dot) separating the bytes.
• In classful addressing, the portion of the IP address that identifies the network is called the netid.
• In classful addressing, the portion of the IP address that identifies the host or router on the network is called the hostid.
• An IP address defines a device's connection to a network.
• There are five classes in IPv4 addresses. Classes A, B, and C differ in the number of hosts allowed per network. Class D is for multicasting and Class E is reserved.
• The class of an address is easily determined by examination of the first byte.
• Addresses in classes A, B, or C are mostly used for unicast communication.
• Addresses in class D are used for multicast communication.
• Unicast communication is one source sending a packet to one destination.
• Multicast communication is one source sending a packet to multiple destinations.
• Subnetting divides one large network into several smaller ones, adding an intermediate level of hierarchy in IP addressing.
• Subnetting adds an intermediate level of hierarchy in IP addressing. 
• Default masking is a process that extracts the network address from an IP address. 
• Subnet masking is a process that extracts the subnetwork address from an IP address 
• Supernetting combines several networks into one large one.
• In classless addressing, we can divide the address space into variable-length blocks. 
• In classless addressing, there are variable-length blocks that belong to no class. The entire address space is divided into blocks based on organization needs. 
• The first address and the mask in classless addressing can define the whole block. 
• A mask can be expressed in slash notation which is a slash followed by the number of 1s in the mask.
• The mask in classless addressing is expressed as the prefix length (ln) in CIDR notation.
• To find the first address in a block, we set the rightmost 32 - n bits to O.
• To find the number of addresses in the block, we calculate 2^{32 - n}, where n is the prefix length.
• To find the last address in the block, we set the rightmost 32 - n bits to 1s.
• In IPv4 addressing, a block of addresses can be defined as x.y.z.t /n in which x.y.z.t defines one of the addresses and the /n defines the mask.
• The number of addresses in the block can be found by using the formula 2³²⁻ⁿ.
• Subnetting increases the value of n.
• Every computer attached to the Internet must know its IP address, the IP address of a router, the IP address of a name server, and its subnet mask (if it is part of a subnet). 
• DHCP is a dynamic configuration protocol with two databases. 
• The DHCP server issues a lease for an IP address to a client for a specific period of time.
• Network address translation (NAT) allows a private network to use a set of private addresses for internal communication and a set of global Internet addresses for external communication. 
• NAT uses translation tables to route messages.
• The IP protocol is a connectionless protocol. Every packet is independent and has no relationship to any other packet. 
• Every host or router has a routing table to route IP packets.
• In next-hop routing, instead of a complete list of the stops the packet must make, only the address of the next hop is listed in the routing table.
• In network-specific routing, all hosts on a network share one entry in the routing table.  
• In host-specific routing, the full IP address of a host is given in the routing table. 
• In default routing, a router is assigned to receive all packets with no match in the routing table.
• A static routing table's entries are updated manually by an administrator. 
• Classless addressing requires hierarchial and geographic routing to prevent immense routing tables.
• The global authority for address allocation is ICANN.  ICANN normally grants large blocks of addresses to ISPs, which in turn grant small subblocks to individual customers.
• IPv6 addresses use hexadecimal colon notation with abbreviation methods available.
• There are three types of addresses in IPv6: unicast, anycast, and multicast. 
• In an IPv6 address, the variable type prefix field defines the address type or purpose.
• An IPv4 address is 32 bits long. An IPv6 address is 128 bits long.
• Classful addressing assigns an organization a Class A, Class B, or Class C block of addresses. Classless addressing assigns an organization a block of contiguous addresses based on its needs.
• A block in class A address is too large for almost any organization. This means most of the addresses in class A are wasted and not used. A block in class C is probably too small for many organizations.
• The network address in a block of addresses is the first address. The mask can be ANDed with any address in the block to find the network address.
• Multicast addresses in IPv4 are those that start with the 1110 pattern. Multicast addresses in IPv6 are those that start with the 11111111 pattern.

There are three restrictions in classless addressing:

• a. The number of addresses needs to be a power of 2. 
• b. The mask needs to be included in the address to define the block.
• c. The starting address must be divisible by the number of addresses in the block.

Finding the classes in binary and dotted-decimal notation

Number of blocks and block size in classful IPv4 addressing

Default masks for classful addressing

IPv6 address in binary and hexadecimal colon notation

Definition of Terms

• Virtual-circuit switching is a data link layer technology in which links are shared.
• A virtual-circuit identifier (VCI) identifies a frame between two switches.
• The three phases in virtual circuit switching are setup, data transfer, and teardown. 
• The setup phase can use the permanent virtual circuit (PVC) approach or the switched virtual circuit (SVC) approach.
• Frame Relay is a relatively high-speed, cost-effective technology that can handle bursty data.
• Frame Relay is a virtual-circuit wide-area network that was designed in response to demands for a new type of WAN in the late 1980s and early 1990s.
• Frame Relay operates only at the physical and data link layers.
• Frame Relay does not provide flow or error control; they must be provided by the upper-layer protocols.
• To handle frames arriving from other protocols, Frame Relay uses a device called a
  Frame Relay assembler/disassembler (FRAD).  A FRAD assembles and disassembles
  frames coming from other protocols to allow them to be carried by Frame Relay frames.
• Frame Relay networks offer an option called Voice Over Frame Relay (VOFR) that
  sends voice through the network.
• Local Management Information (LMI) is a protocol added recently to the Frame Relay protocol to provide more management features.
• One of the nice features of Frame Relay is that it provides congestion control and quality of service (QoS).
• Both PVC and SVC connections are used in Frame Relay.
• The data link connection identifier (DLCI) identifies a virtual circuit in Frame Relay.
• VCIs in Frame Relay are called DLCIs.
• Asynchronous Transfer Mode (ATM) is a cell relay protocol that, in combination with SONET, allows high-speed connections.
• A cell is a small, fixed-size block of information.
• The ATM data packet is a cell composed of 53 bytes (5 bytes of header and 48 bytes of payload).
• Note that a virtual connection is defined by a pair of numbers: the VPI and the VCI.
• ATM eliminates the varying delay times associated with different-size packets.
• ATM can handle real-time transmission.
• A user-to-network interface (UNI) is the interface between a user and an ATM switch.
• A network-to-network interface (NNI) is the interface between two ATM switches.
• In ATM, connection between two endpoints is accomplished through transmission paths (TPs), virtual paths (VPs), and virtual circuits (VCs).
• In ATM, a combination of a virtual path identifier (VPI) and a virtual-circuit identifier identifies a virtual connection.
• ATM technology can be adopted for use in a LAN (ATM LAN).
• In a pure ATM LAN, an ATM switch connects stations.
• In a legacy ATM LAN, the backbone that connects traditional LANs uses ATM technology.
• A mixed architecture ATM LAN combines features of a pure ATM LAN and a legacy ATM LAN.
• Local-area network emulation (LANE) is a client/server model that allows the use of ATM technology in LANs.
• LANE software includes LAN emulation client (LECS), LAN emulation configuration server (LECS), LAN emulation server (LES), and broadcast/unknown server (BUS) modules.

The ATM standard defines three layers:

• a.   Application adaptation layer (AAL) accepts transmissions from upper-layer services and maps them into ATM cells. The AAL is divided into two sublayers: convergence sublayer (CS) and segmentation and reassembly (SAR).
• b.  ATM layer provides routing, traffic management, switching, and multiplexing services.
• c.  Physical layer defines the transmission medium, bit transmission, encoding, and electrical-to-optical transformation.

There are four different AALs, each for a specific data type:

• a.  AAL1 for constant-bit-rate stream
• b.  AAL2 for short packets.
• c.  AAL3/4 for conventional packet switching (virtual-circuit approach or datagram approach).
• d.  AAL5 for packets requiring no sequencing and no error control mechanism.

Frame Relay network

Three address formats

Virtual connection identifiers in UNIs and NNIs

An ATM cell

ATM layers

ATM LANs

Definition of Terms

• Synchronous Optical Network (SONET) is a standard developed by ANSI for fiber-optic networks: Synchronous Digital Hierarchy (SDH) is a similar standard developed by ITU-T.
• SONET was developed by ANSI; SDH was developed by ITU-T.
• Each synchronous transfer signal STS-n is composed of 8000 frames. Each frame is a two-dimensional matrix of bytes with 9 rows by 90 × n columns.
• A SONET STS-n signal is transmitted at 8000 frames per second.
• Each byte in a SONET frame can carry a digitized voice channel.
• In SONET, the data rate of an STS-n signal is n times the data rate of an STS-1 signal.
• STS multiplexers/demultiplexers mark the beginning points and endpoints of a SONET link.
• An STS multiplexer multiplexes signals from multiple electrical sources and creates the corresponding optical signal.
• An STS demultiplexer demultiplexes an optical signal into corresponding electric signals.
• Add/drop multiplexers allow insertion and extraction of signals in an STS. An add/drop multiplexer can add an electrical signals into a given path or can remove a desired signal from a path.
• SONET has defined a hierarchy of signals called synchronous transport signals (STSs). SDH has defined a similar hierarchy of signals callefd synchronous transfer modules (STMs). 
• An OC_-n signal is the optical modulation of an STS_-n (or STM_-n) signal.
• Pointers are used to show the offset of the SPE in the frame or for justification.
• SONET uses two pointers show the position of an SPE with respect to an STS.
• SONET use the third pointer for rate adjustment between SPE and STS. 
• A regenerator takes a received optical signal and regenerates it.
• The SONET regenerator also replaces some of the existing overhead information with new information.
• SONET defines four layers: path, line, section, and photonic.
• The path layer is responsible for the movement of a signal from its source to its destination.
• The line layer is responsible for the movement of a signal across a physical line.
• The section layer is responsible for the movement of a signal across a physical section.
• The photonic layer corresponds to the physical layer of the OSI model. It includes physical specifications for the optical fiber channel.
• SONET uses NRZ encoding with the presence of light representing 1 and the absence of light representing 0.
• SONET is a synchronous TDM system in which all clocks are locked to a master clock.
• SONET sends 8000 frames per second; each frame lasts 125 µs. 
• Section overhead is recalculated for each SONET device (regenerators and multiplexers).
• Path overhead is only calculated for end-to-end (at STS multiplexers).
• An STS-3c signal can carry 44 ATM cells as its SPE.
• An STS-I frame is made of 9 rows and 90 columns; an STS_-n frame is made of 9 rows and n x 90 columns.
• STSs can be multiplexed to get a new STS with a higher data rate.
• SONET network topologies can be linear, ring, or mesh.
• A linear SONET network can be either point-to-point or multipoint.
• A ring SONET network can be unidirectional or bidirectional.
• To make SONET backward-compatible with the current hierarchy, its frame design includes a system of virtual tributaries (VTs).
• SONET is designed to carry broadband payloads. Current digital hierarchy data rates, however, are lower than STS-1. To make SONET backward-compatible with the current hierarchy, its frame design includes a system of virtual tributaries (VTs). A virtual tributary is a partial payload that can be inserted into an STS-1.

A SONET system can use the following equipment:

• 1.  STS multiplexers
• 2.  STS demultiplexers
• 3.  Regenerators
• 4.  Add/drop multiplexers
• 5.  Terminals

SONET/SDH rates

A simple network using SONET equipment

SONET layers compared with OSI or the Internet layers

Taxonomy of SONET networks

Virtual tributary types

Definition of Terms

• Cellular telephony provides communication between two devices. One or both may be mobile.
• A cellular service area is divided into cells.
• Reusing cells is cells with the same number in a pattern that can use the same set of frequencies.
• A mobile switching center coordinates communications between a base station and a telephone central office.
• Handoff - If the strength of the signal diminishes, the MSC seeks a new cell that can better accommodate the communication. The MSC then changes the channel carrying the call (hands the signal off from the old channel to a new one).
• In a hard handoff, a mobile station only communicates with one base station. When the MS moves from one cell to another, communication must first be broken with the previous base station before communication can be established with the new one. This may create a rough transition. 
• In Soft Handoff, a mobile station can communicate with two base stations at the same time. This means that, during handoff, a mobile station may continue with the new base station before breaking off from the old one.
• Roaming means, in principle, that a user can have access to communication or can be reached where there is coverage.
• Advanced Mobile Phone System (AMPS) is a first-generation cellular phone system.
• AMPS is an analog cellular phone system using FDMA.
• Digital AMPS CD-AMPS) is a second-generation cellular phone system that is a digital version of AMPS.
• D-AMPS, or IS-136, is a digital cellular phone system using TDMA and FDMA.
• Global System for Mobile Communication (GSM) is a second-generation cellular phone system used in Europe. 
• GSM is a digital cellular phone system using TDMA and FDMA.
• Interim Standard 95 (IS-95) is a second-generation cellular phone system based on CDMA and DSSS. 
• IS-95 is a digital cellular phone system using CDMA/DSSS and FDMA.
• The third-generation cellular phone system will provide universal personal communication.  
• A satellite network uses satellites to provide communication between any points on earth.
• A satellite network is a combination of nodes, some of which are satellites, that provides communication from one point on the Earth to another. A node in the network can be a satellite, an Earth station, or an end-user terminal or telephone. 
• An artificial satellite needs to have an orbit, the path in which it travels around the Earth.
  The orbit can be equatorial, inclined, or polar. 
• A footprint is the area on earth at which the satellite aims its signal.
• Transmission from the earth to the satellite is called the uplink. Transmission from the satellite to the earth is called the downlink.
• Based on the location of the orbit, satellites can be divided into three categories: geostationary Earth orbit (GEO), low-Earth-orbit (LEO), and middle-Earth-orbit (MEO).
• A geosynchronous Earth orbit (GEO) is at the equatorial plane and revolves in phase with the earth.
• Global Positioning System (GPS) satellites are medium-Earth-orbit (MEO)satellites that provide time and location information for vehicles and ships.
• Iridium satellites are low-Earth-orbit (LEO) satellites that provide direct universal voice and data communications for handheld terminals.
• The Iridium system has 66 satellites in six LEO orbits, each at an altitude of 750 km.
• Iridium is designed to provide direct worldwide voice and data communication using handheld terminals, a service similar to cellular telephony but on a global scale.
• The main difference between Iridium and Globalstar is the relaying mechanism. Iridium requires relaying between satellites. Globalstar requires relaying between satellites and earth stations.
• Teledesic satellites are low-Earth-orbit satellites that will provide universal broadband Internet access.
• Teledesic has 288 satellites in 12 LEO orbits, each at an altitude of 1350 km.

Cellular system

Cellular bands for AMPS

Second-generation cellular phone systems

GSM bands

IMT-2000 radio interfaces

Satellite orbits

What is the period of the Moon, according to Kepler’s law?

Satellite categories

Satellite frequency bands

Definition of Terms

• A repeater is a connecting device that operates in the physical layer of the Internet model. A repeater regenerates a signal, connects segments of a LAN, and has no filtering capability.
• A passive hub is just a connector. It connects the wires coming from different branches.
• An active hub is actually a multipart repeater. It is normally used to create connections between stations in a physical star topology.
• A bridge is a connecting device that operates in the physical and data link layers of the Internet model.
• A bridge has filtering capability. It can check the destination address of a frame and decide if the frame should be forwarded or dropped.
• A bridge has a table used in filtering decisions. A bridge does not change the physical (MAC) addresses in a frame.
• A transparent bridge can forward and filter frames and automatically build its forwarding table.
• A transparent bridge is a bridge in which the stations are completely unaware of the bridge’s existence. If a bridge is added or deleted from the system, reconfiguration of the stations is unnecessary.
• A bridge can use the spanning tree algorithm to create a loopless topology.
• In graph theory, a spanning tree is a graph in which there is no loop.
• Note that there is only one single path from any LAN to any other LAN in the spanning tree system. This means there is only one single path from one LAN to any other LAN. No loops are created.
• The bridges send special messages to one another, called bridge protocol data units (BPDUs), to update the spanning tree.
• A hub is a multiport repeater.
• Another way to prevent loops in a system with redundant bridges is to use source routing bridges. A transparent bridge's duties include filtering frames, forwarding, and blocking.
• A three-layer switch is used at the network layer; it is a kind of router.
• The two-layer switch performs at the physical and data link layers. A two-layer switch is a bridge, a bridge with many ports and a design that allows better (faster) performance.
• Some new two-layer switches, called cut-through switches, have been designed to forward the frame as soon as they check the MAC addresses in the header of the frame.
• A router is a three-layer device that routes packets based on their logical addresses (host-to-host addressing).  A router normally connects LANs and WANs in the Internet and has a routing table that is used for making decisions about the route. 
• A three-layer switch is a router, but a faster and more sophisticated. The switching fabric in a three-layer switch allows faster table lookup and forwarding.
• A gateway is normally a computer that operates in all five layers of the Internet or seven layers of OSI model. A gateway takes an application message, reads it, and interprets it.
• A backbone LAN allows several LANs to be connected.
• A backbone is usually a bus or a star.
• In a bus backbone, the topology of the backbone is a bus; in a star backbone, the topology is a star.
• A point-to-point link acts as a LAN in a remote backbone connected by remote bridges.
• A virtual local area network (VLAN) is configured by software, not by physical wiring. 
• VLANs create broadcast domains.
• Membership in a VLAN can be based on port numbers, MAC addresses, IP addresses, IP multicast addresses, or a combination of these features.
• Members of a VLAN can send broadcast messages with the assurance those users in other groups will not receive these messages.
• VLANs are cost- and time-efficient, can reduce network traffic, and provide an extra measure of security.
• In 1996, the IEEE 802.1 subcommittee passed a standard called 802.1Q that defines the format for frame tagging. The standard also defines the format to be used in multiswitched backbones and enables the use of multivendor equipment in VLANs.
• An amplifieramplifies the signal, as well as noise that may come with the signal, whereas a repeater regenerates the signal, bit for bit, at the original strength.
• Stations can be grouped by port number, MAC address, IP address, or by a combination of these characteristics.

Five categories of connecting devices

1. Those which operate below the physical layer such as a passive hub.
2. Those which operate at the physical layer (a repeater or an active hub).
3. Those which operate at the physical and data link layers (a bridge or a two-layer
   switch).
4. Those which operate at the physical, data link, and network layers (a router or a
   three-layer switch).
5. Those which can operate at all five layers (a gateway).

Definition of Terms

• The IEEE 802.11 standard for wireless LANs defines two services: basic service set (BSS) and extended service set (ESS). An ESS consists of two or more BSSs; each BSS must have an access point (AP).
• A BSS without an AP is called an ad hoc network; a BSS with an AP is called an infrastructure network.
• The basic service set (BSS) is the building block of a wireless LAN.
• An extended service set (ESS) is made up of two or more BSSs with APs. In this case, the BSSs are connected through a distribution system, which is usually a wired LAN.
• The physical layer methods used by wireless LANs include frequency-hopping spread spectrum (FHSS), direct sequence spread spectrum (DSSS), orthogonal frequency-division multiplexing (OFDM), and high-rate direct sequence spread spectrum (HR-DSSS).
• FHSS is a signal generation method in which repeated sequences of carrier frequencies are used for protection against hackers.
• One bit is replaced by a chip code in DSSS.
• OFDM specifies that one source must use all the channels of the bandwidth.
• The orthogonal frequency-division multiplexing (OFDM) method for signal generation in a 5-GHz ISM band is similar to frequency division multiplexing (FDM), with one major difference: All the subbands are used by one source at a given time. Sources contend with one another at the data link layer for access.
• HR-DSSS is DSSS with an encoding method called complementary code keying (CCK).
• The wireless LAN access method is CSMA/CA.
• The access method used in the distributed coordination function (OCF) MAC sublayer is CSMAICA.
• The access method used in the point coordination function (PCF) MAC sublayer is polling.
• The network allocation vector (NAV) is a timer used for collision avoidance.
• Network Allocation Vector (NAV) forces other stations to defer sending their data if one station acquires access. In other words, it provides the collision avoidance aspect. When a station sends an RTS frame, it includes the duration of time that it needs to occupy the channel. The stations that are affected by this transmission create a timer called a NAV.
• The MAC layer frame has nine fields. The addressing mechanism can include up to four addresses.
• Wireless LANs use management frames, control frames, and data frames.
• IEEE 802.11 defines several physical layers, with different data rates and modulating techniques.
• The CTS frame in CSMA/CA handshake can prevent collision from a hidden station.
• Bluetooth is a wireless LAN technology that connects devices (called gadgets) in a small area.
• A Bluetooth network is called a piconet. Multiple piconets form a network called a scatternet.
• A Bluetooth network consists of one primary device and up to seven secondary devices.
• The Bluetooth radio layer performs functions similar to those in the Internet model's physcial layer.
• The Bluetooth baseband layer performs functions similar to those in the Internet model's MAC sublayer.
• A Bluetooth network consists of one master device and up to seven slave devices.
• A Bluetooth frame consists of data as well as hopping and control mechanisms. A frame is one, three, or five slots in length with each slot equal to 625 µs.
• A Bluetooth LAN is an ad hoc network, which means that the network is formed spontaneously.
• In multiple-secondary communication, the primary sends on the even-numbered slots; the secondary sends on the oddnumbered slots.

Basic service sets (BSSs)

Extended service sets (ESSs)

CSMA/CA flowchart

Physical layers

Industrial, scientific, and medical (ISM) band

Piconet

Scatternet

Bluetooth layers

Layer comparison of Bluetooth and the Internet model

• Radio layer → Internet physical layer
• Baseband layer → MAC sublayer of Internet data link layer
• L2CAP layer → LLC sublayer of Internet data link layer

Definition of Terms

• Ethernet is the most widely used local area network protocol.
• The original Ethernet was created in 1976 at Xerox’s Palo Alto Research Center (PARC). Since then, it has gone through four generations.
• The IEEE 802.3 Standard defines I-persistent CSMA/CD as the access method for first-generation 10-Mbps Ethernet.
• The data link layer of Ethernet consists of the LLC sublayer and the MAC sublayer.
• The MAC sublayer is responsible for the operation of the CSMAlCD access method and framing.
• Each station on an Ethernet network has a unique 48-bit address imprinted on its network interface card (NIC).
• The minimum frame length for lO-Mbps Ethernet is 64 bytes; the maximum is 1518 bytes.
• The common implementations of lO-Mbps Ethernet are lOBase5 (thick Ethernet), 10Base2 (thin Ethernet), lOBase-T (twisted-pair Ethernet), and lOBase-F (fiber Ethernet).
• The 10Base5 implementation of Ethernet uses thick coaxial cable. lOBase2 uses thin coaxial cable. lOBase-T uses four twisted-pair cables that connect each station to a common hub. lOBase-F uses fiber-optic cable.
• A bridge can increase the bandwidth and separate the collision domains on an Ethernet LAN.
• A switch allows each station on an Ethernet LAN to have the entire capacity of the network to itself.
• Full-duplex mode doubles the capacity of each domain and removes the need for the CSMAlCD method.
• Fast Ethernet has a data rate of 100 Mbps. 
• Fast Ethernet was designed to compete with LAN protocols such as FDDI or Fiber Channel. IEEE created Fast Ethernet under the name 802.3u. Fast Ethernet is backward-compatible with Standard Ethernet, but it can transmit data 10 times faster at a rate of 100 Mbps.
• In Fast Ethernet, autonegotiation allows two devices to negotiate the mode or data rate of operation.
• The Fast Ethernet reconciliation sublayer is responsible for the passing of data in 4-bit format to the MII.
• The Fast Ethernet MII is an interface that can be used with both a 10- and a 100-Mbps interface.
• The Fast Ethernet PHY sublayer is responsible for encoding and decoding.
• The common Fast Ethernet implementations are 1OOBase-TX (two pairs of wistedpair cable), lOOBase-FX (two fiber-optic cables), and 100Base-T4 (four pairs of voice-grade, or higher, twisted-pair cable).
• Gigabit Ethernet has a data rate of 1000 Mbps.
• Gigabit Ethernet access methods include half-duplex using traditional CSMA/CD (not common) and full-duplex (most popular method).
• The Gigabit Ethernet reconciliation sublayer is responsible for sending 8-bit parallel data to the PHY sublayer via a GMII interface.
• The Gigabit Ethernet GMII defines how the reconciliation sublayer is to be connected to the PHY sublayer.
• The Gigabit Ethernet PHY sublayer is responsible for encoding and decoding.
• The common Gigabit Ethernet implementations are 1000Base-SX (two optical fibers and a short-wave laser source), 1000Base-LX (two optical fibers and a long-wave laser source), and 1000Base-T (four twisted pairs).
• The latest Ethernet standard is Ten-Gigabit Ethernet that operates at 10 Gbps. The three common implementations are lOGBase-S, 10GBase-L, and 10GBase-E. These implementations use fiber-optic cables in full-duplex mode.
• In the full-duplex mode of Gigabit Ethernet, there is no collision; the maximum length of the cable is determined by the signal attenuation in the cable.
• In 1985, the Computer Society of the IEEE started a project, called Project 802, to set standards to enable intercommunication among equipment from a variety of manufacturers. Project 802 is a way of specifying functions of the physical layer and the data link layer of major LAN protocols.
• Medium access methods can be categorized as random, controlled, or channelized.
• In the carrier sense multiple-access (CSMA) method, a station must listen to the medium prior to sending data onto the line.
• A persistence strategy defines the procedure to follow when a station senses an occupied medium.
• Carrier sense multiple access with collision detection (CSMA/CD) is CSMA with a postcollision procedure.
• Carrier sense multiple access with collision avoidance (CSMA/CA) is CSMA with procedures that avoid a collision.
• Reservation, polling, and token passing are controlled-access methods.
• In the reservation access method, a station reserves a slot for data by setting its flag in a reservation frame.
• In the polling access method, a primary station controls transmissions to and from secondary stations.
• In the token-passing access method, a station that has control of a frame called a token can send data.
• Channelization is a multiple-access method in which the available bandwidth of a link is shared in time, frequency, or through code, between stations on a network.
• FDMA, TDMA, and CDMA are channelization methods.
• In FDMA, the bandwith is divided into bands; each band is reserved fro the use of a specific station.
• In TDMA, the bandwidth is not divided into bands; instead the bandwidth is timeshared.
• In CDMA, the bandwidth is not divided into bands, yet data from all inputs are transmitted simultaneously.
• CDMA is based on coding theory and uses sequences of numbers called chips. The sequences are generated using Walsh tables.
• The preamble is a 56-bit field that provides an alert and timing pulse. It is added to the frame at the physical layer and is not formally part of the frame. SFD is a one byte field that serves as a flag.
• A multicast address identifies a group of stations; a broadcast address identifies all stations on the network. A unicast address identifies one of the addresses in a group.
• A layer-2 switch is an N-port bridge with additional sophistication that allows faster handling of packets.
• The least significant bit of the first byte defines the type of address. If the bit is 0, the address is unicast; otherwise, it is multicast.
• The broadcast destination address is a special case of the multicast address in which all bits are 1s.

Ethernet evolution through four generations

The Data Rates

• Standard Ethernet -10 Mbps
• Fast Ethernet - 100 Mbps
• Gigabit Ethernet - 1 Gbps
• Ten-Gigabit Ethernet - 10 Gbps

Categories of Standard Ethernet

Summary of Standard Ethernet implementations

The common Fast Ethernet implementations:

• 100Base-TX
• 100Base-FX
• 100Base-T4

Summary of Fast Ethernet implementations

The common Gigabit Ethernet implementations:

• 1000Base-SX
• 1000Base-LX
• 1000Base-CX
• 1000Base-T

Summary of Gigabit Ethernet implementations

The common Ten-Gigabit Ethernet implementations:

• 10GBase-S
• 10GBase-L
• 10GBase-E

Summary of Ten-Gigabit Ethernet implementations