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Questions and Answers
What are the major disadvantages of the star network?
What are the major disadvantages of the star network?
Costs of cabling tend to be higher than alternatives; Entire system is inoperable if central hub is disabled
Which are the two basic types of networks mentioned in the content?
Which are the two basic types of networks mentioned in the content?
In a ring network, data flow is always bidirectional.
In a ring network, data flow is always bidirectional.
False
Packet switching divides the system bandwidth into ___________.
Packet switching divides the system bandwidth into ___________.
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What layer in the OSI model is responsible for data transfer between end systems and hosts?
What layer in the OSI model is responsible for data transfer between end systems and hosts?
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Which layer handles the direct interaction with users and displays incoming data to the user?
Which layer handles the direct interaction with users and displays incoming data to the user?
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The Transport Layer in the OSI model is primarily responsible for packet forwarding and routing.
The Transport Layer in the OSI model is primarily responsible for packet forwarding and routing.
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The RS-485 interface standard is a balanced system with increased data rates and up to 32 transmitters and receivers possible, making it very useful for ____________ and ____________ systems.
The RS-485 interface standard is a balanced system with increased data rates and up to 32 transmitters and receivers possible, making it very useful for ____________ and ____________ systems.
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Match the following network types with their descriptions:
Match the following network types with their descriptions:
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Which type of cable is the most commonly used standard in 100BaseTX Fast Ethernet?
Which type of cable is the most commonly used standard in 100BaseTX Fast Ethernet?
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A repeater is used to connect two segments and only carries out collision checking.
A repeater is used to connect two segments and only carries out collision checking.
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What is the purpose of the preamble field in Ethernet frames?
What is the purpose of the preamble field in Ethernet frames?
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A switching hub acts as a ______ and forwards each packet to the relevant port based on the hardware address information in the header.
A switching hub acts as a ______ and forwards each packet to the relevant port based on the hardware address information in the header.
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Match the following layers with the correct OSI model layers:
Match the following layers with the correct OSI model layers:
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Which network device is used to connect two or more dissimilar networks?
Which network device is used to connect two or more dissimilar networks?
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What is another name for an Ethernet card?
What is another name for an Ethernet card?
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What is the primary function of a router?
What is the primary function of a router?
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Coaxial cables are used for all antennas operating between the HF band of frequencies up to the SHF band around 2 GHz, where __________ begin to take over.
Coaxial cables are used for all antennas operating between the HF band of frequencies up to the SHF band around 2 GHz, where __________ begin to take over.
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A switch uses circuit switching technique to forward data packets on the network.
A switch uses circuit switching technique to forward data packets on the network.
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Match the IP address version with its number of bits:
Match the IP address version with its number of bits:
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Study Notes
Data Network Fundamentals
- Data communication refers to the transfer of information from one point to another.
- Data is represented by a sequence of zeros and ones, handled by computers.
- Communications systems can handle analog or digital data.
- Modern instrumentation is primarily concerned with digital data transfer.
OSI Model
- The OSI model provides a framework for defining specific protocols.
- The model consists of seven layers: Application, Presentation, Session, Transport, Network, Data Link, and Physical.
- Each layer has a specific function:
- Application Layer: receives information directly from users and displays incoming data.
- Presentation Layer: represents data independently of the application layer.
- Session Layer: sets up, coordinates, and terminates connections between applications.
- Transport Layer: responsible for data transfer between end systems and hosts, using TCP/IP.
- Network Layer: responsible for packet forwarding, including routing through different routers.
- Data Link Layer: provides node-to-node data transfer, with two sublayers: MAC and LLC.
- Physical Layer: represents the electrical and physical representation of the system.
Protocols and Standards
- Protocols are structures used within a communications system to facilitate communication between devices.
- Standards are necessary for developing integrated instrumentation and control systems.
- The OSI model provides a framework for defining specific protocols.
- Examples of physical standards include RS-232, RS-422, RS-423, and RS-485.
Modern Instrumentation and Control Systems
- Data is acquired by measuring instruments and transmitted to a controller, typically a computer.
- The controller transmits data or control signals to control devices, which act upon a given process.
- The main purpose of an instrumentation and control system is to provide control, monitoring, and alarm functions.
- Modern systems use integrated systems such as DCS, PLCs, and smart instruments.
Networking
- There are three broad classes of networks: LANs, MANs, and WANs.
- Network topologies include Star, Ring, and Bus.
- Circuit switching and packet switching are two types of network switching methods.
- Packet switching is cheaper and more efficient, but may have slower transmission rates.
Circuit and Packet Switching
- Circuit switching establishes a direct connection between two ends for the duration of the message exchange.
- Packet switching breaks the message into packets, each carrying the destination address, and transmits them independently.
Network Topologies
- Star topology: a central node or hub connects to outlying nodes on separate communication links.
- Ring or loop topology: nodes are connected in a loop, with data flowing in one direction.
- Bus topology: nodes are connected to a common communication path, with data transmitted in one direction.
Transmission Techniques
- Baseband transmission uses time division multiplexing (TDM) to allow one device to transmit at a time.
- Broadband transmission uses frequency division multiplexing (FDM) to allow multiple devices to communicate simultaneously.
IEEE Standards
- IEEE 802.2 defines services for the LLC sublayer.
- IEEE 802.3 defines the CSMA/CD protocol used by Ethernet.
- IEEE 802.4 defines the token passing bus access method.
- IEEE 802.5 defines the token ring access method.
Ethernet
- Ethernet was developed by Xerox in the 1970s and standardized by Xerox, Digital Equipment, and Intel in 1978.
- It uses the CSMA/CD protocol and is a popular LAN technology.### IEEE LAN Standards
- IEEE 802 is a series of standards administered by the IEEE 802 LAN Standards Technologies Committee.
- The standard has several sections, each with its own co-coordinating committee.
- Some standards have been superseded by ISO standards.
Ethernet
- Uses CSMA/CD as a medium access control method.
- Standard (or thick) Ethernet (10Base5) uses 10 Mbps baseband operation on coaxial cable with a maximum segment length of 500 m.
- Thin Ethernet (10Base2) uses 10 Mbps baseband operation on coaxial cable with a maximum segment length of 185 m.
- 10BaseT uses unshielded twisted pair cables and operates at 10 Mbps.
- 100BaseT is similar to 10BaseT but operates at 100 Mbps.
- 1000BaseT (gigabit Ethernet) is similar to Fast Ethernet, but operates at 1000 Mbps.
- 1BaseT is similar to 10BaseT but limited to a 1 Mbps data rate.
Ethernet Topology
- Standard and thin Ethernet use a bus topology.
- 10BaseT (Ethernet) uses a star configuration.
Fast Ethernet
- Operates at 100 Mbps on different forms of physical media.
- Retains the existing Ethernet MAC layer.
- IEEE 802.3u standard defines:
- 100BaseTX, which uses two pairs of category 5 UTP or STP.
- 100BaseFX, which uses two pairs of multimode (or single node) fiber.
- 100BaseT4, which uses four pairs of category 3, 4 or 5 UTP.
Ethernet Protocol Operation
- All data transfer is in the form of a packet or frame.
- Each packet consists of an envelope containing control information and the actual message data.
- Each node examines the destination address and reads the data if the frame is directed at that node.
Frame Structure
- Preamble: 7 bytes, each with the binary value 10101010.
- Start of frame delimiter: 1 byte, with the binary value 10101011.
- Destination Address: 16 or 48 bits, depending on the system configuration.
- Length Indicator: 2 bytes, specifying the length of the data field.
- Data: 46 to 1500 bytes in length.
- Frame Check Sequence: 32-bit cyclic redundancy check value for error detection.
Network Devices
- Modem: enables a computer to send or receive data over telephone or cable lines.
- Types of Modem:
- Simplex: transmits data in one direction.
- Half-duplex: transmits data in both directions, but only one at a time.
- Full-duplex: transmits data in both directions simultaneously.
- Ethernet Card (NIC): connects computers to Ethernet LAN and communicates with other devices on the LAN.
- Router: transmits data from one LAN to another if both networks support the same set of protocols.
- Switch: connects devices to Ethernet networks through twisted pair cables and uses packet switching technique to receive, store, and forward data packets.
Cabling Basics
- Twisted pair cables: the most economical solution for data transmission, allowing for rates of up to 180 Mbps on communication links of up to 100 meters.
- Types of Twisted Pair Cables:
- Shielded Twisted Pair (STP)
- Unshielded Twisted Pair (UTP)
- EIA-568 standard divides UTP cables into five application categories:
- Category 1: low-speed data and analogue voice
- Category 2: ISDN data
- Category 3: high-speed data and LAN (10 Mbps)
- Category 4: extended distance LAN
- Category 5: extended frequency LAN (100 Mbps)
- Coaxial cables: used for antennas operating between the HF band of frequencies up to the SHF band around 2 GHz.
Routing Algorithms
- Non-Adaptive Routing Algorithm:
- Also known as static routing algorithm
- Routing process is designed in advance and stored in the router after booting
- Doesn't affect with the change of network topology and traffic
- Examples:
- Flooding: every incoming packet is sent to all the outgoing links except the one from it has been reached.
- Random walks: a packet sent by the node to one of its neighbors randomly.
- Adaptive Routing Algorithm:
- Also known as dynamic routing algorithm
- Routing changed based on the network topology and traffic### Fiber-Optic Cables
- Normally used for digital signal transmission
- Capabilities satisfy future data communication requirements
- Transmission rates in Gigabits per second (Gbps), with current systems operating at around 10 Gbps
- Benefits include:
- Enormous bandwidth
- Low signal attenuation
- Inherent signal security
- Low error rates
- Noise immunity
- Logistical considerations (light, small, and safe for hazardous areas)
- Total galvanic isolation between ends
Routing Algorithm
- Provides the best path from source to destination based on "least-cost path"
- Divided into two categories: adaptive and non-adaptive
- Three types of algorithms:
- Centralized algorithm: uses global information and computes the least cost path
- Isolation algorithm: uses local information and decides routing based on neighboring links
- Distributed algorithm: computes the least cost path based on iterative calculations
IP Addressing
- IP version 4 (IPv4) addresses: 32 bits in length, typically communicated in dotted decimal format
- Broken into four octets (1 octet = 8 bits)
- IP version 6 (IPv6) addresses: 128 bits in length, provides enough globally unique IP addresses
- IP address classes: A, B, C, D (Multicast), and E (Reserved)
- Class A, B, and C addresses defined based on the number of bits in the network portion
- Subnetting: allows creation of multiple logical networks within a single Class A, B, or C network
Subnetting
- Extends the mask using bits from the host ID portion to create a subnetwork ID
- Example: 192.168.5.0/24 with a mask of 255.255.255.0 can be subnetted
Private IP Addressing
- RFC 1918 addresses reserved for internal network infrastructure
- Includes three blocks of IP address space:
- 10.0.0.0 – 10.255.255.255 (10.0.0.0/8)
- 172.16.0.0 – 172.31.255.255 (172.16.0.0/12)
- 192.168.0.0 – 192.168.255.255 (192.168.0.0/16)
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Description
Explore the basics of data communication, representation, and transfer, including the OSI model and its seven layers.
