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Network Form and Function

chapter. 5. Network Form and Function. Outline. Assess desired reach of network – the purpose of network Forms of data transmission Signal reliability. Where it All Started. Evolution of modern data communications equipment began with electrical means of communication.

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Network Form and Function

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  1. chapter 5 Network Form and Function Outline Assess desired reach of network – the purpose of network Forms of data transmission Signal reliability

  2. Where it All Started • Evolution of modern data communications equipment began with electrical means of communication. • Telegraph (circa 1837); Example for today’s times: Home door buzzer • Sender: translates information to be communicated into a Morse code: Samuel Morse • Medium: copper wire • Receiver: decodes the clicks into the receiver’s language and writes it down • Modern data communication uses the machine-to-machine communication mode.

  3. Reach of Networks • Networks connect the organization and give it a cohesive quality • Topology – layout of a particular network • Physical connectivity pattern • High speed network of a computer - internal communications bus of the machine • Peripheral equipment is an extension of the primary device • Personal area network (PAN) – the smallest labeled network in two forms: • Networking to peripherals on the person • Synchronizing of multiple personal devices

  4. Reach of Networks (cont’d) Figure 5.2 – The Onion Model of Network Connectivity

  5. Internal Network Level • The lowest level of organization connectivity • Local area networks (LAN): cover less than 1 km in radius • Greatest visibility • Potentially greatest influence • Example: Apple in 1976, IBM in 1981 • Circuit switching: an early form of resource sharing • Non-LAN solution • SOHO – Small office home office networks • Provides for sharing of resources • Supports primary applications - email • Extranet – extension of an organizations network

  6. Internal Network Level (cont’d) • Campus area network (CAN) – extended form of LAN • Single LAN or connection of LANs by way of a backbone network • Example of CAN: Fiber optic backbone network (AU-NET) at Auburn University • LAN can be generally defined as a broadcast domain • Virtual LANs (VLANs) – can be used for two purposes: • Allow easy entry to LAN and support physical movement • Provide separate nodes from general broadcast

  7. Intermediate Network Level • Each LAN has its own server for the operating system and shared resource for its group. • Each LAN is bridged to the other LANs for connectivity across a division or corporation. • Metropolitan area network (MAN) • Fiber strand network • Fiber distributed data interference (FDDI)

  8. Wide Network Level • Wide area networks (WANs) – can be privately or publicly owned – the global public internet. • Value added networks (VANs) – a special form of WAN provides additional services such as: • Speed translation, store-and-forward messaging • Protocol conversion and data handling • Packet assembly and disassembly • Galactic area network (GAN) – uses radio to extend the network to other bodies such as Mir Space Station, weather satellites, etc. • Packet data network (PDN) – provides connectivity anywhere at moderate speed.

  9. Securing Networks • Virtual private networks (VPNs) – make users of the network secure • Encryption techniques – tunneling • Authentication • Access control technologies

  10. Connectivity in Networks • Two commonly used media: • UTP • Coaxial cables • Standard speed of Ethernet (1990) – 10 Mbps • Category 3 UTP wiring – constructed with two pairs of wires - 10BaseT • Fast Ethernet – four wire pairs, extends the bandwidth to 100Mbps • Historically, anticipated high bandwidth usage called for use of category 5 wiring for a 100BaseT network • Gigabit-Ethernet - 1000BaseT running on category 6 wiring (1000BaseT) or fiber (1000BaseFX)

  11. Forms of Data Transmission • Data communication requires the generation of streams of character, composed of bits. • Forms of data communication are: • Asynchronous communications • Synchronous communication • Protocols of both communications provide a feature called transparency. • Objective of data communication: effective throughput of useful information.

  12. Asynchronous Communication • Binary digits (bits) • Data is sent one character at a time • A group of 10 bits - 8 bits of data, 1 bit for parity checking, 1 bit for character stop bit • Communication is established – handshaking • Sending and receiving machine agree on the bit pattern. Figure 5.4 (a) – Asynchronous Data Transmission

  13. Synchronous Communication • A block of data is sent at one time with significant reliability • Total block of data – packet contains: • Header – timing and address information • Payload – data group • Trailer - block check characters (BCCs) • Two forms of synchronous communication: • Continuous synchronous communications • Packet switching

  14. Synchronous Communication • Synchronous data transmission: Figure 5.5 (a) – Synchronous Data Transmission

  15. Parameters of A Valuable Network • Reliability: Constancy, dependability, stability, durability • Error free or error detection capability with greater certainty • Available 24/7 to support mission-critical capabilities • Performs as designed • Whether supported in-house or outsourced through a service level agreement (SLA) with a committed information rate (CIR)

  16. Parameters of A Valuable Network (cont’d) • Provide stable bandwidth under varying conditions: • Bursty traffic • Bandwidth-on-demand • Dynamic bandwidth allocation • Security • Must not allow itself to be used to access attached resources • Monitor and log events, authentications, and audits • Software to protect against viruses, hackers, and spam

  17. Power for Network Equipment • Continuity – power must be available as needed. • There must be access to power wherever it is needed. • The power should be regulated so that voltage levels are between specified limits. • Brownout – voltage falls below lower limit for extended periods • Waveform of the power should follow a sine wave format.

  18. Providing Continuous Reliable Power • Dirty power – electrical power with too many variations • Surge protectors – shorts out high-voltage spikes • Line conditioning: equipment has no storing capacity • Uninterruptible power supplies (UPS): Power outage • Motor-generated (MG) sets: AC motor public power supply AC generator flywheel • Backup generators: gasoline, diesel or natural gas powered engines with generators attached

  19. Signal Reliability • To avoid potential change when using data communications to transport digital data we require: • Error checking and notification • Error correction

  20. Error Detection • Echo checking • Checksum • Negative acknowledgment (NAK) • Error checking used in asynchronous communications: • Vertical redundancy checking (VRC) or parity checking • Longitudinal redundancy checks (LRC) • Block check character • Error checking used in synchronous communications: • Cyclic redundancy checks (CRC)

  21. Error Correction • Retransmission involving automatic repeat request (ARQ) • Positive acknowledgment (ACK) • Negative acknowledgment character (NAK) • Hamming codes - forward error correction (FEC)

  22. Network Storage • Storage requirements grow at approximately 80% per annum. • Access to data is dependent on data communications. • Network-attached storage (NAS) fuelled by: intranets, internet, e-commerce, e-mail, voice recognition etc. • Storage area networks (SANs) • Business initiatives have given rise to the demand for storage and management of data. • Examples: data warehousing, data mining, CRM, supply-chain management, eBusiness, etc.

  23. Storage Area Networks (SAN) • High-speed sub-network of shared storage devices • Makes all storage devices available to all servers on a LAN or WAN • Advantages: • Satisfy demand for storage and use networking to improve data access • Manage more data • IP networking forecasted to accommodate the largest part of the world’s networking requirements • Storage service provider (SSP)

  24. Network-Attached Storage (NAS) • File sharing system incorporating software and hardware preconfigured to make network storage system • Seemingly tailor-made for eBusiness • Advantages: • Extra hard disk space can be added to the network • Need not shut down servers connecting a network for maintenance and up gradation • Need not be located within the server but can be located anywhere in the LAN • Fibre channel software – consolidates storage requirements into a common repository

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