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Introduction to networking

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© Sergiusz Patela, 2001

(c) Sergiusz Patela 2001-2002 Fiber-optic computer networks 2/26

Wire pair

Bandwidth comparison of networking media

1 MHz 1 GHz 1 THz

0.1

1.0

10.0

Atte

nuat

ion

[dB

/km

]

Bandwidth

Coaxial cable

Microwave waveguides

Single mode optical fiber

Multi mode optical fiber


Two basic network types

Local Area Network - LANs connect computers and peripheral devices in a limited physical area, such as a business office, laboratory, or college campus, by means of permanent links (wires, cables, fiber optics, radio) that transmit data rapidly

Wide Area Networks (long haul networks) - Wide-area networks connect computers and smaller networks to larger networks over greater geographic areas, including different continents. They link the computers by means of cables, optical fibers, or satellites.


Contemporary LAN technologies - examples1. Ethernet (802.3)

Coax: 10Base T - 180m

Fiber 10Base FL - 2 km

2. Token Ring (802.5)

802.5j - TR over fiber

3. FDDI (Ansi X3T12,

ISO-IEC 9314)

4. Fibre Channel, ...


Computer network - a definition

In plain English: system of several computers which are connected to one another by cables

A network of data processing nodes that are interconnected for the purpose of data communication

General non-computer-based example: Communications network - roads, bus stations, buses, containers, actual load


Operating principles and fundamental terms

Fundamental terms: layer and protocol

Other terms: frame, access method, coding

Protocol: set of rules describing how to prepare data for sending, establish

communication, control data transfer etc. Protocols are standardized.

Protocol description - according to OSI (Open System Interconnection)

model have layered structure. For computers connected by the network

layers of given level communicate between themselves, transferring data

only to the layer immediately above and beneath them.


The OSI -ISO Network Model (Open Systems Interconnection)

Device 1 Device 2 7 Application <---> 7 Application 6 Presentation <---> 6 Presentation program 5 Session <---> 5 Session 4 Transport <---> 4 Transport 3 Network <---> 3 Network 2 Data Link <---> 2 Data Link hardware 1 Physical layer <---> 1 Physical layer


Layers of the OSI modelLayer 7 - (Application): Common protocols such as network virtual terminal, file transfer protocol (FTP), electronic mail, and directory lookupLayer 6 - (Presentation)- Encoding/decoding including compression and cryptography, terminal emulation.Layer 5 - (Session)- Communication between processes including data exchange, remoteProcedure Call (RPC), synchronization, and activity managementLayer 4 - (Transport)- Lowest level at which messages are handled. Segmentation and reassembly of data to and from session layer. Transmission Control Protocol (TCP), UserDatagram Protocol (UDP)Layer 3 - (Network) Flow control to avoid congestion and also customer use and accounting. Link Layer Control (LLC). Internet Protocol (IP), routing protocols.Layer 2 - (Data Link) Presentation of error-free transmission to the network layer. Creates data frames and receives acknowledge frames. Media Access Control (MAC)Layer 1 - (Physical) Physical Layer Protocol (PHY) specifies coding (e.g. 4B/5B), clock synchronization. Physical Medium Dependent (PMD) sublayer provides digital communications between nodes. This layer specifies fiber-optic drivers, receivers, mechanical, cables, connectors, optical signal requirements including power levels, jitter and BER


OSI model - an example

From Computer Desktop Encyclopedia (C) 1998, The Computer Language Co. Inc.


Protocol

Protocol: standards way of dealing with data transfer

Definition: A formal set of conventions governing the format and control of interactions among communicating functional units.

Protocols may govern portions of a network, types of service, or administrative procedures.

e.g.

CSMA/CD - carrier sense multiple access / collision detection,

CSMA/CA- carrier sense multiple access / collision avoidance,

IP, …


Signal encodingSignal encoding is used to increase system robustness against noise.

Examples:

FDDI uses 4b/5b NRZI (Non-Return to Zero Invert on ones) with 125 Mb/s baud rate to achieve 100 Mb/s data rate.

Ethernet uses Manchester encoding with 20 Mb/s baud rate (20 MBd) to achieve 10 Mb/s data rate.

High

0 0 0 0 01 1 1 1 1 1Low

0

time

Clock

NRZ - used by PCBinary 1 = highBinary 0 = low

NRZ - used in combination with 4b/5b by FDDIBinary 1 = transitionBinary 0 = no transition

Manchester - used by EthernetBinary 1 = high to low transitionBinary 0 = low to high transition


Fiber advantages for network planers

•Error-free transmission over longer distances. More flexibility in planning networks, possibility to take advantage of new architectures.

•Ability to support higher data rates.

•Ease of handling, installing, and testing. Fiber can now be installed and tested in the same or less time than copper networks.

•Long term economic benefits over copper (over the lifetime of the network),

•superior reliability reduces operating costs by minimizing network outages

•higher bandwidth can produce considerable savings by eliminating the need to pull new cable when the network is upgraded to support higher bandwidth

•long distance capability allow all hub electronics to be centrally located. Centralization reduces the cost of cabling and electronics, and reduces administration and maintenance efforts .


Fiber advantages for network engineers and technicians

• Fiber is immune to EMI/RFI signals.

• Fiber is immune to crosstalk.

• Fiber systems are easier to test. (For copper cabling, there are now more than 20 specified parameters for Gigabit Ethernet as opposed to two for optical fiber - attenuation and bandwidth).

• Fiber provides greater reliability and equipment safety.


FibersShort overview of fibers found in communication systems:

Multimode Singlemode Panda PM

62.5/125 50/125 9/125 8/125


F-O Cables - short overview for networkersNumber of fibers1. Simplex2. Zip-cord (duplex)3. Multi-fiber

Technology

1. Tight-buffered

2. Loose tube

Other names and classifications: distribution, raiser, breakout; indoor, outdoor; short distance, long distance; military grade, oceanic, …

fiberbuffer

Kevlar strength memberjacket

Ripcord

PE jacket

Dielectric strength member

Water swellable tapeBuffer tube

FibersDielectric central member

Water swellable yarn


Fiber-optic connector types and standards

There is more then 100 types of fiber optic connectors. Main connector types are described by TIA/EIA-604 standards. They are called Fiber Optic Connector Intermateability Standards (FOCIS) and published with a document number format TIA-604-XX. To date, the following FOCIS documents exist:

FOCIS 1: BiconicFOCIS 2: STFOCIS 3: SCFOCIS 4: FCFOCIS 5: MTP/MPOFOCIS 6: Panduit FJFOCIS 7: 3M Volition

FOCIS 8: Mini-MAC (Withdrawn)FOCIS 9: Mini MPO (Withdrawn)FOCIS 10: Lucent LCFOCIS 11: Siecor SCDC/SCQC (not yet approved)FOCIS 12: Siecor/Amp MT-RJFOCIS 15: MFFOCIS 16: LSH (LX-5)The MU currently has no FOCIS document.


ConnectorsShort overview

ST

FC, FC/PC

SC

FDDI

Comparison of standard and SFF connector dimensions (FC and LC)


Outline of fiber optic network design

1. Define Environmental Requirements, e.g. office LAN vs. under-see system

2. Select Transmission Standard, e.g. Ethernet, FDDI

3. Select System Architecture (topology, fiber length, number of connectors, splices, fiber length)

4. Select Type of Fiber (MM, SM, POF, verify fiber attenuation and bandwidth)

5. Select Optoelectronic Packages (for standard or harsh environment, standard interfaces of pigtailed elements)

6. Select Type of Connector

7. Select the Cable Configuration/Type

8. Select Backshell for Multichannel (Multifiber) Connectors

9. Select Cable Clamping Method

10. Select Tools for Inspection, Cleaning and Testing

11. System Qualification (according to the proper standard)


Calculating the cost of fiber optic network

1. Cabling-system-components cost. Cable, wall outlets, patch panels, patch cords and connectors.

2. Installation and testing costLabor cost of cabling and termination. Cables may be packed close together, no separation from power lines is necessary.

3. Electronic costOptoelectronic modules steadily lower their cost. Already fewer networking components is needed when fiber is used.

4. Productivity costFiber's better reliability minimizes data errors and requires less time and effort in troubleshooting and correcting cabling problems

5. Recabling cost


Ethernet

Picture from the presentation of dr Robert M. Metcalfa (June 1976, National Computer Conference)


Elements of Ethernet systemThe Ethernet system consists of three basic elements:

1. The physical medium used to carry Ethernet signals between computers

2. A set of medium access control rules embedded in each Ethernet interface that allow multiple computers to negotiate access to the shared Ethernet channel

3. An Ethernet frame that consists of a standardized set of bits used to carry data over the system

Ethernet network topology R

R

R


Ethernet area networks - evolution of “LAN” technology

LANLocal Area

Network

CANCampus

Area Network

MANMetropolitan

Area Network

WANWide Area

Network

10Base F 100Base FX 100Base SX

1000Base SX 100Base LX

802.3z

10GBE

802.3ae


Networking with fibers - recommendations (1/2)Application Baud

Rate Mbaud

Horizontal < 100 M

Media TX

Building < 300 m

Media TX

Campus < 2,000 m

Media TX 10BaseF 20 MM S MM S MM S

Token Ring 32 MM S MM S MM S

100VG- AnyLAN

120 MM S MM S MM LE

100BaseF 125 MM S MM S MM LE

1000Base-SX 1250 MM SL MM SL

1000Base-LX 1250 MM LL MM LL SM LL

FDDI 125 MM S MM S MM LE

S – 850nm LED, SL – 850nm LD, LE – 1300nm LED; LL – 1300nm LD

By Fiber Optics LAN Section (FOLS) of the Telecommunications Industry Association (TIA)


Networking with fibers - recommendations (2/2)

Application Baud Rate

Mbaud

Horizontal < 100 M

Media TX

Building < 300 m

Media TX

Campus < 2,000 m

Media TX

Fibre Channel

133 266 532

1062

MM S MM SL/LE MM SL/LE MM SL

MM S MM SL/LE MM SL/LE MM SL

MM LE SM LL SM LL SM LL

SDH/Sonet/ATM

52 155 622

1244 2488

MM S MM SL/LE MM SL/LE MM SL MM SL

MM S MM SL/LE MM SL/LE MM SL MM SL

MM LE MM SL/LE SM LL SM LL SM LL

S – 850nm LED, SL – 850nm LD, LE – 1300nm LED; LL – 1300nm LD

By Fiber Optics LAN Section (FOLS) of the Telecommunications Industry Association (TIA)


„Summary”

• Optical fiber provides users with higher reliability, superior performance and greater flexibility than copper-based systems.

• The construction of optical fiber makes it essentially immune to many of the factors that adversely impact copper, factors that often become more pronounced at higher data rates, thereby increasing network cost and complexity.


Control questions

1. What are the basic network types? How introduction of optical fibers modifies the traditional classification?

2. Describe OSI layered network model. Explain which layers are influenced by the presence of different photonics elements.

3. List fiber advantages. Indicate which are important for network planners, engineers and users.

4. Which computer-networks are suitable for optical fiber networking. Shortly characterize active and passive optoelectronics elements of the network. How selection of the elements influences network design?

5. Describe optoelectronic elements (passive and active ) used in Ethernet networks.

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