NETE0510: Communication Media and Data Communications 1 NETE0510 Physical Layer Protocols and Access...

NETE0510: Communication Media and Data Communications

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NETE0510Physical Layer Protocols and

Access Technologies

Supakorn [email protected]


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Virtual Tributary (VT)

VTs are the building blocks of the SPE VTxx designates VTs of xx Mbps


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Virtual Tributary (VT)7 VT groups (VTGs) per STS-1, each VTG contain• 4 VT1.5s 1 STS-1 can carry 28 DS1s• 3 VT2s 1 STS-1 can carry 21 E1s• 2 VT3s•1 VT6


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Outline

Physical Layer Protocols and Interfaces Accessing the Network Copper Access Technologies Cable Access Technologies Fiber Access Technologies Air Access Technologies


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Physical Media

Three major types of physical media Copper

Twisted-pair, coaxial, twin-axial (twin-ax), broadband (used in CATV)

Fiber Resistance to electromagnetic signals, not affected by

crosstalk, interference, but require more protection Air

Point-to-point wireless, wireless LAN, cellular, microwave, or satellite


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RS-232-C, EIA-232-E, ITU-T V.24/V.28

RS-232-C and EIA-232-E are defined by the Electronic Industries Association (EIA) as synchronous interface standards for use with the physical layer D-shaped 25-pin connector DTE interface to voice-grade

modems (DCE) ITU V.24/V.28 is similar to RS-232-C and provides the

international version of the RS-232-C standard V.24 defines physical interface and V.28 defines electrical

interface


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RS-232


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T1/E1 Framing and Formating

A T1 circuit operates at a speed of 1.544 Mbps circuit capacity Throughput is less than 1.536 Mbps

Took twisted wire pairs and accommodated 24 voice conversations instead of one with the use of multiplexers

24 channels, 8 bits per channel, in a time frame of 125 µs 192 bits + 1 framing bit = 193 bits per T1 frame T1 transmits 8000 frames per second

E1 is European standard of the T1 Offer 2.048-Mbps bandwidth


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HSSI

HSSI is a physical interface at speeds up to 52 Mbps Become standard interface between DS3 rate of 45

Mbps and the OC-1 SONET interface of 51.84 Mbps for everything from WAN connectivity to a DTE-DCE direct-channel interface


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HSSI (cont’d)

Fiber-optic modem


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IEEE802 Physical Interfaces

3 common MAC physical interfaces for the IEEE 802 architecture model are: Ethernet (802.3) Token Ring (802.5) Wireless LAN (802.11)


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10-Mbps (Legacy) Ethernet

Many different types of Ethernet access: 1 Base5, 10Base2, 10Base5, 10BaseF

Each type defines both wiring and device terminating the end of the wiring

10Base5 (thicknet) and 10Base2 (thinnet) 10 refers to 10-Mbps Ethernet Base stands for baseband

Baseband signaling indicates that Ethernet signals are the only signals carried over the media system

Most common connectivity is via twisted-pair using 10BaseT or 100BaseT standards with no more than 100 m from the central bus or switch


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Comparisons of Ethernet Cabling Specifications


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Fast Ethernet

100 Mbps, new preferred standard FastEthernet specifications include mechanisms for

autonegotiation of the media speed. Vendor can produce dual-speed Ethernet interfaces that can

be installed and run at either 10 Mbps or 100 Mbps automatically

Autonegotiation allows the devices to perform automatic configuration to achieve the best possible mode of operation over a link


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Fast Ethernet (cont’d)

Three media varieties 100BaseTX: uses 2-pair Category 5 UTP cable

TX segment type is a twisted-pair segment that uses two pairs of wires and is based on data grade twisted-pair physical medium standard developed by ANSI

100BaseFX: uses fiber-optic cable FX is based on fiber-optic physical medium standard

developed by ANSI and uses two strands of fiber cable 100BaseT4: uses 4-pair Category 3, 4, or 5 UTP cable

T4 segment type is a twisted-pair segment that uses four pairs of telephone-grade twisted-pair wire


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Gigabit Ethernet

1000 Mbps Idea when budget is tight but require higher bandwidth Employ all the same specifications defined by the

original Ethernet standard, including the same Ethernet frame format and size

1000BaseT physical layer provides 1-Gbps Ethernet signal transmission over four pairs of Cat-5 UTP cable

Use five-level (PAM-5) encoding along with four wire pairs, able to provide 250 Mbps per pair

Can transmit signal for 100 m over twister-pair cable and longer with fiber-optic cable


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Gigabit Ethernet (cont’d)

1000BaseT: use 4-pair CAT-5 balanced copper cabling and a 5-level coding scheme

1000BaseCX: use 150-ohm shielded copper cable and supports a max length of 25 m

1000BaseF: use fiber-optic 1000BaseFX: use 62.5/125 multimode fiber and supports a max

distance of 412 m 1000BaseSX: use 50.125 or 62.5/125 multimode fiber with max

distance of 550 m 1000BaseLX: use 9/125 single-mode, 50/125 multimode, or

62.5/125 multimode fiber with max distance of 5 kms 1000BaseZX: use 9/125 single-mode fiber with max distance of 100

kms 10-Gbps Ethernet: only fiber-optic cable


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Step-index Profile

The proportion between diameters of core and cladding e.g. 62.5/125 (µm)


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Wireless LAN (IEEE802.11)

IEEE802.11 specifies connectivity between LAN devices using radio-based equipment

802.11 is similar to 802.3 for wired LANs but use CSMA/CA instead of CSMA/CD

Collision detection cannot be used for radio frequency transmission because when a node transmits over the air, it cannot hear other nodes on the network

Support two types of operating configurations: Independent or ad-hoc do not need an access point Infrastructure need an access point

Access point acts as a bridge in a wired LAN


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Wireless LAN (cont’d)


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Wireless LAN (cont’d)


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Token Bus and Token Ring

Physical interface for IEEE802.4 Token Bus and IEEE802.5 Token Ring is the DB connector, interfacing with IBM Type 1 shielded twisted-pair cable. Coaxial cable connections are also available

Token Ring is usually run in Type 1 (2-pair STP), Type 2 (4-pair STP), Type 3 (UTP), and Type 5 (fiber-optic cable)

Media access unit(provide logical ring)

MDI: medium dependent interface used to connect to other hub or switch without crossover cable required


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Physical Media Comparison


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Outline



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Consumer or Residential Alternatives

Existing copper phone line: Plain old telephone service (POTS) Dialup ISDN Basic rate interface (BRI) DSL

Cable line Cable modem

Wireless Direct broadcast satellite (DBS) Very small aperture satellite (VSAT)


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Consumer or Residential Alternatives


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Corporate or Business Access Alternatives

Copper All consumer methods DS1, FT3, DS3 ISDN

Fiber DS3 SONET OC-N


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Corporate or Business Access Alternatives


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Outline



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UTP

A transmission repeater system over a four-wire twisted-pair is defined and called T1

Signal and service is referred as a DS1 T1 circuits are brought to the customer location

via either copper or fiber UTP is very popular type of copper wiring


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UTP Ratings (EIA/TIA Standards)

Category 1 used for voice and low-speed data transmission up to 56 kbps

Category 2 Ideal for 4-Mbps token ring, RS-232, RS-422, and AS/400

Category 3 Ideal for telephone, $-Mbps token ring, and 10BaseT applications

Category 4 Used for 16-Mbps token ring

Category 5 Suitable for 100BaseT Ethernet, 10-Mbps token ring, and OC-3 ATM

Category 5e Support speed up to 1.2 Gbps and typically used for Gigabit Ethernet

Category 6 Newly designed for Gigabit Ethernet and future apps


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Dialup or Legacy Analog Modem

Current standard for 56-Kbps modem is V.92 Prior to 56-Kbps modems, the best speed between two

modems was 33.6 Kbps. With V.90, connection speeds can exceed 50 Kbps

Up to 54 Kbps download, 33.6 Kbps upload V.92 provides 56 Kbps with enhancements:

Upload speed increased to 48 Kbps: improve video conferencing and file uploading

Startup time reduced from about 20 seconds to about 10 seconds

Internet call waiting Receive a call while the modem is still connected


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Dialup or Legacy Analog Modem


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ISDN

ISDN BRI provides one of the best disaster discovery alternatives for services such as FR and IP (VPNs and Internet access)


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ISDN Basics

Built on the TDM hierarchy developed for digital telephony

ITU-T defines two standards for physical interface to ISDN BRI (Basic Rate Interface) PRI (Primary Rate Interface)

The physical layer provides transmission capability, activation, and deactivation of terminal equipment (TE) and network termination (NT) data (D)-channel access for TE, maintenance functions, and channel status indications


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ISDN (cont’d)


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ISDN Devices


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ISDN Devices

Terminal Adapter

ISDN router (TE1)

NT1 or NT2

ISDN PCI card


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ISDN Reference Points

R — References the connection between a non-ISDN compatible device Terminal Equipment type 2 (TE2)and a Terminal Adapter (TA), for example an RS-232- serial interface.

S — References the points that connect into the customer switching device Network Termination type 2 (NT2) and enables calls between the various types of customer premises equipment.

T — Electrically identical to the S interface, it references the outbound connection from the NT1 to the ISDN network or Network Termination type 1 (NT1).

U — References the connection between the NT1 and the ISDN network owned by the telephone company.


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ISDN Access Options

TE1ISDN router

TE1

TE1ISDN router

TE2


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BRI and PRI

BRI Provides two 64-kbps bearer (B)-channels for the

carriage of user data and one 16-kpbs control and network management D-channel

PRI 23 64-kbps bearer (B) channels and one 64-kbps

signaling channel (North America) 23B+D 30B+D for international Higher bandwidth or shared customer devices


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ISDN: BRI


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ISDN PRI (cont’d)

ISDN PRI provides a single 1.544 Mbps DS1 or a 2.048-Mbps E1 data rate channel over a full-duplex synchronous point-to-point channel using TDM hierarchy

DS1 data stream comprises 24 DS0 channels of 64 kbps each containing 23 B-channels at 64 kbps each and one D-channel at 64 kbps


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ISDN: PRI


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T1 Frame Structure


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E1 PRI Frame Structure


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ISDN Protocol Model

Primary ISDN architecture concepts consists of multiple devices connecting through an ISDN network termination device (TE) into the central office environment where information services are provided


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ISDN Information Services Concept


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ISDN Protocol Architecture


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ISDN introduced the notion of multiple planes: Bearer service (or user plane) Control plane Management plane


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The user protocol (or bearer service) is Layer 1 for circuit-mode, Layer-2 for frame-mode, and Layer 3 for packet-mode services

Intermediate nodes might provide only physical connectivity.

The purpose of control plane is to establish, configure, and release the user plane capabilities

The management plane is responsible for monitoring the status, configuring the parameters, and measuring the performance of the user and control planes


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DSL

DSLAM: DSL Access Multiplexer


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DSL Types


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DSL Modem

The existing copper telephone network line connects the customer’s xDSL modem to a service provider model in the public network.

The xDSL modem can create the following three channel types: High-speed downstream channel ranging from 1.5 to 5.2

Mbps Medium-speed duplex channel ranging from 16 kbps to 2.3

Mbps POTS channel


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DSL Equipments

DSL modem Connect the customer across the local loop to the

provider’s DSL access multiplexer (DSLAM) Support routing, switching, or firewall functionality

DSLAM Use statistical multiplexing to combine many DSL lines Support different types of DSL in a single central office

with additional features e.g. IP routing or DHCP


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Advantages of DSL

Always on connection Simultaneous voice and data communications Higher speed than legacy V.92 modem Not require new wiring


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Disadvantages of DSL

Limitation of distance ADSL, ADSL Lite, IDSL, RADSL, UDSL: 18,000 ft HDSL, FDSL 2: 12,000 ft SDSL: 10,000 ft VDSL: 4,500 ft

The achievable high-speed downstream data rate depends on Length of twisted-pair line Presence of bridged taps (repeaters) and load coils (filters)

from the old party-line days Cross-coupled interference from other lines


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DSL Standards

The ANSI standard for ADSL is discrete multitone (DMT) DMT is a FDM that divides the data into 256 downstream and 32

upstream channels, each 4-kHz wide DMT constantly searches for the best channels for transmission and

reception and shifts the signals between the different channels QAM uses phase and amplitude modulation to create 16 different

channels Support two carriers having the same frequency buy differ in phase by

90 degrees Enable twice the rate of standard pulse amplitude modulation

CAP: a version of QAM divides signals on the telephone line into three distinct bands: Voice conversation: 0-4 kHz Upstream channel: 25-160 kHz Downstream channel: 240 kHz – 1.5 MHz


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Outline



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Cable Access Technologies

Enable people to view cable TV and get high-speed internet over the same (coax) access circuit


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Coaxial Cable

Installed approx 60% of all homes in the US Less distance sensitive than DSL Coaxial cable is more resistant to interference

and attenuation than twisted-pair cabling Attenuation is the loss of signal strength, which

begins to occur as the signal travels further along a copper wire


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Coaxial CableGround and protecting the core from electrical noise and crosstalk, a signal overflow from an adjacent wire


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Two-way Cable System


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Two-way Cable Operation (cont’d)

Coaxial cable can carry hundreds of MHz of signals Each TV signal is supported by a 6-MHz channel on the

cable High-end coaxial cable supported 550 MHz carrying 75

TV channels Recently install fiber from cable headend to distribution

channel, then transmit signals through coaxial cable Fiber supports 750 MHz to support more channels and

high-speed Internet, cable telephpony, and interactive video services


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Two-way Cable System (cont’d)

To enable internet access, need to put data into a 6-MHz channel

The first user to connect to the Internet through a specific 6-MHz channel can use almost the entire bandwidth of that channel.

More users, performance drops Service provider resolve performance degradation by

adding a new channel and splitting the numbers of users on each channel

The average throughput is typically about 1 Mbps


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Equipment Associated with Cable Access

2 types of equipments required Cable modem on the customer end Cable-Modem Termination System (CMTS) at the cable

provider’s end Cable Modem

A set-top box device that supports, Internet access, cable TV programming, and telephone access to the PSTN

Provide high-speed Internet access through a cable TV network on average of 3-50 Mbps and a distance of 100 kms

Use a tuner to separate data channels from cable TV programming


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Equipment Associated with Cable Access

CMTS Located at the cable provider’s headend Similar to DSLAM acting as a multiplexer combining

traffic from multiple users onto a single channel A CMTS supports up to as many as 2,000 connections

to the Internet through a single 6-MHz channel Support both upstream and downstream

Upstream data is transferred from the customer in a separate division of time not used by other customers

Downstream data is supported much like an Ethernet LAN


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Cable Modem Standards

In the US, Data Over Cable Service Interface Specification (DOCSIS) accepted by ITU in 1998 Has become ITU J.112

DOCSIS supports data services over a cable TV network using one 6-MHz channel in the 50-750 MHz spectrum range for downstream traffic the 5-42 MHz band for the upstream traffic


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Outline



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Fiber Access Technologies

Preferred cable media for servicing access rates at DS3 and above

Wide range of fiber access solutions and technologies offered including SONET/SDH, ATM, MPLS (Multiprotocol Label Switching), and Ethernet/IP/PPP networks


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Services Offered via Fiber Access

DS3 service Support transmission of 44.736 Mbps of voice, data,

video, and/or switched services SONET/SDH access

Service providers offer SDH/SONET extension over fiber–optic cable at rates from T1/E1 to OC-12/STM-4

SONET/SDH is supported with a wide range of modems, multiplexers, multiservice access nodes, and converters


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Outline



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Air Access Technologies

Mobile wireless technologies include cellular and wireless LAN

Fixed wireless technologies include point-to-point, fixed radio, and satellite


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Wireless Internet Access


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Mobile Wireless

Cellular and analog network work using a hierarchical model consisting of base stations and antennas.

The area a base station covers is called a “cell” Macro cells are the largest of the cells and

provide extensive coverage, often first built to provide coverage

Micro cells support selected outdoor areas Pico cells are the smaller of the cells and are

built to provide capacity Usually cover the interior of buildings


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Cellular Hierarchical Model


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Evolution of Cellular Technologies


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Fixed Wireless Wireless local loop (WLL) using radio technology has been

implemented for places too expensive to wire such as mountain, swamp, and rural cluster areas.

Multichannel multipoint distribution system (MMDS) A line-of-sight service that operates in the 2.1-2.7 GHz frequency

range Use microwave channels to distribute a varied range of

telecommunications services to subscribers Support 6-MHz channels Can reach up to 70 miles in flat area

Local multipoint distribution service (LMDS) Allocated at 27.5-29.5 GHz Provide two-way wireless cable TV and high-speed data service Similar to MMDA but use higher frequencies and has higher

transmission capacity Require only 6-inch antenna, but must be within 3-5 miles of the

subscriber’s house


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Questions?

Next LectureCommon Protocols and Interfaces

in the LAN Environment

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