NETE0510: Communication Media and Data Communications 1 NETE0510 Introduction to Transmission Technologies Supakorn Kungpisdan

NETE0510: Communication Media and Data Communications

1

NETE0510Introduction to Transmission

Technologies

Supakorn Kungpisdan


2

Outline

General Network Topologies Connecting and Circuit Types and Services Private Leased Lines VS Switched Networks Transmission Basics Hardware Selection in the Design Process


3

General Network Topologies

5 most common used network topologies: Point-to-point Multipoint (bus) Star Ring (or loop) Mesh

Node: a network data communication element e.g. router, switch

Link: a circuit connection between nodes Logical link PVC (Permanent Virtual Circuit) Physical link dedicated private link


4

Point-to-Point

Simplest, a single link between two nodes Can be composed of multiple physical and/or

logical circuits Most commonly used in MANs and WANs E.g. private line or dedicated circuit


5

Point-to-Point (cont’d)

A. single link with single physical and logical circuit

B. single link with multiple logical circuits

C. single path with multiple physical circuits, each carrying multiple circuits


6

Common Bus (Multipoint)

All nodes are physically connected to a common bus structure

E.g. IEEE802.3 Ethernet protocol


7

Common Bus (cont’d)

Point-to-multipoint (broadcast) used in Broadband Integrated Services Digital Network (B-ISDN)

Multipoint-to-point (incast) Multipoint-to-multipoint: combination of

broadcast and incast


8

Common Bus (cont’d)


9

Star

Developed during mainframe era Central node only provides point-to-point connections

between any edge on wither a physical or a logical switched basis

Hub and switch: physical star, logical bus Hub-and-spoke: a central hub site where main

applications reside and to which all remote sites are connected


10

Star (cont’d)


11

Ring

Used in a network in which communications data flow is unidirectional

IEEE 802.5 Token Ring protocol and FDDI (Fiber Distributed Data Interface) A bandwidth reservation scheme compare to the collision

scheme used in Ethernet


12

Ring (cont’d)


13

Mesh

Many nodes are connected to multiple links Used in most switched networks, providing

alternate routes for backup and traffic loads Full VS partial mesh No. of links in full-mesh network = n(n-1)/2 links Networks with n greater than 4 to 8 nodes

employ partial mesh.


14

Mesh (cont’d)


15

Mesh (cont’d)


16

Outline



17

DCE VS DTE

Data Communications Equipment (DCE) sits between Data Terminal Equipment (DTE) and transmission circuit

DCE provides a local limited-distance physical connection between DTEs and terminal equipment (TE) e.g. computer

DCE: e.g. modems or channel service unit/data service unit (CSU/DSU) CSU/DSU is a digital-interface device connecting a router to a

digital circuit e.g. T1 and T3


18

DCE VS DTE (cont’d)

DCE performs signal conversion and coding and may be part of DTE or intermediate equipment

DTE converts user information into signals and reconverts received signals into user information

DCE device provides clock signal and DTE devices synchronizes on the provided clock

To connect DTEs, a DCE is needed Connecting 2 DTEs without DCE requires a null modem

(over RS-232 interface) Physical medium can be two-wire, four-wire, coaxial,

fiber optic, etc.


19

Connection Types: Simplex, Half-Duplex, and Duplex

Simplex and half-duplex


20

Connection Types: Simplex, Half-Duplex, and Duplex (cont’d)

Full-duplex


21

Multidrop Circuits


22

Multidrop Circuits (cont’d)


23

Private Lines and Local Loops

A circuit leased from a service provide for a specified period of time

Guarantee minimum availability, delay, throughput, and loss Access line or local loop: leased line used to connect other

services Leased access lines can be purchased through Local

Exchange Carriers (LECs), competitive access providers (CAPs), or inter-exchange carriers (IXCs)

Expensive especially transoceanic private-line service, statistical multiplexing services like FR is a good alternative

Ebrium-doping technique uses lasers to activate ebrium ion in fiber optic to boost signal transmitted through the fiber.


24

Outline

General Network Topologies Connecting and Circuit Types and Services Private Leased Lines VS Switched Networks Transmission Basics Hardware Selection in the Design Process Review


25

Data Transport Networks

Private-line or dedicated leased-line networks Switched networks Hybrid networks


26

Private (Leased) Line Networks

Leased from providers, not share with others, available 24/7

Simplest form of point-to-point communications Electrical speed conventions

DS0 (Digital Signal 0) (56/64 Kbps) NxDS0 (56/64 Kbps increments) 1.544 Mbps NxDS1 (1.5 Mbps increments)

Optical speed conventions OC-N, where N is in increments of 51.83 Mbps

Use leased line when always require entire bandwidth between two points

Reach the highest level of security and performance predictability


27

Private Line Networks (cont’d)

Require modem to transfer over analog line, CSU/DSU for digital line

Traditional services: Analog grade service DS0, fractional DS0, DS1, fractional DS3, DS3 Digital Data Service (DDS): more expensive, more reliability

Optional higher bandwidth access SubRate Data Multiplexing (SRDM): same rate as DDS but enables

aggregation of many low-speed channels into a single DS0 for cost savings

Fractional T1 (FT1) and Fractional T3 (FT3): same type of service but at a DS1 and DS3 levels

To guarantee high availability and reliability, providers has configured their SONET backbones to alternate facilities during a backbone circuit or node failure


28

Switched Networks

Circuit and packet switched networks Characteristics of switched networks

Addressing capability Multiple protocol and interface support One-to-many, many-to-one, and many-to-many

connectivity Network intelligence above the physical Open Systems

Interconnection Reference Model (OSI) layer


29

Hybrid Networks

Use private lines for predictable volumes of constant-bandwidth traffic

Use switched network for users requiring one-to-many connectivity, bandwidth-on-demand, and flexible or more dynamic access


30

Outline



31

Asynchronous and Synchronous Data Transmission

No clock, but have start-stop bits instead


32

Asynchronous and Synchronous Data Transmission (cont’d)


33

Asynchronous VS Synchronous Time Division Multiplexing

The current approach is to carry ATDM cells over very high-speed STDM transmission networks, such as SONET/Synchronous Digital Hierarchy (SDH)


34

Outline



35

Repeaters

Offer the capability to extend an existing LAN or WAN segment at the L1 protocol interface

Commonly used as signal regenerators, protecting against signal attenuation while improving signal quality

Maintain integrity of all data being passed Completely transparent to all data content Form the core component of hubs May cause jitter

An unwanted variation of one or more signal characteristics, such as the interval between successive pulses, the amplitude of successive cycles, or the frequency or phase of successive cycles


36

Modems

Signals are transmitted and received over unshielded twisted pair phone lines

56 Kbps using V.90 standard derived from the x2 technology of 3Com (US Robotics) and Rockwell’s K56flex technology

DSL modems use various modulation techniques including Discrete Multi-tone Technology (DMT), Carrier Amplitude Modulation (CAP), and Multiple Virtual Line (MVL)

Cable modems modulate between analog and digital signals, and attach to the coaxial cable with a Cable Modem Termination System (CMTS) at the local cable TC company office 27 Mbps downstream/2.5 Mbps upstream


37

CSU/DSU

Originally, Channel Service Unit (CSU) was developed to protect CPE (Customer Premises Equipment) from voltage surges in the access line Higher speed, used at DS1 rates

Data Service Unit (DSU) was typically the lower-speed device, providing signal format and protocol translation, timing recovery, and synchronous sampling.

Currently, CSU/DSU is a device that merges the CSU and DSU functionality Have the capability of Extended Super Frame (ESF) (a T1 standard that

includes CRC check) monitoring and testing Advanced SNMP monitoring with their own management information

bases (MIBs) Multiplex traffic from multiple input ports into a single point-to-point or

multidrop circuit


38

CSU/DSU (cont’d)


39

CSU/DSU (cont’d)


40

CSU/DSU (cont’d)

With the emergence of broadband service e.g. SMDS (Switched Multi-megabit Data Services) and ATM Data Exchange Interfaces (DXIs), CSU has additional function: Some SMDS and ATM CSUs perform some protocol conversion and

cell segmentation E.g. with SMDS DXI, special SMDS CSUs takes L3_PDU frame and

segment it into L2_PDU cells, performing part of the SMDS protocol function within the CSU

Then CSU interfaces to the SMDS network through a SMDS Interface Protocol (SIP)

CSU/DSU standard interfaces include 56-Kbps, FT1 (Fractional T1), and DS1 using EIA-232-C, V.35, and HSSI (on DS-3 models)

CSU/DSU is a layer-1 device (except the SMDS, ATM DSU, and some FR CSU/DSUs)


41

CSU/DSU (cont’d)


42

Hubs and LAN Switches

Hub is Layer 1 device used to: combine multiple workstations or servers onto a single

LAN segment Combine multiple LAN segments onto a single LAN

segment


43

Hubs and LAN Switches (cont’d)

1st Generation hubs Single bus, single LAN architecture

2nd Generation hubs Single bus, multiple architectures e.g. Ethernet and Token Ring Remote network management and configuration

3rd Generation hubs/switches Multiple buses, add L2 bridging functions L2 switch, aka

smart hubs Network management e.g. SNMP

4th Generation switching hubs MAC-layer switching, transparent bridging, standard wide area

trunk interfaces Simple routing and elementary firewall functions


44


NM = Network Management


45



46



47



48

Bridges

Normally, bridges provide connectivity between LANs of similar architecture

Translation bridge can translate from one media format to another

Bridging can be performed in intelligent hubs, LAN switches, L3 switches or routers

Pass traffic from one segment to another based on destination MAC address

Store and forward packets between bridges as packet switches


49

Bridges (cont’d)


50

Types of Bridging

Transparent bridging Both ends of a transmission support the same physical

media and link-layer protocols from IEEE 802.X suite Transparent, no part in the route discovery or selection

process


51

Transparent bridging


52

Types of Bridging (cont’d)

Translating bridging Translate data between different physical media and

link (MAC) protocols Protocols in the network layer and higher must still be

compatible Do not provide segmentation services, so the frame size

must be configured for the same supportable length Encapsulating bridging

Provide a network interconnection or extension by placing received frames within a media-specific “envelope” and forwarding the encapsulated frame to another bridge for delivery to the destination


53

Encapsulation Bridging


54

Source Route Bridging

Source route bridging Has the ability to perform routing based on L2

information


55

Disadvantages of Bridges

Susceptible to multicast of broadcast storms When bridging loop occurs Spanning-tree protocol (STP)

Bridge should not be used in network designs calling for multiple protocol support, dynamic networks requiring frequent changes, or large networks of greater than 50 nodes


56

Switches

4 classes of switches Workgroup or local switches: switch traffic within a

workgroup Enterprise switches: connect multiple departments or

workgroups Edge switches: serve as access or entry switches to a

public data service Can be packet (X.25 or IP), frame (FR, Ethernet, or

FDDI), or cell (ATM), or optical SONET/WDM switches. Service provider backbone (CO) switches: act as

high-speed interconnects for edge switches


57

Switches (cont’d)


58

Types of Switches

L2 switches (LAN switches) Ethernet, Token Ring, FDDI, and ATM)

Hybrid L2 and L3 switches Used when some form of packet, frame, or cell

switching is being used, e.g. when routing IP or accessing FR or ATM services

Used in backbone networks Perform the same tasks as routers do, but operate

faster


59

Routers

Provide interconnectivity between devices on LANs and WANs

Route packets from node to node using packet-defined protocol information used by routing protocols (routing/forwarding tables)

Routing protocols e.g. OSPF, IGRP, RIP Employ address scheme, 4-byte address Router’s main functionality reside in L2 and L3 Applications of both ends do not need to support the same

LAN protocol Current routers can forward packets in excess of 40 mil

packets per second


60

Routers (cont’d)


61

Routers (cont’d)


62

Bridging to routing Comparison


63

Brouters

Bridge + router Have the capability to route some protocols and

bridge others Routing function is done in L2 based on MAC

address. Transparent to both the network-layer protocols and end

stations Do not look at the network-level addresses


64

Gateway

Provide all interconnectivity provided by routers and bridges, up to L7

Can be performed in hardware, software, and both Slower than bridges, switches, and routers Protocol translator of architectures e.g. SNA, IPX.

TCP/IP and OSI Translate between IEEE 802.X architectures e.g.

between Ethernet and Token Ring Can reside within workstations, servers, etc.


65

Gateway (cont’d)


66

Disadvantages of Gateway

Low throughput during peak traffic conditions May become the main network’s congestion point Spend to much time to translate between many protocol

suites User-to-gateway priority handling Store-and-forward characteristics

However, gateway has a growing need for their functionality

E.g. voice gateway acts as the intermediate node connecting a voice call between a packetized voice user (from an IP network) and a circuit-switched user (from PSTN)


67

Questions?

Next LectureMultiplexing and Switching Technologies: An Overview

Documents

NETE0510: Communication Media and Data Communications 1 NETE0510 Introduction to Transmission Technologies Supakorn Kungpisdan