Telecommunication Switching

Circuit-Switching

�� Intro

• Circuit-Switched Set up a circuit that will be used during a data transmission

• We have 2 types dedicated or leased

• A private circuit is dedicated analog or digital point-to-point connection joining

geographically diverse networks

�� Dedicated Line

• Reserved by a communications carrier for a customer's private use

• Are the most expensive type of connectivity

• T1 T3 are examples of decicated lines

• Type and speeds

�� Digital Signal Level 0 (DS-0) Transmitting digital signal over a single channel at 64KBps

on T1

�� Digital Signal Level 1 (DS-1) Transmitting digital signal at 1.544MBps on T1 (USA) or

2.108MBps on E1 (Europe)

�� Digital Signal Level 3 (DS-3) Transmitting digital signal 44.736MBps on T3

�� Digital Signal Level 3 (DS-3) Transmitting digital signal 44.736MBps on T3

�� T1 transmits DS-1 formated data at 1.544MBps through a telephone switching network

�� T3 transmits DS-3 formated data at 44.736MBps through a telephone switching network

�� E1 Wide area digital transmission used in Europe that carries data at a rate of

2.048MBps

�� E2 Wide area digital transmission used in Europe that carries data at a rate of

34.368MBps

�� Both E1, E2 can be leased for private use

�� Serial Line IP (SLIP)

• Developed in 1984 to support TCP/IP over low speed serial interfaces

• Support only IP not login or password

�� PPP

• Point-To-Point Protocol

• PPP - is an encapsulation protocol fpr Dial-up connections

• It replace SLIP

• PPP - is ideal for connecting different types of devices over serial lines

• Support loging, password and error correction

• Has built-in security such as CHAP PAP

• PPP is data Link Layer protocol (layer 2)

�� ISDN

• Integrated Services Digital Network is a combination of digital telephony and datatransport

services

• It consists of digitization of the telephone network by permitting voice and other

digital services to be transmitted over existing wires

• ISDN and Analog allow for the use of "callback" as an extra security measure.

• Integrated Services Digital Network (ISDN) is a set of CCITT/ITU standards

• Two types are BRI, basic rate, and PRI, primary rate

• Basic Rate Interface

�� Two B-channels 64 Kbps combien = 144Kbps

�� One D- channel at 16 Kbps

�� Basic Rate user can have up to 128 Kbps service

• The Primary Rate

�� USA

�� 23 B-channels

�� One D-channel at 64 Kbps

�� Total bandwidth is equivalent to a T1 1.544 Mbps

�� Europe

�� 30 B-channels

�� 1 D-channel

• Broadband ISDN (BISDN

�� 2 Mbps up to much higher

�� Can handle many different types of services at the same time

�� Used within telecommunication carrier backbones

• It is been reaplaced by xDSL

�� XDSL

• Intro

�� Digital Subscriber Line

�� Use existng twisted pair telephone line

�� Consists of Point-To-Point public network accessed through copper phone wire

�� Becoming the standard for inexpensive remote connectivity

�� DSL - transmits high-speed bandwidth over existing phone lines

• Types

�� ADSL

�� Asymmetric Digital Subscriber Line

�� Deliver more bandwidth downstream 1.5 to 9 MBps

�� Upstream 16 to 640KBps

�� Work at distance up to 18,000 feet over a single twisted pair

�� 14,400 feet is the maximum practical lenght

�� SDSL

�� Single-Line Digital Subscriber Line

�� Synchronous Data Link Control

�� Is a transmission protocol developed by IBM in the 1970s

�� Based on dedicated, leased lines with permanent physical connections

�� SDLC is equivalent to layer 2 of the OSI

�� SDLC uses the primary station-secondary station model of communication

�� Use a polling media-access method

�� It has evolved into HDLC

�� Delivers 1.544 MBps both downstream upstream

�� Work at distance up to 10,000 feet over a single twisted pair

�� HDSL

�� High-Rate Digital Subscriber Line

�� Derived from SDLC

�� Is a group of protocol or rules for transmitting data between network points

�� In HDLC, data is organized into a unit (called a frame) and sent across a network

�� HDLC protocol also manages the flow or pacing at which data is sent

�� HDLC (layer 2) encapsulates the layer 3 frame, adding data link control information

�� It was created to support both point-to-point and multi-point configurations.

�� HDLC is equivalent to layer 2 of the OSI

�� Delivers 1.544 MBps both downstream upstream

�� Work at distance up to 12,000 feet over TWO twisted pairs

�� VDSL

�� Very-High Data-rate Digital Subscriber Line

�� Deliver more bandwidth downstream 13 to 52MBps (from central office to client) than upstream

1.5 to 2.3MBps

�� Work at distance 1,000 to 4,500 feet over a single twisted pair

�� HSSI

�� High Speed Serial Interface

�� Address the need for High Speed communications over WAN

�� It defines the electrical and physical interfaces to be used by DTE/DCEs.

�� HSSI is equivalent to layer 1

�� Packet-Switching

�� Intro

• PSN or PSDN Packet Switching Network

• Packet-Switching DO NOT Set up circuits

• Packets can travel along many different routes

• Nodes share bandwitdth with each other

• Data in packet is broken up into packets and then sent to destination

• At the destination packets are reassembled based on their sequence numbers

• Packets are assigned a sequence numbers

• Packet switched network is Connection less

• Packet switched network are characterized by "Brusty" traffic

• Virutal Circuit

�� PVC - Permanent Virtual Circuit

�� PVC - Permanent programmed into the WAN devices

�� SVC - Switched Virtual Circuits

�� SVC - Require steps similar to dial-up

�� SVC - are temporary connections

�� Packet Switched VS Circuit Switched <>

• Circuit

�� Constant traffic

�� Fixed delays

�� Connection-oriented

�� Sensitive to loss of connection

�� Voice-oriented

• Packet

�� Brusty traffic

�� Variable delays

�� Connection-less

�� Sensitive to loss of data

�� Data-oriented

�� Types

• X.25

�� The first packet switching networks

�� It defines point-to-point communication between DTE and DCE or DSU/CSU

�� Frame Relay and X.25 use virtual circuits instead of dedicated ones

�� Support switched virtual circuit SVC's and Permanent Virtual Circuit PVC's

�� Work on network layer 3

�� X.25 define how WAN devices are established and maintained

�� Was designed to operate effectively regardless of the type of the systems

�� It has become international standard

• LAPB Link Access Procedure Balanced

�� Created for use with X.25, LAPB

�� Defines frame types

�� Capable of:

�� Retransmitting

�� Exchanging

�� Acknowledging frames

�� Detecting out-of-sequence or missing frames

• SMDS Switched Multimegabit Data Service

�� High-speed

�� Used over public networks

�� Used to exchange LARGE amounts of data

�� Brusty traffic

�� Connection-less

• Frame Relay

�� Frame Relay and X.25 use virtual circuits instead of dedicated ones

�� High performance WAN protocol

�� Operates at the physical (1) and data link layers (2)

�� Fee is based on bandwidth usage

�� Designed for cost efficient data transmission

�� It uses a simplified framing approach and utilizes no error correction

�� It uses SVCs, PVCs, and DLCIs for addressing.

�� Originally designed for ISDN

�� Used now in WAN communications

�� It is considered as UPGRADE from X.25 and LAPB

�� Has no error correction

�� It is not available everywhere

• ATM Asynchronous Transfer Mode

�� Used more in WAN

�� ATM transfers data in fixed cells 53 bytes

�� Use cell relay technology that combines conventional circuit and packet based systems

�� ATM is an example of a fast packet-switching network

�� ATM - transmit data at very high rates

�� ATM- support voice, data and video

�� Use both switching and multiplexing

�� Very High Bandwidth and Low delay

�� It can allocate bandwidth upon demand

�� Good solution for Brusty applications

�� It can run in both WAN and LAN environments

�� Require high-speed medium like fiber

• VoIP Voice Over IP

�� Multi-service access IP

�� Combiens many types of data such voice, audio, video into a Single IP packet

�� Is very new area of technology

�� Has exciting potential

Posted in: Telecomunication