ISDN
Integrated Services Digital Network is a set of comminucation protocol, developed by Telco to digitalized their services to carry VOICE,VIDEO and DATA. Analog services are called PLAIN OLD TELEPHONE SERVICES POTS
ISDN is a set of protocols which cover 3 OSI layes NETWORK,DATA LINK AND PHYSICAL. It’s a low cost reliable and high speed link, run on both COPPER and FIBER media. It’s a circuit switched network.

B Chanels Circuit switch and D Chanels Packet Switch. ... ?? it is true

ADVANTAGES
1- 5+ times faster then 28.8kpbs analog modem.
2- use multiple devices on the same fone line like Video, Voice, Fax,Video Confrence etc
3-Drops from 2 B Chanels to 1 when incomig call detected.
4-Dynamic allocation

DISADVANTAGES
1-Central office OR Service Provider should be in 5 mile radius.
2-Difficult Setup

ITU-T define standerd which are important for Exam (difficult for candidate to digest)

SERIES--OSI--EXAMPLE------DESCRIPTION
E...........E-163........Packet Switch Telephone Network its a International Telephone Numbering System
E...........E-164........ISDN numbering Standerd
I...........I-100........Concepts, Stractures, Termonology
I...........I-200........Services Aspects
I...........I-300........Network Aspects
I...........I-400........User Network Interface (Uni)
I......1....I-430........Define Connectors, Encoding Frames, Reference Points
I......1....I-431........Define Connectors, Encoding Frames, Reference Points
I...........I-411........ISDN REFERENCES POINT (IMPORTANT Detail is following)
Q......2....I-921........Signaling, Switching at Data link Layer LAPD(Link Access Procedure Dedicated)
Q......3....I-931........its works on Network Layer in ISDN

Tool To remember
Focus on 2nd Digit in Q Series. It matches to the layer e.g. Q921 = Layer 2 Standerd and Q931 = Layer3 Standerd

SERVICES - 2 Services r supported on ISDN:
BRI (BASIC RATE INTERFACE)
PRI (PRIMARY RATE INTERFACE)

BRI + B & D Channels - 2B+D

B Channels are aslo called CLEAR CHANNELS because they are clear to send data. Data is transfered in B Channel and Singnals (Call setup etc) are resposiblity of D CHANNELS.
D makes it posssible to connect relativly much faster. D is called OUT OF BAND Channel because it only takes Signalling (Rest of every thing OUT).
B Chanel 64 Kbps Each
D Chanel 16 Kbps

B........128Kbps (64*2)
D.........16Kbps
------------
.........144Kbps
------------
Plus Frame OverHead= 144 + 48Kbps (Frame Overhead)
so total bandwidth supported by this chanel is 192Kbps is Total Bandwidth of BRI channel

ANY ROUTER WITH A SERIAL INTERFACE CAN BE CANNECTED TO A BRI WITH A TERMINAL ADAPTER (TA).

????????question is the following statment true ??????????????????????????????

D CHANNEL operated on LAPD and LapD depends on HDLC

PRI
It’s also known as (23B+D for T1 ) and (30B+D for E1 ). B Channels are aslo called CLEAR CHANNELS because they r clear to send data.

B Chanel 64 Kbps Each
D Chanel 64 Kbps--------Different then BRI(16Kbps)

Transfer RATE
T1.... 1.544Mpbs.....23 B Channels.....USA and Japan
E1.... 2.048Mpbs.....30 B Channels.....Rest of world

in E1 Sequence of Channels
1--15 channels....B
16th .Channel.....D
1--15 channels....B

PRI uses DSU\CSU for T1\E1 Connection.
Terminals \ Functional Groups
These are PHYSICAL DEVICES involved in ISDN connectivity.

TERMINAL EQUIPMENT 2 (Functional Group)
TE2 is old technology (like ordinary fone sets working on analog) that dont support ISDN series so it need a Conversion Device named TERMINAL ADAPTOR. (THINK LIKE SOMETHING MODEM)

TERMINAL EQUIPMENT 1 (Functional Group)
TE1 is ISDN Ready Devices that dont need any converion device like Terminal Adaptors.

TERMINAL ADAPTOR. (Functional Group)
Takes the analog data from TERMINAL EQUIPMENT 1 and make it ISDN READY. Converts EIA\TIA-232, V35 & into BRI SIGNAL..

Network Termination 2 (Functional Group)
NT2 is the point (Device) at which all ISDN lines at Customer Premises are agregated and Switched using cusmtomer Switch Device Private Branch Exchange(PBX). they are very rare in usage. So even most documents dont Discuss them.

Network Termination 1 (Functional Group)
NT1 is a LOCAL LOOP TERMINAER. it converst BRI singnals intor formused by ISDN DIGITAL LINE. It can be in Customer premises or in TELCO (diffent in Europe and USA)

REFERENCE POINTS (I-411 STANDERD)
RP are used to characterised the interfaces between ISDN Devices. (RF are logical)
RF--Location (Function Group)-------
R---Between TE2 and TA--------------between NON ISDN DEVICE AND TERMINAL ADAPTOR
S---Between TE1\TA and NT2----------ISDN READY to Network Terminator
T---Between NT2 and NT1
U---Between NT1 and ISDN Network

Note: Electronically S and T are same so some devices are labeled as ST. They are identical so in most cases we dont see the S R Point and our networks work properly.


TOOL TO REMEMBER
R---- not isdn ready old device-->R=REGULAR
S---- isdn ready devices--------->S=SPECIAL
T-------------------------------->T=TERMINATION POINT
U----if its in Cus. Premises then customer will provide power to the NT1

so->U=UNPOWER

Functional Groups + References Points altogather
-------R-----------S--------------T--------------U
TE2-------->TA----------->NT2------------>NT1------------>TELCO
.
--------------S-------------------T--------------U
TE1---------------------->NT2------------>NT1------------>TELCO

ALSO TRY TO DRAW FUNCTION GROUPS AND REFERENCE POINT ON PAPER SO THAT U CAN VISUALISE THEM PROPERLY.

IF you have BRI interface in your Router, it’s NT1 so U Labled on interfce
No Bri Interface but Serial interface(TE2) Use External T.A
If u must supply NT1 (in US) make sure Router have U interface otherwise purchase NT1.

SPID
Many books gave it many names like SERVICE PROFILE ID, SERVICE PROVIDER ID, PSEUDO PASSWORD ID Etc. It is a numerical string of 14 characters assigned by TELCO to EACH B CHANNEL on an ISDN link.

GENERIC FORMAT OF SPID
NUMBER OF DIGITS---NAME-------------------RANGE
10-----------------Digit form-------------
02-----------------Sharing Terminal ID----01-32
02-----------------Terminal ID------------01-08

SWITCH TYPE
There are different switch types around the globe (No Standard). And unfortunatly Cisco supports then so do CCNA. Switch type and SPID is informed by the telco to customer. And it can be configurable in Global or Interface Mode.

Router(config)#isdn switch-type
example
Router(config)#isdn basic-ni1

Switch type value---Description
basic-5ess----------AT&T in USA
basic-dms100--------NorTel USA
basic-ni1-----------National ISDN1 North America
basic-ts013---------Australia
basic-net3----------net3 & net5 are used in UK and Europe
basic-nit-----------Japan

note
missed topic are
DDR
ISDN SBus