1. Emerged Technologies ISDN Nirmala Shenoy Information Technology Dept Rochester Institute of Technology

2. ISDN Purpose –Digital interface between user and network –An all digital network to support the transport for digitized information –For the user the type of transport network is transparent, voice, video, data –ISDN nodes provides this transparency Based on technologies used in T1/E1

3. ISDN Topology –Similar to X.25 –UNI protocol –Comprises of Functional groupings –Set of capabilities, –Multiple pieces of equipment or software

4. ISDN Topology –Comprises of Reference Points –Interfaces between the functional groupings –Physical interface between two pieces of equipment

5. ISDN Topology

6. ISDN Topology –Functional Groupings –TE1 Terminal equipment type 1 – ISDN compatible equipment Uses twisted pair – 4 wire digital link

7. ISDN Topology –Functional Groupings –NT2 -Network Termination type 2 An intelligent equipment, layer 2 & 3 functions Concentration, multiplexing of channels to a defined rate Support multiple terminals

8. ISDN Topology –Functional Groupings –NT1 -Network Termination type 1 Connects 4 wire subscriber to 2 wire local loop Physical layer – signaling, synchronization and timing TEs can connect direct to NT1 – can address up to 8 TEs NT1 + NT2 = NT12 - combined functions

9. ISDN Topology –Functional Groupings –TE2 – non-ISDN compatible TE type 2 Requires an adapter to connect to ISDN –TA – Terminal Adapter provides adaptive function for non-ISDN terminals

10. ISDN Topology –Reference points –S – logical interface between TE and network –R – between non-ISDN TE and adapter –U – 2 wire side of the NT equipment TE – user related, NT – Network related

11. ISDN Topology –TDM based –2B + D channels – Basic Rate Interface- BRI –B – user data – 64 Kbps –D – signaling – 16kbs – out-of band –8 TE1s can share a 2B+D channel

12. ISDN Topology –PRI – Primary Rate interface –23B + D channels – NA & Japan 1.544 Mbps –31B + D channels – Europe 2.048 Mbps

13. ISDN Layers

14. ISDN Layers –3 layers, Network, data link and physical –Physical – Basic Rate Interface & Primary Rate Interface –Data Link layer LAPD – Link Access Procedures for D channel

15. ISDN Layers –Network Layer – Q.931 Establishing and releasing connection

16. ISDN PDUs –LAPD- subset of HDLC –Carries Q.931 messages –SAPI – Service Access point identifier Port used between adjacent layers –TEI – Terminal Equipment Identifier Identifies one or several TEs

17. ISDN PDUs –LAPD- –SAPI+TEI = DLCI = Data link connection identifier

18. ISDN PDUs –Q.931 – signaling protocol –Four categories Establishment Tear Down Information phase Miscellaneous

19. ISDN Conclusions –Starting problems – policies –Later problems – upcoming technologies –LAPD and Q.931 – very useful contributions