| A | B |
|---|
| What is ISDN? | ISDN allows digital signals to be transmitted over existing telephone wiring. This became possible when the telephone company switches were upgraded to handle digital signals. ISDN is generally viewed as an alternative to leased lines, which can be used for telecommuting and networking small and remote offices into LANs. |
| Benefits of ISDN | 1) ISDN can carry a variety of user traffic signals. 2) ISDN offers much faster call setup than modem connections because it uses out-of-band (D, or delta, channel) signaling. 3) ISDN provides a faster data transfer rate than modems by using the bearer channel (B channel of 64Kbps) offering more bandwidth on WANs than some leased lines. 4) ISDN can provide a clear data path over which to negotiate PPP links. |
| ISDN design issues | Security issues and Cost and Containment issues |
| ISDN Security issues | Because network devices can now be connected over the Public Switched Telephone Network (PSTN), it is crucial to design and confirm a robust security model for protecting the network. |
| ISDN Cost and Containment issues | A primary goal of selecting ISDN for your network is to avoid the cost of full-time data services (such as leased lines or Frame Relay). Therefore, it is very important to evaluate your data traffic profiles and monitor ISDN usage patterns to ensure that your WAN costs are controlled |
| Basic ISDN components | terminal adapters (TAs); Terminal Equipment type 1 (TE1); Terminal Equipment type 2 (TE2); Network Termination type 1 (NT1) or Network Termination type 2 (NT2) device. |
| TA | The ISDN TA can be either a standalone device or a board inside the TE2. If the TE2 is implemented as a standalone device, it connects to the TA via a standard physical-layer interface. |
| TE1 | TE1s connect to the ISDN network through a four-wire, twisted-pair digital link |
| TE2 | TE2s connect to the ISDN network through a TA. |
| NT1 | NT1 is part of the network provided by the carrier |
| NT2 | The NT2 is a more complicated device, typically found in digital Private Branch eXchanges (PBXs), that performs Layer 2 and Layer 3 protocol services. |
| ISDN Reference Points | R, S, T, U. R = connection between a non-ISDN-compatible device and a TA; S = connects NT2 to DCE; T = just like S (outbound from NT2); U = relevant only in N. America where NT1 not supplied by provider. |
| SPIDs | Service Profile Identifiers - The ISDN carrier provides a SPID to identify the line configuration of the ISDN service. SPIDs are a series of characters (that can look like phone numbers) that identify you to the switch at the CO. |
| ISDN Protocols | E, I and Q |
| ISDN Protocol E | Telephone network standards |
| ISDN Protocol I | Concepts, terminology and methods. |
| ISDN Protocol Q | Switching and signaling |
| ISDN ITU-T standards | Use the first 3 layers of OSI model |
| ISDN encapsulation | The two most common encapsulations are PPP and HDLC |
| Three uses for ISDN | Remote access; Remote nodes; Small office/home office (SOHO) connectivity |
| two ISDN services | BRI and PRI |
| ISDN BRI service | delivers a total bandwidth of a 144-kbps line into three separate channels (8000 frames per second * (2*8-bit B channel+2 bit D channel)=8000*18 = 144kbps). BRI B channel service operates at 64 kbps (8000 frames per second* 8-bit B channel) and is meant to carry user data and voice traffic. |
| ISDN PRI service | ISDN PRI in Europe, Australia, and other parts of the world provides 30 8-bit B channels plus one 8-bit D channel plus one 8-bit Framing channel, for a total interface rate of 2.048 Mbps (8000 frames per second* (30*8-bit B channels + 8-bit D channel + 8-bit Framing channel = 8000*8*32 =2.048 Mbps). |
