ISDN

1. Integrated services digital network
   1. Q.920/921
   2. Q.930/931
      1. Q.931 message
      2. Information elements
2. Basic rate interface (BRI)
3. Primary rate interface (PRI)
4. Clear channel dialing
5. BONDING

Integrated services digital network

• modem replacement, reuses cable infrastructure
• converts phone analog signal to digital form and vice versa
• channels:
  • B-channel:
    • 64 kbps
  • D-channel:
    • signalling
    • 16 kbps
• on-demand connection, separate channel for signalling compared to POTS
• link access procedure (LAPD)
  • based on HDLC
  • L2 ISDN, D-channel

TE-A                       local
           SETUP           ISDN
      --------------->   exchange        SETUP
                                    --------------->
           CALPRC
      <---------------
                                         ALERT
           ALERT                    <---------------
      <---------------

        Ringing tone
      <---------------
                                          CONN
            CONN                    <---------------
      <---------------
                                         CONACK
           CONACK                   --------------->
      --------------->

                        Voice/Data
      <--------------------------------------------->

                                          DISC
            DISC                    <---------------
      <---------------
                                          RLSE
            RLSE                    --------------->
      <---------------
                                          RLCON
            RLCON                   --------------->
      --------------->

Q.920/921

• L2 ISDN

Q.930/931

• L3 ISDN
• alerting ≡ phone rings + ringback tone
• connect ≡ off-hook

Q.931 message

 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Proto discrim |  0x0  | LCRV  | Call ref val  |0|  Msg type   |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\                                                               \
/                     Information elements                      /
\                                                               \
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Protocol discriminator:

• 0x08: Q.931
• 0x09: Q.2931
• 0x10: X.25
• 0x40: national use

LCRV: length of call reference value, octets

Message type:

• 0x01: ALERT
• 0x02: CALPRC, call processing
• 0x03: PROG, progress
• 0x05: SETUP
• 0x07: CONN
• 0x0d: SETACK, setup ack
• 0x0f: CONACK
• 0x45: DISC, disconnect
• 0x4d: RLSE, release
• 0x5a: RLCOM, release complete
• 0x7b: INFO

Information elements

1. bearer capability
   • mandatory: SETUP
2. called party number
   • mandatory: SETUP
3. calling party number
   • optional: SETUP
4. called party subaddress
   • optional: SETUP
5. calling party subaddress
   • optional: SETUP
6. cause
   • mandatory: DISC
   • optional: RLSE, RLCOM, PROG
7. channel identification
   • mandatory: CALPC (user → network), SETUP and SETACK (network → user)
   • optional: SETUP, ALERT, CONN
8. high-layer compatibility
   • optional: SETUP
9. keypad
   • mandatory: INFO
   • optional: SETUP
10. low-layer compatibility
    • optional: SETUP
11. transit network selection
    • optional: SETUP
12. user-to-user info
    • optional: SETUP, ALERT, CONN, DISC, RLSE, RLCOM, SETACK
13. signal
    • mandatory: SETUP and ALERT (network → user)
    • optional: SETACK, PROG, CONN, CONACK, DISC, RLSE, RLCOM, INFO
14. progress indication
    • mandatory: PROG
    • optional: SETUP, SETACK, ALERT, CONN

Basic rate interface (BRI)

• line to client
• 2×B + 1×D

U: 2×B + D + 16kbps (overhead), 2 wire
S/T: 2×B + D, 4 wire
R: non-ISDN (RS-232, V.35)
NT1: network termination 1
TE1: terminal equipment 1, ISDN-capable
TE2: terminal equipment 2, not ISDN-capable
TA: terminal adapter

Primary rate interface (PRI)

• line to ISP
• more channels:
  • T1: 23×B + 1×D
  • E1: 30×B + 2×D

U: T1/E1, 4 wire

Clear channel dialing

• H.221
• alias dial per line: 6 × DS0 required ⇒ 6 different numbers to dial

BONDING

• IMUX on receiver can request extra lines by dialing extra numbers (sequential from the primary number) to reach required BW
• user dials manually only one number