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Principles of Voice & Data

Principles of Voice & Data. Lesson 5: Analog and Digital Signaling Bellevue Community College Bob Young, Instructor. Signaling Categories. Supervision Addressing Alerting Let's look at each of these three categories in more detail. Signaling Categories: Supervision.

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Principles of Voice & Data

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  1. Principles of Voice & Data Lesson 5: Analog and Digital Signaling Bellevue Community College Bob Young, Instructor

  2. Signaling Categories • Supervision • Addressing • Alerting Let's look at each of these three categories in more detail...

  3. Signaling Categories: Supervision • Detects changes to the line • On hook • Off hook • Call transfer • et cetera

  4. Signaling Categories: Addressing • Responsible for routing functions • Passes analog or digital routing information to the correct location to establish the connection • What are some analog routing signals? • What are some digital routing signals?

  5. Signaling Categories:Alerting • Signals intended for the user • often audible • ring • busy • call waiting • caller ID (inaudible) • et cetera

  6. In-Band & Out-of-Band Signaling • In-band signaling shares the same circuit or path as the voice or data • Out-of-band signaling uses a separate path

  7. In-Band Signaling • Also called "Channel Associated Signaling," or CAS

  8. In-Band Signaling • Standard for POTS lines • Standard for T1 circuits • Several inherent problems: • slow • susceptible to line noise • security issues

  9. Out-of-Band Signaling • Also called "Common Channel Signaling," or CCS

  10. Out-of-Band Signaling • Standard between Central Offices • Standard for ISDN • Several advantages: • faster • more reliable • more secure

  11. E & M Signaling • E & M Signaling is (was) used between Central Offices on trunks • It is (was) also used to connect DID trunks to PBX's

  12. E & M Signaling To prevent glare on E & M trunks: Use wink-start signaling!

  13. Wink-Start Signaling • A momentary change in line status sent as an acknowledgement. • Momentary loop current ("off-hook") • Momentary battery reversal • Momentary ground

  14. Glare • "Glare" is the condition that occurs when both ends of the same trunk are seized by two different switches for two different calls.

  15. 2-Wire E&M Voice Voice Voice Voice E-Lead E-Lead M-Lead M-Lead

  16. 4-Wire E&M RX Voice TX Voice RX Voice TX Voice TX Voice RX Voice TX Voice RX Voice E-Lead E-Lead M-Lead M-Lead

  17. E&M Signaling Types

  18. Ground Start Signaling Like E & M Signaling, • Ground Start Signaling is (was) used between Central Offices on trunks • It is (was) also used to connect DID trunks to PBX's

  19. Ground Start Signaling Primary advantage/reason for Ground Start Signaling: Prevents glare!

  20. Ground Start Signaling • To initiate a call, a ground is applied to the ring wire momentarily • The far end responds by grounding the tip momentarily • Start loop current, send DTMF or MF

  21. T1's and In-Band Signaling • Channelized T1 • 24 DS0's • 64 kbps channels • Minus 8 kbps for signaling • Leaves 56 kbps per DS0

  22. T1's and In-Band Signaling • Unchannelized T1 • One complete data "pipe" • 24 x 64 kbps = 1.536 Mbps

  23. T1's and In-Band Signaling • Bit robbing • Superframe (SF) robs 2 bits • A & B • Extended Superframe (ESF) robs 4 bits • A, B, C, & D • Indicate on-hook and off-hook for both ends of the circuit

  24. Uses for A & B Bits • Used for supervision in: • Digital E&M circuits • Digital loop start circuits • Digital ground start circuits • Digital OPX circuits

  25. ISDN • Integrated Services Digital Network • "ISmell Dollars Now!" • "It Still Does Nothing!"

  26. ISDN • All digital, from subscriber premise to Central Office • Uses out-of-band signaling • Also called "common channel signaling (CCS)

  27. Channel Structure Bearer Service -- 64 Kbs Data Channel -- 16 Kbs Overhead -- 48 Kbs

  28. Service Levels • Basic Rate Interface (BRI) • 2 Bearer Services plus 1 Data Channel • (2B+D) • Linking (Bonding) of Bearer Services • Primary Rate Interface (PRI) • 23 Bearer Services plus 1 Data Channel • (23B+D) • Linking (Bonding) of Bearer Services

  29. Let's Do the Math… • 2B+D = (2 x 64) + 16 = 144 Kbs • With overhead: 2B+D+O = (2 x 64) + 16 + 48 = 192 Kbs

  30. The Data Channel At the PRI level, a single Data Channel can support multiple "T1's" with 24 Bearer Services each.

  31. PRI Bearer Services • For example: • 3 "T1's" 24 + 24 +23 B channels 1 D channel

  32. "Parts" and Service • ISUP • Integrated Services User Part • SCCP • Signaling Connection Control Part • TCAP • Transaction Capability

  33. H Channels • Whenever ISDN B channels are combined, they are called H Channels

  34. ISDN H Channels

  35. ISDN in the UK • UK: ISDN 2e equivalent to US BRI • Bearer channels are called e-channels • Multiple Subscriber Numbering (MSN) service is used to provide voice and data signaling services

  36. ISDN in the UK • ISDN 30 equivalent to US PRI • ISDN 30 (ADS 2) provides up to 30 bearer channels • Not compatible with Europe • ISDN 30 (I.421) provides up to 30 bearer channels • Compatible with Europe

  37. ISDN Protocols • I.430 • Q.921 • Q.931 • Q.932 • Let's examine these...

  38. ISDN Protocols: I.430 • Defines the reference points between the CO and the terminal equipment (user's equipment)

  39. ISDN Protocols: I.430Reference Points • U Interface: 2 wire connection, terminated by an RJ-11 • S/T Interface: 4 wire connection, terminated by an RJ-45 • Network Termination Equipment (NTE) • Converts U Interface to S/T Interface • Terminal Adaptor: connects multiple devices to the S/T Interface

  40. ISDN Protocols: Q.921 • This protocol is specific to ISDN • Also known as LAP-D

  41. LAP-D (Q.921) • Stands for, "Link Access Procedure - D Channel" • Part of the Q.921 Protocol • Used to control connections

  42. LAP-D (Q.921) • Operates solely in the ISDN D-channel • Provides flow control • Provides data reliability

  43. ISDN Protocols: Q.931 • This protocol is used to establish and end sessions (voice or data) in other words, it is for: • Establishing connections • Terminating connections

  44. Q.931 Message Types

  45. Q.931Session Termination Caller B Caller A Step 1 On hook - send DISCONNECT message Step 2 Receive DISCONNECT message Send RELEASE message Step 3 Send RELEASE COMP message Send RELEASE COMP message

  46. ISDN Protocols: Q.932 • Used to modify a call (session) in progress • Transfer a call • Place a call on hold • etc.

  47. PISN Private Integrated Services Network Connects standard telco services AND LAN and data services

  48. PINX • Private Integrated Services Network Exchange • Also called an Integrated Services PBX • Core element in a PISN

  49. PISN Advantages • Multiple vendors can be mixed • Multiple communications protocols • Multiple topologies • star, token ring, etc. • Multiple technologies • Ethernet, wireless, satellite • VPN capabilities on public networks

  50. PISN: Two Main Elements • End Nodes • VoIP Phones • Computer Work Stations • Servers • Transport Nodes • PBX • Router

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