Customer Premise Equipment
description
Transcript of Customer Premise Equipment
COMT 220
1
Customer Premise Equipment
COMT 220
COMT 220
2
Definitions
• CPE - Customer Premise Equipment– Correctly defined as “anything the
customer connects to the network”– In practice we use CPE to mean
“equipment other than simple terminals” (phones, PCs, etc.)
• We will discuss mainly voice, but the arguments apply to video and data also
COMT 220
3
Rationale
• Placed between End-Users and CO connections
• Provide on-premise functions• Make cost-efficient use of CO connections
User
User
User
COCPE
COMT 220
4
Different Types…
• PBX - Private Branch Exchange– Full Premise Based Switching
• Key System– Smaller System, usually non-switching– Difference to PBX often unclear
• CENTREX– PBX functionality, but implemented in
the Central Office Switch
COMT 220
5
Switching Principles and Methods
COMT 220
6
Cross-Point Switching“Space Division Switching
”1
1
4
4
COMT 220
7
Three-Stage Switch
From Stallings, Voice and Data Communications.
COMT 220
8
Time Division Switching
• Each Line Card “Samples” the inbound signal (8000 times per second, each sample is taken over 0.125 msec)
• While the cards collect the next sample (during the next 0.125 msec), the Time Slot Interchanger collects all samples and delivers them to the correct line card outputs
• The TSI must process 8000*2*(number of conversation) samples
COMT 220
9
Time Division Switching
TSI
COMT 220
10
PBX “Block Diagram”
PBXSwitching
System
Administration
LINES
TRUNKS
AnalogPhones
DigitalPhones
SpecialWorkstations
LocalSwitched Access
IXCSpecial Access
Private Lines
CTIMaintenance SMDR
COMT 220
11
Packet Switching?
PBXSwitching
System
LINES
TRUNKS
AnalogPhones
DigitalPhone
DigitalPhone
COMT 220
12
Categories of Features
• Features for the System User (Internal Customer)
• Features for the System Administrator
• Features for the Caller (External Customer)
COMT 220
13
Handling Outbound Calls
• Call destination restrictions• Least cost route selection• Automatic redial
COMT 220
14
Handling Inbound Calls
• Routing Calls– Attendant– Direct Inward Dialing
• Handling Unanswered Calls– Call Forwarding -- General– Call Forwarding -- Busy/No-Answer– Hunt Groups– Queuing and Message Services
COMT 220
15
Handling Unanswered Calls
• Hunt Groups• Queuing• UCD
– Universal Call Distributor
• ACDs– Specialized PBX software for inbound
call handling
COMT 220
16
PBX Capacity
• Traffic (usually measured in call minutes per hour)– How Many Simultaneous Calls
• Processor– Total Calling Volume– Busy Hour Call Attempts
• Physical Interfaces– Stations and Trunks
COMT 220
17
“Programming a PBX”
• Moves, Adds, and Changes (MAC)– Establish New Service– Disconnect Service– Change Features On Existing Service
COMT 220
18
Adding an Analog Station
• Physical Install• Assign Extension Number• Assign Class of Service and Other
Features– Often uses a template (or “Table”)
1234A
B
C
COMT 220
19
Adding a Digital Phone
• Physical Installation• Define Feature Buttons on the
Digital Phone• Define Line Appearance Buttons• Assign Extension(s) to Line
Appearances• Assign Class of Service
COMT 220
20
Button Assignments
A
B
C1 2 3
4 5 6
7 8 9
* 0 #1
2
3
COMT 220
21
Button Assignments
A
B
C1 2 3
4 5 6
7 8 9
* 0 #1
2
3
Line 2
Line 1
Hold Xfer
COMT 220
22
Extension Assignments
A
B
C1 2 3
4 5 6
7 8 9
* 0 #1
2
3
1234
5678
Hold Xfer1234
5678
COMT 220
23
Extra Slides
COMT 220
24
Multi-Stage Crosspoint Switching - Concept