Date post: | 31-Mar-2015 |
Category: |
Documents |
Upload: | isabel-lampert |
View: | 217 times |
Download: | 3 times |
Digital Circuit Switches
CET 533
Communication Systems
It is all about interfacing Point-to-point is not efficient
Communication networks Sharing resources to make interconnections
efficient The main question is how to reserve and release
resources Communication network categories
Broadcast networks Switching networks
Switching Networks
Three basic approaches Circuit switched networks
Telephone network Packet switched networks
ATM; TCP/IP Message switched networks
Telegraph; emails
Digital Circuit Switches
Advent of digital technology microprocessors and computers
Deployed in 1979 Reliable, high capacity Offers many different features Small and cheap! Vary depending on where the switch is
located and what features it offers
TrunkInterface Module
InterfaceController
SwitchFabric
InterfaceController
Line Module
Network Control Processor
Central Processing
Architecture of DCS CP: call processing, system
recovery, storage, software upgrade, maintaining records, billing information, routing
NCP: transfer routing information, switch setup, line module setup
LM: interfaces with the subscriber (analog side); check for off-hook/on-hook
IC: format the signal before going to the switch
Line Side Trunk Side
Control plan and data plane
TrunkInterface Module
InterfaceController
SwitchFabric
InterfaceController
Line Module
Network Control Processor
Central Processing
Architecture of DCS
Other features: Optical Electrical Interface Framing and parity check
Digital v.s. Analog Switch Fabric Control section
Reliability: 5-9s (99.999%) Redundancy
Line Side Trunk Side
Local Switch (class 5)
Also called End office switch Resides in the Central Office Most complex Contain different line and trunk interfaces
Analog Lines, ISDN, T1, ISDN-PRI (Line/Trunk) Provides call recording on each line Terminates thousands of subscriber lines Provides special features: call waiting,
forwarding, blocking, etc. Routes many calls
Local calls; 911 calls; Operator; Long distance
Regional Toll SW
Sectional Switch
Toll Center
Tandem Switch
Local Switch
Tandem Switch (class 4)
Switches trunks Provides routing between class 5
switches Resides between the toll switch
(center) and the local switch No need to have line modules (only
trunk interface) – otherwise similar to the local switch
Many local switches has class 4 capabilities
Regional Toll SW
Sectional Switch
Toll Center
Tandem Switch
Local Switch
Toll Switch (class 3)
Resides between the international gateway switches and class 4
Also called the long distance switch Determines which trunk is available for the
cheapest and shortest connection Determines the route for calls between
subscribers in different area codes The call is routed to toll switch when
you dial 1+ Long distance carriers have toll
switches
Regional Toll SW
Sectional Switch
Toll Center
Tandem Switch
Local Switch
Sectional Toll Switch (class 2) Regional Toll Switch (class 1)
Regional Toll SW
Sectional Switch
Toll Center
Tandem Switch
Local Switch
Providing redundant routing through the national network
Assuming ALL Class 4 switches are busy; class 4 can be connected to Class 2
Typically low-end fixed switch Not expandable Not much flexibility Not very configurable Affordable and simple
Not used extensively
https://www.microsoft.com/technet/security/topics/networksecurity/secmod40.mspx#ESAA
Other Switch Types International Gateway Switch
Performs three basic functions: Connect trunks between domestic and international toll
networks Performs signaling conversion
SS7C7 (out of band signaling) Performs physical interface conversion
T1ETSI
Mobile Telephone Switch Office (MTSO) Connecting cell phone towers together via cable
Private Branch Exchange (PBX) Small local class 5 switch for small campuses
A few issues:
Why SS-7 Provides fast setup connection Out-of-band signaling
Billing is a tough process in all these!
When B is in IntraLATA and the same rate center, no extra charge
Switch Interfaces
Local Access and Transport Area LATA
Switches allow call routing Depending on where you are on the network
Following break off of AT&T 161 LATA (Local access and transport area)
Each LATA has many rate centers Today there are many competitive companies
providing phone services ILEC (Incumbent LECs) CLEC (Competitive LECs)
Routing: IntraLATA and InterLATA LATA boundaries become less significant if
ILECs can provide end-to-end phone service
LATA
IntraLATA
InterLATA
Call Routing in Telephone Network
North American Numbering Plan (NPAN)
International Direct Distance Dialing (IDDD) Each country has a country code To access the country code you need a
notification code (0 or 011) Local Number Portability (LNP)
Your telephone number is not tied to a switch According to 1996 Telecom Act: You can
maintain your number even if you change the carrier
NPA – NXX - XXXX
Area Code
Exchange Code
Subscriber Line Number
InternSW
Long Distance
Long Distance
Access Tandem
EndOffice
End Office
911 PSAP
Operator ServicesSwitch
ISP
PBXPBX
Interconnection Between Different Switch Types
Subscribe
r
911 Trunk
Operator ServicesTrunk
Analog Trunk
Featured Group IST: Interswitch Trunk/T1IMT: Intermachine TrunkPSAP: Public Safety Answer Position
IST
ISTIST
Featured Group
IST
IMT
Featured Group
Digital ISDN PRI
POT Line
Making an Intra Switch Call
A Calling B; A & B are connected to the same end-office
End OfficeSW
A B
1. A is off-hook 2. The switch sends a tone 3. A dials a number 4. NCP checks the number Number
belongs to the subscriber on the sw5. NCP can route the number 6. NCP checks B if it is busy 7. If B is idle, NCP establishes a route 8. NCP sends a ringing voltage (ring
back) 9. If B picks up, connection is
maintained and circuit is marked as busy
10.When on-hook, connection is released all tables are updates
11.Lines is idle!
Line Module
InterfaceController
SwitchFabric
InterfaceController
Line Module
Network Control Processor
Central Processing
Making an IntraLATA Call
A Calling B; A & B are services by different end-offices both belong to the same ILEC
End OfficeSW (SA)
A B
1. A is off-hook 2. The switch sends a tone 3. A dials a number 4. NCP checks the number Number does
not belongs to the subscriber on the sw5. NCP pass the number to local Tandem
(via SS-7 signaling)6. SS-7 tells SA to seize trunk 10 between
SA & T7. SS-7 tells T to setup trunk 8 between T &
SB8. SS-7 tells SB to seize trunk 89. SB receives the request and check B if
idle10.If B is idle, trunk 8 is setup; ring back is
provided11.SA receives the ring back B is idle;
sends the ring back to A12.same as before
End OfficeSW (SB)
TandemSW (T)
Making an IntraLATA Call
A Calling B; A & B are services by different end-offices belonging to different carriers
End OfficeSW (SA)
A B
End OfficeSW (SB)
TandemSW (T)
Class 5 SW
Qwest Facility (ILEC)
Chapar Facility (CLEC)
Carriers:
Collocation
Q & C
Note: ILEC owns allThe copper lines!
LNP
LNP: Local Number Portability
Making an IntraLATA Call
LNP: Local Number Portability
End OfficeSW (SA)
A B
End OfficeSW (SB)
TandemSW (T)
Class 5 SW
Qwest Facility (ILEC)
Chapar Facility (CLEC)
Carriers:
Collocation
Q & C
Note: ILEC owns allThe copper lines!
1. A is off-hook 2. ChaparCom sees a call
request and send a dial tone to A
3. A dials a number 4. NCP of ChaparCom checks
the number Number does not belongs to the subscriber on ChaparCom
5. ChaparCom check the data base for number (query on the number to see whose subscriber it is and where located) – via SS-7
6. LNP dB indicates B is a subscriber of Qwest and connected to SB
7. Chapar notifies T SW for a a call request to B
8. The tandem makes a connection as described before
LNP
Cell Phone Switches
911 Trunks