1 tcom 555 network management and design george mason university school of information technology...
TRANSCRIPT
![Page 1: 1 TCOM 555 Network Management and Design George Mason University SCHOOL OF INFORMATION TECHNOLOGY & ENGINEERING](https://reader035.vdocuments.us/reader035/viewer/2022070412/5697bf881a28abf838c89acf/html5/thumbnails/1.jpg)
1
TCOM 555 Network Management and Design
George Mason UniversitySCHOOL OF INFORMATION
TECHNOLOGY & ENGINEERING
![Page 2: 1 TCOM 555 Network Management and Design George Mason University SCHOOL OF INFORMATION TECHNOLOGY & ENGINEERING](https://reader035.vdocuments.us/reader035/viewer/2022070412/5697bf881a28abf838c89acf/html5/thumbnails/2.jpg)
2
First Meeting Agenda
1. INTRODUCTION 2. E-MAIL ADDRESSES ([email protected])3. SYLLABUS REVIEW
A. GRADING STANDARDSB. GROUP PROJECT
(1) System analysis & protocol specification(2) Proposed system design and management plan (3) Presentations
D. SUPPLEMENTAL READING4. QUIZES & HOMEWORK 5. FOCUS OF COURSE6. THE BOOK’S RELATIONSHIP TO THE COURSE7. BACKGROUND & CHAPTER 1
![Page 3: 1 TCOM 555 Network Management and Design George Mason University SCHOOL OF INFORMATION TECHNOLOGY & ENGINEERING](https://reader035.vdocuments.us/reader035/viewer/2022070412/5697bf881a28abf838c89acf/html5/thumbnails/3.jpg)
3
Telecom-Data-Network Management
Homework: 1. Send me an e-mail to [email protected]. Revise the flowchart on page 42 of the text to conform to your idea of how it would be more efficient or effective.
![Page 4: 1 TCOM 555 Network Management and Design George Mason University SCHOOL OF INFORMATION TECHNOLOGY & ENGINEERING](https://reader035.vdocuments.us/reader035/viewer/2022070412/5697bf881a28abf838c89acf/html5/thumbnails/4.jpg)
4
Background-Concepts & Chapter 1
1. BASIC BASICS 2. X.25 3. FRAME RELAY 4. ATM 5. GIGABIT ETHERNET 6. COMPARISONS 7. dBs & S/N 8. NYQUIST 9. SHANNON10. NETWORK OPERATION & MANAGEMENT
![Page 5: 1 TCOM 555 Network Management and Design George Mason University SCHOOL OF INFORMATION TECHNOLOGY & ENGINEERING](https://reader035.vdocuments.us/reader035/viewer/2022070412/5697bf881a28abf838c89acf/html5/thumbnails/5.jpg)
5
Protocol
• A set of Rules Used to Enable Data Communications
• Procedures for Adding Order to the Exchange of Data
• Rules Relating to the Timing and Format of Data Transmissions
• Standard Procedures that Devices Must Accept and Use
![Page 6: 1 TCOM 555 Network Management and Design George Mason University SCHOOL OF INFORMATION TECHNOLOGY & ENGINEERING](https://reader035.vdocuments.us/reader035/viewer/2022070412/5697bf881a28abf838c89acf/html5/thumbnails/6.jpg)
6
Standards
• Agreed Principles– De Jure– EIA (RS232)– ANSI (X.25)– ITU-T (CCITT) - (X & V Series
“Recommendations”)
• De Facto– IBM, Bell System, et.al.
![Page 7: 1 TCOM 555 Network Management and Design George Mason University SCHOOL OF INFORMATION TECHNOLOGY & ENGINEERING](https://reader035.vdocuments.us/reader035/viewer/2022070412/5697bf881a28abf838c89acf/html5/thumbnails/7.jpg)
7
Do It Yourself
![Page 8: 1 TCOM 555 Network Management and Design George Mason University SCHOOL OF INFORMATION TECHNOLOGY & ENGINEERING](https://reader035.vdocuments.us/reader035/viewer/2022070412/5697bf881a28abf838c89acf/html5/thumbnails/8.jpg)
8
WHO
• Naming - Addresses– Format
– Aliases
![Page 9: 1 TCOM 555 Network Management and Design George Mason University SCHOOL OF INFORMATION TECHNOLOGY & ENGINEERING](https://reader035.vdocuments.us/reader035/viewer/2022070412/5697bf881a28abf838c89acf/html5/thumbnails/9.jpg)
9
Addressing
Curly Larry
Mo Jim
![Page 10: 1 TCOM 555 Network Management and Design George Mason University SCHOOL OF INFORMATION TECHNOLOGY & ENGINEERING](https://reader035.vdocuments.us/reader035/viewer/2022070412/5697bf881a28abf838c89acf/html5/thumbnails/10.jpg)
10
HOW
• Connections– Type– Linkage– Bandwidth
• More Names
![Page 11: 1 TCOM 555 Network Management and Design George Mason University SCHOOL OF INFORMATION TECHNOLOGY & ENGINEERING](https://reader035.vdocuments.us/reader035/viewer/2022070412/5697bf881a28abf838c89acf/html5/thumbnails/11.jpg)
11
Connectivity
Curly Larry
Mo Jim
A
B C
D
E
F
![Page 12: 1 TCOM 555 Network Management and Design George Mason University SCHOOL OF INFORMATION TECHNOLOGY & ENGINEERING](https://reader035.vdocuments.us/reader035/viewer/2022070412/5697bf881a28abf838c89acf/html5/thumbnails/12.jpg)
12
WHEN
• Timing & Synchronization
• Channel Availability
• Device Availability
• Batch vs. Real Time
![Page 13: 1 TCOM 555 Network Management and Design George Mason University SCHOOL OF INFORMATION TECHNOLOGY & ENGINEERING](https://reader035.vdocuments.us/reader035/viewer/2022070412/5697bf881a28abf838c89acf/html5/thumbnails/13.jpg)
13
Connectivity
X
Curly Larry
Mo Jim
A
B C
D
E
F
12
![Page 14: 1 TCOM 555 Network Management and Design George Mason University SCHOOL OF INFORMATION TECHNOLOGY & ENGINEERING](https://reader035.vdocuments.us/reader035/viewer/2022070412/5697bf881a28abf838c89acf/html5/thumbnails/14.jpg)
14
WHEN2
• Routing
• Quality Assurance– Data Integrity– Error Handling
![Page 15: 1 TCOM 555 Network Management and Design George Mason University SCHOOL OF INFORMATION TECHNOLOGY & ENGINEERING](https://reader035.vdocuments.us/reader035/viewer/2022070412/5697bf881a28abf838c89acf/html5/thumbnails/15.jpg)
15
Routing
Curly Larry
Mo Jim
A
B C
D
E
F
12
34
![Page 16: 1 TCOM 555 Network Management and Design George Mason University SCHOOL OF INFORMATION TECHNOLOGY & ENGINEERING](https://reader035.vdocuments.us/reader035/viewer/2022070412/5697bf881a28abf838c89acf/html5/thumbnails/16.jpg)
16
WHAT
• Payload– Character– Block– Packet/Frame– Assemble/Disassembly
![Page 17: 1 TCOM 555 Network Management and Design George Mason University SCHOOL OF INFORMATION TECHNOLOGY & ENGINEERING](https://reader035.vdocuments.us/reader035/viewer/2022070412/5697bf881a28abf838c89acf/html5/thumbnails/17.jpg)
17
Background Chapter 1
1. Data & Telecom Networks2. X.25 3. FRAME RELAY4. ATM5. GIGABIT ETHERNET
![Page 18: 1 TCOM 555 Network Management and Design George Mason University SCHOOL OF INFORMATION TECHNOLOGY & ENGINEERING](https://reader035.vdocuments.us/reader035/viewer/2022070412/5697bf881a28abf838c89acf/html5/thumbnails/18.jpg)
18
Packets
TO FROM data…...# of #
![Page 19: 1 TCOM 555 Network Management and Design George Mason University SCHOOL OF INFORMATION TECHNOLOGY & ENGINEERING](https://reader035.vdocuments.us/reader035/viewer/2022070412/5697bf881a28abf838c89acf/html5/thumbnails/19.jpg)
19
Layers In The OSI Stack
ApplicationPresentationSessionTransportNetworkData LinkPhysical
Network Managementuses some of theselevels to manage others
But how do they relateto each other?
![Page 20: 1 TCOM 555 Network Management and Design George Mason University SCHOOL OF INFORMATION TECHNOLOGY & ENGINEERING](https://reader035.vdocuments.us/reader035/viewer/2022070412/5697bf881a28abf838c89acf/html5/thumbnails/20.jpg)
20
Services
Service ExampleReliable message stream Sequence of pages
Reliable byte stream Remote login
Unreliable connection Digitized voice
Unreliable datagram Electronic junk mail
Acknowledged datagram Registered mail
Request-reply Database query
![Page 21: 1 TCOM 555 Network Management and Design George Mason University SCHOOL OF INFORMATION TECHNOLOGY & ENGINEERING](https://reader035.vdocuments.us/reader035/viewer/2022070412/5697bf881a28abf838c89acf/html5/thumbnails/21.jpg)
21
Services & Interfaces
ICI SDU
IDU
SAP
ICI SDU
Layer N+1
Interface
Layer N
SDU
Header
N-PDU
Interface Data UnitInterface Control InfoService Data UnitService Access PointProtocol Data Unit
Note: It is very important to appreciate this.
![Page 22: 1 TCOM 555 Network Management and Design George Mason University SCHOOL OF INFORMATION TECHNOLOGY & ENGINEERING](https://reader035.vdocuments.us/reader035/viewer/2022070412/5697bf881a28abf838c89acf/html5/thumbnails/22.jpg)
22
Service Primitives
Primitive MeaningRequest An entity wants the service to do some work
Indication An entity is to be informed about an event
Response An entity wants to respond to an event
Confirm The response to an earlier request has come back
![Page 23: 1 TCOM 555 Network Management and Design George Mason University SCHOOL OF INFORMATION TECHNOLOGY & ENGINEERING](https://reader035.vdocuments.us/reader035/viewer/2022070412/5697bf881a28abf838c89acf/html5/thumbnails/23.jpg)
23
Accasionally On Line
PC N+1PC N
Svr N+1Svr N
1 2 3 4 5 6 7 8 min
![Page 24: 1 TCOM 555 Network Management and Design George Mason University SCHOOL OF INFORMATION TECHNOLOGY & ENGINEERING](https://reader035.vdocuments.us/reader035/viewer/2022070412/5697bf881a28abf838c89acf/html5/thumbnails/24.jpg)
24
Layers In The OSI Stack
ApplicationPresentationSessionTransportNetworkData LinkPhysical
![Page 25: 1 TCOM 555 Network Management and Design George Mason University SCHOOL OF INFORMATION TECHNOLOGY & ENGINEERING](https://reader035.vdocuments.us/reader035/viewer/2022070412/5697bf881a28abf838c89acf/html5/thumbnails/25.jpg)
25
The Market Dropped!Sell!
7654321
7654321
7654321
7654321
7654321
7654321
APrSTNDLPh
Process 1Computer 1
P(1)OS-SQ P(2,3,4,5)
Add $, CompressP(1)OS-SQ P(n)
C(1)P(1)OS-SQ C(n)P(n)
C(1)P(1)OS C(n)P(n)
C(1)P(1)SQ C(n)P(n)
HHC(1)P(1)OS C(n)P(n)
HHC(1)P(1)SQ C(n)P(n)
GW
321
Router
21
Bridge
P2 on C2P3 on C3 P4 on C4
P5 on C5
1
![Page 26: 1 TCOM 555 Network Management and Design George Mason University SCHOOL OF INFORMATION TECHNOLOGY & ENGINEERING](https://reader035.vdocuments.us/reader035/viewer/2022070412/5697bf881a28abf838c89acf/html5/thumbnails/26.jpg)
26
Standards & ProtocolsConcepts Review
1. Interface:
2. Entities:
3. Peer Entities: 4. Primitives:
![Page 27: 1 TCOM 555 Network Management and Design George Mason University SCHOOL OF INFORMATION TECHNOLOGY & ENGINEERING](https://reader035.vdocuments.us/reader035/viewer/2022070412/5697bf881a28abf838c89acf/html5/thumbnails/27.jpg)
27
X.25
• Packet Based
• Mesh/Partial Mesh/Star Topologies
• Layers 1 & 2 of the Protocol Stack
• First successful WAN protocol
• Connection oriented communications
![Page 28: 1 TCOM 555 Network Management and Design George Mason University SCHOOL OF INFORMATION TECHNOLOGY & ENGINEERING](https://reader035.vdocuments.us/reader035/viewer/2022070412/5697bf881a28abf838c89acf/html5/thumbnails/28.jpg)
28
X.25
DTE DCE DCE DTE
Call RequestIncoming Call
Call AcceptedCall Connected
Full Duplex Data
Clear RequestClear Indication
Clear ConfirmClear Confirmed
CallSetup
CallClear
![Page 29: 1 TCOM 555 Network Management and Design George Mason University SCHOOL OF INFORMATION TECHNOLOGY & ENGINEERING](https://reader035.vdocuments.us/reader035/viewer/2022070412/5697bf881a28abf838c89acf/html5/thumbnails/29.jpg)
29
Frame Relay
• Packet Based
• Mesh/Partial Mesh/Star Topologies
• Layer 11/2 Protocol of the Stack
• X.25 on Steroids
• Lobotomized X.25
![Page 30: 1 TCOM 555 Network Management and Design George Mason University SCHOOL OF INFORMATION TECHNOLOGY & ENGINEERING](https://reader035.vdocuments.us/reader035/viewer/2022070412/5697bf881a28abf838c89acf/html5/thumbnails/30.jpg)
30
X.25 vs. Frame Relay
• X.25– 9.6Kbps - T1– High Overhead– Each Hop
• Frame Relay– 56Kbps - T3– Low Overhead– CRC at End
Nodes Only– Limited QoS
![Page 31: 1 TCOM 555 Network Management and Design George Mason University SCHOOL OF INFORMATION TECHNOLOGY & ENGINEERING](https://reader035.vdocuments.us/reader035/viewer/2022070412/5697bf881a28abf838c89acf/html5/thumbnails/31.jpg)
31
Frame Relay Characteristics
• WAN Application
• CIR/CDR
• VCs & PVCs
• Variable Packet Length
• Multicast Capabilities
• Service Provider Based
![Page 32: 1 TCOM 555 Network Management and Design George Mason University SCHOOL OF INFORMATION TECHNOLOGY & ENGINEERING](https://reader035.vdocuments.us/reader035/viewer/2022070412/5697bf881a28abf838c89acf/html5/thumbnails/32.jpg)
32
X.25 & Frame Relay Structures
Flag Address Data FCS Flag
Flag Address Data FCS Flag
Control X.25
FrameRelay
![Page 33: 1 TCOM 555 Network Management and Design George Mason University SCHOOL OF INFORMATION TECHNOLOGY & ENGINEERING](https://reader035.vdocuments.us/reader035/viewer/2022070412/5697bf881a28abf838c89acf/html5/thumbnails/33.jpg)
33
Frame Relay Structure
Flag Address Data FCS Flag
DLCI
6
CR
1*
EA
1
DLCI
4
FECN
1
BECN
1
DE
1
EA
1
![Page 34: 1 TCOM 555 Network Management and Design George Mason University SCHOOL OF INFORMATION TECHNOLOGY & ENGINEERING](https://reader035.vdocuments.us/reader035/viewer/2022070412/5697bf881a28abf838c89acf/html5/thumbnails/34.jpg)
34
Frame Relay Address
DLCI
6
CR
1
EA
1
DLCI
4
FECN
1
BECN
1
DE
1
EA
1
DLCI - Data Link Connection Identifier: Identifies logical connection (within multiplexed channel) with which the frame is associated
CR - Command Response: Not used in DL-CORE protocols EA - Address Field Extension Bit: 0 indicates another octet comingFECN - Forward Explicit Congestion Notification: Notifies to initiate congestion
avoidance (e.g., We got a lot of stuff coming.)BECN - Backward Explicit Congestion Notification: Notifies to initiate congestion
avoidance in the opposite direction of frame (e.g., We see congestion on ourreceive side.)
DE - Discard Eligibility Indicator
![Page 35: 1 TCOM 555 Network Management and Design George Mason University SCHOOL OF INFORMATION TECHNOLOGY & ENGINEERING](https://reader035.vdocuments.us/reader035/viewer/2022070412/5697bf881a28abf838c89acf/html5/thumbnails/35.jpg)
35
Frame Relay Structure
Flag Address Data FCS Flag
DLCI
6
CR
1
EA
1
DLCI
4
FECN
1
BECN
1
DE
1
EA
1
01111110
Frame Check Sequence (16 bit CRC)
![Page 36: 1 TCOM 555 Network Management and Design George Mason University SCHOOL OF INFORMATION TECHNOLOGY & ENGINEERING](https://reader035.vdocuments.us/reader035/viewer/2022070412/5697bf881a28abf838c89acf/html5/thumbnails/36.jpg)
36
ATM
• Fixed Frame Based
• Mesh/Switched Topologies
• Layers 1 - 3 Protocol Stacks
• SVCs & PVCs
![Page 37: 1 TCOM 555 Network Management and Design George Mason University SCHOOL OF INFORMATION TECHNOLOGY & ENGINEERING](https://reader035.vdocuments.us/reader035/viewer/2022070412/5697bf881a28abf838c89acf/html5/thumbnails/37.jpg)
37
ATM
• WAN/MAN/LAN Application
• Multicast Capabilities
• Enterprise and/or Service Provider Based
• QoS
![Page 38: 1 TCOM 555 Network Management and Design George Mason University SCHOOL OF INFORMATION TECHNOLOGY & ENGINEERING](https://reader035.vdocuments.us/reader035/viewer/2022070412/5697bf881a28abf838c89acf/html5/thumbnails/38.jpg)
38
Frame Relay vs. ATM
• ATM– 25Mbps - OC12+– Low Overhead– CRC at End
Nodes– High QoS– Fixed Payload
• Frame Relay– 56Kbps - T3– Low Overhead– CRC at End
Nodes Only– Limited QoS– Variable Packet
![Page 39: 1 TCOM 555 Network Management and Design George Mason University SCHOOL OF INFORMATION TECHNOLOGY & ENGINEERING](https://reader035.vdocuments.us/reader035/viewer/2022070412/5697bf881a28abf838c89acf/html5/thumbnails/39.jpg)
39
Gigabit Ethernet
• Supports Shared & Switched Configurations
• Switching Accomplished by:
– MAC Addressing (Layer 2 Switching)
– Network Layer Addressing (Layer 3 Switching)
– ATM
![Page 40: 1 TCOM 555 Network Management and Design George Mason University SCHOOL OF INFORMATION TECHNOLOGY & ENGINEERING](https://reader035.vdocuments.us/reader035/viewer/2022070412/5697bf881a28abf838c89acf/html5/thumbnails/40.jpg)
40
Speed Comparisons (Mbps)
Ethernet 10 100 1000
ATM 25 155/622 622
TokenRing
16 100 1000
Megabits
![Page 41: 1 TCOM 555 Network Management and Design George Mason University SCHOOL OF INFORMATION TECHNOLOGY & ENGINEERING](https://reader035.vdocuments.us/reader035/viewer/2022070412/5697bf881a28abf838c89acf/html5/thumbnails/41.jpg)
41
Cost Comparisons
Technology 1996 2004
Shared Fast Ethernet
$137 $102
Switched Fast Ethernet
$785 $476
ATM (622) $6600 $3200
Switched Gigabit Ethernet
N/A $1505
![Page 42: 1 TCOM 555 Network Management and Design George Mason University SCHOOL OF INFORMATION TECHNOLOGY & ENGINEERING](https://reader035.vdocuments.us/reader035/viewer/2022070412/5697bf881a28abf838c89acf/html5/thumbnails/42.jpg)
42
Decibells & Logarithms
Converting watts to dB (or milliwatts to dBm): 10 log10 1000 watts = 30 dBw
Converting dB to watts (or dBm to milliwatts):30 dBw = log-1, or log-1 (3) or 10 raised
to the 3rd power = 103 = 1000 watts
35 dBw = 103.5 = 3162.3 watts
Note: There’s a point between the 3 & 5.
![Page 43: 1 TCOM 555 Network Management and Design George Mason University SCHOOL OF INFORMATION TECHNOLOGY & ENGINEERING](https://reader035.vdocuments.us/reader035/viewer/2022070412/5697bf881a28abf838c89acf/html5/thumbnails/43.jpg)
43
Decibells & Logarithms
dBW Watts -3 .5 0 1 3 2 6 4 9 8 10 10 20 100 30 1000 40 10000
Note: The same relationship holds with dBm and miliwatts
![Page 44: 1 TCOM 555 Network Management and Design George Mason University SCHOOL OF INFORMATION TECHNOLOGY & ENGINEERING](https://reader035.vdocuments.us/reader035/viewer/2022070412/5697bf881a28abf838c89acf/html5/thumbnails/44.jpg)
44
Nyquist Nyquist Nyquist
Nyquist: The maximum practical data rate (samples) per channel.
Max R = 2 H log2 V
Logarithmic function to the base 2: For each # V, log V = the exponent to which 2 must be raised to produce V. Then if V = 16, the log2 of V = 4. If V = 2, the log2 of V = 1.
Then what is the maximum practical data rate for BPSK signal on a line with a bandwidth of 3000 Hz?
What is the maximum practical data rate for a QPSK signal on a line with a bandwidth of 3000 Hz?
![Page 45: 1 TCOM 555 Network Management and Design George Mason University SCHOOL OF INFORMATION TECHNOLOGY & ENGINEERING](https://reader035.vdocuments.us/reader035/viewer/2022070412/5697bf881a28abf838c89acf/html5/thumbnails/45.jpg)
45
Shannon Shannon Shannon
Shannon: The maximum theoretical data rate per channel.
Max R = CBW x log2 (1 + S/N)
[CBW = H in Nyquist Theorem]
Then what is the maximum practical data rate for signal with a 30 dB S/N on a line with a bandwidth of 3000 Hz?
![Page 46: 1 TCOM 555 Network Management and Design George Mason University SCHOOL OF INFORMATION TECHNOLOGY & ENGINEERING](https://reader035.vdocuments.us/reader035/viewer/2022070412/5697bf881a28abf838c89acf/html5/thumbnails/46.jpg)
46
Telecom-Data-Network Management
Telecom from where & using what?
Data from where & using what?
Networks from where & using what?
![Page 47: 1 TCOM 555 Network Management and Design George Mason University SCHOOL OF INFORMATION TECHNOLOGY & ENGINEERING](https://reader035.vdocuments.us/reader035/viewer/2022070412/5697bf881a28abf838c89acf/html5/thumbnails/47.jpg)
47
Telecom-Data-Network Management
User AplPresent SvcsFlow ControlXmt ControlPath ControlData LinkPhysical
ApplicationPresentationSessionTransportNetworkData LinkPhysical
Apl ProtocolTransportTCP UDP
Network
SNA OSI Internet
![Page 48: 1 TCOM 555 Network Management and Design George Mason University SCHOOL OF INFORMATION TECHNOLOGY & ENGINEERING](https://reader035.vdocuments.us/reader035/viewer/2022070412/5697bf881a28abf838c89acf/html5/thumbnails/48.jpg)
48
ApplicationPresentationSessionTransportNetworkData LinkPhysical
SNICPSNDCPSNDAP
Subnet Independent ConvergenceSubnet Dependent ConvergenceSubnet Dependent Access Protocol
Telecom-Data-Network Management
![Page 49: 1 TCOM 555 Network Management and Design George Mason University SCHOOL OF INFORMATION TECHNOLOGY & ENGINEERING](https://reader035.vdocuments.us/reader035/viewer/2022070412/5697bf881a28abf838c89acf/html5/thumbnails/49.jpg)
49
Telecom-Data-Network Management
NetworkManagement
NetworkMaintenance
NetworkOperations
NetworkProvisioning
![Page 50: 1 TCOM 555 Network Management and Design George Mason University SCHOOL OF INFORMATION TECHNOLOGY & ENGINEERING](https://reader035.vdocuments.us/reader035/viewer/2022070412/5697bf881a28abf838c89acf/html5/thumbnails/50.jpg)
50
Telecom-Data-Network Management
NetworkMaintenance
NetworkOperations
NetworkProvisioning
Planning Fault Management Fault ManagementDesign Configuration Mgt Trouble Ticket Admin
Performance Mgt Network Installation Security Management Network Repairs Accounting Mgt Install & Maintenance Reports Management Routine Net Tests Inventory Management Data Gathering Data Analysis
![Page 51: 1 TCOM 555 Network Management and Design George Mason University SCHOOL OF INFORMATION TECHNOLOGY & ENGINEERING](https://reader035.vdocuments.us/reader035/viewer/2022070412/5697bf881a28abf838c89acf/html5/thumbnails/51.jpg)
51
DSN - Global Voice Network