Session 11
Broadband Management
MJ11/0704
Adapted from Network Management: Principles and Practice © Mani Subramanian 2000 and solely used for Network
Management course at Universitas Bina Nusantara
1
Broadband Access Networks
Cable Modem
Network
Cable
Modem
HFC
CM Head
End
Central
Office
Telephone
Loop
XDSL
Mode
m
MJ11/0704
DSL
Network
2
Access Technologies
Broadband
Access
Technology
HFC
TelephonyReturn
xDSL
TwoWay
ADSL
HDSL
VDSL
ISM
MMDS
OneWay
MJ11/0704
Satellite
Communication
Wireless
LMDS
TelephonyReturn
TwoWay
TwoWay
3
Access Technologies
• Hybrid fiber coaxial technology plant / cable modem
at customer premises
• Telephony return is one-way, downstream
(forward direction) cable, upstream (reverse
direction) telephone
• Two-way downstream at high frequency band
and upstream at low frequency band
• Carries voice, video and data
• Upstream bandwidth requirements less compared
to downstream bandwidth
MJ11/0704
4
Access Technologies
• xDSL: Digital subscriber line technology
• Asymmetric DSL (ADSL)
• High-speed DSL (HDSL)
• Very-high speed DSL (VDSL)
• Uses existing local loop telephone facilities
MJ11/0704
5
HFC Network
Ethernet
Cable
Modem
NIU
Satellite
WAN
Head
End
Fiber
Fiber
Node
2-WAY
COAX
Amplifier
NIU
ISP
Cable
Modem
NIU
Network Interface Unit
TV Monitor
Workstation
MJ11/0704
6
HFC Network
• Fiber - 2 one-way transmission
• Coaxial - 2-way transmission
• 2-way amplifiers
• Fiber node: optical - RF conversion
•Head end:
• Signals from multiple sources multiplexed
• Frequency conversion for local signal
• Network interface device (NID) / unit (NIU)
Demarcation point between customer network and
service provider networks
• Cable modem: RF Ethernet, analog telephony,
and video
MJ11/0704
7
HFC Technology
• Broadband LAN
• Asymmetric bandwidth allocation for
2-way communication
• RF spread-spectrum that carries multiple
signals over HFC
• RF spectrum allocation to carry multimedia
services - voice, video and data
MJ11/0704
10-12
8
Broadband LAN
Downstream Signal
50 - 860 MHz
Head
End
Cable
Modem A
Cable
Modem B
Upstream Signal
5 - 42 MHz
MJ11/0704
Termination
Cable
Modem C
Termination
9
Cable Modem
• HFC uses tree topology
• Downstream in broadcast mode
• Upstream transmission by cable modem
coordinated by head end
• Data over cable service specifications (DOCSIS)
for cable modem ensures interoperability
• One-way cable modem uses telco-return
MJ11/0704
10
Cable Modem Termination System
• Equipment at the head end
• All cable modems terminated on the head end
• Gateway to the external network
• Multiplexes and demultiplexes signals
• Frequency converts upstream to downstream
signals
• Can be designed either as a bridge or router
MJ11/0704
11
HFC Plant
• Multiple fiber pairs run from head end to fiber node;
each pair carries 2 one-way signals
• Head end converts all (telephony, digital video,
data, and analog video) signals to optical carrier
to transmit on the fiber
• Houses are connected from fiber node via
coaxial cables
• Coaxial cable are in tree topology and carries
2-way signal
• Amplifiers on the coaxial cable have 2-way
amplifiers that amplify the signals in both directions
• “Drop from coaxial cable to NID (also called NIU)
- called “Tap-to-TV” in CATV
MJ11/0704
12
RF Spectrum
Upstream
(Reverse)
5-42 MHz
Guard
Band
42-54 MHz
Downstream (Forward)
54-750 MHz
Analog
Video
54-550 MHz
Digital
Data Services
550-560 MHz
Digital
Video
560-700 MHz
Telephony
700-750 MHz
Upstream (Reverse)
5-42 MHz
Digital
Video Control
6-8 MHz
MJ11/0704
Digital
Data Services
10-25 MHz
Telephony
25-40 MHz
13
DOCS Reference Architecture
Telco Return
4
Head
End
WAN
HFC Link
6
Cable Modem Data
Termination System
(CMTS)
Mod
Switch / Router
2
Term
6
1
Subscriber
PC
Transmitter
Fiber
Data
6
Servers
5
Splitter&
Filter
Demod
Operations Support System/
3
Element Manager
Combiner
Video
Cable
Modem
Receiver
Security & Access
Controller
The architecture shows two-way (HFC link)
and one-way (HFC link & telco return).
MJ11/0704
14
CMTS Components
Cable Modem Data
Termination System
(CMTS)
Mod
Switch / Router
2
Term
6
Fiber
5
Splitter&
Filter
6
Servers
MJ11/0704
Transmitter
Data
Demod
Operations Support System/
3
Element Manager
Combiner
Video
Receiver
Security & Access
Controller
15
CMTS Components
• Switch / router routes the traffic between cable modems
and to the external network. It interfaces to CMTS via
the terminator (term).
• Modulator (mod) and demodulator (demod) transform
digital data from and to analog format.
• Combiner and splitter and filter perform the
complimentary functions of mux’ing and demuxing.
• Transmitter converts the RF signals to optical carrier;
receiver down-converts the optical signal.
• Servers handle the applications and databases.
• Security is managed by the security and access
controller.
• OSS and element manager perform network and service
management.
MJ11/0704
16
CMTS Components
• Three groups of interfaces:
• Data interfaces
• Cable modem to CPE (1)
• CMTS-NSI (2)
• Operations support systems and telco-return
• OSS (3)
• Telco-return (4)
• RF and security
• DOCS security system (5)
• RF interface (6)
MJ11/0704
17
HFC Management Challenges
• More complex than either computer network or
telecommunication network
• Involves both physical and data layers
• Multiple physical facilities
• Legacy cable system
• Multimedia service
• RF spectrum management
• Service and business management important for
MSOs and customer
• Shared media impacts security and bandwidth
• Security and privacy of home network
MJ11/0704
18
HFC Protocol Architecture
Head End
Applications,
SNMP Manager
SDH
Cable Modem
Modem Applications
SNMP Agent
Applications
SNMP, FTP,
HTTP, ETC
SNMP
SNMP, FTP,
HTTP, ETC
TCP / UDP
TCP / UDP
TCP / UDP
IP
IP
IP
ATM
Link
HFC
Link
HFC
Link
Ethernet
Link
Ethernet
Link
• Head end has both NM applications and manager
• Cable modems have SNMP agents
• NMS can be regionalized; then, head ends could behave as RMONs
MJ11/0704
19
HFC / CM Management
• Cable modem management
• CMTS management
• HFC link management
• RF spectrum management
MJ11/0704
20
CM Management MIBs
mib-2
(internet.2.1)
system (1)
interfaces (2)
docsDev (69)
transmission (10)
ifMIB (31)
docsIfMib (127)
MJ11/0704
docsTrCmMIB (128)
21
CM Management MIBs
• Three categories of MIBs
• Standard MIBs:
• system, interfaces, ifMIB
•CM and CMTS interfaces
• docIfMIB .. RF Interfaces in CM and CMTS,
base line privacy and QoS
• docsTrCmMIB .. telephony-return interface
•CM and CMTS objects
•docsDevMIB
MJ11/0704
22
DOCS Interface MIB
transmission
(mib-2 10)
docsIfMIB
(127)
docsIfMIBObjects (1)
docsQosMIB (6)
docsIfNotification (2) docsBpiMIB (5)
docsIfConformance
(3)
docsIfBaseObjects(1)
docsIfCmtsObjects (3)
docsIfCmObjects (2)
docsBpiConformance
docsBpiMIBObjects
(1)
(3)
docsBpiNotification
(2)
docsQosMIBObjects
(6)
docsQosIpPktClassTable (1)
docsQosEthPktClassTable (2)
docsQosServiceClassGroup (3)
MJ11/0704
docsFlowToClassTable (6)
docsSidToClassTable (5)
docsQosFlowTable (4)
23
RF MAC Interface
Network Layer
RF MAC Layer
Downstream1
Upstream1
Upstream2
RF Physical Layer
• Multiple RF channels upstream and downstream
• Layered structure
• Specified using RFC 1573 ifMIB
MJ11/0704
24
DOCS Cable Device MIB
Entity
docsDevMIBObjects
Description
Objects of the cable
modem and CMTS device
docsDevBase
docsDevMIBObjects 1 Extends MIB-II System
Group with objects
needed for cable device
system management
docsDevNmAccessTable docsDevMIBObjects 2 Defines the minimum
level of SNMP access
security
docsDevSoftware
docsDevMIBObjects 3 Provides information for
network-downloadable
software upgrades
docsDevServer
docsDevMIBObjects 4 Provides information
about the progress of the
interaction with various
provisioning servers
docsDevEvent
docsDevMIBObjects 5 Provides control and
logging for event
reporting
docsDevFilter
docsDevMIBObjects 6 Configures filters at link
layer and IP layer for
bridged data traffic
docsDevCpe
docsDevMIBObjects 7 CPE IP management and
anti-spoofing group on
cable modems
MJ11/0704
OID
docsDev 1
25
Link & Spectrum Management
• HFC Link Management
• Signal strength critical
• Requires continuous monitoring of amplifiers
using transponders (CheetahNet)
• Legacy system requires proxy server
• RF Spectrum Management
• Allocation of spectrum for services upstream and downstream
• Frequency agility management
MJ11/0704
26
DSL Access Technology
• Why is DSL attractive?
• Shannon limit of data rate is 30,000 bps
(3-KHz, 30 dB S/N channel)
• Digital transmission over loop (DSL) improves
data rate
• T1/DS1 (1.544Mbps)
18,000 feet
• T2/DS2 (6.312 Mbps)
12,000 feet
MJ11/0704
27
DSL Limitations
• Loop conditions with no direct copper to the house
• Loaded coils in loop (used to increase analog
distance) cannot carry digital signal
• Modern subdivisions have fiber to the
neighborhood or curb with digital mux
• Operating company inventory dated (administrative
issue)
MJ11/0704
28
xDSL Technologies
Copper Access Transmission Technologies [ADSL Forum]
Name
Meaning
Modem Voice Band
Modems
ISDN
Mode Cable
Duplex 2-pair
Integrated
160 kbps
Services Digital
Network
High data rate
1.544 Mbps
Digital
2.048 Mbps
Subscriber Line
Duplex
SDSL
Single line
1.544 Mbps
Digital
2.048 Mbps
Subscriber Line
Duplex 1-pair
Duplex
ADSL
Asymmetric
1.5 to 9 Mbps Down
Digital
16 to 640 kbps Up
Subscriber Line
1-pair
VDSL
Very high data 13 to 52 Mbps
rate Digital
1.5 to 2.3
Subscriber Line Mbps
2-pair
HDSL
MJ11/0704
Data rate
1200 bps to
28,800 bps
Duplex 2-pair
Duplex
Down
Up
Applications
Low data rate
data
communications
ISDN service
Voice and data
communications
T1/E1 service
Feeder plant,
WAN, LAN
access, server
access
Same as HDSL
plus premises
access for
symmetric
services
Internet access,
video demand,
simplex video,
LAN access,
interactive
multimedia
Same as ADSL
plus HDTV
29
ADSL Network
Broadband
Network
ADSL
Loop
ATU-C
Splitter
Splitter
Voice
Voice
ATU-R
• ADSL .. Asymmetric Digital Subscriber Line
• ATU-C ADSL transmission unit - central office
• ATU-C ADSL transmission unit - remote/residence
• Splitter separates voice and data
MJ11/0704
30
ADSL Spectrum Allocation
With Guard Band
FDM
Upstream
POTS
4 KHz
MJ11/0704
25 KHz
Downstream
200 KHz
Frequency
1.1 MHz
31
ADSL Spectrum Allocation
With Echo Cancellation
Echo Cancellation
Upstream
POTS
4 KHz 25 KHz
200 KHz
Downstream
1.1 MHz
Frequency
• Echo cancellation separates upstream and downstream signals
• Increases (low-frequency) upstream bandwidth
MJ11/0704
32
Modulation Schemes
• Carrierless amplitude phase (CAP) modulation
• Discrete multiTone modulation (DMT): 4kHz tones
• Both CAP and DMT are QAM-based
• DMT outperforms CAP
• 4-to-1 downstream throughput
• 10-to-1 upstream throughput
• Rate adaptive
•On-going active monitoring
• Maximum loop variation coverage
• Standard and hence interoperability
MJ11/0704
33
ADSL Network
Private
Network
Public
Network
Premises
Network
ADSL Access Network
OS
Service
Systems
OS
Broadband
Network
Narrowband
Network
Access
Node
Packet
Network
ATU-C
ATU-R
ADSL
ADSL
PDN
SM
Settop
TE
TV
SM
PC I/O
TE
PC
SM
ISDN
TE
ISDN
STM
Packet
ATM
STM
Packet
ATM
ATM
Transport Modes
ADSL
ATM
STM
TE
OS
PDN
SM
MJ11/0704
Asynchronous Digital Subscriber Line
Asynchronous Transfer Mode
Synchronous Transfer Mode
Terminal Equipment
Operations System
Premises Distribution Network
Service Module
34
ADSL System Reference Model
VC
U-C2 U-C
VA
T
B
ATU-C
Broadband
Network
ATU-C
Narrowband
Network
ATU-C
ATU-C
Access
Node
MJ11/0704
T-SM
Splitter
Digital
Broadcast
Network
Management
U-R U-R2
Loop
T.E.
ATU-R
T.E.
T.E.
POTS-C
PSTN
POTS-R
T.E.
Premises
Distribution
Phone(s) Network
35
Interfaces
• An interface can have multiple physical connections
• V interface
• VC interface between access node and
external network and interfaces
• U interfaces - off the splitters; Will be eliminated with
ADSL-Lite
• POTS interfaces - low pass filter interfaces for POTS
• T and B are customer premises network interfaces
• T between PDN and service modules
• B auxiliary data input (e.g., satellite feed)
MJ11/0704
36
ADSL Channeling Schemes
ATU-C
Downstream bearer channels
ATU-R
Duplex bearer channels
ATU-C
Fast channel
ATU-R
Interleaved channel
• Transport bearer channels
• Seven AS downstream channels
- multiples (1-, 2-, 3- or 4-) T1 rate of 1.536 Mbps
• Three LS duplex channels
- 160. 384, and 576 Kbps
•Buffering scheme
• Fast channel: uses fast buffers for real-time data
• Interleaved channel: used for non-real-time data
• Both fast and interleaved channels carried on the
same physical channel
MJ11/0704
37
Management Reference Model
T-R
V-C
T/S
Service
Module
Network Termination
Broadband PHY
Network
Layer
Switch
Switch
ATU-C
ATU-R
PHY
Layer
Home
Network
U-C2
Service
Module
U-R2
High
Pass
Filter
PSTN
PSTN
Low
Pass
Filter
Splitter-C
High
Pass
Filter
Loop
U-C U-R
Low
Pass
Filter
POTS
Telephone Set
or
Voice-Band Modem
Splitter-R
Interfaces:
T-R Interface between ATU-R and Switching layers
T/S Interface between ADSL Network Termination and customer installation or home network
U-C Interface between Loop and ATU-C (analog)
UC2 Interface between POTS splitter and ATU-C
U-R Interface between Loop and ATU-R (analog)
U-R2 Interface between POTS splitter and ATU-R
V-C Logical interface between ATU-C and a digital network element such as one or more
switching systems
MJ11/0704
38
Management Elements
• Management of elements done across V-interface:
• Management communications protocol across V-interface
• Management communications protocol across U-interfaces
• Parameters and operations across ATU-C
• Parameters and operations across ATU-R
• ATU-R side of the T interface
• Note addition of physical layer and switching in the management
architecture representation
• Management of physical layer involves:
• Physical channel
• Fast channel
• Interleaved channel
• Management of type of line encoding
• DMT
• CAP
MJ11/0704
39
Signal Power and Data Rate Mgmt
Maximum noise margin
Upshift noise margin
Target noise margin
Downshift noise margin
Minimum noise margin
Reduce power
Increase rate if noise margin >
Upshift noise margin
Steady state operation
Steady state operation
Decrease rate if noise margin
< Downshift noise margin
Increase power
•
•
•
•
MJ11/0704
Five levels of noise margin
Signal power controlled by noise margin
Data rate: Increase or decrease based on threshold margins
Data rate adaptation modes: Manual (1), automatic at start-up (2),
and dynamic (3)
40
Configuration Mgmt Parameters
MJ11/0704
Parameter
ADSL Line type
Component
ADSL Line
ADSL Line coding
Target noise margin
ADSL Line
ATU-C/R
Max. noise margin
ATU-C/R
Min. noise margin
ATU-C/R
Rate adaptation mode
ATU-C/R
Upshift noise margin
ATU-C/R
Min. time interval for upshift
rate adaptation
Downshift noise margin
ATU-C/R
Min. time interval for downshift
rate adaptation
Desired max. rate
Desired min. rate
Rate adaptation ratio
ATU-C/R
Max. interleave delay
ATU-C/R
Alarm thresholds
ATU-C/R
Rate up threshold
Rate down threshold
Vendor ID
Version No.
Serial No.
ATU-C/R
ATU-C/R
ATU-C/R
ATU-C/R
ATU-C/R
ATU-C/R
ATU-C/R
ATU-C/R
ATU-C/R
Line
Description
N/A Five types: no channel, fast,
interleaved, either or both
N/A ADSL coding type
Phy Noise margin under steady
state (BER=<10 -7)
Phy Modem reduces power above
this threshold
Phy Modem increases power below
this margin
Phy Mode 1: Manual
Mode 2: Select at start-up
Mode 3: Dynamic
Phy Threshold for modem increases
data rate
Phy Time interval to upshift
Phy Threshold for modem
decreases data rate
Phy Time interval to downshift
F/I Max rates for ATU-C/R
F/I Min. rates for ATU-C/R
Phy Distribution ratio between fast
and interleaved channels for
available excess bit rate
F/I Max. transmission delay
allowed by interleaving process
Phy 15-minute count threshold on
loss of signal, frame, poser and
error-seconds
F/I Rate-up change alarm
F/I Rate-down change alarm
Phy Vendor ID assigned by T1E1.4
Phy Vendor specific version
Phy Vendor specific Serial No.
41
Fault Management
Parameter
ADSL Line status
Component
ADSL Line
Line
Phy
Alarms thresholds
ATU-C/R
Phy
Unable to initialize ATU-R ATU-C/R
Phy
Rate change
Phy
ATU-C/R
Description
Indicates operational and
various types of failures of
the link
Generates alarms on failures
or crossing of thresholds
Initialization failure of ATU-R
from ATU-C
Event generation when rate
changes when crossing of
shift margins in both
upstream and downstream
• Failure indication of physical channel by NMS
• Failure indication of logical channels
• Failure indication of ATU-C/R
• Self-test of ATU-C/R as per T1.413
• Noise margin threshold alarms
• Rate change due to noise margin
MJ11/0704
42
Performance Management
Parameter
Line attenuation
Component
ATU-C/R
Line
Phy
Noise margin
ATU-C/R
Phy
Total output power
ATU-C/R
Phy
Max. attainable rate
ATU-C/R
Phy
Current rate
ATU-C/R
F/I
Previous rate
ATU-C/R
F/I
Channel data block length
ATU-C/R
F/I
Interleave delay
ATU-C/R
F/I
Statistics
ATU-C/R
Phy
F/I
Description
Measured power loss in dB
from transmitter to receiver
ATU
Noise margin in dB of the
ATU with respect to received
signal
Total output power from the
modem
Max. currently attainable
data rate by the modem
Current transmit rate to
which the modem is adapted
Rate of the modem before
the last change
Data block on which CRC
check is done
Transmit delay introduced
by the interleaving process
15 minute / 1 day failure
statistics
• Line attenuation
• Noise margin
• Output power
• Data rate
• Data integrity check
• Interleave channel delay
• Error statistics
MJ11/0704
43
ADSL SNMP MIB
adslForum
(1.3.6.1.4.1.xx)
adslMIB
(1)
adslLineMib
(1)
adslTraps (2)
adslConformance (2)
adslMibObjects(1)
adslLineTable (1)
adslAtucPhysTable (2)
adslAturPhysTable (3)
adslAtucChanTable (4)
adslAturChanTable (5)
adslAtucPerfDataTable (6)
adslAturPerfDataTable (7)
adslAtucIntervalTable (8)
adslDMTMib (1)
MJ11/0704
adslLineAlarmConfProfileTable(15
adslLineConfProfileTable(14) )
adslAturChanIntervalTable (13)
adslAtucChanIntervalTable(12)
adslAturChanPerfDataTable (11)
adslAtucChanPerfDataTable (10)
adslAturIntervalTable (9)
adslLCSMib (16)
adslCAPMib (1)
44
ADSL Interfaces Table
MIB Variable
Physical Line (i)
ifDescr
ifType (IANA)
ifSpeed
NORMAL
94
ATU-C Line Tx
rate
NULL
NORMAL
NORMAL
NORMAL
NORMAL
(default: Enable)
True
NULL
ifPhyAddress
ifAdminStatus
ifOperStatus
ifLastChange
ifLinkUpDownTrap
Enable
ifConnectPresent
ifHighSpeed
MJ11/0704
Interleaved
Channel (j)
NORMAL
124
ATU-C channel
Tx rate
NULL
NORMAL
NORMAL
NORMAL
NORMAL
(default: Enable)
False
NULL
Fast
Channel (k)
NORMAL
125
ATU-C channel
Tx rate
NULL
NORMAL
NORMAL
NORMAL
NORMAL
(default: Enable)
False
NULL
45
ADSL Profiles Management
• Configuration profile
• Performance profile
• Alarm profile
• Traps
• Generic
• Loss of frame
• Loss of signal
• Loss of power
• Error-second threshold
• Data rate change
• Loss of link
• ATU-C initialization failure
MJ11/0704
46
Configuration Profile: Mode I - Dynamic
ADSL-Line
1
ifIndex
i1
ADSL Line Entry
j1
Interleaved Chan
k1
2
x
i2
profileIndex
Configuration
Profile Table
1
Profile-1
2
Profile-2
n
Profile-n
Fast Chan Entry
ADSL Line Entry
j2
Interleaved Chan
k2
Fast Chan Entry
ix
ADSL Line Entry
jx
Interleaved Chan
kx
MJ11/0704
ifTable
Fast Chan Entry
47
Configuration Profile:Mode II - Static
ADSL-Line
1
ifIndex
i1
j1
k1
2
i2
j2
x
MJ11/0704
ifTable
profileIndex
Configuration
Profile Table
i1
Profile-i1
ADSL Line Entry
Interleaved Chan
Fast Chan Entry
ADSL Line Entry
i2
Profile-i2
Interleaved Chan
k2
Fast Chan Entry
ix
ADSL Line Entry
jx
kx
Interleaved Chan
ix
Profile-in
Fast Chan Entry
48