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Simulation 1: Process for Provisioning a Cable Modem
Internet
Subscribers
To connect a subscriber to Cable Services, Internet
connectivity serves as the endpoint to the subscriber.
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Simulation 1: Process for Provisioning a Cable Modem
CMTS
Cable
Service
Provider
Internet
Subscribers
Next, the Cable Service Provider defines connectivity
between the Internet and the subscribers.
The Cable Service Provider utilizes the Cable Modem
Termination System (CMTS) to assign port connectivity to
each subscriber.
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Simulation 1: Process for Provisioning a Cable Modem
Cable Modem
CMTS
(Headend)
Cable
Service
Provider
Internet
Subscribers
The Cable Modem then connects to the CMTS to
provide the subscriber with individual connectivity to the
Service Provider via the CMTS. Subscription services
may therefore differ among subscribers.
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Simulation 1: Process for Provisioning a Cable Modem
DOCSIS Configuration File 
Cable Modem
Network Access: ENABLED
Step 1: The cable
modem must obtain a
Data Over Cable
Service Interface
Specifications
(DOCSIS) configuration
file, using the CMTS
Trivial File Transfer
Protocol (TFTP) server.
Class of Service:
Class ID: 1
Max DS Rate: 512000 bps
Max US Rate: 512000 bp
US Channel Priority: 7 (highest)
Guaranteed min US rate: 0 (no guaranteed rate)
Max US Transmit Burst: 1600 bits
Baseline Privacy: DISABLED
Concatenation: DISABLED
Shared Secret: (is dependent upon CMTS configuration)
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Simulation 1: Process for Provisioning a Cable Modem
DOCSIS Configuration File 
Cable Modem
Network Access: ENABLED
In this DOCSIS
configuration file,
"Network Access:
ENABLED" and "Class
of Service" are
absolutely required to
enable the cable modem
to send and receive
Internet traffic.
Class of Service:
Class ID: 1
Max DS Rate: 512000 bps
Max US Rate: 512000 bp
US Channel Priority: 7 (highest)
Guaranteed min US rate: 0 (no guaranteed rate)
Max US Transmit Burst: 1600 bits
Baseline Privacy: DISABLED
Concatenation: DISABLED
Shared Secret: (is dependent upon CMTS configuration)
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Simulation 1: Process for Provisioning a Cable Modem
Cable Modem
Step 2: Next, the cable
modem obtains its IP
network address through
the CMTS DHCP
server.
CMTS
CMTS
DHCP
Server
CMTS
TFTP
Server
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Cable
Service
Provider
Simulation 1: Process for Provisioning a Cable Modem
Cable Modem
* Applications * Processes * Memory
TCP/IP Stack
Layer 1
DOCSIS
Headend Network
Layer 2
DOCSIS
Physical
DOCSIS
MAC Address
Engine
Ethernet
MAC/LLC
Layer 3
CPE
Network
Subscriber
Personal
Computer (PC)
Step 3: The cable modem operates at Layer 1 (physical) and Layer 2 (media access control
[MAC]/logical link control) of the Open System Interconnect (OSI) Reference Model. Therefore,
Layer 3 (network) protocols (e.g. IP traffic) can be transmitted over the cable modem to the
subscriber. A cable modem has at least two MAC addresses, one for the coax interface (or, HFC
MAC) and one for the Ethernet interface (or, CMCI MAC for cable modem to CPE MAC).
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Simulation 1: Process for Provisioning a Cable Modem
Downstream
CMTS
Cable Modem
Upstream
Subscriber
Personal
Computer (PC)
Step 4: The cable modem next obtains upstream parameters. The
CMTS continuously broadcasts three separate messages on every
downstream channel that relates to the MAC layer. The messages are:
[1] the synchronization message (SYNC), [2] the upstream channel
descriptor (UCD), and [3] the bandwidth allocation map (MAP). The
cable modem must continuously identify and decode these messages in
order to properly transmit data onto the cable upstream path.
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Simulation 1: Process for Provisioning a Cable Modem
Downstream
CMTS
QoS Profiles
Cable Modem
Upstream
Subscriber
Personal
Computer (PC)
Step 5: The cable modem registers and ensures Quality of Service (QoS)
settings with the CMTS.
Cisco routers can also use command statements to enforce various QoS
profiles on the cable modem. Command statements such as:
‘Router(config)# show cable qos profile’ and
‘Router(config)# cable qos permission enforce index’
assign and provision classes of service to the cable modems using QoS
profiles.
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Simulation 1: Process for Provisioning a Cable Modem
CMTS
Cable Modem
!-- for a non-lab environment 64 QAM is suggested
Subscriber
Personal
Computer (PC)
cable downstream interleave-depth 32
cable downstream frequency 525000000
Step 6: The cable modem next must scan and lock on the
downstream frequency.
The Cisco ‘cable downstream frequency’ command statement sets
the downstream frequency which is recognized by the cable modem,
during the initialization process. An example configuration snippet is
shown.
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Simulation 1: Process for Provisioning a Cable Modem
Cable Modem
Step 7: The last step is
for the cable modem to
obtains its IP network
address through the
CMTS DHCP server.
CMTS
CMTS
DHCP
Server
CMTS
TFTP
Server
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Cable
Service
Provider
Simulation 1: Process for Provisioning a Cable Modem
Therefore, the seven (7) steps to provision a cable modem to
connect to a headend, as defined by the DOCSIS standard are:
1. Acquire DOCSIS configuration file from TFTP
2. Perform IP network initialization
3. Establish OSI Layer 1 and Layer 2 communications
4. Obtain upstream parameters
5. Register and ensure QoS settings with the CMTS
6. Scan and lock the downstream frequency
7. Acquire IP configuration parameters via DHCP
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End of Simulation 1
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