Transcript Slide 1
Establishing IPv6 Connectivity for a
Cable Modem
Presented By: Neel Mukeshkumar Jadia
09/25/2010
Advisor: Dr. Chung-E-Wang
Department of Computer Science
California State University, Sacramento
Motivation
I had the opportunity to work with Cisco Systems as an intern .
During my internship I learned about Data Over Cable Service
Interface Specification 3.0 (DOCSIS)
We were supposed to test the software that ran over a cable router
and communicated with physical cable modems (CM’s) abiding
Docsis 3.0
Due to shortage of CM’s, team wished to build a simulator that can
help test the software with more flexibility in terms of various
conditions.
Finally, my curiousness in the field of IPv6 and DOCSIS led me to
choose this project.
Background
•
•
What is a cable modem ?
A cable modem is a sophisticated modem that provides bidirectional data communication via radio frequency channels on a
hybrid fiber co-axial (HFC) network.
They are capable to provide (voice, video, data) internet services
over cable network coming to our home.
What is a cable router ?
A cable router is a specific router for cable network. On one end it
is connected to cable modems via HFC and on the other end it
connects to internet backhaul of Internet Service Providers.
What is HFC / Hybrid fiber co-axial cable network ?
It is a huge network created of optical nodes to disintegrate the coaxial cable that runs from cable service providers (At&t, Comcast)
headend office to our homes.
Initialization Lifecycle of a Cable Modem
When a cable modem is powered on / reset, the following stages are
required to be passed on before it could provide any service to the
customer.
1.
Offline.
Initial ranging phase.
IP Connectivity.
{ can be Ipv4 only, Ipv6 only, dual stack }
I am working on IPv6 only connectivity part in my project
Time of day.
Trivial file transfer protocol phase.
Online.
2.
3.
4.
5.
6.
IPv6 only Provisioning Mode
IPv6 only
provisioning
mode
Acquire IPv6
Address
IPv6 Address Acquisition
Successful
Perform ToD &
TFTP phase
TFTP successful
IPv6 Connectivity
failed
IPv6 Connectivity
Successful
Establish Ip
Connectivity End
Message Exchange
CM
DHCP
Server
CMTS
MLD Report (Solicited Node Multicast Address)
Link Local
Address
Assignment
NS (Duplicate Address Detection)
No response expected to DAD
Router Solicit (RS)
Router
Discovery
Router Advertise (RA)
DHCP Solicit
DHCP v6
DHCP Advertise
DHCP Request
DHCP Reply
Relay-Forward
Relay-Reply
Relay-Forward
Relay-Reply
Previous diagram provides the detailed roadmap for message
passing required between the CMTS and a CM.
Before initiating IPv6 address acquisition, CM would create a link
local address (LLA) for its interface. This LLA would be checked
for uniqueness over the link via DAD protocol by router.
Once the link local address is verified as unique over the link, no
response would be sent . After a timer expire’s the CM would
consider it accepted.
Now, CM can start using the LLA for an IPv6 address acquisition
from the DHCPv6 server.
CM would send a DHCPv6 solicit message to the network via a
multicast with the created LLA.
CMTS would forward the request to the DHCPv6 server and in
reply DHCPv6 server sends a DHCPv6 advertise message.
CMTS would act as a transparent body for the DHCPv6 solicit,
advertise message. It would act as a dumb relay agent.
After receiving a DHCPv6 advertise from the server, a DHCPv6
request is initiated by CM
The server would assign a specific IPv6 address to the requesting
CM in the form of a DHCPv6 reply.
Future Work
It is an interesting field that combines computer networks,
communications and its usage for cable industry.
There can be many possible future projects from this small
demonstration.
(1) You could take up another phase from the life cycle such as
initial ranging phase and develop the functionality.
(2) There are security factors to be checked. So providing security
measures for cable modems is a new area.
Moreover, you have a solid guideline in terms of live specification
(DOCSIS from cable labs). Moreover, industry follows this specs
for their product development.
Currently, there is growth and demand in industry for such
professionals that are working in networks and providing service for
integrating cable industry.
Questions ??
Thank you