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 bi- directional 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 co- axial 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. 2. Initial ranging phase. 3. IP Connectivity. { can be Ipv4 only, Ipv6 only, dual stack } I am working on IPv6 only connectivity part in my project 4. Time of day. 5. Trivial file transfer protocol phase. 6. Online.

IPv6 only Provisioning Mode

Message Exchange

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