Telecommunications Networking IICable ModemsWhy do we want to utilize existing infrastructures?Cable Distribution InfrastructureSlide 5Cable Modem ArchitectureSlide 7Slide 8Slide 9Slide 10Copyright 1999, S.D. Personick. All Rights Reserved.Telecommunications Networking IILecture 37Topics in 21st Century Networking: Cable ModemsCopyright 1999, S.D. Personick. All Rights Reserved.Cable Modems•What is the opportunity we are trying to address?-Utilize existing coaxial cable television infrastructure (that reaches most residences) to provide high speed internet accessCopyright 1999, S.D. Personick. All Rights Reserved.Why do we want to utilize existing infrastructures?•Because the cost of installing a new infrastructure that can reach a broad base of potential customers would not be recovered during a period in which the number of actual customers is still small. I.e., you can’t make a credible business case for building a new infrastructure.Copyright 1999, S.D. Personick. All Rights Reserved.Cable Distribution InfrastructureHead EndSuper Trunk (cable or fiber)Distribution NodeTrunkDrops to homesCopyright 1999, S.D. Personick. All Rights Reserved.Cable Distribution InfrastructureHead EndSuper Trunk (cable or fiber)Distribution NodeTrunkDrops to homesIssues: noise, interference, distortionCopyright 1999, S.D. Personick. All Rights Reserved.Cable Modem ArchitectureHead End RouterCable modemHome LAN TrunkSuperTrunkTo the InternetTV setsDropCopyright 1999, S.D. Personick. All Rights Reserved.Cable Modem Architecture•Each cable modem shares a 6MHz channel on a cable system with a number of other cable modems. The data rate that can be delivered downstream (toward the customer) is roughly 6MHz x 3-6 bits per second per Hz of bandwidth ~ 18-36 Mbps•The upstream (toward the head end router) communication can be done over the cable or using a telephone lineCopyright 1999, S.D. Personick. All Rights Reserved.Cable Modem Architecture•Technical/Engineering issues:The downstream communication data rate is much higher than upstream communication data rate…a problem for TCP connectionsIngress noise, poor condition of cable plant and customers’ inside cablingCopyright 1999, S.D. Personick. All Rights Reserved.Cable Modem Architecture•Practical issuesTraditional cable engineering, installation and maintenance processes are not compatible with the complexity of cable modem/Internet technologyCopyright 1999, S.D. Personick. All Rights Reserved.Cable Modem Architecture•Business issuesInternet service providers want cable modem broadband access service to be unbundled from the provision of Internet services that utilize broadband
View Full Document
Unlocking...