Tài liệu Chapter7_cablenetwork

Cable Networks Chapter 7 Cable Networks Korea-Vietnam Friendship IT College Cable Networks Overview • • • • • Introduction Technical basics and Standards Wireline cable network transmission Cable network architecture Cable network protocols 2 Korea-Vietnam Friendship IT College Cable Networks Introduction • Initially, cable systems re-transmitted broadcast television signals. • 1980s, upgraded to an HFC (Hybrid Optical Fiber Coaxial Cable) infrastructure – to support delivery of additional cable television programs and enable improvements in signal quality by reducing line noise and signal attenuation. • By the turn of the century, wireline and wireless cable networks routinely facilitated access to voice, video, and data services and interactive broadband applications in fields – such as tele-education, telemedicine, E-business, and teleentertainment. 3 Korea-Vietnam Friendship IT College Cable Networks Technical Basics and Standards • • • • Cable modem & operations CMTS Headend equipement Standards 4 Korea-Vietnam Friendship IT College Cable Networks Cable Modem Cable modems perform conventional signal modulation and demodulation operations at the subscriber premise for enabling voice, video, and data transport via a cable network. 5 Korea-Vietnam Friendship IT College Cable Networks Cable Modem • In terms of operations, the cable modem is attached to the subscriber PC for enabling connectivity via coaxial cable or the upgraded HFC infrastructure to the CMTS (Cable Modem Termination System). • The CMTS is located at the local cable operator facility. • Headend or distribution hub supports downstream transmissions over the local loop from the CMTS at the local cable operator facility to the subscriber premise over the local loop. 6 Korea-Vietnam Friendship IT College Cable Networks Cable Modem Operation Cable modems are constantly on, thereby eliminating the need for redialing to reestablish connectivity to cable provider services. As with cable modems, STBs enable e-mail, IP telephony, encryption, Web browsing, and connectivity to broadband services. 7 Korea-Vietnam Friendship IT College Cable Networks Cable Modem Operation A typical home-based cable network configuration. 8 Korea-Vietnam Friendship IT College Cable Networks CMTS •The CMTS performs an array of gateway, server, routing, management, and security functions to ensure trouble-free voice, video, and data transport. •The CMTS also processes billing information and tracks network usage. 9 Korea-Vietnam Friendship IT College Cable Networks CMTS (2) • On the downstream path – a DOCSIS-certified CMTS amplifies, transforms, processes, and routes data via trunks and feeder cables from the NSP (Network Service Provider) to the subscriber PC based on the subscriber IP address. • On the upstream or return path – Data are transported from the subscriber PC cable modem via feeder cables and trunks to the CMTS at the local cable operator facility. – The CMTS routes subscriber data to the NSP for transport to networks such as the Internet, extranets, and intranets, depending on the destination address. 10 Korea-Vietnam Friendship IT College Cable Networks Headend equipment • Also called a distribution hub, headend equipment inserts voice, video, and data signals for transmission in the downstream direction or from the cable network to the subscriber premise. • Headend equipment is situated next to the CMTS. 11 Korea-Vietnam Friendship IT College Cable Networks Standards • • • • • • • • Cable Broadband Forum ETSI ITU-T IETF MPEG NCTA WCA W3C 12 Korea-Vietnam Friendship IT College Cable Networks Wireline Cable Network Transmission • Asymmetric cable transmission solutions remain popular in the present-day environment – Typically, downstream rates at 27 Mbps and upstream rates at 10 Mbps are supported by the HFC platform. – Transmission rate limits by the 10BASE-T Ethernet NIC (Network Interface Card). • Affected by – amount of traffic on the neighborhood cable network segment, – quantity of shared bandwidth, – the age and condition of the HFC plant or the coaxial cable wiring, faulty connections, and impulse noise generated by household appliances. 13 Korea-Vietnam Friendship IT College Cable Networks Hybrid Optical Fiber Coaxial Cable (HFC) To promote high-speed one-way or equivalent speeds in both directions, replaced large segments of in-place coaxial cable with higher-capacity optical fiber. 14 Korea-Vietnam Friendship IT College Cable Networks Cable Network Protocols • • • • TDMA (Time-division Multiple Access) FDMA (Frequency-division Multiple Access) CDMA (Code-Division Multiple Access) QPSK (Quadrature Phase Shift Key) and QAM (Quadrature Amplitude Modulation) • OFDM (Orthogonal Frequency-Division Multiple Access) 15 Korea-Vietnam Friendship IT College Cable Networks Cable Network Architecture • Physical layer – Upstream and downstream data channels • Data Link layer – employ the Medium Access Control (MAC) protocol to facilitate collision detection and retransmission, error detection and error recovery, and timing and synchronization functions. • Network layer – Wireline cable: transmission of IP (Internet Protocol) packets via the HFC infrastructure. – Wireless cable: support transmission of IP packets as electromagnetic signals through free space. 16 Korea-Vietnam Friendship IT College Cable Networks Cable Network Architecture (2) • Transport layer – operate in conjunction with the UDP and the TCP. • Upper layers – Employ SNMPv3 (Simple Network Management Protocol version 3) for managing and administering network operations. 17 Korea-Vietnam Friendship IT College Cable Networks Summary 18 Korea-Vietnam Friendship IT College