Linksys WCM300 Cisco Cable Wideband Solution Design and Implementation Guide, - Page 46
Quality of Service, Gigabit Ethernet Switch Functionality, Edge QAM Device Functionality
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Gigabit Ethernet Switch Functionality Chapter 3 Cisco Cable Wideband Architecture Quality of Service For quality of service (QoS) on a wideband downstream channel, a wideband cable modem can be assigned multiple service flows. Only Best Effort (BE) service flows are currently supported. The CMTS sends data traffic on a non-guaranteed best-effort basis. For the traditional DOCSIS upstream channel associated with a wideband channel, QoS capabilities supported are identical to those in DOCSIS 2.0. Gigabit Ethernet Switch Functionality The Gigabit Ethernet (GE) switch is an optional device that receives downstream packets from the Cisco Wideband SPA and passes the packets to the edge QAM device. The Gigabit Ethernet switch is used for these purposes: • To concentrate traffic from multiple Gigabit Ethernet links to a smaller number of Gigabit Ethernet links prior to fiber transport to the edge QAM devices • To provide 1+1 or N+1 redundancy for downstream Gigabit Ethernet links • To multiplex wideband DOCSIS traffic and video traffic onto the same edge QAM devices If more than two EQAM devices are required for two Wideband SPAs, a Gigabit Ethernet switch is needed to connect the SPAs to the EQAM devices. If video-on-demand (VOD) traffic and the RF channels for wideband channels are mixed on the same EQAM device, a Gigabit Ethernet switch is required. When an RF channel for a wideband channel is configured using Cisco IOS commands on the uBR10012 router, the rf-channel command's mac-address argument specifies the MAC address for the next-hop interface on the switch if it is a Layer-2 GE switch. The rf-channel command's ip-address argument specifies the IP address of the Gigabit Ethernet interface on the edge QAM device. The MAC address on the switch and the IP address on the EQAM device are used to route downstream traffic for the RF channel to the correct destinations. Edge QAM Device Functionality The edge QAM (EQAM) device receives wideband as MPEG-TS over IP on its Gigabit Ethernet interfaces. The edge QAM device extracts the MPEG-TS packets from the MPEG-TS over IP stream and routes them to the proper QAM RF outputs to the HFC plant for transmission to the wideband cable modem. The edge QAM devices are not involved in the active management of bandwidth or QOS for wideband channels. The edge QAM devices are not aware of the IP addressing used by the wideband cable modems. A single QAM's total bandwidth can be divided up and statically allocated to more than one wideband channel. When a wideband channel is configured on the CMTS, the wideband channel uses multiple specified logical RF channels on the Wideband SPA. Each RF channel is associated with a QAM output on the edge QAM device.The bandwidth of an RF channel can be divided between one or more wideband channels as long as the total allocated bandwidth for an RF channel (and QAM) does not exceed 100 percent. For more information on configuring RF channels, see the Cisco uBR10012 Universal Broadband Router SIP and SPA Software Configuration Guide. Cisco Cable Wideband Solution Design and Implementation Guide, Release 1.0 3-8 OL-10705-02