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Cisco Content Delivery Engine 205/220/250/280/285/420/460/475 Hardware Installation Guide
Chapter 1 Overview of the Content Delivery Engines
OMD Overview
VQE Major Software Components
The two major VQE software components that implement Unicast Retransmission, FEC, RCC, and IPTV
Packet Loss Monitoring are:
VQE-C—Software embedded in the CPE of the subscriber-typically an STB. The VQE-C provides the
CPE interface to the VQE Server (VQE-S) to support Unicast Retransmission, RCC, and IPTV Packet
Loss Monitoring statistics. The VQE-C receives the primary media data packets and, if FEC is enabled,
one or two streams with FEC packets. When the VQE-C software detects packet loss on a channel that
is configured for FEC and Unicast Retransmission, the following occurs:
If there are packet losses in the primary media stream, the VQE-C first tries to repair the lost packets
using the FEC streams. If some packet losses cannot be corrected by FEC, the VQE-C requests a Unicast
Retransmission of the missing packets from the VQE-S.
VQE-S—Software that runs on a Linux-based CDE250 and CDE280 appliance located in the intelligent
edge of the service provider’s network. For Unicast Retransmission and RCC, the VQE-S caches primary
video packets from an encoder or other headend device.
For Unicast Retransmission, working with the VQE-C, the VQE-S monitors the subscriber’s reception
of video packets and uses its cached video data to service Unicast Retransmission requests from the
VQE-C on the STB.
For RCC, when the subscriber requests a channel change, the VQE-C on the STB sends a request for a
new channel to the VQE-S. To service the RCC request, the VQE-S sends the VQE-C a unicast burst of
video packets from its cached video data for the channel and also sends some MPEG priming
information to facilitate immediate decoding. With both Unicast Retransmission and FEC, the missing
packets are resequenced by the STB without interruption.
OMD Overview
For details about the Open Media Distribution (OMD), see Cisco Open Media Distribution Data Sheet
Hardware Features
The following CDEs are used with Cisco VDS-IS:
• CDE205
• CDE220 (see Table 1-3 for models)
• CDE250 (see Table 1-3 for models)
• CDE280
The following CDEs are used with VDS-TV:
• CDE220
• CDE250 (see Table 1-3 for models)
• CDE280
• CDE420
• CDE460
• CDE475
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