QoS on SkyWay 7000David GellVP Engineering
New Applications The Internet and private enterprise intranets have been evolving steadily over the last 5-10 years and are responsible for the effective communication of ever-growing applications.
Three of the fastest growing are real time voice, video and wireless communication.
Video Tremendous gains in standardized video compression and IP conversion technologies has created an important, but difficult to implement purpose for IP networks real time video transport.
Applications include CCTV and IP camera-based surveillance, video conferencing and video streaming.
While the technology to convert video to and from IP packets is highly standardized (e.g. Motion JPEG, MPEG2, MPEG4, H.264), the ability to transport such IP packets in a timely manner has been left to other technologies.
VoIP International groups (ITU, IETF) have standardized a series of end-to-end protocols for IP based telephony. Such standards encompass and address necessary functions at OSI layer 4 and above (e.g. H.323, SIP, RTP, H.245, G.711, G.72x)
Like with real-time video, the technology to convert voice to and from IP packets is highly standardized but the ability at layer 3 and below to deliver IP packets in a timely manner has been left to other technologies.
The need for QoS It is clear that in both voice and video standardization, the means to assure timely and error free packet delivery is left to other, QoStechnologies.
When combined with Broadband Wireless systems, it becomes clear that an effective mechanism is needed
Main Site Satellite Office A Satellite Office B Typical Enterprise BWA applicationIn this example, how can VoIP intranet performance be properly managed?....
Despite gains in throughput performance, a long-distance,fixed wireless system can often become a network bottleneck during peak times of network usage.
At such times, latency and packet-loss sensitive payload, such as voice or video can suffer significant degradation.
Conceptually simple, priority queuing uses multiple queuesto allow higher priority traffic to jump ahead of lower priority traffic.
Dest Addr.Src AddrTPIDCFITCILenDataFCSSFDPREPriorityVIDPriority Tagging
Multiple approaches are available to tag frames with desired priority:
Ethernet frame tagging (802.1q)
Ethernet Frame 3 bits: 0-7
Dest Addr.Src AddrTPIDTCILenDataFCSSFDPREToSLenIdenFlagsTTLProtocolIHLVersH CksmSrcDestOptDataFragEthernet FrameIP PacketPriority Tagging, cont.IP frame tagging via ToS (RFC 791)
3 priority bits: 0-7
Priority Tagging, cont.IP frame tagging via DiffServ (RFC 2474)Redefines ToS byte as DS byte. Supercedes ToS definitionDest Addr.Src AddrTPIDTCILenDataFCSSFDPREDS LenIdenFlagsTTLProtocolIHLVersH CksmSrcDestOptDataFragEthernet FrameIP Packet 6 priority bits: 0-63
SkyWay 7000 QoS FeaturesPriority Queuing System4 Queues. From highest priority to lowest: Voice, Video, Best Effort, BackgroundLine speed packet inspection supports the three most common tagging methods:1) 802.1p VLAN tag priority bits 2) IP ToS field3) IP Diffserv
Note: QoS requires end-to-end network support. SkyWay 7000 will prioritize traffic but will not actually tag the data. Endpoint devices/appliances are responsible for tagging data.
SkyWay 7000 Queue mapping
VoiceVideoBest EffortBackground802.1q bits:0x6, 0x7 0x3, 0x4, 0x0 0x1, 0x2 0x5IP ToS/Diffserv Byte: 0x30, 0xe0 0x28, 0x88, Default 0x08, 0x20 0xa0 Note: If a frame has multiple tags, then the tag with the highest priority will establish queue assignment
SkyWay 7000 System Design for QoS
The SkyWay 7000 provides support for QoS, but the proper, end-to-end network design is critical for QoS performance.Tagging device: the closer to the data source the better. Ideally, the voice or video generation device itself will tag frames.
Examples: Uniden VoIP phonesVbrick CCTV/IP converterPolycom Video Conferencing systems
QoS-enabled network. For best results all switches, routers and gateways should be QoS enabled.