Transcript Slide 1
QoS on SkyWay 7000 David Gell VP 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, QoS technologies. When combined with Broadband Wireless systems, it becomes clear that an effective mechanism is needed… ‘Typical’ Enterprise BWA application Satellite Office A … … … … … … Main Site Satellite Office B PSTN Internet In this example, how can VoIP intranet performance be properly managed?.... Congested Networks 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. Priority Queuing Conceptually simple, priority queuing uses multiple queues to allow higher priority traffic to ‘jump ahead’ of lower priority traffic. 6 5 4 3 2 1 Input traffic High Priority Queue 5 Low Priority Queue 4 6 2 3 1 Priority Engine Output traffic 5 4 6 2 3 1 Priority Tagging Multiple approaches are available to tag frames with desired priority: Ethernet frame tagging (802.1q) Ethernet Frame PRE SFD Dest Addr. Src Addr TPID Priority 3 bits: 0-7 TCI CFI Len Data VID FCS Priority Tagging, cont. IP frame tagging via ToS (RFC 791) Ethernet Frame PRE SFD Dest Addr. Src Addr TPID TCI Len Data FCS IP Packet Vers IHL ToS Len Iden Flags Frag TTL 3 priority bits: 0-7 Protocol H Cksm Src Dest Opt Data Priority Tagging, cont. IP frame tagging via DiffServ (RFC 2474) Redefines ToS byte as DS byte. Supercedes ToS definition Ethernet Frame PRE SFD Dest Addr. Src Addr TPID TCI Len Data FCS IP Packet Vers IHL DS Len Iden Flags Frag TTL 6 priority bits: 0-63 Protocol H Cksm Src Dest Opt Data SkyWay 7000 QoS Features Priority Queuing System 4 Queues. From highest priority to lowest: Voice, Video, Best Effort, Background Line speed packet inspection supports the three most common tagging methods: 1) 802.1p VLAN tag priority bits 2) IP ToS field 3) 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 Voice 802.1q bits: IP ToS/Diffserv Byte: Video Best Effort Background 0x1, 0x2 0x6, 0x7 0x3, 0x4, 0x5 0x0 0x30, 0xe0 0x28, 0x88, 0xa0 Default 0x08, 0x20 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-toend 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 phones Vbrick CCTV/IP converter Polycom Video Conferencing systems QoS-enabled network. For best results all switches, routers and gateways should be QoS enabled.