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802.1D – Expedited Traffic

802.1D – Expedited Traffic. Network Protocols and Standards Autumn 2004-2005. Expedited Traffic Preview. Traffic types Network Control Voice Video Controlled Load Excellent Effort or CEO Effort Best Effort Background. Traffic Types.

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802.1D – Expedited Traffic

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  1. 802.1D – Expedited Traffic Network Protocols and Standards Autumn 2004-2005 CS573: Network Protocols and Standards

  2. Expedited Traffic Preview • Traffic types • Network Control • Voice • Video • Controlled Load • Excellent Effort or CEO Effort • Best Effort • Background CS573: Network Protocols and Standards

  3. Traffic Types • Problem: Different applications with varying data communication requirements • Solutions: • Design a network according to given requirements • Differentiate between traffic classes • For different applications, IEEE enumerated traffic types in a typical LAN environment CS573: Network Protocols and Standards

  4. Traffic Types: Network Control • Network Control • Characterized by “must get there” requirement • Maintain and support the network infrastructure • Placed above “voice” • Meaningless to require that the [voice] traffic be delivered with a maximum delay when the correct [network] infrastructure is absent … CS573: Network Protocols and Standards

  5. Traffic Types: Voice • Interactivity is the desired feature • End-to-end delay of 100ms to 150ms • What about the delay on a single LAN? • 10ms is specified • Data Rates are several kb/s to few tens kb/s CS573: Network Protocols and Standards

  6. Traffic Types: Video • Interactivity may not be the required feature • Specifications for Interactive video such as Video Conferencing aren’t too different from the voice specifications • For non-interactive video • High data rates (1Mb/s to 8Mb/s) • Achieving 10ms delay is difficult • LAN delay of 100ms is specified CS573: Network Protocols and Standards

  7. Traffic Types: Controlled Load • Important business applications subject to some form of “admission control” • Critical but no delay requirements • Some biz applications might be more appealing if the response is better • As if a user is using the network alone!!! • Load on the network is fairly controlled • More control on the “other” traffic • Idea came from IntServ CS573: Network Protocols and Standards

  8. Traffic Types: Excellent Effort • Excellent Effort or CEO best-effort • Applicable to data traffic • Requirements are traditionally not very stringent • File transfer will happen… when? • Some important people in a company might need faster data transfers without having to wait for long CS573: Network Protocols and Standards

  9. Traffic Types: Best Effort • LAN traffic as we know today • The default traffic class CS573: Network Protocols and Standards

  10. Traffic Types: Background • Bulk transfers • Other activities permitted on the network but should not impact the use of network by other applications • Example: backups CS573: Network Protocols and Standards

  11. How Many Types? • Every switch is not able to handle all types of traffic • How many traffic types should be used? • Initial answer: 2 • High and Low • People came up with other applications and scenarios • Finally 8 levels were specified • Only 7 traffic classes have been uniquely identified so far CS573: Network Protocols and Standards

  12. Traffic Type to User Priority Mapping All manufacturers should agree to this mapping… CS573: Network Protocols and Standards

  13. User Priority Regeneration • On an incoming port of a bridge, you would like to maintain the priority • Not all MAC layer frame formats include priority field in their headers • IEEE 802.5 token ring defines 8 priority levels • Ethernet, IEEE 802.3 do not include a priority field • For maximum flexibility, user priority for frames received on a given port may be regenerated according to information that is preset by management procedures CS573: Network Protocols and Standards

  14. Traffic Type to User Priority Mapping User priority value for the outgoing frame should be either the value received in the frame itself (by default!) or mapped to some value in the range 0—7 (preset for that port!). CS573: Network Protocols and Standards

  15. Example H1 sends voice to D1 H2 sends controlled load to D2 H3 sends best effort to D2 What should Bridge B1 do? CS573: Network Protocols and Standards

  16. Example CS573: Network Protocols and Standards

  17. Example • - Bridge B1 sets priority of incoming frames on port 2 • (traffic type to user priority mapping) • Bridge B1 places all the frames in the outgoing queues • (user priority to traffic class mapping) CS573: Network Protocols and Standards

  18. User Priority to Traffic Class Mapping • For a given bridge, there may be more than one traffic class specified, thus one transmission queue for each traffic class • Frames are assigned to the transmission queues on the basis of their user priority, using the traffic class table that is part of the state information associated with that port CS573: Network Protocols and Standards

  19. RecommendedTraffic Type to Traffic Class Mapping CS573: Network Protocols and Standards

  20. RecommendedUser Priority to Traffic Class Mapping CS573: Network Protocols and Standards

  21. ExampleUser Priority to Traffic Class Mapping Consider the previous example: The number next to the queues represents the priority class for that queue; higher values represent higher priority. The next step is to determine the frame selection and the outgoing priority of the frame CS573: Network Protocols and Standards

  22. Selection of Frames for Transmission • According to IEEE 802.1D (portion of new 802.1D that was previously 802.1p), selection of frames for transmission is based on highest priority first • Frames are selected from a given transmission queue if all the queues corresponding to numerically higher values of traffic supported by that port are empty at the time of selection • Other algorithms as selected by the management may also be supported CS573: Network Protocols and Standards

  23. Outbound Access Priorities CS573: Network Protocols and Standards

  24. ExampleFrame Selection and outbound Priority Mapping CS573: Network Protocols and Standards

  25. Conclusions • Expedited Traffic Capabilities • Not intended to provide guaranteed quality of service • Allows the transmission of time critical data to be expedited when it is in competition with other non time critical data CS573: Network Protocols and Standards

  26. Selective Multicast: Preview • Part of IEEE 802.1D standard • Reasons of Selective Multicast • Broadcasting of multicast traffic overloads slower links • Even for high speed links, transmitting something that no one will use is not a good idea • Solution • Allow users to explicitly indicate their interest in receiving traffic on given multicast addresses CS573: Network Protocols and Standards

  27. Use of FDBs • Bridges maintain filtering databases for unicast addrresses • Static Entries • Explicitly configured by management • Dynamic Entries • Automatically entered into the FDB by the normal operation of the bridge • Each entry (static or dynamic) consist of: • A MAC address specification • A port map specifying the filtering state for that MAC address CS573: Network Protocols and Standards

  28. Basic Filtering Services • A bridge must support these services • Allow the specification of: • For individual MAC addresses • Static entries • Dynamic entries • For a specific group MAC address • Static entries • No static entry  Broadcast CS573: Network Protocols and Standards

  29. Extended Filtering Services • Add the following capabilities • For individual addresses • Static entries may contain a value which indicates that the dynamic filtering information should be used • For a specific group MAC address • Static entries may contain a value which indicates that the dynamic filtering information should be used • Group registration entries that are created and maintained through the use of GMRP protocol • Entries corresponding to all group addresses which may not have a specific group MAC address entry OR unregistered group addresses CS573: Network Protocols and Standards

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