AVB intro

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A _very_ short and shallow overview of AVB, mostly with focus on what is required by the networking infrastructure.

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AVB intro

  1. 1. 1© 2014 Cisco and/or its affiliates. All rights reserved. AVB-Audio/Video Bridging Henrik Austad - haustad@cisco.com Cisco Systems Norway
  2. 2. © 2014 Cisco and/or its affiliates. All rights reserved. 2 AVB: What is it Collection of (mostly) IEEE standards ● IEEE 1722 (Layer 2 transport protocol) ● IEEE 802.1Qat (Stream Reservation) ● IEEE 802.1AS & IEEE 1588 (PTP) ● IEEE 1722.1 (Device discovery) ● IEEE 802.1Qav (Queueing enhancements) ● IEEE 802.1BA (Network setup) ● IEC 61883 (audio/video over firewire)
  3. 3. © 2014 Cisco and/or its affiliates. All rights reserved. 3 AVB is... ● “This standard specifies the protocol, data encapsulation, and presentation time procedures used to ensure interoperability between audio- and video-based end stations that use standard networking services provided by all IEEE-802 networks meeting quality-of-service requirements for time-sensitive applications by leveraging the concepts of IEC 61883.” IEEE 1722:2011 ● “Use an existing network to connect media gear together and get decent quality without buying more expensive stuff” Henrik; 2014
  4. 4. © 2014 Cisco and/or its affiliates. All rights reserved. 4 AVB ● Use existing network infrastructure ● Data streams from a Talker to a Listener across a set of Bridges. ● PTP for synchronization of presentation (think lipsync) ● Stream reservation to minimize jitter ● 2 types of devices, End-Stations (Talkers and Listeners) and Bridges.
  5. 5. © 2014 Cisco and/or its affiliates. All rights reserved. 5 802.1Qat – SRP: Stream Reservation Protocol ● SRP uses 3 signaling protocols ● Multiple MAC Registration Protocol (optional, used for controlling the propagation of Talker registration) ● Multiple VLAN Reg. Protocol (declare membership for a VLAN, required for MSRP) ● Multiple Stream Reg. Protocol (reservation of network resources to guarantee Rx/Tx of dataframes across the network) ● Will not allow more than 75% of total system BW to be reserved (this can change, especially in a wireless network)
  6. 6. © 2014 Cisco and/or its affiliates. All rights reserved. 6 MSRP: Multiple Stream Reservation Protocol in a Bridged Network ● Talkers define stream attributes via “Talker Advertise” ● Listeners request reception of streams via “Listener Ready” ● Bridges: - process/adjust/modify attributes - Talker advertise → Talker Failed - Listener Ready→ Listener Ready Failed / Listener Failed - allocate stream resources - Find/define domain boundaries - Handle stream importance ● Traffic over a shared medium (wireless, simplex point-to-point) require DMN ● Designated MSRP Node (DMN) has absolute control over which node is allowed to transmit at any given time.
  7. 7. © 2014 Cisco and/or its affiliates. All rights reserved. 7 PTP: Precision Time Protocol ● Operation of Time-Aware Systems (TAS) on a bridged, packet- switched LAN ● A TAS is a system that has its time adjusted by PTP. ● Time is of ns granularity since PTP epoch (Jan 01 1970 00:00:00 TAI) ● A set of TAS connected by PTP-capable LAN is a domain. ● Precise synchronization of clocks of all TAS in a domain (typically <1us error). ● Master-slave hierarchy with “GrandMaster” (GM) at the top ● All nodes exchange timing information to determine delay and domain boundaries. ● Best Clock Master Algorithm used to find the GM. ● Same time more important than right time (having the right time is a close second). ● AVB uses “generalized PTP”, which is pretty close to standard PTP.
  8. 8. © 2014 Cisco and/or its affiliates. All rights reserved. 9 Why AVB is a good step forward ● Network is common infrastructure ● An open standard for Audio/Video over ethernet with QoS guarantees (several proprietary solutions exists, many have failed). ● AVB-traffic can coexist with normal traffic, no dedicated network to AV only. SRP will only allow up to 75% for AVB traffic Excessive cabling is annoying/messy/<whateverfuelsyourgrudge> ● Interop between devices
  9. 9. Cisco Confidential 10© 2014 Cisco and/or its affiliates. All rights reserved. Thank You!

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