802.1 Audio Video Bridging and 802.11 Overview Month Year doc.: IEEE 802.11-yy/xxxxr0 May 2007 802.1 Audio Video Bridging and 802.11 Overview Date: 2007-05-07 Authors: Myron Hattig, Michael Johas Teener, Kevin B. Stanton Notice: This document has been prepared to assist IEEE 802.11. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Release: The contributor grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEE’s name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEE’s sole discretion to permit others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor also acknowledges and accepts that this contribution may be made public by IEEE 802.11. Patent Policy and Procedures: The contributor is familiar with the IEEE 802 Patent Policy and Procedures <http:// ieee802.org/guides/bylaws/sb-bylaws.pdf>, including the statement "IEEE standards may include the known use of patent(s), including patent applications, provided the IEEE receives assurance from the patent holder or applicant with respect to patents essential for compliance with both mandatory and optional portions of the standard." Early disclosure to the Working Group of patent information that might be relevant to the standard is essential to reduce the possibility for delays in the development process and increase the likelihood that the draft publication will be approved for publication. Please notify the Chair stuart@ok-brit.com as early as possible, in written or electronic form, if patented technology (or technology under patent application) might be incorporated into a draft standard being developed within the IEEE 802.11 Working Group. If you have questions, contact the IEEE Patent Committee Administrator at <patcom@ieee.org>. M. Hattig, M Johas Teener, K. Stanton John Doe, Some Company

Introduction Goal of presentation Process: Provide active mechanism for long-term, on-going discussion between 802.11 and 802.1. Process: Present to and discuss with both 802.11 and 802.1 groups. Gather input from both groups when it appears aspects of both specifications overlap or somehow inter-relate to each other . Determine best path for resolving those issues (e.g. specify mapping of one protocol to another). First Step (and focus of this presentation): Relating 802.11 Quality of Service to 802.1 AVB Present to 802.11 in May Meeting. Update presentation based on feedback. Present to 802.1AVB in May Meeting. Update presentation based on feedback. Joint 802.11/802.1 session in July Meeting. Potential Future Step: Relating 802.1 Logical Link Discovery Protocol (LLDP) to 802.11u Generic Advertisement Services (GAS).

Agenda IEEE 802.1 AVB 802.11 Quality of Service Basics Applying 802.1 AVB to 802.11 Standards

IEEE 802.1 Audio Video Task Group Formed late 2005 to provide the specifications that will allow time-synchronized low latency streaming services through 802 networks Based on current work: 802.1Q - bridges/switches. 802.3 - Ethernet MAC/PHY 802.11 - MAC/PHY Three current projects: P802.1AS: Time Synchronization P802.1Qat: Stream Reservation P802.1Qav: Forwarding and Queuing for Time-Sensitive Streams Expect technical closure in 2007, final draft standards in 2008

802.1 AVB Target Topology & Connectivity Home Networks with limited number of segments intended market.

Traffic Class? 802.1Q introduced 8 different traffic classes Highest (6 & 7) reserved for network management low utilization, for emergencies Next two for streaming (4 & 5) AV bridging: Class 5 is for lowest latency streaming (2ms through 7 hops) Class 4 is for moderate latency streaming Class 5 is roughly 250 usec per bridge hop for 100baseTX, near 125 usec for 1G or better: interactive audio/video Class 4 is roughly 1ms per bridge hop, longer for wireless, MoCA, power line: voice over IP, movies

Admission controls (p802.1Qat - added to 802.1Q) Priorities and shaping work only if the network resources are available along the entire path from the talker to the listener(s). For AV streams it is the listener’s responsibility to guarantee the path is available and to reserve the resources. Done via 802.1ak “Multiple Multicast Registration Protocol” and the new SRP (“Stream Registration Protocol”) Registers streams as multicast addresses using MMRP Reserves resources for streams as bandwidth/traffic class Streaming priority mechanism can reliably deliver data with a deterministic low latency and low jitter but only if the network resources (bandwidth, in particular) are available along the entire path from the talker to the listener(s). For AV streams it is the listener’s responsibility to guarantee the path is available and to reserve the resources. Done via 802.1ak “Multiple Multicast Registration Protocol” and the new SRP (“Stream Registration Protocol”) Registers streams as multicast addresses using MMRP Reserves resources for streams as bandwidth/traffic class Specifics for “bandwidth” include at least max packet size and number of packets per traffic class measurement intervals Perhaps other information useful for stream management such as path availability, egress port MAC addresses, etc.

Admission Control (1) (registration) With MMRP registration, the talker and intermediate bridges know where are potential listeners and how to get to them

Admission Control (2) (successful reservation) When a registration reaches the talker for that stream, it triggers a reservation back towards the registering listener. Reservation signaling triggers admission control operations in intermediate bridges. It also locks resources and updates filtering database if the admission control is successful. In this example, admission control is successful along the whole path. Reservation signaling serves as the end-to-end explicit ACK signaling to listener.

Admission Control (3) (failed reservation) In this example, admission control fails at B2. The SI (Status Indication) flag of the reservation signaling will be set to FAIL. The reservation is still forwarded to the listener. However, down-stream bridges (i.e., B1, B2) will not lock resources for the reservation whose SI is set to FAIL. Listener is noted of the failure since a reservation with FAIL SI serves as an end-to-end explicit NACK

Precise synchronization (P802.1AS) All AV devices participate in a “native IEEE 802 layer 2 profile” of IEEE 1588v2 This precise synchronization has three purposes: allow multiple streams to be synchronized (e.g. networked speakers), provide a common time base for sampling data streams at a source device and presenting those streams at the destination device with the same relative timing, and to enable traffic shaping. Traffic shaping results in more deterministic performance if is synchronized with it’s peers Multiple stream synchronization is useful for lip-sync, and particularly for multiple speaker systems

AVB (1588) Grand Master clock There is a single device within an AVB cloud that provides a master timing signal. All other devices (“ordinary clocks”) synchronize their clocks with this master.

Master clock selection Selection of the master is largely arbitrary, but can be overridden if the network is used in an environment that already has a “house clock”. Professional A/V studios Homes with provider time-synchronization service Carrier networks Selection algorithm and clock attributes are the same as IEEE 1588 Typically, fully automatic and transparent to the end user Note that all AV devices that can source data will be master-capable

802.11 Quality of Service Basics Agenda IEEE 802.1 AVB 802.11 Quality of Service Basics Applying 802.1 AVB to 802.11 Standards

General 802.11 MAC Layer Operation Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) STA only transmit when the channel is idle STA can start to transmit immediately if channel is idle for distributed Inter-frame spacing (DIFS) period. Short Inter-Frame Spacing (SIFS) for ACK Network Allocation Vector (NAV) in RTS/CTS reserves medium time. If busy, STA starts a binary backoff mechanism as follows: Selects a random # between the contention window min and max. Uses random # to calculate back off time. Backoff timer decreases only when the channel is idle, otherwise frozen STA waits DIFS each time the channel is idle STA is authorized to transmit when then backoff timer expires DIFS Source (Tx) Data Each STA maintains an internal timer called Network Allocation Vector which indicates when the channel is busy SIFS = short inter-frame spacing SIFS ACK Destination (Rx) DIFS Contention Window Other NAV Backoff Defer access = NAV+DIFS

Enhanced Distributed Channel Access (EDCA) AP AC3 (Voice) AC2 (video) AC2 (video) AC2 (video) STA3 AC0 (Best Effort) STA1 STA2 EDCA is Prioritized Transmission of packets (similar to 802.1Q). Access Category (AC) is set of EDCA parameters used by STA to contend for the channel to transmit MSDU within a certain priority.

EDCA Access Categories (AC) AIFS - Arbitration Inter-Frame Spacing CWMIN - Contention Window – Min Time CWMAX - Contention Window – Max Time AC CWmin CWmax AIFS Best Effort 2 Back Ground 1 Video [CWmin +1]/2 ─ 1 Voice 3 [CWmin +1]/4 ─ 1 AIFS = Arbitration inter-frame spacing (period). CWmin =31, CWmax =1203 Slot time is determined from the PHY layer

EDCA Queuing Examine 802.1Q Tags to determine AC of Packet Low Priority High Priority AC0 AC1 AC2 AC3 Rationale: Eight kinds of applications do not transmit at the same time Backoff (AIFSN0) (CWmin0) (CWmax0) Backoff (AIFSN1) (CWmin1) (CWmax1) Backoff (AIFSN2) (CWmin2) (CWmax2) Backoff (AIFSN3) (CWmin3) (CWmax3) Scheduler/Transmit Selection (resolves virtual collisions by granting TXOP to highest priority) Transmission Attempt

Inter-Frame Spacing Earliest transmission for high-priority AC DIFS = 50 microseconds for 802.11b, PIFS = 30 microsecond NAV Network Allocation Vector Short Inter-Frame Spacing – CTS/RTS PCF Inter-Frame Spacing – PIFS DCF Inter-Frame Spacing – DIFS AC Inter-Frame Spacing - AIFS

EDCA + Admission Control Admitted flows AP Rejected Video stream TSPEC (AC3) AC2 (video) AC3 (Voice) TSPEC (AC2) AC2 (video) AC2 (video) AC1 STA1 STA3 STA2 Capability Negotiation of Admission Control per AC occurs during association. If STA and AP support Admission Control on an AC, then STA will request bandwidth from AP prior to sending packet with the AC. STA request is in the form of ADDTS request with a TSPEC. TSPEC can be for upstream, downstream, or bi-directional traffic. AP has proprietary algorithm to accept/deny ADDTS request based on medium time consumed.

TSPEC Main Parameters User priority (UP): 0 (lowest) to 7 (highest). Maximum MSDU size (M): maximum size of the packets (octets). Maximum Burst Size (MBS): maximum size of the data burst that can be transmitted at the peak data rate (octets) Minimum PHY rate (R): physical bit rate assumed by the scheduler for transmit time and admission control calculations (b/s). Peak data rate (PR): maximum bit rate allowed for transfer of the packets. Mean data rate (ρ): average bit rate for transfer of the packets (bs). Delay bound (D): maximum delay allowed to transport a packet across the wireless interface (including queuing delay, in ms). Nominal MSDU size (L): nominal size of the packets (octets). Maximum Service Interval (MSI): interval required by TS in this TSPEC between the start of two successive TXOPs.

Applying 802.1 AVB to 802.11 Standards Agenda IEEE 802.1 AVB 802.11 Quality of Service Basics Applying 802.1 AVB to 802.11 Standards

Applying 802.1 AVB to 802.11 Standards Audio/Video Bridging in the home between Ethernet and 802.11 starts to make sense with 802.11n throughput rates (e.g. 100Mbps). Non-Focus of applying these to 802.11 is: P802.1Qav: Forwarding and Queuing for Time-Sensitive Streams is meant to guarantee latency per hop and bandwidth per class. 802.11 is a lossy network; can’t guarantee latency per hop or bandwidth per class. Currently no work planned related P802.1Qav. . Current focus: Priority Mapping P802.1Qat defined Stream Reservation Protocol (SRP) can be related to 802.11 EDCA with Admission Control. P802.1AS defined Precision Synchronization maps directly to part of 802.11v Draft (name section).

AC values mapping to Traffic Class values 802.1Q introduced 8 different traffic classes Highest (6 & 7) reserved for network management low utilization, for emergencies Next two for streaming (4 & 5) Lowest four for “best effort” AV bridging using 802.1Q values of: Class 5 is for lowest latency streaming (2ms through 7 hops) Class 4 is for moderate latency streaming Class 5 and 4 map well to AC_VI, Video Access Category. 802.11 User Priority should be set to 5 and 4 as well. Any issues with this mapping? Should voice be included? Is this mapping Static or Dynamic in 802.11 AP/STA? Where is this mapping specified? 802.11? 802.1AVB? A SIG like DLNA? Class 5 is roughly 250 usec per bridge hop for 100baseTX, near 125 usec for 1G or better: interactive audio/video Class 4 is roughly 1ms per bridge hop, longer for wireless, MoCA, power line: voice over IP, movies

Stream Reservation Protocol (SRP) and 802.11e Admission Control Any combination of links may be 802.11. Today, a bridge in the diagram may be STA or AP. Some day it may be a device within a Wi-Fi Mesh network; however, Mesh does not include Admission Control today, so SRP would not work over Mesh Networks. If bridge is AP propagating reservation, AP looks at current load to propagate reservation or decline request. No 802.11 protocol. OR, should AP always propagate the reservation then simply allow the STA to always make the ADDTS request? If bridge is STA propagating reservation, STA sends ADDTS with appropriate TSPEC to AP. ADDTS response from AP determines if reservation is propagated or not. Next steps: Should AP (that is a bridge) always pass reservation propagation to STA so STA can send ADDTS. Or should AP internally allocate medium time (or not) if the AP can support the bandwidth requested by the stream reservation? Define exact translation of SRP packet to 802.11 packets. 802.11 or 802.1AVB spec? Define exact translation of TSPEC to 802.1AVB stream identifier and stream definition. 802.11 or 802.1AVB spec? Understand implications of Multicast over 802.11 wrt MMRP, SRP, and Stream Identification. When a registration reaches the talker for that stream, it triggers a reservation back towards the registering listener. Reservation signaling triggers admission control operations in intermediate bridges. It also locks resources and updates filtering database if the admission control is successful. In this example, admission control is successful along the whole path. Reservation signaling serves as the end-to-end explicit ACK signaling to listener.

Multiple MACs supported by 802.1AS 802.1AS architecture Changes exist in 802.11v D0.11 Multiple MACs supported by 802.1AS