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 AES67 Practical Guide 

 

 

 

Page 1 of 28 

 

AES67

 

P

RACTICAL 

G

UIDE

 

Content 

1

 

Basic Principles of AES67 ................................................................................................ 2

 

1.1

 

Synchronization

 ........................................................................................................................ 2 

1.2

 

Multicast packet transport

 ........................................................................................................ 2 

1.3

 

Quality of Service

 ...................................................................................................................... 3 

1.4

 

Session information

 .................................................................................................................. 4 

2

 

Guidelines for Configuration of an AES67 System ............................................................. 5

 

2.1

 

System planning

 ....................................................................................................................... 5 

2.2

 

Device configuration

 ............................................................................................................... 11 

2.3

 

Check for proper synchronization (PTP)

 ................................................................................. 12 

2.4

 

Stream configuration

 .............................................................................................................. 14 

3

 

Outlook on emerging Technologies and Industry Standards ............................................ 26

 

3.1

 

ANEMAN

 ................................................................................................................................. 26 

3.2

 

NMOS

 ...................................................................................................................................... 26 

3.3

 

SMPTE ST 2110

 ....................................................................................................................... 27 

4

 

Conclusion ................................................................................................................... 28

 

 

Abstract 

AES67  is  a  standard  for  high-performance  audio-over-IP  interoperability.  By  implementing  the 
standards definitions and requirements, devices otherwise adhering to specific AoIP protocols that 
don’t  interoperate  with each  other  (i.e.  Dante,  Livewire,  QLAN  or  RAVENNA)  can  establish  direct 
connectivity and become interoperable. 

However, while the standard defines what protocols and functions need to be supported, it still leaves 
various choices open to the implementer and – by nature – doesn’t serve very well as a user’s guide; 
thus, some background knowledge on networking in general and on AoIP-related topics

 

in particular 

is certainly helpful when planning for an AES67 setup.   

This guide explains some of the choices and ambiguities left open by the standard and describes how 
to circumvent the most commonly observed obstacles when setting up an AES67 network. 

Содержание AES67

Страница 1: ...y By implementing the standards definitions and requirements devices otherwise adhering to specific AoIP protocols that don t interoperate with each other i e Dante Livewire QLAN or RAVENNA can establish direct connectivity and become interoperable However while the standard defines what protocols and functions need to be supported it still leaves various choices open to the implementer and by nat...

Страница 2: ...best available master clock is elected to serve as the Grandmaster for all participating AES67 nodes In the guidelines section hints are provided on how the Grandmaster selection can be modified if required Once a node is synchronized to the wall clock time served by the Grandmaster any desired media clock can be generated locally If the synchronization precision is accurate enough all locally gen...

Страница 3: ...PTP and audio stream traffic receive prioritized forwarding on their way through the network AES67 mandates for support of Differentiated Services DiffServ 5 a QoS scheme where different types of traffic can be categorized into service classes DiffServ works with 64 different priority tags DSCP6 values which can be applied to individual IP packets End nodes can apply different tags to different tr...

Страница 4: ... streams has also been deliberately excluded from the standard requirements While a number of protocols exist to announce available streams and transport the related SDP data the creators of the AES67 standard felt that it would have been too stringent to actually mandate for a specific method instead they decided to just mention some widely used protocols and to leave it to the device manufacture...

Страница 5: ...rse makes configuration relatively easy As the network becomes larger star or tree topologies11 come in to play In larger corporate networks spanning multiple subnets it can be essential to have a deterministic route for any given connection in this case a leaf spine architecture12 would be the most preferred topology 2 1 1 3 Bandwidth In any case it needs to be assured that ample bandwidth on any...

Страница 6: ...ed installation running on a single LAN IP addressing is required In general there are three methods to assign IP addresses and every device including the switches requires an IP address DHCP an automatic IP address assignment which requires the presence of a DHCP server in most cases this can be one of the switches if a dedicated DHCP server is not present While this method is very convenient as ...

Страница 7: ...able depending on your network situation16 2 1 4 QoS Since clock and audio traffic require high forwarding priorities AES67 end nodes support DiffServ QoS and assign certain DSCP tags to those IP packets The switches need to be configured to support DiffServ QoS and prioritized forwarding Most switches have layer 2 CoS QoS17 enabled by default this needs to be changed to layer 3 DiffServ QoS Once ...

Страница 8: ...olved in configuration of such networks we limit the discussion of PTP planning to a single LAN segment without PTP aware switches 2 1 5 1 PTP parameters In most cases PTP aware switches are not required in LAN segments up to a medium size several tenths of end nodes With standard COTS switches proper QoS configuration should result in a decent PTP performance However there are a few parameters of...

Страница 9: ...sages contain certain parameters about the clock quality which are compared in certain precedence 1 Priority 1 Field This is a user settable value The lowest number wins Normally this is set at 128 for master capable devices and 255 for slave only devices However if you want to overrule the normal selection criteria you can change Priority 1 and create any pecking order you wish 2 Clock Class This...

Страница 10: ...Most AES67 systems or devices provide means of discovering available streams on the network and support protocol based communication of these SDP parameters The methods and protocols supported usually relate to the native networking solution those devices adhere to RAVENNA Livewire and Dante all offer discovery and connection management functionality which of course includes the transfer of SDP da...

Страница 11: ...s discovery and SDP related data traffic no audio is passed through the PC unless your PC also hosts an AES67 capable virtual sound card 2 2 Device configuration 2 2 1 IP configuration Select the method of IP assignment DHCP Zeroconf manual static In case of static IP assignment make sure you don t assign any IP address twice and that the subnet mask matches your intended network configuration In ...

Страница 12: ...nfiguring individual streams 2 2 3 3 Discovery While most devices also use their native discovery method for announcement of AES67 streams some devices offer the ability to enable other discovery options on demand i e enable SAP support 2 2 3 4 Audio related configuration Some devices support different sampling rates but only one may be selected at any given time usually because a device only has ...

Страница 13: ...roseconds are usually sufficient sub microseconds are perfect If you don t have proper sync on all end nodes you have to resolve this situation before proceeding any further i e configuring streams You may want to check on these potential issues SYNC message rate too low some devices require a certain sync message rate in order to reach a stable locking situation Try to decrease the SYNC message i...

Страница 14: ...t streaming only as this is the method commonly available on all AES67 devices Configuring and connecting to multicast streams almost always follows these two basic steps 1 Configure and start a multicast stream on the sender node 2 Make the related SDP data available to the desired receiving node 3 Connect to the selected stream Execution of these steps usually varies between individual devices i...

Страница 15: ...used Payload select from pre defined stream formats here AES67 standard stereo Address enter desired multicast address27 or leave at auto for automatic assignment The most essential choice is of course on the number of channels in the stream and which channels to incorporate from the individual device Select the desired audio channel pair from the drop down menu 27 See 2 2 3 2 Multicast address ra...

Страница 16: ...reo stream in L24 48 kHz data format from audio channels 7 8 with an automatically assigned multicast address The stream is immediately started and available on the network The stream packets will reach the first switch where they are dropped unless another device has registered to this stream by IGMP RVSC SCREEN SHOT OVERVIEW WITH 1 TX STREAM CREATED ...

Страница 17: ...o this stream the desired receiver device needs access to the respective SDP data While AES67 specifies the required SDP data it does not mandate for a specific method to convey this data Most AoIP solutions offer means for advertising discovering available streams and transporting the SDP data automatically If no common method is available between sender and receiver device manual SDP data transf...

Страница 18: ... later pasted by opening the related SDP data record The RVSC provides a link to the SDP data set when creating the Tx stream RVSC SCREEN SHOT TX STREAM SDP LINK The link allows direct access to the SDP data by any device supporting RTSP Since RTSP is very similar to HTTP and the SDP data is formatted in ASCII text the link can also be used to access the SDP data with any browser simply copy and p...

Страница 19: ...respective stream to the desired receiver This can either be done manually or with support of a discovery connection management method 2 4 4 1 Connecting to an AES67 stream with discovery support If a common discovery method is supported by both the sender and receiver connecting to a stream should be as easy as identifying the desired stream in the receiver s user interface usually by name and ex...

Страница 20: ... 28 RVSC SCREEN SHOT RX STREAM PROPERTIES STREAM SOURCE SELECTION In the Stream Source drop down box select the desired stream from the list The related SDP file will automatically be accessed and all relevant parameters are filled in ...

Страница 21: ... time plus any jitter the packet may experience while being transported across the network Since the packet time in AES67 is 1 ms the delay needs to be larger than 48 samples plus sufficient delay to cope with the packet jitter29 Other devices or AoIP systems may offer predefined sometimes even system wide latency classes like low medium high or the equivalent The final step is to assign the chann...

Страница 22: ...AES67 Practical Guide Page 22 of 28 RVSC SCREEN SHOT RX STREAM PROPERTIES CHANNEL ASSIGNMENT Once assigned from the drop down list hit Apply and the receiver will connect to the selected stream ...

Страница 23: ...IEW WITH 1 RX STREAM CONNECTED The RVSC offers statistic displays where the current packet jitter can be visualized other devices may offer numerical values to indicate current PDV RVSC SCREEN SHOT STATISTICS WITH PACKET JITTER AND RECEIVER BUFFER UTILIZATION ...

Страница 24: ...to manually type in the respective values The RVSC offers the option to type in or paste a complete SDP data set Open the Rx creation dialog Connect Rx Stream select Show raw SDP and double click into the large empty field which just opened up This field is now in edit mode and ready to accept the SDP data input30 Simply paste the copied SDP data provided by the sender into this field and modify i...

Страница 25: ...again apply desired latency setting and assign channels as in the previous example and hit Apply The stream is now being connected to and it shows up with the edited name in the Rx section of the overview screen RVSC SCREEN SHOT OVERVIEW WITH 2 RX STREAMS CONNECTED ...

Страница 26: ... aneman 3 2 NMOS NMOS Networked Media Open Specifications 31 hosted by the AMWA Advanced Media Workflow Association 32 is a growing family of specifications which are available to both suppliers and end users at no cost to support the development of products and services which work within an open industry framework The goal for this initiative and the Open Specifications is to deliver interoperabi...

Страница 27: ...eveloped using Internet standards or Internet friendly techniques They are complementary to and co exist with industry specifications and standards for example VSF TR 03 SMPTE ST 2110 and AES67 3 3 SMPTE ST 2110 SMPTE ST 2110 is an emerging suite of standards defining synchronized elementary essence transport video audio metadata on IP networks The basic principles are very similar or even identic...

Страница 28: ...erved obstacles when setting up an AES67 network We have seen how to prepare for network setup with particular emphasis on IP addressing network topology and switch configuration followed by device configuration to be checked before connecting to the network Some tools have also been presented that will help establishing interoperability or even manage devices More tools and industry standards are...

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