On Sun, Jun 12, 2016 at 12:22:14AM +0200, Henrik Austad wrote: > From: Henrik Austad <haustad@xxxxxxxxx> Clearing up the netdev-typo > > Describe the overall design behind the TSN standard, the TSN-driver, > requirements to userspace and new functionality introduced. > > Cc: "David S. Miller" <davem@xxxxxxxxxxxxx> > Signed-off-by: Henrik Austad <haustad@xxxxxxxxx> > --- > Documentation/TSN/tsn.txt | 147 ++++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 147 insertions(+) > create mode 100644 Documentation/TSN/tsn.txt > > Index: linux/Documentation/TSN/tsn.txt > =================================================================== > --- /dev/null > +++ linux/Documentation/TSN/tsn.txt > @@ -0,0 +1,188 @@ > + Time Sensitive Networking (TSN) > + ------------------------------- > + > +[work in progress] > + > +1. Motivation > +============= > + > +TSN is a set of open standards, formerly known as 'AVB' (Audio/Video > +Bridging). It was renamed to TSN to better reflect that it can do much > +more than just media transport. > + > +TSN is a way to create reliable streams across a network without loss of > +frames due to congestion in the network. By using gPTP (a specialized > +IEEE-1588v2 PTP profile), the time can be synchronized with sub-us > +granularity across all the connected devices in the AVB domain. > + > +2. Intro to AVB/TSN > +=================== > + > +The original standards were written with Audio/Video in mind, so the > +initial standards refer to this as 'AVB'. In later standards, this has > +changed to TSN, and AVB now refers to a service you can add on top of > +TSN. Hopefully it will not be too confusing. > + > +In this document, we refer to the infrastructure part as TSN and AVB to > +the ALSA/V4L2 shim which can be added on top of TSN to provide a > +media-service. > + > +TSN operates with 'streams', and one stream can contain pretty much > +whatever you like. Currently, only media has been defined properly > +though, which is why you only have media-subtypes for the > +avtp_subtype-field. > + > +For a media-setup, one stream can contain multiple channels, all going > +to the same destination. A destination can be a single Listener > +(singlecast) or a group of Listeners (multicast). > + > +2.1 Endpoints > + > +A TSN 'endpoint' is where a stream either originates or ends -what > +others would call sources (Talkers) and sinks (Listeners). Looking back > +at pre-TSN when this was called AVB, these names make a bit more sense. > + > +Common for both types, they need to be PTPv2 capable, i.e. you need to > +timestamp gPTP frames upon ingress/egress to improve the accuracy of > +PTP. > + > +2.1.1 Talkers > + > +Hardware requirements: > +- Multiple Tx-queues > +- Credit based shaper on at least one of the queues for pacing the > + frames onto the network > +- VLAN capable > + > +2.1.2 Listener > + > +A Listener does not have the same requirements as a Talker as it cannot > +control the pace of the incoming frames anyway. It is beneficial if the > +NIC understands VLANs and has a few Rx-queues so that you can steer all > +TSN-frames to a dedicated queue. > + > +2.2 Bridges > + > +What TSN calls switches that are TSN-capable. They must be able to > +prioritize TSN-streams, have the credit-based shaper available for that > +class, support SRP, support gPTP and so on. > + > +2.3 Relevant standards > + > +* IEEE 802.1BA-2011 Audio Video Bridging (AVB) Systems > + > +* IEEE 802.1Q-2011 sec 34 and 35 > + > + What is referred to as: > + IEEE 802.1Qav (Forwarding and Queueing for Time-sensitive Streams) > + IEEE 802.1Qat (Stream Registration protocol) > + > +* IEEE 802.1AS gPTP > + > + A PTPv2 profile (from IEEE 1588) tailored for this domain. Notable > + changes include the requirement that all nodes in the network must be > + gPTP capable (i.e. no traversing non-PTP entities), and it allows > + traffic over a wider range of medium that what "pure" PTPv2 allows. > + > +* IEEE 1722 AVTP Layer 2 Transport Protocol for Time-Sensitive > + Applications in Bridged Local Area Networks > + > +* IEEE 1722.1 Device Discovery, Connection Management and Control for 1722 > + > + What allows AVB (TSN) devices to handle discovery, enumeration and > + control, basically let you connect 2 devices from a 3rd > + > + In this (in the scope of the Linux kernel TSN driver) must be done > + purely from userspace as we do not want the kernel to suddenly attach > + to a remote system without the user's knowledge. This is further > + reflected in how the attributes for the link is managed via ConfigFS. > + > + > +3. Overview and/or design of the TSN-driver > +=========================================== > + > +The driver handles the shifting of data for TSN-streams. Anything else > +is left for userspace to handle. This includes stream reservation (using > +some sort of MSRP client), negotiating multicast addresses, finding the > +value of the different attributes and connect application(s) to the > +exposed devices (currently we only have an ALSA-device). > + > + /--------------------\ > + | | > + | Media application | > + | | > + \--------------------/ > + | | > + +----------+ +----+ > + | | > + | | > + +------------+ | > + | ALSA | | > + +------------+ | > + | | > + | | > + +------------+ +--------------+ > + | avb_alsa | | tsn_configfs | > + | (tsn-shim) | +--------------+ > + +------------+ | > + | | > + | | > + +------+ | > + | | > + | | > + +------------+ | > + | tsn_core |<--------+ > + +------------+ > + | > + | > + +------------+ > + | tsn_net | > + +------------+ > + | > + | > + +------------+ > + | network | > + | subsystem | > + +------------+ > + | > + | > + ... > + > + > +3.1 Terms and concepts > + > +TSN uses the concept of streams and shims. > + > +- A shim is a thin wrapper that binds TSN to another subsystem (or > + directly to userspace). avb_alsa is an example of such a shim. > + > +- A stream is the only data TSN cares about. What the data inside the > + stream represents, is left for the associated shim to handle. TSN will > + verify the headers up to the protocol specific header and then pass it > + along to the shim. > + > +Note: currently, only the data-unit part is implemented, the control > +part, in which 1722.1 (discovery and enumeration) is part, is not > +handled. > + > +3.2 Userspace requirements > + > +(msrp-client, "tsnctl"-tool > + > +4. Creating a new link from userspace > +===================================== > + > +[coming] > + > + > +5. Creating a new shim > +====================== > + > +shim_ops > +[coming] > + > + > +6. Other resources: > +=================== > + > +https://en.wikipedia.org/wiki/Audio_Video_Bridging -- Henrik Austad -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
