On Sun, Jun 12, 2016 at 12:22:14AM +0200, Henrik Austad wrote:
From: Henrik Austad haustad@cisco.com
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@davemloft.net Signed-off-by: Henrik Austad haustad@cisco.com
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: +===================