Path Tracing Midpoint HLD #1456

cscarpitta · 2023-08-31T18:01:56Z

Path Tracing provides a record of the packet path as a sequence of interface ids. In addition, it provides a record of end-to-end delay, per-hop delay, and load on each egress interface along the packet delivery path.

Path Tracing supports fine grained timestamp. It has been designed for linerate hardware implementation in the base pipeline.

Path Tracing enjoys a very rich ecosystem both from Vendor and Open-Source point of view.

Path Tracing is supported across many HW ASIC including Cisco Silicon One, Cisco Light Speed, Broadcom Jericho, Broadcom Jericho2, Marvell and many others.

Path Tracing has also a very opensource ecosystem that includes the Linux Kernel, FD.io VPP, an open P4 implementation, and support in applications such as Wireshark and TCPDump.

The list routing of platforms that have successfully participated in the Path Tracing interop testing are reported in
draft-filsfils-spring-path-tracing.

This PR provides the HLD to support the PT Midpoint in SONiC.

The document that describes the HLD is available here:
https://github.com/cscarpitta/SONiC/blob/srv6_pt_midpoint_hld/doc/path_tracing/path_tracing_midpoint.md

Repo	PR title	State
sonic-utilities	[config, show] Add CLI commands for Path Tracing Midpoint
sonic-swss	[orchagent] Add support for Path Tracing Midpoint
sonic-buildimage	[sonic-yang-models] Add Path Tracing attributes to SONiC Port YANG model
sonic-mgmt	[tests] Add packet level tests for Path tracing Midpoint

Signed-off-by: Carmine Scarpitta <cscarpit@cisco.com>

kperumalbfn · 2023-09-18T22:36:52Z

doc/srv6/srv6_path_tracing_midpoint.md

+The existing `config interface` command is extended by introducing a new subcommand `pt` that allows users to configure the Interface ID and Timestamp Template parameters required for the PT Midpoint functionality. The Timestamp Template is optional. The default template is *template3*.
+
+```
+admin@sonic:~# config interface pt <interface_name> <pt_interface_id> [pt_timestamp_template]


Does this enable PT for all the MYSIDs? Do we need to configure the PT instance and specify the list of MYSIDs?

Any PT enable/disable flag per port?

@kperumalbfn Thanks for the comment. This comment has been addressed.

As suggested, we extended the CLI to have an explicit add/del.

The updated CLI is as follows:

Disable PT on the interface
config interface path-tracing del Ethernet8

Enable PT on the interface and set its parameters
config interface path-tracing add Ethernet8 --interface-id 128 --ts-template template2

kperumalbfn · 2023-09-18T22:42:27Z

doc/srv6/srv6_path_tracing_midpoint.md

+**Example 1:**
+
+```
+admin@sonic:~# config interface pt Ethernet8 128


Instead of generic 'pt', should we have this as 'srpt' as this is only for SR

suggest to use full name path-tracing

@kperumalbfn @lguohan Thanks for the comment. This comment has been addressed.

We used the full name path-tracing instead of the abbreviation pt, as suggested.

venkatmahalingam · 2023-09-19T15:29:39Z

doc/srv6/srv6_path_tracing_midpoint.md

+admin@sonic:~# config interface pt <interface_name> <pt_interface_id> [pt_timestamp_template]
+
+    <interface_name>: interface name 
+    <pt_interface_id>: Path Tracing Interface ID (0-4095)


Can we use path-tracing instead of "pt" keyword?

Can we have explicit add/del option instead of assuming interface-ID is for the delete operation?

@venkatmahalingam Many thanks for the comment. This comment has been addressed.

As suggested, we extended the CLI to have an explicit add/del and use the full name path-tracinginstead of pt.

The updated CLI is as follows:

Disable PT on the interface
config interface path-tracing del Ethernet8

Enable PT on the interface and set its parameters
config interface path-tracing add Ethernet8 --interface-id 128 --ts-template template2

zhangyanzhao · 2023-09-19T15:43:06Z

community review recording https://zoom.us/rec/share/KXIvrUaqMzYGe1rXnIwNkUrxQ6LM9rE9vqP46Xo1eQYT67kNWDEn3b9o4JyBMXWk.nkzFHaTnToC2mr7U

doc/srv6/srv6_path_tracing_midpoint.md

lguohan · 2023-09-19T16:05:58Z

doc/srv6/srv6_path_tracing_midpoint.md

+To validate PT Midpoint, two test cases are added to the existing `tests/test_port.py` (in the `sonic-swss` repository):
+
+- `test_PortPtDefaultTimestampTemplate` writes a port configuration to the CONFIG_DB (with PT Interface ID non-zero and default PT Timestamp Template) and verifies that APPL_DB and ASIC_DB are updated correctly.
+- `test_PortPtTimestampTemplate2` writes a port configuration to the CONFIG_DB (with PT Interface ID non-zero and PT Timestamp Template specified) and verifies that APPL_DB and ASIC_DB are updated correctly.


missing packet level test for this HLD. sonic-mgmt tests.

@lguohan Thanks for the comment. We are preparing the packet level tests for this HLD. We will submit them in the next few days.

@lguohan I pushed the packet level tests.
Here is the link to the PR: sonic-net/sonic-mgmt#10486

lguohan · 2023-09-19T16:07:08Z

doc/srv6/srv6_path_tracing_midpoint.md

+
+The above command assigns Ethernet9 a Path Tracing Interface ID of 129 and a Timestamp Template template2.
+
+#### CLI Show Commands


please define the behavior when the underlying sai attribute is not support. we should query from sai and get the capability, put into state db, and cli will check the state db flag first, if not supported, then return error to the user.

@lguohan This comment has been addressed.

We updated the orchagent code and HLD, as suggested.

madhupalu · 2023-09-22T23:29:10Z

doc/srv6/srv6_path_tracing_midpoint.md

+
+## Open/Action items
+
+The PT Midpoint feature proposed in this document depends on the following PRs:


Can SRv6 midpoint pt feature records switchId addition to interface ?

@madhupalu, the Path Tracing midpoint records what is called Midpoint Compressed Data (MCD) [1]. The MCD contains Interface ID, Truncated Timestamp, and Interface Load. The MCD is recorded in the Path Tracing Hop-by-Hop header [2] which is optimzed for this MCD format. The switchId isn't recorded.

[1] https://datatracker.ietf.org/doc/html/draft-filsfils-spring-path-tracing-04#name-midpoint-compressed-data
[2] https://datatracker.ietf.org/doc/html/draft-filsfils-spring-path-tracing-04#name-ipv6-hop-by-hop-path-tracin

madhupalu · 2023-09-22T23:30:23Z

doc/srv6/srv6_path_tracing_midpoint.md

+- [orchagent] Add support for SRv6 Path Tracing Midpoint: https://github.com/sonic-net/sonic-swss/pull/2903
+
+## References
+


Suggestion to add high level packet flow diagram how the SRv6 path-tracing.

@madhupalu We added a packet flow diagram to the HLD, as suggested.

madhupalu · 2023-09-22T23:30:55Z

doc/srv6/srv6_path_tracing_midpoint.md

+**Example 1** - Show PT Midpoint configuration for all interfaces:
+
+```
+admin@sonic:~$ show interfaces pt


Do you have provided CLI to validate SAI capabilities for this feature ?

During the PortsOrch initialization, we query the SAI capabilities for Path Tracing:

IF supported, We set PATH_TRACING_CAPABLE = true in the SWITCH_CAPABILITY table of STATE DB

Else, We set PATH_TRACING_CAPABLE = false in the SWITCH_CAPABILITY table of STATE DB

When the user tries to configure Path Tracing Interface ID using the SONiC CL, We check PATH_TRACING_CAPABLE in the SWITCH_CAPABILITY table of STATE DB

IF PATH_TRACING_CAPABLE = TRUE, We config Path Tracing Interface ID and Timestamp Template in CONFIG DB

Else, we return an error

madhupalu · 2023-09-22T23:31:38Z

doc/srv6/srv6_path_tracing_midpoint.md

+      Ethernet9   fortyGigE0/0/9      up       up                129               template2 
+```
+
+**Example 2** - Show PT Midpoint configuration for interface Ethernet8:


CLI improvements -
pt recording happens at the egress interface. - config interface path-tracing egress <interface_name> <pt_id> --template template2

We are extending the CLI based on the feedback we got during the call to address the following:

have an explicit add/del

use path-tracing instead of pt

The updated CLI will be as follows

Disable PT on the interface
Config interface path-tracing del Ethernet8

Enable PT on the interface and set its parameters
Config interface path-tracing add Ethernet8 –interface-id 128 –ts-template template2

Signed-off-by: Carmine Scarpitta <cscarpit@cisco.com>

Changes requested by SONiC community Signed-off-by: Carmine Scarpitta <cscarpit@cisco.com>

reshmaintel

Thank you. In the example section of this document, would it be possible to add 1-2 lines on how the Timestamp Template is used in the overall solution (in the PT Sink node). Also the reason why there are overlapping bits in each Timestamp Template ? And lastly info on why the Template 3 is chosen as default.

ahsalam · 2023-10-11T19:37:41Z

Thank you. In the example section of this document, would it be possible to add 1-2 lines on how the Timestamp Template is used in the overall solution (in the PT Sink node). Also the reason why there are overlapping bits in each Timestamp Template ? And lastly info on why the Template 3 is chosen as default.

Hi Reshma, Each port in the device is configured with a timestamp template. The timestamp template defines the position of 8-bits to be selected from the timestamp.
The SAI header currently supports for the timestamp templates. Each template provides a certain time precision.
Template1 timestmap[08:15] Precision = 0,000256 ms
Template2 timestmap[12:19] Precision = 0,004096 ms
Template3 timestmap[16:23] Precision = 0,065536 ms
Template4 timestmap[20:27] precision = 1,048576 ms

Template3 is the default. This is inherited from the SAI header. We agreed to use template3 as the default in SAI as it provides a latency precision that can be good for many use-cases. However, you can always override the default template. Also in the future more timestamp templates can be added to the SAI header and according inherited in SONiC.

ahsalam · 2023-10-14T09:08:01Z

@zhangyanzhao could you please have a look at this PR ?
@cscarpitta addressed the comments and it is ready for merge

ahsalam · 2023-10-30T21:36:04Z

Hi @zhangyanzhao @kperumalbfn @lguohan

All the comments of this PR has been addressed and has been approved by two reviewers. Could we merge the PR ?

* [orchagent]: Add support for SRv6 Path Tracing Midpoint What I did Extended PortsOrch to process the attributes required for Path Tracing. Why I did it This PR is required for the SRv6 Path Tracing Midpoint feature. HLD: sonic-net/SONiC#1456

zhangyanzhao · 2024-06-04T17:18:23Z

code PRs are still open, move to backlog for future release

This was referenced Sep 15, 2023

[orchagent] Add support for Path Tracing Midpoint sonic-net/sonic-swss#2903

Merged

[config, show] Add CLI commands for Path Tracing Midpoint sonic-net/sonic-utilities#2983

Open

Add SRv6 Path Tracing Midpoint HLD

e3c08cd

Signed-off-by: Carmine Scarpitta <cscarpit@cisco.com>

cscarpitta force-pushed the srv6_pt_midpoint_hld branch from b1475fe to e3c08cd Compare September 15, 2023 15:56

kperumalbfn reviewed Sep 18, 2023

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venkatmahalingam reviewed Sep 19, 2023

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lguohan reviewed Sep 19, 2023

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doc/srv6/srv6_path_tracing_midpoint.md Outdated Show resolved Hide resolved

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madhupalu reviewed Sep 22, 2023

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cscarpitta added 2 commits September 25, 2023 08:33

Move SRv6 Path Tracing HLD outside of the srv6 folder

491356a

Signed-off-by: Carmine Scarpitta <cscarpit@cisco.com>

Update HLD based on reviewer suggestions

e96f354

Changes requested by SONiC community Signed-off-by: Carmine Scarpitta <cscarpit@cisco.com>

reshmaintel reviewed Oct 6, 2023

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cscarpitta changed the title ~~SRv6 Path Tracing Midpoint HLD~~ Path Tracing Midpoint HLD Oct 12, 2023

reshmaintel approved these changes Oct 12, 2023

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ahsalam mentioned this pull request Oct 14, 2023

[sonic-yang-models] Add Path Tracing attributes to SONiC Port YANG model sonic-net/sonic-buildimage#16758

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cscarpitta mentioned this pull request Oct 25, 2023

[tests] Add packet level tests for Path tracing Midpoint sonic-net/sonic-mgmt#10486

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kperumalbfn approved these changes Oct 25, 2023

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lguohan merged commit c2022f4 into sonic-net:master Oct 31, 2023
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Path Tracing Midpoint HLD #1456

Path Tracing Midpoint HLD #1456

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zhangyanzhao commented Jun 4, 2024


		The above command assigns Ethernet9 a Path Tracing Interface ID of 129 and a Timestamp Template template2.

		#### CLI Show Commands


		## Open/Action items

		The PT Midpoint feature proposed in this document depends on the following PRs:

		- [orchagent] Add support for SRv6 Path Tracing Midpoint: https://github.com/sonic-net/sonic-swss/pull/2903

		## References

Path Tracing Midpoint HLD #1456

Path Tracing Midpoint HLD #1456

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