# Issue related to implementing INT

**URL:** <https://forum.p4.org/t/issue-related-to-implementing-int/153>\
**Category:** Getting Started with P4\
**Created:** [October 23, 2021, 8:26am UTC](https://forum.p4.org/t/issue-related-to-implementing-int/153 "2021-10-23T08:26:16Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![akshara](https://avatars.discourse-cdn.com/v4/letter/a/3d9bf3/32.png) [@akshara](https://forum.p4.org/u/akshara)\
**Post date:** [October 23, 2021, 8:26am UTC](https://forum.p4.org/t/issue-related-to-implementing-int/153/1 "2021-10-23T08:26:16Z")

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What is the significance of queue depth in the MRI exercise in P4 tutorial and where exactly is inband network telemetry used ?

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**Author:** ![ederollora](https://sea1.discourse-cdn.com/flex019/user_avatar/forum.p4.org/ederollora/32/21_2.png) [@ederollora](https://forum.p4.org/u/ederollora)\
**Post date:** [October 23, 2021, 5:33pm UTC](https://forum.p4.org/t/issue-related-to-implementing-int/153/2 "2021-10-23T17:33:55Z")

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Hi akshara, welcome to the community.

Consider that my answer is just a personal opinion about the exercise and its significance. I did not make it so this is just my understanding about it.

The exercise you point seem to be [this one](https://github.com/p4lang/tutorials/tree/master/exercises/mri). Answering your questions, let me first go with the second question:

> and where exactly is inband network telemetry used

In-band Network Telemetry (INT), as defined [in the specification](https://p4.org/p4-spec/docs/INT_v2_1.pdf), includes multiple headers like the INT shim, INT meta (in INt-MD mode) and possibly the INT metadata stack (if any has been appended). Different INT modes will require different configurations, but as a general view, you can see that it requires a deeper approach than the one followed in the exercise. In fact, if you check the first sentence from the exercise:

> The objective of this tutorial is to extend basic L3 forwarding **with a scaled-down version of In-Band Network Telemetry (INT)**, _which we call Multi-Hop Route Inspection (MRI)_.

So there is no real INT used, but instead, a custom “protocol” named MRI which follows the same (or almost the same) principles as INT. I believe that the developers mention INT in the exercise because MRI follows those principles (like carrying in-band telemetry data). In general terms it is the same as using INT but a scaled down protocol and exercise, much more suitable for a tutorial than actual INT implementations [[1](https://github.com/GEANT-DataPlaneProgramming/int-platforms)][[2](https://wiki.onosproject.org/display/ONOS/In-band+Network+Telemetry+%28INT%29+with+ONOS+and+P4)] (there are more examples around, easy to Google 🙂).

So checking your first question:

> What is the significance of queue depth in the MRI exercise in P4 tutorial

I believe that the whole “spirit” of the exercise is to learn how to integrate a custom protocol that can track the path (multi route hop inspection), and additionally, include some metadata in the packet. I have checked the exercise and I do not see any particular use of the `qdepth` apart from verification purposes at the destination.

Cheers,