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Bug #4447

DSCP value should be a 6 bit field

Added by osmith 8 months ago. Updated 8 months ago.

Status:
New
Priority:
Normal
Assignee:
Category:
-
Target version:
-
Start date:
03/09/2020
Due date:
% Done:

0%

Spec Reference:

Description

TOS was 8bits, but only the upper 6 bits became DSCP. The VTY command for DSCP in OsmoMGW accepts an 8 bit value. We are setting the setsockopt for TOS with that value without bit-shifting.

This came up while writing a similar patch for setting DSCP for OsmoBTS.

Should we

a) shift it two bits up and adjust the command syntax (and config template) to restrict to 0..63 (backwards incompatible)

or

b) change the description of the VTY command, so it is obvious that we are actually setting the TOS? (probably confusing)

CC: laforge


Related issues

Related to OsmoBTS - Feature #4438: Allow configuring DSCP value in OsmoBTS for RTPResolved03/06/2020

History

#1 Updated by osmith 8 months ago

  • Related to Feature #4438: Allow configuring DSCP value in OsmoBTS for RTP added

#2 Updated by laforge 8 months ago

I think this cannot really be changed/fixed in a backwards-compatible way.

Please note that the kernel will likely mask the lower two bits, and any intermediate
router can modify them on congestion (that's what ECN is for, after all).

So I guess the best we can do is to document that we expect the 6-bit DCSP value shifted
left two bits, and that the lower two bits should be zero.

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