Meters Precedence level

[EnasAhmad]

Hi,

I am using Aruba 2930F switch and trying to create a DSCP meter with two bands. I want the two bands to change the DSCP to two different values, this is why I set the prec_level to 28 and 18 respectively. However, the meter mod is rejected with error: Bad_Band_Vlaue. 

I understand as per to the documentation that the prec_level will replace the DSCP value( therefore, 28 and 18 seem like valid DSCP values):

"Precedence level in meters As per the OpenFlow specification 1.3.1, the prec_level given in the ofp_meter_band_dscp_remark indicates by what amount the DSCP value in the packets must be incremented if the packets exceed the band. However, the switch implementation directly replaces the DSCP value in the IP packets with the prec_level when the band exceeds the meter defined by the controller"

What is the vaild range for prec_level and how is it mapped to the DSCP values?

Thanks,

Enas

[Abhay_B · Accepted solution]

Hello Enas,

The valid range of precedence values in meter is [0, 7], both inclusive.

In standard pipeline-model, we write the class of the packet based on the prec_level in the band.

That is, if the prec_level is 1, then the DSCP value of the packet metered would be class 1.

In case of custom pipeline-model, we ignore the prec_level in the band. Instead the out going DSCP value is determined by a flat global remap table and the band to which the packet is classified into.

Input DSCP             Green                  Yellow                   Red
===============================================================================
0			0			0			0
1			1			1			1
2			2			2			2
3			3			3			3
4			4			4			4
5			5			5			5
6			0			0			0
7			1			1			1
8			8			0			0
9			9			1			1
10			10			2			2
11			11			3			3
12			12			4			4
13			13			5			5
14			0			0			0
15			1			1			1
16			16			8			0
17			17			9			1
18			18			10			2
19			19			11			3
20			20			12			4
21			21			13			5
22			8			0			0
23			9			1			1
24			24			16			8
25			25			17			9
26			26			18			10
27			27			19			11
28			28			20			12
29			29			21			13
30			16			8			0
31			17			9			1
32			32			24			16
33			33			25			17
34			34			26			18
35			35			27			19
36			36			28			20
37			37			29			21
38			24			16			8
39			25			17			9
40			40			32			24
41			41			33			25
42			42			34			26
43			43			35			27
44			44			36			28
45			45			37			29
46			32			24			16
47			33			25			17
48			48			40			32
49			49			41			33
50			50			42			34
51			51			43			35
52			52			44			36
53			53			45			37
54			40			32			24
55			41			33			25
56			56			48			40
57			57			49			41
58			58			50			42
59			59			51			43
60			60			52			44
61			61			53			45
62			48			40			32
63			49			41			33

In case of a single band DSCP remark meter, a packet below the mark rate is classified into Green band and a packet above the mark rate is classified into the Red band. And in case of dual band remark meter, a packet below commit rate is classified into Green band, a packet between the commit and peak is classified into Yellow band and a packet above the peak rate is classified into Red band.

Hope this helps!

Thanks!

Abhay

[EnasAhmad]

Yes it is helpful. Thank you Abhay.

I just find it strange why so many details like this one are not included in the guide! A comprehensive guide would save so much time for users (and would save your time as well answering their questions). These are technical implementation details that cannot be logically figured out by the user on his own, so I highly encourage you to include all such details in the next release of the guide.

Thanks again,

Enas

[Abhay_B]

Hello Enas,

I do agree that such pieces of information should be part of the OpenFlow Administrator Guide. We will work on getting these into the next release of the OF Administrator Guide.

Thanks!

Abhay