Queues assignment on C3650 and C3850

[JAN DEVOS]

Hello,

Allthough auto qos creates exactly the same classes and policy-maps on both platforms, I observe that other queues are used.

On C3650, the 8 Q's are well-aligned to the 8 defined classes, as per my empirically developped table below.  In fact, I marked traffic in the different DSCP values of col 2 and could find which queue those DSCPs go in, per the command : 'show platform qos queue stats '

Type traffic	PHB/CS	DSCP	Q#	Class name
Priority (voice)	CS4,CS5,EF	32,40,46	0	AutoQos-4.0-Output-Priority-Queue
NW control	CS2,CS3,CS6,CS7	16,24,48,56	1	AutoQos-4.0-Output-Control-Mgmt-Queue
Video	AF41,AF42,AF43	34,36,38	2	AutoQos-4.0-Output-Multimedia-Conf-Queue
Transactional	AF21,AF22,AF23	18,20,22	3	AutoQos-4.0-Output-Trans-Data-Queue
Bulk data	AF11,AF12,AF13	10,12,14	4	AutoQos-4.0-Output-Bulk-Data-Queue
Scavenger	CS1	8	5	AutoQos-4.0-Output-Scavenger-Queue
Signaling	AF31,AF32,AF33	26,28,30	6	AutoQos-4.0-Output-Multimedia-Strm-Queue
Best Effort	DF	0	7	class-default

On C3850 however, the Classes Scavenger and MultimediaStrm  generated by Auto Qos are assigned to respectively queue Q4 and Q1, whereas Q5 and 6 are left empty.

Apart from the fact of discrepancy between both switchtypes, I'm afraid Scavenger will compete with Bulk and Strmg with Mgmt within their respective shared queue.  Despite the fact that all traffic types are policed with a 'remaining %' in the policy map.  To my knowledge, scheduling for a remaining % can only be done between queues, not inside the same queue.

Your help is highly appreciated.

[Joseph W. Doherty]

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Posting

What help are you looking for?

Confirmation that there's no same queue scheduling?  If so, that's probably correct.  (I write probably because I haven't worked with the 3650/3850, but that seems most likely.  Of course, I suspect you might have different drop limits within the same queue.)

As to 3650 and 3850 auto-QoS being just a little bit different, the only way to really avoid that, I believe, is to use your own QoS config.  This also avoids "revisions" to the auto-QoS model with different IOS releases.

[JAN DEVOS]

Joseph, thank you for your reply.

I want to place on the 3850 Scavenger in Queue 5 and MultimediaStrm in Queue 6, just the same like in 3650. 

If you can tell me how I can do a DSCP-to-Queue mapping like in the legacy C3750, I'm done.  In MQC obviously, classes are directly policed (for bandwidth, thresholds and so on) but you have no control of which DSCP goes to which queue.   I can only observe that CS1 (Scav) goes to the same queue as AF11, 12, 13.  And I see no way to dissociate them to separate Q's, like the 3650 does.