1810 v2 qos DSCP

[Basil95]

I posted this in another HP forum and I was told I should probably post here

http://h30434.www3.hp.com/t5/Other-HP-Consumer-Products-and-Technologies/1810-v2-qos-DSCP/m-p/5146431/highlight/false#M20484

I've got an HP Procurve 1810-24g v2. According to the documentation it supports mapping DSCP to 802.1p.

I cannot find any documentation on how it maps the many DSCP codes to the 802.1p codes.

I could try to make an educated guess, but I have two conflicting thoughts on this

1) The 1810v2 maps the 8 802.1p codes to 4 internal queues. DSCP has 4 primarly classifications that they recommend, so I thought these 4 classes would map to the 4 internal queues.

2) There are 8 other DSCP classifications, 4 of which are subsets of the 4 primary classifications.

I have no idea if the 8 classifications map to the 8 802.1p classifications and would be prooperly mapped to the 4 hardware queues or if the first 4 classfications would be considered part of the 4 primary classfications and get mapped directly to the hardware queues.

Does ECN break these mappings? ECN changes the two rightmost bits in the ToS field, which is used by DSCP.

If the 1810v2 maps the 8 Class selector values to the 8 802.1p queues, the Class selector values don't use the 3 right most bits, so if the 1810v2 only looks at the left most bits, then it should be fine.

[Basil95]

Another question I thought about is DSCP is layer 3, but the switch is technically only Layer 2. Is the DSCP to 802.1p mapping done at line rate? Does the switch support DSCP for IPv6?

[Vince-Whirlwind · Accepted solution]

The usual mapping would be:

look at the bits that make up the DSCP field.

remove the last 3 bits

the three bits you have left are the 802.1p priority (least-significant bit rightmost).

eg,

EF is 101110 ... makes 101...makes IP Precedence 5

AF41 is 100010.....100....4

Having said that, HP for some reason use different values for 802.1p than they do for IP precedence, which requires re-marking.

Queue scheduling is a different kettle of fish: you have 4 queues by default because queues use up resources and you don't want to do that.