Using Hardware flows-table with hp 2920 24g

[MariusCachelin]

Hi,

I am using an HP 2920 24g (J9727A)  switch as an OpenFlow switch. I have 3 PCs connected to this switch:

- PC1 : Beacon controller as SDN Controller

- PC2 and PC3 : Hosts in the Data Plane

My switch configuration is :

- OpenFlow version 1.0 (Beacon Controller only support OpenFlow v1.0)

- Software revision : WB.16.03.0003

- ROM Version : WB.16.03

My problem :

When I Ping PC3 from PC2, flows are added to the switch, and all packets are able to pass through the switch. But, the Round Trip Time is 2 ms (which is very high compared to normal RTT of 0.2 ms) . So I checked the flows-table in the switch, using 'show openflow instance <inst_name> flows' command. This is one of my flow :

 Flow 4
 Match
  Incoming Port : 13                    Ethernet Type    : IP
  Source MAC    : 047d7b-a27aac         Destination MAC  : 003053-14c386
  Destination MAC Mask : ffffff-ffffff
  VLAN ID       : Any                   VLAN Priority    : Any
  Source IP Address      : Any
  Destination IP Address : Any
  IP Protocol   : Any                   IP ToS Bits      : Any
  Source Port   : Any                   Destination Port : Any
 Attributes
  Priority      : 0                     Duration         : 2 seconds
  Hard Timeout  : 0 seconds             Idle Timeout     : 20 seconds
  Byte Count    : 196                   Packet Count     : 2
  Controller ID : 1                     Cookie           : 0x0
  Flow Location : Software
  Hardware Index: NA
  Reason Code        : 2
  Reason Description : The rule has a match criterion for MAC address
 Actions
    Output                  : 11

Additionnal Information :

The match used for the previous flow is only made using the MAC source, MAC destination addresses and the Ethernet type. We can see from the flow displayed above, that "The rule has a match criterion for MAC Address".

So i tried to add an other flow, using a very simple match, only based on the incoming port, and this flow was added in the hardware flows-table.

Questions :

First of all, is it possible to add flow in hardware flow-table, using match based on MAC addresses, , in hp 2920 24g switch?

Secondly, what are the limitations of the hardware flow-table, in term of matching criterion?

Best regards,

Marius.

[ShaunWackerly · Accepted solution]

Hello Marius,

The HP 2920 does not support matching eth_dst in the ASIC, and that's the reason why you are seeing those flows be moved to software. In order to match eth_dst in the ASIC, you'd need to use 3800 (similar age to 2920) or you'd need to use a newer product like 2930F or 3810.

In regard to the match capabilities in the 2920 ASIC, I believe the following matches can be supported in hardware:

• in_port
• eth_src (unless eth_type is wildcarded)
• eth_type
• ipv4_src
• ipv4_dst
• ip_proto
• ip_tos
• tcp_src/udp_src
• tcp_dst/udp_dst

Shaun

[MariusCachelin]

Hello Shaun,

first of all, I really thank you for your reply, because it was my problem. You were rigth, using a match without MAC addresses, but with IP Addresses is supported in the hardware. But I really don't understand why the switch does not support matching MAC addresses in hartdware, I thought it was the main functionnality of a 'normal' switch.

Secondly, could you please tell me where did you find all these information, regarding the matct capabilities supported in hardware? (Not only for the 2920, but for other products)

Marius

[Abhay_B]

Hi Marius,

You can use the switch CLI to figure that one out if you are using an OpenFlow 1.3 instance.

show openflow instance <instance-name> flow-table <table-id> table-capability

This would show the match and action capability associated with the table. Table 100 is the hardware table when the 1.3 instance is configured with pipeline-model standard-match (default).

In case of OF 1.0, I suggest you refer to Appendix A of the OpenFlow Admin Guide. It talks about the various match fields and actions supported in hardware based on the ASIC type (v1, v2 or v3). (The ones under standard-match are applicable for 1.0 flows that would sit in hardware)

Hope this helps.

Thanks!

Abhay

PS: I know the text in the appendix is not very clear. I would be happy to clarify any questions on it.

[MariusCachelin]

Hi Abhay,

thank for your reply about the match and action capability.

I am using OpenFlow 1.0 (because of my SDN controller) so I've taken a look to Appendix A of the OpenFlow admin Guide.

You are right, this part is not so clear, but enough to understand how to build match, and to push it in the hardware. Again, I thank you for your help.

Marius