[pox-dev] implementing vlans

[Murphy McCauley]

On Nov 4, 2013, at 9:32 PM, durga <c.vijaya.durga at gmail.com> wrote:

> Hello All,
> 
> I tried to replicate vlan behaviour and succeeded to some extent(excl. Broadcasts). The procedure I followed is to maintain another vlanport table within the controller and map for vlanID to port ID based on simple calculation of even and odd ports. if both src and dest port are in same vlan , then controller inserts a flowtable entry , else drop the packet. I am yet to implement a Broadcast scenario within a single vlan.
> 
> Now, 
> 1.is there already a built in feature for implementing vlans? I understand, there is an action type vlan_vid to set the vlanID in flow tables, so does it mean that  if a match exists in the Openflow switch, the switch is capable of figuring out if two ports belong to same vlan or not?

It's not the action which helps with that.  It's that ofp_match can match on VLAN ID.  The VLAN ID write action can then be used to handle switching between access and trunk.  Together, the two mean that you can interact with existing VLANs.

> 2.also can vlans be implemented as group tables?

First off: not in POX, since these are an OpenFlow 1.1 feature, and POX doesn't support 1.1 (yet?).

Secondly: it depends what you mean.  They certainly might be helpful.

Thirdly: with Open vSwitch / Nicira extensions, I have found its multiple table support useful for working with VLANs.  These aren't 1.1 group tables; just normal tables (which *are* supported by POX).  A rough approximation of the design involves four tables:

Ingress table.  This matches on input port and VLAN ID.  It validates that only trunked VLAN IDs for a port are allowed (others are dropped) and sets the appropriate tag for untagged traffic on access ports.  Then it jumps to the forwarding table.

Forwarding table.  This actually does whatever your forwarding logic is (e.g., L2 learning, IP prefixes, whatever).  If outputting to a specific port, it sets the output port in a meta register and jumps to the output table.  If flooding, it jumps to the flood table.

Output table. This table matches on the output port set by the forwarding table and the VLAN ID.  For trunked VLANs, it doesn't do anything (a low priority match-all just outputs the packet).  For access ports, there's a rule to strip the VLAN tag and then output.

Flood table.  Matches on the VLAN ID.  Each entry outputs to each of the trunk ports, then strips the tag and outputs to each of the access ports.

-- Murphy
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.noxrepo.org/pipermail/pox-dev-noxrepo.org/attachments/20131105/346b58f7/attachment-0002.htm>