Again, I may not be remembering correctly, but things are complex if you have multiple OF switches connected to a single non-OF switch. You can get timeouts which create wierdnesses such as hosts attached to internal ports (causing a software flood since the location is unknown). Hop-by-hop simplifies the forwarding logic so you're reasonably assured that packet processing will be done on the fast path.
Hi Martin,

I do not understand.  This should not make a difference, since routing
still have calculate a route, for which some OpenFlow switches might
be connected directly.  Doing it hop-by-hop does not make a
difference.  What am I missing here?

Regards
KK

On 24 February 2010 13:58, Martin Casado <[email protected]> wrote:
I believe it is simpler integration with a legacy network in which all
switches are not running OF.

Hi,

What is the motivation for hop-by-hop routing?  Does seems novel in
some aspects.

Regards
KK

On 24 February 2010 13:52, Martin Casado <[email protected]> wrote:

From Natasha:

"I'm wondering if maybe the server is showing up on hpsw3, and so the
packet
is first getting routed there, and then re-routed again when it reaches
hpsw1. This is probably a result of all the authenticator code commented
out
that was making it depend on routing.  It's in a couple places (wherever
the
word "routing" is used)."

This is likely the culprit.  Currently Nox 0.6 is doing hop-by-hop
routing
rather then setting up the full path.  Can you search for routing_mode in
authenticator.hh, authenticator_modify.cc and authenticator_util.cc,
uncomment the code and see if this fixes the problem?


I notice that the routing module is behaving differently with NOX0.6
causing each switch en route to generate independent packet_ins, while
NOX0.4 generates only 1 packet_in. This behavior incurs higher flow
setup time.

I have a topology of client <-> hpsw3 <-> hpsw1 <-> server . I
performed a wget operation from client to server. Following is the
control traffic sent/received by the controller (Timestamp was what my
tcpdump captured):

  1266984715.446715   PACKET_IN   hpsw3
  1266984715.446895   FLOW_MOD    hpsw3
  1266984715.446936   PACKET_OUT  hpsw3

  1266984715.452756   PACKET_IN   hpsw1
  1266984715.452913   FLOW_MOD    hpsw1
  1266984715.452937   PACKET_OUT  hpsw1

Ideally, I would've expected to see the controller to push out the
second FLOW_MOD soon enough (and not 6 ms after the PACKET_OUT).

When I use NOX0.4, the action sequence is:
  1266987591.116579    PACKET_IN    hpsw3
  1266987591.116725    FLOW_MOD     hpsw3
  1266987591.116755    FLOW_MOD     hpsw1
  1266987591.116787    PACKET_OUT   hpsw3

Any idea if there is a code change?

Thanks
Srini.

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