hm.. My problem here is that the switches don't have a ping capabilitie..
or am I wrong? I'm not sure I understand your answer, and that i was clear
enough in my original mail.
Let's say my topology is the following:
C
> ___|___
> / \
> / \
> h1------p1:s1:p2-----p1:s2:p2--------h2
>
>
what i need, is to know the latency between s1 and s2. As the switches are
dumb, I cannot simply ask them to ping each other, can I?
I hope the question is clearer now, and I thank you for your answer.
Regards,
Walid van Boetzelaer
2011/12/19 Bob Lantz <rla...@cs.stanford.edu>
> Since I don't have a switch which is capable of timestamping, I would
> simply loop the packet back to the sender on a different interface:
>
> eth0 -> ingress switch ... egress switch -> eth1
>
> This is a common approach - you don't need NOX or OpenFlow to do this, and
> no time synchronization is required since there is a single clock.
>
>
> On Dec 19, 2011, at 1:59 PM, Walid van Boetzelaer wrote:
>
> Hello, and thank you for your answer.
>
> I got this working and using send_stats_request was the way to go. I now
> have something similar to an available bandwith (assuming speed is the
> max_bandwidth, i do speed-link_utilization)
>
> I would like now to get the latency between two switches. I would be
> curious to know what the best way to do this is.
> My idea, though i can't figure out which commands to use, is the following:
> have a switch send a packet to the neighbor switch, have it timestamp it,
> send it back to the first switch, have it timestamp it, return it to the
> controller, and from that, get the latency.
>
> If someone has thought of this already, could you point me to the
> functions i should be using to get this working?
>
> Thank you in advance,
>
> Walid van Boetzelaer
>
>
>
>
>
> 2011/12/18 Murphy McCauley <jam...@nau.edu>
>
>> On Dec 18, 2011, at 11:52 AM, Walid van Boetzelaer wrote:
>>
>> > Openflow does maintain counters for each flow table, and these counters
>> have the number of received packets per port, etc... How can I retrieve
>> these?
>>
>> At the OpenFlow level, you do this by sending an ofp_port_stats_request
>> asking for stats of type OFPST_PORT. You'll get back a response of
>> ofp_port_stats which contains byte and packet counters for the port.
>>
>> The easiest way to do this from Python in NOX is using component's
>> register_for_port_stats_in() to set a callback for port stats messages, and
>> then using pycontext's send_port_stats_request() to send an actual request.
>> (From inside your component, I think these are
>> self.register_for_port_stats_in() and self.ctxt.send_port_stats_request().)
>>
>> Alternatively, the switchstats or monitoring components may do what you
>> need.
>>
>> Hope that helps.
>>
>> -- Murphy
>
>
>
> Walid wrote:
>
>> Hi all!
>>
>> I need to calculate the bandwidth and latency between two switches. To
>> achieve this, I plan to:
>>
>> C
>> ___|___
>> / \
>> / \
>> h1------p1:s1:p2-----p1:s2:p2--------h2
>> -bandwidth:
>>
>> 1. stat0 = number of packets that went through s1_p1 and s2_port1 at
>> time t1
>>
>>
>> 1. generate traffic from s1 to s2
>>
>>
>> 1. stat1 = number of packets that went through s1_p1 and s2_port1 at
>> time t2
>>
>>
>> 1. bandwidth = (stat1-stat0)*size_of_packet/(t2-t1)
>>
>> -latency:
>>
>> 1. latency = send a packet from s1 to s2, check the timestamp at s1,
>> s2, subtract them
>>
>>
>> However, I am having trouble as to generating traffic. I checked the stats
>> *variable* passed to the datapath_join events, and i get the following:
>> I've been looking into these stats (and switchstats as well) for a while,
>> because I believe they can help me retrieve the information I need.
>> However, I am unsure as to what '*speed*' here means. Also, I can't see
>> where the number of packets that traverse a port is.
>> Openflow does maintain counters for each flow table, and these counters
>> have the number of received packets per port, etc... How can I retrieve
>> these?
>> Thank you in advance!
>> Best regards
>>
>> {'ports': [
>>
>> {'hw_addr': 'b\x9e\x04\xb9h,', 'curr': 192, 'name': 's1-eth2', 'speed':
>>> 10000, 'supported': 0, 'enabled': True, 'flood': True, 'state': 0, 'link':
>>> True, 'advertised': 0, 'peer': 0, 'config': 0, 'port_no': 2}, {'hw_addr':
>>> '\x00# \xba\xc0\x97', 'curr': 0, 'name': 'dp0', 'speed': 0,
>>> 'supported': 0, 'enabled': False, 'flood': True, 'state': 1, 'link': False,
>>> 'advertised': 0, 'peer': 0, 'config': 1, 'port_no': 65534}, {'hw_addr':
>>> '\x9e\xe7\xf1\xcb\xdd\x17', 'curr': 192, 'name': 's1-eth1', 'speed':
>>> 10000, 'supported': 0, 'enabled': True, 'flood': True, 'state': 0, 'link':
>>> True, 'advertised': 0, 'peer': 0, 'config': 0, 'port_no': 1}], 'n_tables':
>>> 2, 'n_bufs': 256L, 'actions': 4095L, 'caps': 135L}
>>
>> _______________________________________________
> nox-dev mailing list
> nox-dev@noxrepo.org
> http://noxrepo.org/mailman/listinfo/nox-dev
>
>
>
_______________________________________________
nox-dev mailing list
nox-dev@noxrepo.org
http://noxrepo.org/mailman/listinfo/nox-dev
