perfsonar development work

[Nicolas Simar <>]

Nina Jeliazkova wrote:
> Hello all,
> 
> We had recently a discussion with Szymon and Maciej on the best way to
> resolve the case, where a query against gLS returns more than one
> possible homeLS.
> 
> The case was first reported for a traceroute Szymon used for a demo
> 
> 1    49 ms    48 ms    48 ms  pionier-gw.rt1.poz.pl.geant2.net
> [62.40.124.182]
> 
> PerfsonarUI uses an XQuery (attached) to ask for subnets, matching given
> IP address and subnet mask (e.g.  62.40.124.182/32 in this case). The
> The IP address (62.40.124.182) matches two home LS - the GN2 one with
> subnet /23 and Pionier one with /32 . The excerpt of the response is below:
> 
> http://loco4.man.poznan.pl:8180/xml-ls-gn2/services/LookupService
>                 <nmtl3:subnet>
>                     <nmtl3:address type="ipv4">62.40.124.0</nmtl3:address>
>                     <nmtl3:netmask>23</nmtl3:netmask>
>                 </nmtl3:subnet>
>                
> http://ls.perfsonar.pionier.net.pl:8080/xml-ls/services/LookupService
>                 <nmtl3:subnet>
>                     <nmtl3:address type="ipv4">62.40.124.182</nmtl3:address>
>                     <nmtl3:netmask>32</nmtl3:netmask>
>                 </nmtl3:subnet>
> 
> 
> I've updated perfsonarUI to always select most specific subnet, if there
> are more than one, e.g. if there is /32 and /23 then /32 will allways be
> selected.  For the use case PerfsonarUI is dealing with, namely looking
> for matches for a list of  IP addresses coming from a traceroute (subnet
> mask /32 only) , it seems quite reasonable.
> 
> However, Maciej had a different view ( don't restrict the answer to one
> subnet, present everything to the user, see emails below ), so we
> thought it will be best to move the discussion into the developers
> mailing list.

The one case I know are IP address of inter-domain links. E.g. between
GEANT2 and PSNC, the IP addresses used for the link are GN2 IP
addresses. One is being monitored by GEANT2 /xx and one by PSNC /32.

As a user, I don't want to be bother with choice I may not be able to
make. How could I know in which MA the data is stored. (I possibly don't
understand well enough the impact of the selection - in which scenario
would I be interested to chose between two MAs?)

However, if the data cannot be found in one MA, the other one should be
checked.

PS: I don't know how the aggretation is done. E.g. what happens if there
are two circuits between GEANT2 and PSNC how are the two IP addresses
from GEANT aggregated on PSNC side. Currently the question is rather
rhetorical.


Another point, yesterday I talked with Jeff about registration. He
mentioned that in the case of perfsonarobyo, the iperf tests results are
stored in two MA (the one related to the sender and the one related to
the receiver). So there you would automatically get two MAs.

Nicolas


> In summary,  my question is as follows (having in mind only the use case
> when the user is asking for list of IPs coming from a traceroute and a
> given eventtype, i.e. subnet mask 32 )
> 
>     * Is there a chance, that information for a given IP and given
>       eventtype (e.g. utilization) is provided by more than one (MA)
>       service ?  
>     * If yes, how do we visualize that and assure the information is
>       consistent?
>     * If not, what is the reason of looking into multiple options?
> 
> Discussion on other use cases are of course welcome :)
> 
> Best regards,
> Nina
> 
> Maciej Glowiak написа:
>> Nina Jeliazkova wrote:
>>> Szymon,
>>>
>>> I've updated the SVN and the beta version available as Web start to
>>> handle this issue. The logic is to always select most specific
>>> subnet, if there are more than one, e.g. if there is /32 and /23 then
>>> /32 will allways be selected. It doesn't seem likely that there will
>>> be duplicates with netmask /32, for duplicates of other subnets it
>>> depends how the summarization is done. Perhaps Maciej can better
>>> explain if duplicate subnets are to be expected.
>>
>> Nina,
>>
>> Yes, duplicate subnets may occur. I think if there are several matched
>> subnets all of them should be shown to the user. For instance we ask
>> for 150.254.160.194
>>
>> There are two LS-es having:
>>
>> 1. http://ls1.perfsonar.net:8080/xmlls
>>       150.254.160.194/32
>>
>> 2. http://ls2.perfsonar.net:8080/xmlls
>>       150.254.160.0/24
>>
>> In fact responding user with only #1 is not so good, because LS1 has
>> only that one address from the network (or doesn't do summarization)
>> while the other one (LS2) may have full range of addresses from that
>> network.
>>
>> I'd respond with both addresses. Then two separate queries should be
>> done - one to LS1 and the second one to LS2.
>>
>> As far as I remember that way it was described in dLS algorithm. First
>> we ask dLS (gLS here acts as dLS) for Lookup Services that MAY have
>> the IP. Then we need to ask all LSes from result set. Of course it
>> depends on strategy.
>>
>> Maciej 
> 
>> Maciej,
>>
>> Maciej Glowiak написа:
>>> Nina,
>>>
>>>> My reasoning was based only for the case, where we are looking for a
>>>> specific IP address - as in traceroute.  So, if we are looking for
>>>> 150.254.160.194/32 , the first LS is an exact match and there is no
>>>> need to respond with the second one.  If we are looking for e.g.
>>>> 150.254.160.1 , then the first one is not a match at all , and the
>>>> second (/24) is the only match; no need to respond with the first one.
>>>>
>>>> The logic I've proposed is exactly the one followed by IP
>>>> forwarding, when the router needs to select the interface where to
>>>> forward the packets for given destination IP.
>>> > Of course, in other scenarios, where we are interested not in a single
>>> > IP, the logic might be different. Do you have examples of such use
>>> cases?
>>>
>>>
>>> Yes, but the router must select the path as quick as possible and
>>> select the shortest path. The narrower mask the better choice it is.
>>>
>>> We have different approach. We want to give a user opportunity to see
>>> all "sources" that may have information he wants.
>>>
>>> The /32 mask is of course special "use case". I don't have stong
>>> opinion wheteher we should just response with one LS having /32 mask
>>> or give all LSes that matche subnet masks. I'd prefer the second choice.
>>>
>>
>> Well, I will reformulate the question then, having in mind only the
>> use case when the user is asking for list of IPs coming from a
>> traceroute.
>>
>> Is there a chance, that (utilization) information for a given IP is
>> provided by more than one (MA) service ? 
>> If yes, how do we visualize that and assure the information is
>> consistent?
>> If not, what is the reason of looking into multiple options?
>>
>>
>> Regards,
>> Nina
>>
>> P.S. I've talked briefly with Michael Bischoff and he told me gLS API
>> doesn't handle yet the case where more than one hLS are available for
>> a given IP.
>>
>>> Maciej
>>
> 
> 
> -- 
> ---------------------------------
> Dr. Nina Nikolova-Jeliazkova
> Institute for Parallel Processing
> Bulgarian Academy of Sciences
> Acad. G. Bonchev St 25-A
> 1113 Sofia, Bulgaria
> Tel: +359 886 802011
> ICQ: 10705013
> www: http://ambit.acad.bg/nina
> ---------------------------------
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> ---------------------------------------------------------------
> 

-- 
Nicolas
______________________________________________________________________

Nicolas Simar
Network Engineer

DANTE - www.dante.net

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