perfsonar development work

[Nina Jeliazkova <>]

Nicolas,

Nicolas Simar написа:

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?)
  

In case the same data for the same IP is available in two MA (as in case  of inter-domain links), either one of them is to be selected, or information from both of them shown (even if redundant)

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

Do you mean by "data cannot be found" IP address can't be found in LS, or no data available in MA ?

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.
  

The example above is real,  the 62.40.124.182 interface is found in  GEANT2 hLS summarized as 62.40.124.0/23 and  in PIONIER home LS as 62.40.124.182/32

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.
  

OK, I admit there is nonzero chance for receiving multiple services per query IP. Then the rest of the questions come - how do we visualize the duplicate information ?

For example, will it be acceptable for the end user to have multiple rows in the psUI Interface tab with the same IP, but different domains? e.g.

62.40.124.182  octets-in octets-out etc. PIONIER
62.40.124.182  octets-in octets-out etc. GEANT2

Best regards,
Nina

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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-- 
---------------------------------
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
---------------------------------
PGP Public Key
http://cert.acad.bg/pgp-keys/keys/nina-nikolova-0xEEABA669.asc
	8E99 8BAD D804 1A43 27B7  7F87 CF04 C7D1 EEAB A669
---------------------------------------------------------------