Re: [ibr-dtn] How Priority parameter works?

14 Jan 2013


      Thank you very much for your advice.
I will check it and try to understand better how it works.
Regards,
Alex.
2013/1/11 Johannes Morgenroth morgenroth@ibr.cs.tu-bs.de
...
The two implementations are part of two different objects. One is the
Bundle which contains the whole bundle data including all block.
MetaBundle is just a summary of the bundle and used at several places
where only meta-data is needed.
The sorting process is done during the insertion. You should read the
documentation for std::set objects in C++. The objects in there are
always sorted. This sort can customized by using a comparison method.
CMP_BUNDLE_PRIORITY is such a method and implements a strict ordering
based on the priority. "lhs" and "rhs" are just variables for the left
and right bundle to compare.
Kind regards,
Johannes
-------- Weitergeleitete Nachricht --------
Von: Alex López lopalex87@gmail.com
An: Johannes Morgenroth morgenroth@ibr.cs.tu-bs.de
Kopie: ibr-dtn@ibr.cs.tu-bs.de
Betreff: Re: [ibr-dtn] How Priority parameter works?
Datum: Fri, 11 Jan 2013 16:08:51 +0100
Thank you for your fast answer Johannes.
That's the thing that bothers me, why do you have 2 implementations for
the same thing? Which one are you finally using?
About what you explain how bundle priority is working, I have figured it
more or less reading the code, but it would be really helpful to now
where specifically in the code is this ordered list defined, or where
"storage sort all the bundles according to the priority and iterate them
in this order." is implemented in the code.
I found that this function has something to do about this, but I don't
understand really well how it works:
ibrcommon::Mutex _bundleslock;
00112                         std::setdtn::data::Bundle _bundles;
00113
00114                         struct CMP_BUNDLE_PRIORITY
00115                         {
00116                                 bool operator() (const
dtn::data::MetaBundle& lhs, const dtn::data::MetaBundle& rhs) const
00117                                 {
00118                                         if (lhs.getPriority() ==
rhs.getPriority())
00119                                                 return rhs > lhs;
00120
00121                                         return (lhs.getPriority() >
rhs.getPriority());
00122                                 }
00123                         };
00124
00125                         std::setdtn::data::MetaBundle,
CMP_BUNDLE_PRIORITY _priority_index;
00126                         std::map<dtn::data::BundleID, ssize_t>
_bundle_lengths;
00127
00128                         size_t _maxsize;
00129                         size_t _currentsize;
What's the meaning of rhs and lhs? It's maybe _priority_index the
ordered list are you talking about? If it's so, where is the sorting
process done? I think this function works to compare the priorities, but
I can't find the function that pushes forward or pull back the files in
the storage sorted list.
Thanks,
Alex López.
May
2013/1/11 Johannes Morgenroth morgenroth@ibr.cs.tu-bs.de
        Hello Alex!
    Bundle::getPriority() and MetaBundle::getPriority() does exactly
    the
    same thing. Both read the corresponding priority encoded in the
    processing flags. This is defined in the bundle protocol
    specification
    (RFC 5050).

    The effect is, that bundles with higher priority are delivered
    preferential to bundles with a lower priority. This is
    implemented as
    ordered list in the bundle storages. A storage sort all the
    bundles
    according to the priority and iterate them in this order.

    That means, a routing module will process the bundles with
    higher
    priority first.

    Kind regards,
    Johannes Morgenroth


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