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<p style="margin-bottom: 0in; line-height: 100%">Dear NDN
Developers,</p>
<p style="margin-bottom: 0in; line-height: 100%">I’m currently
thinking of methods for redundant data transmission for
real-time
applications. In the case of (some) real-time applications a
retransmission of lost packets is not reasonable. Therefore I
would
like to investigate redundant data transmission over multiple
links.
I think this could be useful especially in wireless access
networks
with higher loss rates.</p>
<p style="margin-bottom: 0in; line-height: 100%">My idea is, to
duplicate Interests and send them out over multiple faces
(similar to
Multicast). This duplication means, that the same Interest will
also
arrive over multiple faces on some hosts. In order to achieve a
redundant data transmission, it is necessary that the Interest
is
registered in the PIT from all in-faces.</p>
<p style="margin-bottom: 0in; line-height: 100%">I recognized,
that
the design of the Interest processing pipeline only allows that
one
Interest arrives from one face. If it arrives from two or more
faces,
only the first is processed, the others are classified as
looping
Interests, what is disadvantageous for my intent.</p>
<p style="margin-bottom: 0in; line-height: 100%">I was thinking
and
testing a lot in order to understand this pipeline design, but I
can’t see, why Interests with the same nonce are classified as
looping if they arrive over different faces. In my opinion, a
loop
can only occur if two Interests with the same nonce arrive over
the
same face.</p>
<p style="margin-bottom: 0in; line-height: 100%">This behavior
also
brings disadvantages in other cases. Imagine two nodes are
connected
over two links, a low latency low-bandwidth link, and a high
latency
high-bandwidth link. If a forwarding strategy like Multicast is
used,
only the low bandwidth link would be used because the Interest
is
faster at the receiver at this link. The Interest which traveled
over
the high bandwidth link is classified as looping, which means
that
the high-bandwidth link is not used, even if there are
congestions on
the low-bandwidth link.</p>
<p style="margin-bottom: 0in; line-height: 100%">I would like to
ask,
if anyone can explain the reason for this pipeline design or
could
give me advices for implementing redundant data transmissions.</p>
<p style="margin-bottom: 0in; line-height: 100%">Best regards,</p>
Philipp Moll
</p>
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