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<div class="moz-cite-prefix">On 5/7/18 8:00 AM, Junxiao Shi wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CAOFH+ObW7_HLR3udmJRG5JixG0Zr9o+vsDhv9BMsVxRA4OvGbw@mail.gmail.com">
<div dir="ltr">Dear folks
<div><br>
</div>
<div>I have a question on how to process an Interest with
HopLimit=1 when the Interest matches an existing PIT entry.</div>
<div><br>
</div>
<div>Topology:</div>
<div><br>
</div>
<div><font face="monospace, monospace">A--\</font></div>
<div><font face="monospace, monospace"> R---P</font></div>
<div><font face="monospace, monospace">B--/</font></div>
<div><br>
</div>
<div>A and B are two downstream nodes. P and Q are two upstream
nodes. All faces are non-local.</div>
<div><br>
</div>
<div>Event sequence:</div>
<div>
<ol>
<li>R receives an Interest with HopLimit=32 from A, and
forwards it to P.</li>
<li>P is preparing a reply and not responding yet.</li>
<li>R receives an Interest with HopLimit=1 from B.</li>
</ol>
</div>
<div>Per v0.3 protocol:</div>
<blockquote style="margin:0 0 0 40px;border:none;padding:0px">
<div>
<div>if the HopLimit value is larger than or equal to 1, a
node should accept the packet and decrease the encoded
value by 1.</div>
</div>
<div>
<div>If the HopLimit value becomes 0, a node can satisfy
this Interest locally (cache or applications bound to
local faces), but must not forward the Interests to any
non-local faces.</div>
</div>
</blockquote>
<div><br>
</div>
<div>R is prohibited from forwarding B's Interest to P. My
question is: Does R add B to the PIT entry
<span
style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:small;font-style:normal;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial;float:none;display:inline">as
a downstream</span>? Or should R respond Nack-NoRoute to B?</div>
</div>
</blockquote>
From my point of view, the HopLimit is just a mechanism to prevent
an Interest from being forwarded further than the expected.
Therefore, except the forwarding part, I don't see why a forwarder
by default should treat an Interest with HopLimit = 0 differently,
so in your case R will add B to the PIT entry as a downstream. You
can always have customized forwarding strategies for different
behaviors.<br>
<br>
Teng <br>
<blockquote type="cite"
cite="mid:CAOFH+ObW7_HLR3udmJRG5JixG0Zr9o+vsDhv9BMsVxRA4OvGbw@mail.gmail.com">
<div dir="ltr">
<div><br>
</div>
<div>My opinion is:</div>
<div>If B's Interest would arrive after P responds, it would
have matched the cached Data. Thus, R can add B to the PIT
entry as a downstream, and send the Data to B when it arrives.</div>
<div>However, B's Interest should not be considered as a
consumer retransmission, so the strategy should not attempt to
resend A's Interest to any non-local face.</div>
<div><br>
</div>
<div>Yours, Junxiao</div>
</div>
<br>
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</pre>
</blockquote>
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