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<div class="moz-cite-prefix">Dear Ado,<br>
<br>
the term "implicit withdrawal" applies to a BGP update U_2 that
comes to a BGP speaker from the same peer P that sent a previous
update U_1. When the peer P sends the second update U_2, the
meaning is that the previous update U_1 is implicitly withdrawn by
P and replaced with U_2. In other words, the sequence U_1, U_2 has
the same effect of U_1, Withdrawal, U_2. <br>
The four BGP announcements that you list in your email do not
come all from the same peer of router 192.65.185.40. However, the
third announcement (FROM: 192.65.185.144, AS_PATH: 6893 3561 209
297) is an implicit withdrawal of the first (FROM: 192.65.185.144,
AS_PATH: 6893 8938 1 297). There is only one implicit withdrawal
in the sequence. <br>
After all four announcements are received by router
192.65.185.40, router 192.65.185.40 has to choose its best route
to prefix <span id="yiv9739217820yui_3_16_0_1_1444557033460_3936"
class="" style="color: rgb(34, 34, 34); border: 1pt none
windowtext; padding: 0in;">192.152.102.0/24. </span><span
id="yiv9739217820yui_3_16_0_1_1444557033460_3936" class=""
style="color: rgb(34, 34, 34); border: 1pt none windowtext;
padding: 0in;">The choice is among the 2nd, 3rd and 4th route,
since the 1st announcement is implicitly withdrawn by the 3rd.</span><br>
<br>
Best,<br>
Maurizio<br>
<br>
On 10/11/2015 12:26 PM, Ado Maja wrote:<br>
</div>
<blockquote
cite="mid:1916664772.2046706.1444559188541.JavaMail.yahoo@mail.yahoo.com"
type="cite">
<div style="color:#000; background-color:#fff;
font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial,
Lucida Grande, sans-serif;font-size:16px">
<div class="" id="yiv9739217820yui_3_16_0_1_1444557033460_3848"
style="margin-bottom: 12pt; line-height: 14.65pt;"><span
id="yiv9739217820yui_3_16_0_1_1444557033460_3850" class=""
style="color: rgb(34, 34, 34);">Dear all,</span></div>
<div class="" id="yiv9739217820yui_3_16_0_1_1444557033460_3854"
style="margin-bottom: 12pt; line-height: 14.65pt;"><span
id="yiv9739217820yui_3_16_0_1_1444557033460_3856" class=""
style="color: rgb(34, 34, 34);">I am trying to account for
all implicit withdrawal messages within a certain period of
time looking at BGP update messages collected at rrc, Ripe. </span></div>
<div class="" id="yiv9739217820yui_3_16_0_1_1444557033460_3860"
style="margin-bottom: 0.0001pt; background: rgb(238, 238,
238);"><span id="yiv9739217820yui_3_16_0_1_1444557033460_3862"
class="" style="color: rgb(34, 34, 34); border: 1pt none
windowtext; padding: 0in;">Implicit Withdrawal Definition:
If the sender announces a route to a currently reachable
address and the new route is identical to the current route,
this is a duplicate announcement. Otherwise, the sender is
replacing the current route with a new route and this is an
implicit withdrawal. (</span><span
id="yiv9739217820yui_3_16_0_1_1444557033460_3864" class=""
style="color: rgb(34, 34, 34); background: white;">Wang et
al. in the "Observation and Analysis of BGP iBehavior under
Stress"</span><span
id="yiv9739217820yui_3_16_0_1_1444557033460_3866" class=""
style="color: rgb(34, 34, 34);">)</span></div>
<div class="" id="yiv9739217820yui_3_16_0_1_1444557033460_3870"
style="margin-bottom: 0.0001pt; background: rgb(238, 238,
238);"><span id="yiv9739217820yui_3_16_0_1_1444557033460_3872"
class="" style="color: rgb(34, 34, 34);"> </span></div>
<div class="" id="yiv9739217820yui_3_16_0_1_1444557033460_3874"
style="margin-bottom: 12pt; line-height: 14.65pt;"><span
id="yiv9739217820yui_3_16_0_1_1444557033460_3876" class=""
style="color: rgb(34, 34, 34);">What I am trying to
understand is how do I count implicit withdrawals? If for
example, I have 4 BGP messages shown below that have same IP
address and different AS-PATH attribute, how many implicit
withdrawals do I have? Is it 3? If I look at consecutive
messages that have same IP address and different AS-PATH
attribute the result would be 3 (I compare first to the
second, second to the third and third to the fourth –
assuming they have same IP address and different AS-PATH I
increment implicit withdrawals). But I have come across a
solution that takes a first message and compares it to the
rest of the messages. Than second message compares to the
rest of the messages. And lastly compares the third to the
fourth. In this case number of implicit withdrawals is 6.
Please advise.</span></div>
<div class="" id="yiv9739217820yui_3_16_0_1_1444557033460_3880"
style="margin-bottom: 12pt; line-height: 14.65pt;"><span
id="yiv9739217820yui_3_16_0_1_1444557033460_3882" class=""
style="color: rgb(34, 34, 34);">Thanks for your help.</span></div>
<div class="" id="yiv9739217820yui_3_16_0_1_1444557033460_3886"
style="margin-bottom: 0.0001pt; background: rgb(238, 238,
238);"><span id="yiv9739217820yui_3_16_0_1_1444557033460_3888"
class="" style="color: rgb(34, 34, 34); border: 1pt none
windowtext; padding: 0in;">TIME: 2001-9-16 00:00:06</span></div>
<div class="" id="yiv9739217820yui_3_16_0_1_1444557033460_3892"
style="margin-bottom: 0.0001pt; background: rgb(238, 238,
238);"><span id="yiv9739217820yui_3_16_0_1_1444557033460_3894"
class="" style="color: rgb(34, 34, 34); border: 1pt none
windowtext; padding: 0in;">TYPE: BGP4MP/BGP4MP_MESSAGE
AFI_IP</span></div>
<div class="" id="yiv9739217820yui_3_16_0_1_1444557033460_3898"
style="margin-bottom: 0.0001pt; background: rgb(238, 238,
238);"><span id="yiv9739217820yui_3_16_0_1_1444557033460_3900"
class="" style="color: rgb(34, 34, 34); border: 1pt none
windowtext; padding: 0in;">FROM: 192.65.185.144</span></div>
<div class="" id="yiv9739217820yui_3_16_0_1_1444557033460_3904"
style="margin-bottom: 0.0001pt; background: rgb(238, 238,
238);"><span id="yiv9739217820yui_3_16_0_1_1444557033460_3906"
class="" style="color: rgb(34, 34, 34); border: 1pt none
windowtext; padding: 0in;">TO: 192.65.185.40</span></div>
<div class="" id="yiv9739217820yui_3_16_0_1_1444557033460_3910"
style="margin-bottom: 0.0001pt; background: rgb(238, 238,
238);"><span id="yiv9739217820yui_3_16_0_1_1444557033460_3912"
class="" style="color: rgb(34, 34, 34); border: 1pt none
windowtext; padding: 0in;">BGP PACKET TYPE: UPDATE</span></div>
<div class="" id="yiv9739217820yui_3_16_0_1_1444557033460_3916"
style="margin-bottom: 0.0001pt; background: rgb(238, 238,
238);"><span id="yiv9739217820yui_3_16_0_1_1444557033460_3918"
class="" style="color: rgb(34, 34, 34); border: 1pt none
windowtext; padding: 0in;">ORIGIN: IGP</span></div>
<div class="" id="yiv9739217820yui_3_16_0_1_1444557033460_3922"
style="margin-bottom: 0.0001pt; background: rgb(238, 238,
238);"><span id="yiv9739217820yui_3_16_0_1_1444557033460_3924"
class="" style="color: rgb(34, 34, 34); border: 1pt none
windowtext; padding: 0in;">AS_PATH: 6893 8938 1 297</span></div>
<div class="" id="yiv9739217820yui_3_16_0_1_1444557033460_3928"
style="margin-bottom: 0.0001pt; background: rgb(238, 238,
238);"><span id="yiv9739217820yui_3_16_0_1_1444557033460_3930"
class="" style="color: rgb(34, 34, 34); border: 1pt none
windowtext; padding: 0in;">NEXT_HOP: 192.65.185.144</span></div>
<div class="" id="yiv9739217820yui_3_16_0_1_1444557033460_3934"
style="margin-bottom: 0.0001pt; background: rgb(238, 238,
238);"><span id="yiv9739217820yui_3_16_0_1_1444557033460_3936"
class="" style="color: rgb(34, 34, 34); border: 1pt none
windowtext; padding: 0in;">ANNOUNCED: 192.152.102.0/24</span></div>
<div class="" id="yiv9739217820yui_3_16_0_1_1444557033460_3940"
style="margin-bottom: 0.0001pt; background: rgb(238, 238,
238);"><span id="yiv9739217820yui_3_16_0_1_1444557033460_3942"
class="" style="color: rgb(34, 34, 34); border: 1pt none
windowtext; padding: 0in;"> </span></div>
<div class="" id="yiv9739217820yui_3_16_0_1_1444557033460_3944"
style="margin-bottom: 0.0001pt; background: rgb(238, 238,
238);"><span id="yiv9739217820yui_3_16_0_1_1444557033460_3946"
class="" style="color: rgb(34, 34, 34); border: 1pt none
windowtext; padding: 0in;">TIME: 2001-9-16 00:00:18</span></div>
<div class="" id="yiv9739217820yui_3_16_0_1_1444557033460_3950"
style="margin-bottom: 0.0001pt; background: rgb(238, 238,
238);"><span id="yiv9739217820yui_3_16_0_1_1444557033460_3952"
class="" style="color: rgb(34, 34, 34); border: 1pt none
windowtext; padding: 0in;">TYPE: BGP4MP/BGP4MP_MESSAGE
AFI_IP</span></div>
<div class="" id="yiv9739217820yui_3_16_0_1_1444557033460_3956"
style="margin-bottom: 0.0001pt; background: rgb(238, 238,
238);"><span id="yiv9739217820yui_3_16_0_1_1444557033460_3958"
class="" style="color: rgb(34, 34, 34); border: 1pt none
windowtext; padding: 0in;">FROM: 192.65.184.3</span></div>
<div class="" id="yiv9739217820yui_3_16_0_1_1444557033460_3962"
style="margin-bottom: 0.0001pt; background: rgb(238, 238,
238);"><span id="yiv9739217820yui_3_16_0_1_1444557033460_3964"
class="" style="color: rgb(34, 34, 34); border: 1pt none
windowtext; padding: 0in;">TO: 192.65.185.40</span></div>
<div class="" id="yiv9739217820yui_3_16_0_1_1444557033460_3968"
style="margin-bottom: 0.0001pt; background: rgb(238, 238,
238);"><span id="yiv9739217820yui_3_16_0_1_1444557033460_3970"
class="" style="color: rgb(34, 34, 34); border: 1pt none
windowtext; padding: 0in;">BGP PACKET TYPE: UPDATE</span></div>
<div class="" id="yiv9739217820yui_3_16_0_1_1444557033460_3974"
style="margin-bottom: 0.0001pt; background: rgb(238, 238,
238);"><span id="yiv9739217820yui_3_16_0_1_1444557033460_3976"
class="" style="color: rgb(34, 34, 34); border: 1pt none
windowtext; padding: 0in;">ORIGIN: IGP</span></div>
<div class="" id="yiv9739217820yui_3_16_0_1_1444557033460_3980"
style="margin-bottom: 0.0001pt; background: rgb(238, 238,
238);"><span id="yiv9739217820yui_3_16_0_1_1444557033460_3982"
class="" style="color: rgb(34, 34, 34); border: 1pt none
windowtext; padding: 0in;">AS_PATH: 513 10764 6509 297</span></div>
<div class="" id="yiv9739217820yui_3_16_0_1_1444557033460_3986"
style="margin-bottom: 0.0001pt; background: rgb(238, 238,
238);"><span id="yiv9739217820yui_3_16_0_1_1444557033460_3988"
class="" style="color: rgb(34, 34, 34); border: 1pt none
windowtext; padding: 0in;">NEXT_HOP: 192.65.185.9</span></div>
<div class="" id="yiv9739217820yui_3_16_0_1_1444557033460_3992"
style="margin-bottom: 0.0001pt; background: rgb(238, 238,
238);"><span id="yiv9739217820yui_3_16_0_1_1444557033460_3994"
class="" style="color: rgb(34, 34, 34); border: 1pt none
windowtext; padding: 0in;">ANNOUNCED: 192.152.102.0/24</span></div>
<div class="" id="yiv9739217820yui_3_16_0_1_1444557033460_3998"
style="margin-bottom: 0.0001pt; background: rgb(238, 238,
238);"><span id="yiv9739217820yui_3_16_0_1_1444557033460_4000"
class="" style="color: rgb(34, 34, 34); border: 1pt none
windowtext; padding: 0in;"> </span></div>
<div class="" id="yiv9739217820yui_3_16_0_1_1444557033460_4002"
style="margin-bottom: 0.0001pt; background: rgb(238, 238,
238);"><span id="yiv9739217820yui_3_16_0_1_1444557033460_4004"
class="" style="color: rgb(34, 34, 34); border: 1pt none
windowtext; padding: 0in;">TIME: 2001-9-16 00:00:36</span></div>
<div class="" id="yiv9739217820yui_3_16_0_1_1444557033460_4008"
style="margin-bottom: 0.0001pt; background: rgb(238, 238,
238);"><span id="yiv9739217820yui_3_16_0_1_1444557033460_4010"
class="" style="color: rgb(34, 34, 34); border: 1pt none
windowtext; padding: 0in;">TYPE: BGP4MP/BGP4MP_MESSAGE
AFI_IP</span></div>
<div class="" id="yiv9739217820yui_3_16_0_1_1444557033460_4014"
style="margin-bottom: 0.0001pt; background: rgb(238, 238,
238);"><span id="yiv9739217820yui_3_16_0_1_1444557033460_4016"
class="" style="color: rgb(34, 34, 34); border: 1pt none
windowtext; padding: 0in;">FROM: 192.65.185.144</span></div>
<div class="" id="yiv9739217820yui_3_16_0_1_1444557033460_4020"
style="margin-bottom: 0.0001pt; background: rgb(238, 238,
238);"><span id="yiv9739217820yui_3_16_0_1_1444557033460_4022"
class="" style="color: rgb(34, 34, 34); border: 1pt none
windowtext; padding: 0in;">TO: 192.65.185.40</span></div>
<div class="" id="yiv9739217820yui_3_16_0_1_1444557033460_4026"
style="margin-bottom: 0.0001pt; background: rgb(238, 238,
238);"><span id="yiv9739217820yui_3_16_0_1_1444557033460_4028"
class="" style="color: rgb(34, 34, 34); border: 1pt none
windowtext; padding: 0in;">BGP PACKET TYPE: UPDATE</span></div>
<div class="" id="yiv9739217820yui_3_16_0_1_1444557033460_4032"
style="margin-bottom: 0.0001pt; background: rgb(238, 238,
238);"><span id="yiv9739217820yui_3_16_0_1_1444557033460_4034"
class="" style="color: rgb(34, 34, 34); border: 1pt none
windowtext; padding: 0in;">ORIGIN: IGP</span></div>
<div class="" id="yiv9739217820yui_3_16_0_1_1444557033460_4038"
style="margin-bottom: 0.0001pt; background: rgb(238, 238,
238);"><span id="yiv9739217820yui_3_16_0_1_1444557033460_4040"
class="" style="color: rgb(34, 34, 34); border: 1pt none
windowtext; padding: 0in;">AS_PATH: 6893 3561 209 297</span></div>
<div class="" id="yiv9739217820yui_3_16_0_1_1444557033460_4044"
style="margin-bottom: 0.0001pt; background: rgb(238, 238,
238);"><span id="yiv9739217820yui_3_16_0_1_1444557033460_4046"
class="" style="color: rgb(34, 34, 34); border: 1pt none
windowtext; padding: 0in;">NEXT_HOP: 192.65.185.144</span></div>
<div class="" id="yiv9739217820yui_3_16_0_1_1444557033460_4050"
style="margin-bottom: 0.0001pt; background: rgb(238, 238,
238);"><span id="yiv9739217820yui_3_16_0_1_1444557033460_4052"
class="" style="color: rgb(34, 34, 34); border: 1pt none
windowtext; padding: 0in;">ANNOUNCED: 192.152.102.0/24</span></div>
<div class="" id="yiv9739217820yui_3_16_0_1_1444557033460_4056"
style="margin-bottom: 0.0001pt; background: rgb(238, 238,
238);"><span id="yiv9739217820yui_3_16_0_1_1444557033460_4058"
class="" style="color: rgb(34, 34, 34); border: 1pt none
windowtext; padding: 0in;"> </span></div>
<div class="" id="yiv9739217820yui_3_16_0_1_1444557033460_4060"
style="margin-bottom: 0.0001pt; background: rgb(238, 238,
238);"><span id="yiv9739217820yui_3_16_0_1_1444557033460_4062"
class="" style="color: rgb(34, 34, 34); border: 1pt none
windowtext; padding: 0in;">TIME: 2001-9-16 00:00:44</span></div>
<div class="" id="yiv9739217820yui_3_16_0_1_1444557033460_4066"
style="margin-bottom: 0.0001pt; background: rgb(238, 238,
238);"><span id="yiv9739217820yui_3_16_0_1_1444557033460_4068"
class="" style="color: rgb(34, 34, 34); border: 1pt none
windowtext; padding: 0in;">TYPE: BGP4MP/BGP4MP_MESSAGE
AFI_IP</span></div>
<div class="" id="yiv9739217820yui_3_16_0_1_1444557033460_4072"
style="margin-bottom: 0.0001pt; background: rgb(238, 238,
238);"><span id="yiv9739217820yui_3_16_0_1_1444557033460_4074"
class="" style="color: rgb(34, 34, 34); border: 1pt none
windowtext; padding: 0in;">FROM: 192.65.185.130</span></div>
<div class="" id="yiv9739217820yui_3_16_0_1_1444557033460_4078"
style="margin-bottom: 0.0001pt; background: rgb(238, 238,
238);"><span id="yiv9739217820yui_3_16_0_1_1444557033460_4080"
class="" style="color: rgb(34, 34, 34); border: 1pt none
windowtext; padding: 0in;">TO: 192.65.185.40</span></div>
<div class="" id="yiv9739217820yui_3_16_0_1_1444557033460_4084"
style="margin-bottom: 0.0001pt; background: rgb(238, 238,
238);"><span id="yiv9739217820yui_3_16_0_1_1444557033460_4086"
class="" style="color: rgb(34, 34, 34); border: 1pt none
windowtext; padding: 0in;">BGP PACKET TYPE: UPDATE</span></div>
<div class="" id="yiv9739217820yui_3_16_0_1_1444557033460_4090"
style="margin-bottom: 0.0001pt; background: rgb(238, 238,
238);"><span id="yiv9739217820yui_3_16_0_1_1444557033460_4092"
class="" style="color: rgb(34, 34, 34); border: 1pt none
windowtext; padding: 0in;">ORIGIN: IGP</span></div>
<div class="" id="yiv9739217820yui_3_16_0_1_1444557033460_4096"
style="margin-bottom: 0.0001pt; background: rgb(238, 238,
238);"><span id="yiv9739217820yui_3_16_0_1_1444557033460_4098"
class="" style="color: rgb(34, 34, 34); border: 1pt none
windowtext; padding: 0in;">AS_PATH: 559 8933 6509 297</span></div>
<div class="" id="yiv9739217820yui_3_16_0_1_1444557033460_4102"
style="margin-bottom: 0.0001pt; background: rgb(238, 238,
238);"><span id="yiv9739217820yui_3_16_0_1_1444557033460_4104"
class="" style="color: rgb(34, 34, 34); border: 1pt none
windowtext; padding: 0in;">NEXT_HOP: 192.65.185.130</span></div>
<div class="" dir="ltr"
id="yiv9739217820yui_3_16_0_1_1444557033460_4108"
style="margin-bottom: 0.0001pt; background: rgb(238, 238,
238);"><span id="yiv9739217820yui_3_16_0_1_1444557033460_4110"
class="" style="color: rgb(34, 34, 34); border: 1pt none
windowtext; padding: 0in;">ANNOUNCED: 192.152.102.0/24</span></div>
</div>
</blockquote>
<br>
<br>
<pre class="moz-signature" cols="72">--
Maurizio "Titto" Patrignani
Dipartimento di Ingegneria, Universita' Roma Tre
Tel +39.06.57333233, Fax +39.06.57333612
<a class="moz-txt-link-freetext" href="http://www.dia.uniroma3.it/~patrigna">http://www.dia.uniroma3.it/~patrigna</a>
</pre>
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