<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
</head>
<body>
<br>
<br>
<div class="moz-cite-prefix">On 16/Jul/20 05:51, Harivishnu Abhilash
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:086ebd2f3d1e473bbf44037699ab95de@mannai.com.qa">
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<meta name="Generator" content="Microsoft Word 15 (filtered
medium)">
<style><!--
/* Font Definitions */
@font-face
{font-family:"Cambria Math";
panose-1:2 4 5 3 5 4 6 3 2 4;}
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0in;
margin-bottom:.0001pt;
font-size:11.0pt;
font-family:"Calibri",sans-serif;}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:#0563C1;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:#954F72;
text-decoration:underline;}
span.EmailStyle17
{mso-style-type:personal-compose;
font-family:"Calibri",sans-serif;
color:windowtext;}
.MsoChpDefault
{mso-style-type:export-only;
font-family:"Calibri",sans-serif;}
@page WordSection1
{size:8.5in 11.0in;
margin:1.0in 1.0in 1.0in 1.0in;}
div.WordSection1
{page:WordSection1;}
--></style><!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]-->
<div class="WordSection1">
<p class="MsoNormal"><b><span
style="font-size:8.0pt;font-family:"Times New
Roman",serif;color:black">Classification:</span></b><b><span
style="font-size:8.0pt;font-family:"Times New
Roman",serif;color:#00C000">Public</span></b><o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Guys, I’m looking for recommendation
regarding BFD timers that we can use for long haul circuit.
RTT is roughly around 110 ms. In fact this is a l2vpn ckt
provided by a telco.<o:p></o:p></p>
<p class="MsoNormal">Can you please advise the factors we can
consider when setting the BFD timers (or any recommended
values)? I have set 10 ms dead time but this is causing BFD to
go down occasionally.
</p>
</div>
</blockquote>
<br>
<font face="Tahoma">We run different intervals and multipliers
depending on whether the connection is LAN or WAN.<br>
<br>
For LAN (so within the same data centre), intervals are set to
150ms and multipliers are set to 3.<br>
<br>
For WAN (any backbone regardless of latency), intervals are set to
250ms and multipliers are set to 5.<br>
<br>
Since our network spans multiple countries and continents, we
wanted a uniform value for the WAN side of things, so we don't
have too many customized configurations. We found these settings
to work well in mixed environments where implementations vary
between CPU and line card processing, and also to strike a balance
between accuracy and false positives.<br>
<br>
We've been running this on IOS XE, IOS XR and Junos platforms
since 2014. The only issues we found were:<br>
</font>
<ul>
<li><font face="Tahoma">BFD on LAG's on IOS XR platforms in a LAN
environment don't work. A point-to-point mechanism is
required, so we disabled it there. Junos and IOS XE have no
problems running BFD on LAG's in LAN's, so we have it on
there. This is for within the data centre.<br>
</font></li>
</ul>
<ul>
<li><font face="Tahoma">BFDv6 on the MX does not run in hardware.
Since IS-IS (for us) ties in BFD for link state event
detection, a transient lack of CPU resources to service BFDv6
traffic will result in not only BFDv6 going down, but also the
entire IS-IS protocol flapping on the assumption that a link
event has occurred. So if you run BFDv6 alongside BFDv4,
recommend that you disable BFDv6 until Juniper introduce
hardware support for it on the MX (and I'm guessing all other
Junos platforms). We have an ER out for this since 2019, and
we are told it should be appearing sometime between Q4'20 -
1H'21.</font></li>
</ul>
<ul>
<li><font face="Tahoma">Syntax for BFD in Junos has changed to
incorporate address families. So while the old syntax will
commit, it will leave an annotation in the configuration about
not being supported anymore. Recommend you convert your Junos
BFD configurations to IPv4 and IPv6 specificity, if you
haven't already done so. I can't remember when this came into
effect, but it likely was Junos 16. We are on Junos 17 now.<br>
</font></li>
</ul>
<p><font face="Tahoma">Our longest circuit point-to-point is 140ms
(Cape Town - London). These settings have been running fine on
there since Day 1 (IOS XR-to-IOS XR), and overall detection and
re-convergence of IS-IS + LFA leaves us happy and sleeping well
at night.<br>
</font></p>
<p><font face="Tahoma">Mark.</font><br>
</p>
</body>
</html>