<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=us-ascii">
<meta name="Generator" content="Microsoft Word 15 (filtered medium)">
<style><!--
/* Font Definitions */
@font-face
{font-family:Courier;
panose-1:2 7 4 9 2 2 5 2 4 4;}
@font-face
{font-family:"Cambria Math";
panose-1:2 4 5 3 5 4 6 3 2 4;}
@font-face
{font-family:DengXian;
panose-1:2 1 6 0 3 1 1 1 1 1;}
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
@font-face
{font-family:"\@DengXian";
panose-1:2 1 6 0 3 1 1 1 1 1;}
/* 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]-->
</head>
<body lang="EN-US" link="#0563C1" vlink="#954F72">
<div class="WordSection1">
<p class="MsoNormal">Hi all,<o:p></o:p></p>
<p class="MsoNormal"> When I used bird, found a question that BGP session received OPEN message, hold_time is updated with min(config_hold_time, peer_hold_time), but keepalive_time is not updated if keepalive_time is not zero, that maybe cause keepalive_time
is more than the updated hold_time after received OPEN message. <o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Line 702 in packets.cc for bgp protocol :<o:p></o:p></p>
<p class="MsoNormal"> conn->keepalive_time = p->cf->keepalive_time ? : conn->hold_time / 3;<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"> RFC 4271:<o:p></o:p></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:10.0pt;font-family:Courier;color:blue">4.4</span><span style="font-size:10.0pt;font-family:Courier;color:black">. KEEPALIVE Message Format<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:10.0pt;font-family:Courier;color:black">BGP does not use any TCP-based, keep-alive mechanism to determine if<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:10.0pt;font-family:Courier;color:black">peers are reachable. Instead, KEEPALIVE messages are exchanged<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:10.0pt;font-family:Courier;color:black">between peers often enough not to cause the Hold Timer to expire.
</span><span style="font-size:10.0pt;font-family:Courier;color:red">A<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:10.0pt;font-family:Courier;color:red">reasonable maximum time between KEEPALIVE messages would be one third<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:10.0pt;font-family:Courier;color:red">of the Hold Time interval.</span><span style="font-size:10.0pt;font-family:Courier;color:black"> KEEPALIVE messages MUST NOT be sent more<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:10.0pt;font-family:Courier;color:black">frequently than one per second. An implementation MAY adjust the<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:10.0pt;font-family:Courier;color:black">rate at which it sends KEEPALIVE messages as a function of the Hold<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:Courier;color:black">Time interval.<o:p></o:p></span></p>
<p class="MsoNormal"><o:p></o:p></p>
<p class="MsoNormal">Thanks<o:p></o:p></p>
<p class="MsoNormal">Arvin<o:p></o:p></p>
</div>
</body>
</html>