rfc9687xml2.original.xml   rfc9687.xml 
<?xml version="1.0" encoding="UTF-8"?> <?xml version='1.0' encoding='UTF-8'?>
<?rfc sortrefs="yes"?>
<?rfc subcompact="no"?>
<?rfc symrefs="yes"?>
<?rfc toc="yes"?>
<?rfc tocdepth="3"?>
<?rfc compact="yes"?>
<?rfc subcompact="no"?>
<rfc
category="std"
docName="draft-ietf-idr-bgp-sendholdtimer-15"
updates="4271"
ipr="trust200902"
submissionType="IETF"
consensus="true">
<front>
<title abbrev="BGP SendHoldTimer">Border Gateway Protocol 4 (BGP-4) Send Hold
Timer</title>
<author fullname="Job Snijders" initials="J." surname="Snijders">
<organization>Fastly</organization>
<address>
<postal>
<street />
<city>Amsterdam</city>
<code />
<country>Netherlands</country>
</postal>
<email>job@fastly.com</email>
</address>
</author>
<author fullname="Ben Cartwright-Cox" initials="B." surname="Cartwright-Cox">
<organization abbrev="Port 179">Port 179 Ltd</organization>
<address>
<postal>
<street />
<city>London</city>
<code />
<country>United Kingdom</country>
</postal>
<email>ben@benjojo.co.uk</email>
</address>
</author>
<author fullname="Yingzhen Qu" initials="Y" surname="Qu">
<organization abbrev="Futurewei">Futurewei Technologies</organization>
<address>
<postal>
<street />
<city>Santa Clara</city>
<code />
<country>United States</country>
</postal>
<email>yingzhen.ietf@gmail.com</email>
</address>
</author>
<date />
<area>Routing</area>
<workgroup>IDR</workgroup>
<keyword>BGP</keyword>
<keyword>TCP</keyword>
<abstract>
<t> <!DOCTYPE rfc [
This document defines the SendHoldtimer, along with the SendHoldTimer_Expi <!ENTITY nbsp "&#160;">
res event, for the Border Gateway Protocol (BGP) Finite State Machine (FSM). <!ENTITY zwsp "&#8203;">
Implementation of the SendHoldTimer helps overcome situations where a BGP <!ENTITY nbhy "&#8209;">
connection is not terminated after the local system detects that the remote syst <!ENTITY wj "&#8288;">
em is not processing BGP messages. ]>
This document specifies that the local system should close the BGP connect
ion and not solely rely on the remote system for connection closure when the Sen
dHoldTimer expires.
This document updates RFC4271.
</t>
</abstract> <rfc xmlns:xi="http://www.w3.org/2001/XInclude" category="std" docName="draft-ie tf-idr-bgp-sendholdtimer-15" number="9687" updates="4271" obsoletes="" ipr="trus t200902" submissionType="IETF" consensus="true" sortRefs="true" symRefs="true" t ocInclude="true" tocDepth="3" version="3" xml:lang="en">
<note title="Requirements Language"> <front>
<title abbrev="BGP SendHoldTimer">Border Gateway Protocol 4 (BGP-4) Send Hol
d Timer</title>
<seriesInfo name="RFC" value="9687"/>
<author fullname="Job Snijders" initials="J." surname="Snijders">
<organization>Fastly</organization>
<address>
<postal>
<city>Amsterdam</city>
<country>Netherlands</country>
</postal>
<email>job@fastly.com</email>
</address>
</author>
<author fullname="Ben Cartwright-Cox" initials="B." surname="Cartwright-Cox"
>
<organization abbrev="Port 179">Port 179 Ltd</organization>
<address>
<postal>
<city>London</city>
<country>United Kingdom</country>
</postal>
<email>ben@benjojo.co.uk</email>
</address>
</author>
<author fullname="Yingzhen Qu" initials="Y" surname="Qu">
<organization abbrev="Futurewei">Futurewei Technologies</organization>
<address>
<postal>
<city>San Jose</city>
<region>CA</region>
<code>95131</code>
<country>United States of America</country>
</postal>
<email>yingzhen.ietf@gmail.com</email>
</address>
</author>
<date month="November" year="2024"/>
<area>RTG</area>
<workgroup>idr</workgroup>
<keyword>BGP</keyword>
<keyword>TCP</keyword>
<abstract>
<t> <t>
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHO This document defines the <tt>SendHoldTimer</tt>, along with the <tt>SendH
ULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in t oldTimer_Expires</tt> event, for the Border Gateway Protocol (BGP) Finite State
his document are to be interpreted as described in BCP 14 <xref target="RFC2119" Machine (FSM).
/> <xref target="RFC8174"/> when, and only when, they appear in all capitals, as Implementation of the <tt>SendHoldTimer</tt> helps overcome situations whe
shown here. re a BGP connection is not terminated after the local system detects that the re
mote system is not processing BGP messages.
This document specifies that the local system should close the BGP connect
ion and not solely rely on the remote system for connection closure when the <tt
>SendHoldTimer</tt> expires.
This document updates RFC 4271.
</t> </t>
</note> </abstract>
</front>
<middle>
<section title="Introduction">
<t>
This document defines the <tt>SendHoldtimer</tt>, along with the <tt>SendH
oldTimer_Expires</tt> event, for the Border Gateway Protocol (BGP) <xref target=
"RFC4271" /> Finite State Machine (FSM) defined in section 8.
</t>
<t> </front>
<middle>
<section>
<name>Introduction</name>
<t>
This document defines the <tt>SendHoldTimer</tt>, along with the <tt>SendH
oldTimer_Expires</tt> event, for the Border Gateway Protocol (BGP) Finite State
Machine (FSM) defined in <xref target="RFC4271" section="8"/>.
</t>
<t>
Failure to terminate a blocked BGP connection can result in network reacha bility issues, and the subsequent failure to generate and deliver BGP UPDATE mes sages to another BGP speaker of the local system is detrimental to all participa nts of the inter-domain routing system. Failure to terminate a blocked BGP connection can result in network reacha bility issues, and the subsequent failure to generate and deliver BGP UPDATE mes sages to another BGP speaker of the local system is detrimental to all participa nts of the inter-domain routing system.
This phenomena is thought to have contributed to IP traffic blackholing ev This phenomena is thought to have contributed to IP traffic packet loss ev
ents in the global Internet routing system <xref target="bgpzombies"/>. ents in the global Internet routing system <xref target="bgpzombies"/>.
</t> </t>
<t> <t>
This specification intends to improve this situation by requiring that BGP connections be terminated if the local system has detected that the remote syst em cannot possibly have processed any BGP messages for the duration of the <tt>S endHoldTime</tt>. This specification intends to improve this situation by requiring that BGP connections be terminated if the local system has detected that the remote syst em cannot possibly have processed any BGP messages for the duration of the <tt>S endHoldTime</tt>.
Through standardization of the aforementioned requirement, operators will benefit from consistent behavior across different BGP implementations. Through standardization of the aforementioned requirement, operators will benefit from consistent behavior across different BGP implementations.
</t> </t>
<t> <t>
BGP speakers following this specification do not rely exclusively on remot BGP speakers following this specification do not rely exclusively on remot
e systems closing blocked connections, but will also locally close blocked conne e systems closing blocked connections; they also locally close blocked connectio
ctions. ns.
</t> </t>
</section> </section>
<section>
<section title="Example of a problematic scenario"> <name>Requirements Language</name>
<t> <t>
The key words "<bcp14>MUST</bcp14>", "<bcp14>MUST NOT</bcp14>",
"<bcp14>REQUIRED</bcp14>", "<bcp14>SHALL</bcp14>", "<bcp14>SHALL NOT</bcp14>
",
"<bcp14>SHOULD</bcp14>", "<bcp14>SHOULD NOT</bcp14>",
"<bcp14>RECOMMENDED</bcp14>", "<bcp14>NOT RECOMMENDED</bcp14>",
"<bcp14>MAY</bcp14>", and "<bcp14>OPTIONAL</bcp14>" in this document are to
be
interpreted as described in BCP&nbsp;14 <xref target="RFC2119"/> <xref
target="RFC8174"/> when, and only when, they appear in all capitals, as
shown here.
</t>
</section>
<section>
<name>Example of a Problematic Scenario</name>
<t>
In implementations lacking the concept of a <tt>SendHoldTimer</tt>, a malf unctioning or overwhelmed remote speaker may cause data on the BGP socket in the local system to accumulate ad infinitum. In implementations lacking the concept of a <tt>SendHoldTimer</tt>, a malf unctioning or overwhelmed remote speaker may cause data on the BGP socket in the local system to accumulate ad infinitum.
This could result in forwarding failure and traffic loss, as the overwhelm ed speaker continues to utilize stale routes. This could result in forwarding failure and traffic loss, as the overwhelm ed speaker continues to utilize stale routes.
</t> </t>
<t>
An example fault state: as BGP runs over TCP <xref target="RFC9293" />, it <t>
is possible for a BGP speaker in the Established state to encounter a BGP speak An example fault state: as BGP runs over TCP <xref target="RFC9293"/>, it
er that is advertising a TCP Receive Window (RCV.WND) of size zero. is possible for a BGP speaker in the Established state to encounter a BGP speake
This 0 window prevents the local system from sending KEEPALIVE, UPDATE, or r that is advertising a TCP Receive Window (RCV.WND) of size zero. The size zer
any other critical BGP messages across the network socket to the remote speaker o of this window prevents the local system from sending KEEPALIVE, UPDATE, or an
. y other critical BGP messages across the
</t> network socket to the remote speaker.
<t> </t>
<t>
Generally BGP implementations have no visibility into lower-layer subsyste ms such as TCP or the speaker's current Receive Window size, and there is no exi sting BGP mechanism for such a blocked connection to be recognized. Generally BGP implementations have no visibility into lower-layer subsyste ms such as TCP or the speaker's current Receive Window size, and there is no exi sting BGP mechanism for such a blocked connection to be recognized.
Hence BGP implementations are not able to handle this situation in a consi stent fashion. Hence BGP implementations are not able to handle this situation in a consi stent fashion.
</t> </t>
<t>
The major issue arising from a BGP speaker being unable to send a BGP mess
age to a given remote speaker is that as a result that speaker subsequently is o
perating based on stale routing information.
Failure of the BGP speaker to send (and thus the remote speaker to receive
) BGP messages on a single BGP session can negatively impact the ability of an e
ntire autonomous system (or even a group of autonomous systems) to converge.
</t>
</section>
<section title="Changes to RFC 4271 - SendHoldTimer">
<t>
BGP speakers are implemented following a conceptual model "BGP Finite State
Machine" (FSM), which is outlined in section 8 of <xref target="RFC4271"/>.
This specification adds a BGP timer, <tt>SendHoldTimer</tt>, and updates the
BGP FSM as follows:
</t>
<section title="Session Attributes">
<t>
The following optional session attributes for each connection are added to
Section 8, before "The optional session attributes support different features o
f the BGP functionality that have implications for the BGP FSM state transitions
":
</t>
<t>NEW</t>
<blockquote>
<list style="empty">
<t>
14) SendHoldTimer
</t>
<t>
15) SendHoldTime
</t>
</list>
</blockquote>
<t>
The <tt>SendHoldTime</tt> determines how long a BGP speaker will stay in E
stablished state before the TCP connection is dropped because no BGP messages ca
n be transmitted to its peer.
A BGP speaker can configure the value of the <tt>SendHoldTime</tt> for eac
h peer independently.
</t>
</section>
<section title="Timer Event: SendHoldTimer_Expires">
<t>
Another timer event is added to Section 8.1.3 of <xref target="RFC4271"/> as
following:
</t>
<t>NEW</t>
<blockquote>
<dl newline="true">
<dt>
Event 29: SendHoldTimer_Expires
</dt>
<dd>
<dl>
<dt>Definition:</dt>
<dd>An event generated when the SendHoldTimer expires.</dd>
<dt>Status:</dt>
<dd>Optional</dd>
</dl>
</dd>
</dl>
</blockquote>
</section>
<section title="Changes to the FSM">
<t>The following changes are made to section 8.2.2 in <xref target="RFC4271"
/>.</t>
<t>In "OpenConfirm State", the handling of Event 26 is revised as follows:</
t>
<t>OLD</t>
<blockquote>
<t> <t>
If the local system receives a KEEPALIVE message (KeepAliveMsg (Event 26 The primary issue that arises when a BGP speaker is unable to send a BGP message
)), the local system: to a remote speaker is that the affected speaker may end up operating with outd
<list style="hanging"> ated routing information.
<t hangText="-">restarts the HoldTimer and</t> Failure of the BGP speaker to send (and thus the remote speaker to receive
<t hangText="-">changes its state to Established.</t> ) BGP messages on a single BGP session can negatively impact the ability of an e
</list> ntire autonomous system (or even a group of autonomous systems) to converge.
</t> </t>
</blockquote> </section>
<section>
<t>NEW</t> <name>Changes to RFC 4271 - <tt>SendHoldTimer</tt></name>
<blockquote>
<t> <t>
If the local system receives a KEEPALIVE message (KeepAliveMsg (Event 26 BGP speakers are implemented following a conceptual model "BGP Finite State
)), the local system: Machine" (FSM), which is outlined in <xref target="RFC4271" section="8" sectionF
<list style="hanging"> ormat="of"/>.
<t hangText="-">restarts the HoldTimer,</t> This specification adds a BGP timer, <tt>SendHoldTimer</tt>, and updates the
<t hangText="-">starts the SendHoldTimer if the SendHoldTime is non-ze BGP FSM as indicated in the following subsections.
ro, and</t>
<t hangText="-">changes its state to Established.</t>
</list>
</t> </t>
</blockquote> <section>
<name>Session Attributes</name>
<t> <t>
The following paragraph is added to section 8.2.2 in "Established State", The following optional session attributes for each connection are added to
after the paragraph which ends "unless the negotiated HoldTime value is zero.": the list in <xref target="RFC4271" section="8" sectionFormat="of"/> appearing j
</t> ust prior to "The optional session attributes support different features of the
BGP functionality that have implications for the BGP FSM state transitions":</t>
<t>NEW</t> <t>NEW</t>
<blockquote> <blockquote>
<list style="empty"> <ul empty="true" spacing="normal">
<t>If the SendHoldTimer_Expires (Event 29) occurs, the local system: <li>
<list style="hanging"> <t>
<t hangText="-">(optionally) sends a NOTIFICATION message with the B 14) <tt>SendHoldTimer</tt>
GP Error Code "Send Hold Timer Expired" if the local system can determine that d </t>
oing so will not delay the following actions in this paragraph,</t> </li>
<t hangText="-">logs an error message in the local system with the B <li>
GP Error Code "Send Hold Timer Expired",</t> <t>
<t hangText="-">releases all BGP resources,</t> 15) <tt>SendHoldTime</tt>
<t hangText="-">sets the ConnectRetryTimer to zero,</t> </t>
<t hangText="-">drops the TCP connection,</t> </li>
<t hangText="-">increments the ConnectRetryCounter by 1,</t> </ul>
<t hangText="-">(optionally) performs peer oscillation damping if th </blockquote>
e DampPeerOscillations attribute is set to TRUE, and</t> <t>
<t hangText="-">changes its state to Idle.</t> <tt>SendHoldTime</tt> determines how long a BGP speaker will stay in the E
</list> stablished state before the TCP connection is dropped because no BGP messages ca
n be transmitted to its peer.
A BGP speaker can configure the value of the <tt>SendHoldTime</tt> for eac
h peer independently.
</t> </t>
</section>
<section>
<name>Timer Event: <tt>SendHoldTimer_Expires</tt></name>
<t> <t>
Each time the local system sends a BGP message, it restarts the SendHo ldTimer unless the SendHoldTime value is zero or the negotiated HoldTime value i s zero, in which cases the SendHoldTimer is stopped. Another timer event is added to <xref target="RFC4271" section="8.1.3" secti onFormat="of"/> as follows:
</t> </t>
<t>NEW</t>
<blockquote>
<ul empty="true">
<li><t> Event 29: <tt>SendHoldTimer_Expires</tt></t>
<ul empty="true">
<li>Definition: An event generated when the <tt>SendHoldTimer</tt
> expires.</li>
<li>Status: Optional</li>
</ul></li>
</ul>
</blockquote>
</section>
<section>
<name>Changes to the FSM</name>
<t>The following changes are made to <xref target="RFC4271" section="8.2
.2" sectionFormat="of"/>.</t>
<t>In "OpenConfirm State", the handling of Event 26 is revised as follow
s:</t>
<t>OLD</t>
<blockquote>
<t>
If the local system receives a KEEPALIVE message (KeepAliveMsg (Event 26
)), the local system:
</t>
<ul empty="true"><li><ul><li>restarts the <tt>HoldTimer</tt> and</li>
<li>changes its state to Established.</li>
</ul></li></ul>
</blockquote>
<t>NEW</t>
<blockquote>
<t>
If the local system receives a KEEPALIVE message (KeepAliveMsg (Event 26
)), the local system:
</t>
<ul empty="true"><li><ul>
<li>restarts the <tt>HoldTimer</tt>,</li>
<li>starts the <tt>SendHoldTimer</tt> if the <tt>SendHoldTime</tt> i
s non-zero, and</li>
<li>changes its state to Established.</li>
</ul></li></ul>
</blockquote>
<t> <t>
The SendHoldTimer is stopped following any transition out of the Estab The following paragraph is added to <xref target="RFC4271" section="8.2.2"
lished state as part of the "release all BGP resources" action. sectionFormat="of"/> in "Established State", after the paragraph that ends "unle
ss the negotiated <tt>HoldTime</tt> value is zero":
</t> </t>
</list> <t>NEW</t>
</blockquote> <blockquote>
</section> <t>If the <tt>SendHoldTimer_Expires</tt> (Event 29) occurs, the lo
cal system:
</t>
<section title="Changes to BGP Timers" anchor="timers"> <ul empty="true"><li><ul> <li>(optionally) sends a NOTIFICATION m
<t> essage with the BGP Error Code "Send Hold Timer Expired" if the local system can
<xref target="RFC4271" section="10"/> summarizes BGP Timers. determine that doing so will not delay the following actions in this paragraph,
</li>
<li>logs an error message in the local system with the BGP Error
Code "Send Hold Timer Expired",</li>
<li>releases all BGP resources,</li>
<li>sets the ConnectRetryTimer to zero,</li>
<li>drops the TCP connection,</li>
<li>increments the ConnectRetryCounter by 1,</li>
<li>(optionally) performs peer oscillation damping if the DampPe
erOscillations attribute is set to TRUE, and</li>
<li>changes its state to Idle.</li>
</ul>
</li>
<li>
<t>
Each time the local system sends a BGP message, it restarts the <tt>Se
ndHoldTimer</tt> unless the <tt>SendHoldTime</tt> value is zero or the negotiate
d <tt>HoldTime</tt> value is zero, in which case the <tt>SendHoldTimer</tt> is s
topped.
</t>
</li>
<li>
<t>
The <tt>SendHoldTimer</tt> is stopped following any transition out of
the Established state as part of the "release all BGP resources" action.
</t>
</li>
</ul>
</blockquote>
</section>
<section anchor="timers">
<name>Changes to BGP Timers</name>
<t>
<xref target="RFC4271" section="10"/> summarizes BGP timers.
This document adds another optional BGP timer: <tt>SendHoldTimer</tt>. This document adds another optional BGP timer: <tt>SendHoldTimer</tt>.
</t> </t>
<t>NEW</t> <t>NEW</t>
<blockquote> <blockquote>
<t>
<tt>SendHoldTime</tt> is an FSM attribute that stores the initial value
for the <tt>SendHoldTimer</tt>.
If <tt>SendHoldTime</tt> is non-zero, then it <bcp14>MUST</bcp14> be gre
ater than the value of <tt>HoldTime</tt>; see <xref target="implcons" /> of [RFC
9687] for suggested default values.
</t>
</blockquote>
</section>
</section>
<section>
<name>Send Hold Timer Expired Error Handling</name>
<t> <t>
SendHoldTime is an FSM attribute that stores the initial value for the S If the local system does not send any BGP messages within the period speci
endHoldTimer. fied in <tt>SendHoldTime</tt>, then a NOTIFICATION message with the "Send Hold T
If SendHoldTime is non-zero then it MUST be greater than the value of Ho imer Expired" Error Code <bcp14>MAY</bcp14> be sent and the BGP connection <bcp1
ldTime, see <xref section="5" target="I-D.ietf-idr-bgp-sendholdtimer"/> for sugg 4>MUST</bcp14> be closed.
ested default values. Additionally, an error <bcp14>MUST</bcp14> be logged in the local system,
indicating the "Send Hold Timer Expired" Error Code.
</t>
</section>
<section anchor="implcons">
<name>Implementation Considerations</name>
<t>
Due to the relative rarity of the failure mode that this specification is
designed to address, and also the fact that network operators may be unfamiliar
with the formal specification of BGP fault detection mechanisms such as <tt>Hold
Timer</tt>, it is likely that a large number of operators will be unaware of the
need for an additional mechanism such as <tt>SendHoldTimer</tt>.
</t>
<t>
Accordingly, it is <bcp14>RECOMMENDED</bcp14> that implementations of this
specification enable <tt>SendHoldTimer</tt> by default, without requiring addit
ional configuration of the BGP-speaking device.
</t>
<t>
The default value of <tt>SendHoldTime</tt> for a BGP connection <bcp14>SHO
ULD</bcp14> be the greater of:
</t> </t>
</blockquote>
</section>
</section>
<section title="Send Hold Timer Expired Error Handling">
<t>
If the local system does not send any BGP messages within the period speci
fied in <tt>SendHoldTime</tt>, then a NOTIFICATION message with the "Send Hold T
imer Expired" Error Code MAY be sent and the BGP connection MUST be closed.
Additionally, an error MUST be logged in the local system, indicating the
Send Hold Timer Expired Error Code.
</t>
</section>
<section title="Implementation Considerations" anchor="implcons">
<t>
Due to the relative rarity of the failure mode that this specification is
designed to address, and also the fact that network operators may be unfamiliar
with the formal specification of BGP fault detection mechanisms such as <tt>Hold
Timer</tt>, it is likely that a large number of operators are unaware of the nec
essity of an additional mechanism such as <tt>SendHoldtimer</tt>.
</t>
<t>
Accordingly, it is RECOMMENDED that implementations of this specification
enable <tt>SendHoldtimer</tt> by default, without requiring additional configura
tion of the BGP speaking device.
</t>
<t>
The default value of <tt>SendHoldTime</tt> for a BGP connection SHOULD be
the greater of:
<ul> <ul>
<li>8 minutes; or</li> <li>8 minutes or</li>
<li>2 times the negotiated HoldTime</li> <li>2 times the negotiated <tt>HoldTime</tt></li>
</ul> </ul>
</t> <t>
<t> Implementations <bcp14>MAY</bcp14> make the value of <tt>SendHoldTime</tt>
Implementations MAY make the value of <tt>SendHoldTime</tt> configurable, configurable, either globally or on a per-peer basis, within the constraints se
either globally or on a per-peer basis, within the constraints set out in <xref t out in <xref target="timers"/>.
target="timers"/> above. </t>
</t> <t>
<t> The subcode for NOTIFICATION message "Send Hold Timer Expired" is set to 0
The subcode for NOTIFICATION message "Send Hold Timer Expired" is set to 0 and is not used; no additional data is to be appended to the end of a "Send Hol
and is not used, no additional data is to be appended to the end of a "Send Hol d Timer Expired" NOTIFICATION message.
d Timer Expired" NOTIFICATION message. </t>
</t> </section>
</section> <section>
<name>Operational Considerations</name>
<section title="Operational Considerations"> <t>
<t> When the local system recognizes that a remote speaker has not processed a
When the local system recognizes a remote speaker is not processing any BG ny BGP messages for the duration of the <tt>SendHoldTime</tt>, it is likely that
P messages for the duration of the <tt>SendHoldTime</tt>, it is likely that the the local system will not be able to inform the remote peer through a NOTIFICAT
local system will not be able to inform the remote peer through a NOTIFICATION m ION message as to why the connection is being closed.
essage as to why the connection is being closed. This document suggests that an attempt to send a NOTIFICATION message with
This documents suggests that an attempt to send a NOTIFICATION message wit the "Send Hold Timer Expired" Error Code still be made, if doing so will not de
h the "Send Hold Timer Expired" error code is still made, if doing so will not d lay closing the BGP connection.
elay closing the BGP connection. Meanwhile, an error message is logged in the local system.
Meanwhile an error message is logged into the local system. </t>
</t> <t>
<t> Other mechanisms can be used as well, for example, BGP speakers <bcp14>SHO
Other mechanisms can be used as well, for example BGP speakers SHOULD prov ULD</bcp14> provide this reason ("Send Hold Timer Expired") as part of their ope
ide this reason as part of their operational state; e.g. bgpPeerLastError in the rational state (for example, bgpPeerLastError in the BGP MIB <xref target="RFC42
<xref target="RFC4273">BGP MIB</xref>. 73"/>).
</t> </t>
</section> </section>
<section>
<section title="Security Considerations"> <name>Security Considerations</name>
<t> <t>
This specification does not change BGP's security characteristics. Impleme nting the BGP <tt>SendHoldTimer</tt> as specified in this document will enhance network resilience by terminating connections with malfunctioning or overwhelmed remote peers. This specification does not change BGP's security characteristics. Impleme nting the BGP <tt>SendHoldTimer</tt> as specified in this document will enhance network resilience by terminating connections with malfunctioning or overwhelmed remote peers.
</t> </t>
</section> </section>
<section>
<section title="IANA Considerations"> <name>IANA Considerations</name>
<t> <t>
IANA has registered code 8 for "Send Hold Timer Expired" in the "BGP Error IANA has registered value 8 for "Send Hold Timer Expired" in the "BGP Erro
(Notification) Codes" registry in the "Border Gateway Protocol (BGP) Parameters r (Notification) Codes" registry within the "Border Gateway Protocol (BGP) Param
" registry group. eters" registry group.
</t> </t>
</section> </section>
<section>
<section title="Acknowledgements"> <name>Acknowledgements</name>
<t> <t>
The authors would like to thank The authors would like to thank
William McCall, <contact fullname="William McCall"/>,
Theo de Raadt, <contact fullname="Theo de Raadt"/>,
John Heasley, <contact fullname="John Heasley"/>,
Nick Hilliard, <contact fullname="Nick Hilliard"/>,
Jeffrey Haas, <contact fullname="Jeffrey Haas"/>,
Tom Petch, <contact fullname="Tom Petch"/>,
Susan Hares, <contact fullname="Susan Hares"/>,
Keyur Patel, <contact fullname="Keyur Patel"/>,
Ben Maddison, <contact fullname="Ben Maddison"/>,
Claudio Jeker, <contact fullname="Claudio Jeker"/>, and
and <contact fullname="John Scudder"/>
John Scudder
for their helpful review of this document. for their helpful review of this document.
</t> </t>
</section> </section>
</middle>
</middle> <back>
<back>
<references title="Normative References">
<?rfc include="reference.RFC.2119.xml"?>
<?rfc include="reference.RFC.4271.xml"?>
<?rfc include="reference.RFC.8174.xml"?>
<reference anchor="RFC9293" target="https://www.rfc-editor.org/info/rfc9293"
>
<front>
<title>Transmission Control Protocol (TCP)</title>
<author fullname="Wesley M. Eddy" initials="W." surname="Eddy" role="edi
tor"/>
<date month="August" year="2022"/>
<abstract>
<t>This document specifies the Transmission Control Protocol (TCP). TC
P is an important transport-layer protocol in the Internet protocol stack, and i
t has continuously evolved over decades of use and growth of the Internet. Over
this time, a number of changes have been made to TCP as it was specified in RFC
793, though these have only been documented in a piecemeal fashion. This documen
t collects and brings those changes together with the protocol specification fro
m RFC 793. This document obsoletes RFC 793, as well as RFCs 879, 2873, 6093, 642
9, 6528, and 6691 that updated parts of RFC 793. It updates RFCs 1011 and 1122,
and it should be considered as a replacement for the portions of those documents
dealing with TCP requirements. It also updates RFC 5961 by adding a small clari
fication in reset handling while in the SYN-RECEIVED state. The TCP header contr
ol bits from RFC 793 have also been updated based on RFC 3168.
</t>
</abstract>
</front>
<seriesInfo name="RFC" value="9293"/>
<seriesInfo name="DOI" value="10.17487/RFC9293"/>
</reference>
<!-- NOTE TO RFC-EDITOR:
The below reference is intended as a 'self-reference', but unsure how to
do that properly in xml2rfc
See https://mailarchive.ietf.org/arch/msg/idr/sY-om-d3kZC1ypoBXAS17NCXtXk
/
and https://mailarchive.ietf.org/arch/msg/idr/L6MinGVjHn94gRhCi2lGAQ9GoHw
/
for discussion on the concern of carrying over a literal non-reference in
to the patched target document content
-->
<reference anchor="I-D.ietf-idr-bgp-sendholdtimer" target="https://datatracker
.ietf.org/doc/html/draft-ietf-idr-bgp-sendholdtimer">
<front>
<title>Border Gateway Protocol 4 (BGP-4) Send Hold Timer</title>
<author fullname="Job Snijders" initials="J." surname="Snijders">
<organization>Fastly</organization>
</author>
<author fullname="Ben Cartwright-Cox" initials="B." surname="Cartwright-Co
x">
<organization>Port 179 Ltd</organization>
</author>
<author fullname="Yingzhen Qu" initials="Y." surname="Qu">
<organization>Futurewei Technologies</organization>
</author>
<date />
<abstract>
<t>This document defines the SendHoldtimer, along with the SendHoldTimer
_Expires event, for the Border Gateway Protocol (BGP) Finite State Machine (FSM)
. Implementation of the SendHoldTimer helps overcome situations where a BGP conn
ection is not terminated after the local system detects that the remote system i
s not processing BGP messages. This document specifies that the local system sho
uld close the BGP connection and not solely rely on the remote system for connec
tion closure when the SendHoldTimer expires. This document updates RFC4271.</t>
</abstract>
</front>
<seriesInfo name="Internet-Draft" value="draft-ietf-idr-bgp-sendholdtimer"/>
</reference>
</references>
<references title="Informative References">
<reference anchor="openbgpd" target="https://marc.info/?l=openbsd-tech&amp;m
=160820754925261&amp;w=2">
<front>
<title>bgpd send side hold timer</title>
<author fullname="Claudio Jeker"><organization>OpenBSD</organization></a
uthor>
<date month="December" year="2020" />
</front>
</reference>
<reference anchor="frr" target="https://github.com/FRRouting/frr/pull/11225"
>
<front>
<title>bgpd: implement SendHoldTimer</title>
<author fullname="David Lamparter"><organization>NetDEF</organization></
author>
<date month="May" year="2022" />
</front>
</reference>
<reference anchor="neo-bgp" target="https://bgp.tools/kb/bgp-support">
<front>
<title>What does bgp.tools support</title>
<author fullname="Ben Cartwright-Cox"><organization>Port 179 Ltd</organi
zation></author>
<date month="Aug" year="2022" />
</front>
</reference>
<reference anchor="BIRD" target="https://gitlab.nic.cz/labs/bird/-/commit/bc
f2327425d4dd96f381b87501cccf943bed606e">
<front>
<title>BIRD Internet Routing Daemon</title>
<author fullname=" Katerina Kubecova"><organization>CZ.NIC</organization
></author>
<date month="Oct" year="2023" />
</front>
</reference>
<reference anchor="bgpzombies" target="https://labs.ripe.net/author/romain_f
ontugne/bgp-zombies/">
<front>
<title>BGP Zombies</title>
<author fullname="Romain Fontugne"><organization>IIJ Research Lab</organ
ization></author>
<date month="april" year="2019" />
</front>
</reference>
<?rfc include="reference.RFC.4273.xml"?>
</references>
<section title="Implementation status - RFC EDITOR: REMOVE BEFORE PUBLICATION"
>
<t>
This section records the status of known implementations of the protocol d
efined by this specification at the time of posting of this Internet-Draft, and
is based on a proposal described in RFC 7942.
The description of implementations in this section is intended to assist t
he IETF in its decision processes in progressing drafts to RFCs.
Please note that the listing of any individual implementation here does no
t imply endorsement by the IETF.
Furthermore, no effort has been spent to verify the information presented
here that was supplied by IETF contributors.
This is not intended as, and must not be construed to be, a catalog of ava
ilable implementations or their features.
Readers are advised to note that other implementations may exist.
</t>
<t> <references>
According to RFC 7942, "this will allow reviewers and working groups to as <name>References</name>
sign due consideration to documents that have the benefit of running code, which <references>
may serve as evidence of valuable experimentation and feedback that have made t <name>Normative References</name>
he implemented protocols more mature. <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.21
It is up to the individual working groups to use this information as they 19.xml"/>
see fit". <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.42
</t> 71.xml"/>
<xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.81
74.xml"/>
<xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.92
93.xml"/>
</references>
<references>
<name>Informative References</name>
<t> <reference anchor="bgpzombies" target="https://labs.ripe.net/author/roma
<list style="symbols"> in_fontugne/bgp-zombies/">
<t> <front>
OpenBGPD <xref target="openbgpd"/> <title>BGP Zombies</title>
</t> <author fullname="Romain Fontugne">
</list> <organization>IIJ Research Lab</organization>
<list style="symbols"> </author>
<t> <date month="April" year="2019"/>
FRRouting <xref target="frr"/> </front>
</t> </reference>
</list>
<list style="symbols">
<t>
neo-bgp (bgp.tools) <xref target="neo-bgp"/>
</t>
</list>
<list style="symbols">
<t>
BIRD <xref target="BIRD"/>
</t>
</list>
</t>
<t>
Patches to recognize error code 8 were merged into OpenBSD's and the-tcpdu
mp-group's tcpdump implementations.
</t>
</section>
</back> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.4 273.xml"/>
</references>
</references>
</back>
</rfc> </rfc>
 End of changes. 33 change blocks. 
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