One document matched: draft-ashesh-bfd-stability-03.xml
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<rfc category="std" docName="draft-ashesh-bfd-stability-03.txt"
ipr="trust200902">
<front>
<title abbrev="BFD Stability">BFD Stability</title>
<author fullname="Ashesh Mishra" initials="A" surname="Mishra">
<organization>Ciena Corporation</organization>
<address>
<postal>
<street>3939 North 1st Street</street>
<city>San Jose</city>
<region>CA</region>
<code>95134</code>
<country>USA</country>
</postal>
<phone/>
<email>mishra.ashesh@gmail.com</email>
<uri>www.ciena.com</uri>
</address>
</author>
<author fullname="Mahesh Jethanandani" initials="M" surname="Jethanandani">
<organization>Ciena Corporation</organization>
<address>
<postal>
<street>3939 North 1st Street</street>
<city>San Jose</city>
<region>CA</region>
<code>95134</code>
<country>USA</country>
</postal>
<phone/>
<facsimile/>
<email>mjethanandani@gmail.com</email>
<uri>www.ciena.com</uri>
</address>
</author>
<author fullname="Ankur Saxena" initials="A" surname="Saxena">
<organization>Ciena Corporation</organization>
<address>
<postal>
<street>3939 North 1st Street</street>
<city>San Jose</city>
<region>CA</region>
<code>95134</code>
<country>USA</country>
</postal>
<phone/>
<facsimile/>
<email>ankurpsaxena@gmail.com</email>
<uri/>
</address>
</author>
<author fullname="Santosh Pallagatti" initials="S" surname="Pallagatti">
<organization>Juniper Networks</organization>
<address>
<postal>
<street>Juniper Networks, Exora Business Park</street>
<city>Bangalore</city>
<region>Karnataka</region>
<code>560103</code>
<country>India</country>
</postal>
<phone>+</phone>
<facsimile/>
<email>santoshpk@juniper.net</email>
<uri/>
</address>
</author>
<author fullname="Mach Chen" initials="M" surname="Chen">
<organization>Huawei</organization>
<address>
<postal>
<street/>
<city/>
<region/>
<code/>
<country/>
</postal>
<phone/>
<facsimile/>
<email>mach.chen@huawei.com</email>
<uri/>
</address>
</author>
<author initials="P." surname="Fan" fullname="Peng Fan">
<organization>China Mobile</organization>
<address>
<postal>
<street>32 Xuanwumen West Street</street>
<city>Beijing</city>
<region>Beijing</region>
<country>China</country>
</postal>
<email>fanp08@gmail.com</email>
</address>
</author>
<date day="10" month="June" year="2015"/>
<area>Network</area>
<workgroup>Routing Working Group</workgroup>
<keyword>Internet-Draft</keyword>
<abstract>
<t>This document describes extensions to the Bidirectional Forwarding
Detection (BFD) protocol to measure BFD stability. Specifically, it
describes a mechanism for detection of BFD frame loss.</t>
</abstract>
<note title="Requirements Language">
<t>The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in <xref
target="RFC2119">RFC 2119</xref>.</t>
</note>
</front>
<middle>
<section title="Introduction">
<t>The Bidirectional Forwarding Detection (BFD) protocol operates by
transmitting and receiving control frames, generally at high frequency,
over the datapath being monitored. In order to prevent significant data
loss due to a datapath failure, the tolerance for lost or delayed frames
(the Detection Time as described in RFC 5880) is set to the smallest
feasible value. </t>
<t>This document proposes a mechanism to detect delayed or lost frames in a BFD
session in addition to the datapath fault detection mechanisms of BFD.
Such a mechanism presents significant value with the ability to measure
the stability of BFD sessions and provides data to the operators.</t>
<t>This document does not propose BFD extension to measure data traffic loss or delay
on a link or tunnel and the scope is limited to BFD frames.</t>
</section>
<section title="Use cases">
<t>Legacy BFD can't detect any BFD frame delay or loss if delay or loss does not last for dead interval.
Frequent delay or loss of BFD frames could potentially lead to flap.</t>
<t>It may be possible that network has healthy link or tunnel but only BFD frames are getting dropped or delayed.
This potentially leads to network convergence or use of suboptimal path when fast reroute is enabled such as:
<list style="empty">
<t>Routing protocols with LFA enabled, BFD is used to monitor the link.</t>
<t>Aggregate Ethernet with BFD to monitor each member link.</t>
<t>Primary and protected tunnels with BFD to monitor tunnels.</t>
</list>
This proposal will help BFD session to give more information to operator about the health of BFD session
that could be used to avoid BFD session flap with faulty BFD path on a healthy link or tunnel.</t>
<t>In a faulty link or tunnel scenario operator can use BFD health information to dynamically run delay and loss
measurement OAM protocol (CFM or LM-DM) to further isolate the issue.</t>
</section>
<section title="BFD Null-Authentication TLV">
<t>The functionality proposed for BFD stability measurement is achieved
by appending the Null-Authentication TLV to the BFD control frame.</t>
<t>The Null-Authentication TLV (called 0-Auth in this document) extends
the existing BFD Authentication TLV structure by adding a new Auth-Type
of <IANA Assigned>. This TLV carries the Sequence Number for frame
loss measurement and optional sender timestmap.</t>
<figure>
<artwork><![CDATA[
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Auth Type | Auth Len | Auth Key ID | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender timestmap |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+]]></artwork>
</figure>
<t>where:</t>
<t>Auth Type: The Authentication Type, which in this case is <IANA
assigned> (Null Authentication).</t>
<t>Auth Len: The length of the Authentication Section, in bytes. Length depends on the Auth Key ID. </t>
<t>Auth Key ID: The Authentication Key ID is used to control optional feature. Vales are:
<figure>
<artwork><![CDATA[
0 -- BFD loss measurement
1 -- BFD loss and delay measurement
2-255 -- Reserved for future use]]></artwork>
</figure>
when value is set to 0 then last 4 bytes of this TLV MUST not be present in the packet, Auth Len MUST
be set to 8 bytes. When set to 1 Auth Len MUST be set to 12.
</t>
<t>Sequence Number: This indicates the sequence number for this packet
and MUST be present in every 0-Auth TLV. This value is incremented by 1
for every frame transmitted while the session state is UP. A value of 0
indicates a request by sender to reset the sequence number correlation
logic at the receiver. The first frame transmitted by the sender MAY set
this field to 0.</t>
<t>Sender timestamp: MUST be set to time when packet is about to leave
the sender system. Sender system MAY time stamp this as close to wire when
packet is about to leave system. Details of how sender system timestamps is out of
the scope of this document.</t>
</section>
<section title="Theory of Operations">
<t>This mechanism allows operator to measure the loss and delay of BFD CC frames.</t>
<section title="Loss Measurement">
<t>This measurement counts the number of BFD control frames missed at
the receiver due to a transient change in the network such as
congestion. Frame-loss is detected by comparing the Sequence Number
field in the 0-Auth TLV in successive BFD CC frames. The Sequence Number
in each successive control frame generated on a BFD session by the
transmitter is incremented by one.</t>
<t>The first BFD 0-Auth TLV processed by the receiver that has a
non-zero sequence number is used for bootstrapping the logic. Each
successive frame after this is expected to have a Sequence Number that
is one greater than the Sequence Number in the previous frame.</t>
<t>BFD being aggressive protocol, sequence number may wrap to 0 within few hundred days.
Sender MUST ensure that when sequence number is wrapped, it starts with value 1. Receiver
MUST accept this BFD packet and adjust his next anticipated sequence number.</t>
</section>
<section title="Delay Measurement">
<t>Delay measurement can be done in two ways.
<list style="empty">
<t>Using sender timestamp in 0-Auth TLV:
<list style="empty">
<t>If AuthKey ID in 0-Auth TLV is set to 1 then sender timestamp MUST be set.
Delay measurement is the difference between the sender timestamp on any two
consecutive BFD CC frames that carry the 0-Auth TLV with AuthKey ID set to 1 for a session.
This is a key metric to determine transient changes in stability of BFD transmission
engine or to determine the systems capability of handling the existing load. A
significant deviation from the negotiated transmission interval on the local node
indicates potential instabilities in the BFD transmission engine. Based on the timestamp measurements,
the operator MAY take action to configure the system to maintain normal operation of the node.</t>
<t>Similar delay measurements on the receiver can be made using timestamps in the meta data when packet
is received. In conjunction with sender delay measurements, these can indicate delays caused by data-path.
While a constant delay may not be indicator of instability, large transient delays can decrease the
BFD session stability significantly.</t>
</list>
</t>
</list>
<list style="empty">
<t>Using centralized controller:
<list style="empty">
<t>When AuthKey ID in 0-Auth TLV is set to 0 then sender timestmap will not be present in the packet.
Peers MAY still choose to do delay measurement by sending their packet sent timestamps to central control unit.
Central control unit MAY gather all timestamp information and can do delay calculation for a BFD session.
Details of how BFD component sends timestamps to central unit is outside the scope of this document.</t>
</list>
</t>
</list>
</t>
</section>
</section>
<section title="IANA Requirements">
<t>IANA is requested to assign new Auth-Type for the Null-Authentication
TLV for BFD Stability Measurement. The following number is
suggested.</t>
<t>Value Meaning</t>
<t>6 Null-Authentication TLV</t>
</section>
<section title="Security Consideration">
<t>Other than concerns raised in <xref target="RFC5880"/> there are no new concerns with this proposal.</t>
</section>
<section title="Contributors">
<t>
<figure>
<artwork><![CDATA[
Manav Bhatia
manav@ionosnetworks.com
Ionos Networks
Bangalore, India]]></artwork>
</figure>
</t>
</section>
<section title="Acknowledgements">
<t>Authors would like to thank Nobo Akiya, Jeffery Haas, Peng Fan, Dileep Singh, Basil Saji, Sagar
Soni and Mallik Mudigonda who also contributed to this document.</t>
</section>
</middle>
<back>
<references title="Normative References">
<?rfc include="reference.RFC.5880"?>
<?rfc include="reference.RFC.2119"?>
</references>
</back>
</rfc>
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