One document matched: draft-bryant-mpls-rfc6374-sfl-00.xml
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<rfc category="std" docName="draft-bryant-mpls-rfc6374-sfl-00"
ipr="trust200902" updates="">
<front>
<title abbrev="RFC6374 SFL">RFC6374 Synonymous Flow Labels</title>
<author fullname="Stewart Bryant" initials="S" surname="Bryant">
<organization>Cisco Systems</organization>
<address>
<email>stbryant@cisco.com</email>
</address>
</author>
<author fullname="George Swallow" initials="G" surname="Swallow">
<organization>Cisco Systems</organization>
<address>
<email>swallow@cisco.com</email>
</address>
</author>
<author fullname="Siva Sivabalan" initials="S " surname="Sivabalan">
<organization>Cisco Systems</organization>
<address>
<email>msiva@cisco.com</email>
</address>
</author>
<author fullname="Greg Mirsky" initials="G" surname="Mirsky">
<organization>Ericsson</organization>
<address>
<email>gregory.mirsky@ericsson.com</email>
</address>
</author>
<author fullname="Mach(Guoyi) Chen" initials="M" surname="Chen">
<organization>Huawei</organization>
<address>
<email>mach.chen@huawei.com</email>
</address>
</author>
<author fullname="Zhenbin(Robin) Li" initials="Z" surname="Li">
<organization>Huawei</organization>
<address>
<email>lizhenbin@huawei.com</email>
</address>
</author>
<date year="2015" />
<area>Routing</area>
<workgroup>MPLS</workgroup>
<keyword>OAM</keyword>
<keyword></keyword>
<keyword>Internet-Draf</keyword>
<abstract>
<t>This document describes a method of providing flow identification
information when making RFC6374 performance measurements. This allows
RFC6374 measurements to be made on multi-point to point LSPs and allows
the measurement of flows within an MPLS construct using RFC6374.</t>
</abstract>
</front>
<middle>
<section anchor="INTRO" title="Introduction">
<t><xref target="I-D.bryant-mpls-flow-ident"></xref> describes the
requirement for introducing flow identities when using RFC6374 <xref
target="RFC6374"></xref> packet Loss Measurements (LM). In summary
RFC6374 uses the LM packet as the packet accounting demarcation point.
Unfortunately this gives rise to a number of problems that may lead to
significant packet accounting errors in certain situations. For
example:</t>
<t><list style="numbers">
<t>Where a flow is subjected to Equal Cost Multi-Path (ECMP)
treatment packets can arrive out of order with respect to the LM
packet.</t>
<t>Where a flow is subjected to ECMP treatment, packets can arrive
at different hardware interfaces, thus requiring reception of an LM
packet on one interface to trigger a packet accounting action on a
different interface which may not be co-located with it. This is a
difficult technical problem to address with the required degree of
accuracy.</t>
<t>Even where there is no ECMP (for example on RSVP-TE, MPLS-TP LSPs
and PWs) local processing may be distributed over a number of
processor cores, leading to synchronization problems.</t>
<t>Link aggregation techniques may also lead to synchronization
issues.</t>
<t>Some forwarder implementations have a long pipeline between
processing a packet and incrementing the associated counter again
leading to synchronization difficulties.</t>
</list></t>
<t>An approach to mitigating these synchronization issue is described in
<xref target="I-D.tempia-ippm-p3m"></xref> and <xref
target="I-D.chen-ippm-coloring-based-ipfpm-framework"></xref> in which
packets are batched by the sender and each batch is marked in some way
such that adjacent batches can be easily recognized by the receiver.</t>
<t>An additional problem arises where the LSP is a multi-point to point
LSP, since MPLS does not include a source address in the packet. Network
management operations require the measurement of packet loss between a
source and destination. It is thus necessary to introduce some source
specific information into the packet to identify packet batches from a
specific source.</t>
<t>draft-bryant-mpls-sfl-framework specifies a method of encoding per
flow instructions in an MPLS label stack using a technique called
Synonymous Flow Labels (SFL) in which labels which mimic the behaviour
of other labels provide the packet batch identifiers and enable the per
batch packet accounting. This memo specifies how SFLs are used to
perform RFC6374 performance measurements.</t>
</section>
<section title="Requirements Language">
<t>The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in <xref
target="RFC2119"></xref>.</t>
</section>
<section title="RFC6374 Packet Loss Measurement with SFL">
<t>The packet format of an RFC6374 Query message using SFLs is shown in
<xref target="RFC6374MSG"></xref>.</t>
<figure anchor="RFC6374MSG" title="RFC6734 Query Packet with SFL">
<artwork><![CDATA[ +-------------------------------+
| |
| LSP |
| Label |
+-------------------------------+
| |
| Synonymous Flow |
| Label |
+-------------------------------+
| |
| |
| RFC6374 Measurement Message |
| |
| +-------------------------+ |
| | | |
| | RFC6374 Fixed | |
| | Header | |
| | | |
| +-------------------------+ |
| | | |
| | Optional SFL TLV | |
| | | |
| +-------------------------+ |
| | | |
| | Optional Return | |
| | Information | |
| | | |
| +-------------------------+ |
| |
+-------------------------------+ ]]></artwork>
</figure>
<t></t>
<t>The MPLS label stack is exactly the same as that used for the user
data service packets being instrumented except for the replacement of
the appropriate label with an SFL . The RFC6374 measurement message
consists of the three components, the RFC6374 fixed header as specified
in <xref target="RFC6374"></xref> carried over the ACH channel type
specified the type of measurement being made (currently: loss, delay or
loss and delay) as specified in RFC6374.</t>
<t>Two optional TLVs MAY also be carried if needed. The first is the SFL
TLV specified in <xref target="SFLTLVSEC"></xref>. This is used to
provide the implementation with a reminder of the SFL that was used to
carry the RFC6374 message. This is needed because a number of MPLS
implementations do not provide the MPLS label stack to the MPLS OAM
handler. This TLV is required if RFC6374 messages are sent over UDP
(draft-bryant-mpls-RFC6374-over-udp). This TLV MUST be included unless,
by some method outside the scope of this document, it is known that this
information is not needed by the RFC6374 Responder.</t>
<t>The second set of information that may be needed is the return
information that allows the responder send the RFC6374 response to the
Querier. This is not needed if the response is requested in-band and the
MPLS construct being measured is a point to point LSP, but otherwise
MUST be carried. The return address TLV is defined in RFC6378 and the
optional UDP Return Object is defined in <xref
target="I-D.ietf-mpls-rfc6374-udp-return-path"></xref>.</t>
<section anchor="SFLTLVSEC" title="RFC6374 SFL TLV">
<t>[Editor's Note we need to review the following in the light of
further thoughts on the associated signaling protocol(s). I am fairly
confident that we need all the fields other than SFL Batch and SFL
Index. The Index is useful in order to map between the label and
information associated with the FEC. The batch is part of the lifetime
management process]</t>
<t>The required RFC6374 SFL TLV is shown in <xref
target="SFLTLV"></xref>. This contains the SFL that was carried in the
label stack, the FEC that was used to allocate the SFL and the index
into the batch of SLs that were allocated for the FEC that corresponds
to this SFL.</t>
<figure anchor="SFLTLV" title="SFL TLV">
<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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |MBZ| SFL Batch | SFL Index |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SFL | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| FEC |
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
</figure>
<t>Where:</t>
<t><list hangIndent="15" style="hanging">
<t hangText="Type">Type is set to Synonymous Flow Label
(SFL-TLV).</t>
<t hangText="Length">The length of the TLV as specified in <xref
target="RFC6374"></xref>.</t>
<t hangText="MBZ">MUST be sent as zero and ignored on receive.</t>
<t hangText="SFL Batch">The SFL batch that this SFL was allocated
as part of (see draft-bryant-mpls-sfl-control)</t>
<t hangText="SPL Index">The index into the list of SFLs that were
assigned against the FEC that corresponds to the SFL.</t>
<t hangText="SFL ">The SFL used to deliver this packet. This is an
MPLS label which is a component of a label stack entry as defined
in Section 2.1 of <xref target="RFC3032"></xref>.</t>
<t hangText="Reserved">MUST be sent as zero and ignored on
receive.</t>
<t hangText="FEC">The Forwarding Equivalence Class that was used
to request this SFL. This is encoded as per Section 3.4.1 of</t>
</list></t>
<t>This information is needed to allow for operation with hardware
that discards the MPLS label stack before passing the remainder of the
stack to the OAM handler. By providing both the SFL and the FEC plus
index into the array of allocated SFLs a number of implementation
types are supported.</t>
</section>
</section>
<section title="The Application of SFL to other PM Types">
<t>SFL can be used to enable other types of PM in addition to loss.
Delay, Delay Variation and Throughput may be calculated based on
measurement results collected through Loss and Delay Measurement test
sessions. Further details will be provided in a future version of this
draft.</t>
</section>
<section anchor="PC" title="Privacy Considerations">
<t>The inclusion of originating and/or flow information in a packet
provides more identity information and hence potentially degrades the
privacy of the communication. Whilst the inclusion of the additional
granularity does allow greater insight into the flow characteristics it
does not specifically identify which node originated the packet other
than by inspection of the network at the point of ingress, or inspection
of the control protocol packets. This privacy threat may be mitigated by
encrypting the control protocol packets, regularly changing the
synonymous labels and by concurrently using a number of such labels.</t>
</section>
<section anchor="SEC" title="Security Considerations">
<t>The issue noted in <xref target="PC"></xref> is a security
consideration. There are no other new security issues associated with
the MPLS dataplane. Any control protocol used to request SFLs will need
to ensure the legitimacy of the request.</t>
</section>
<section title="IANA Considerations">
<t>IANA is request to allocate a new TLV from the 0-127 range on the
MPLS Loss/Delay Measurement TLV Object Registry:</t>
<figure>
<artwork><![CDATA[ Type Description Reference
---- --------------------------------- ---------
TBD Synonymous Flow Label This]]></artwork>
</figure>
<t></t>
<t>A value of 4 is recommended.</t>
</section>
<section title="Acknowledgements">
<t>TBD</t>
</section>
</middle>
<back>
<references title="Normative References">
<?rfc include='reference.RFC.2119'?>
<?rfc include='reference.RFC.3032'?>
<?rfc include='reference.I-D.ietf-mpls-rfc6374-udp-return-path'?>
</references>
<references title="Informative References">
<?rfc include='reference.RFC.6374'?>
<?rfc include='reference.I-D.bryant-mpls-flow-ident'?>
<?rfc include='reference.I-D.tempia-ippm-p3m'?>
<?rfc include='reference.I-D.chen-ippm-coloring-based-ipfpm-framework'?>
</references>
</back>
</rfc>
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