One document matched: draft-xu-sfc-using-mpls-spring-01.xml
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<rfc category="info" docName="draft-xu-sfc-using-mpls-spring-01"
ipr="trust200902">
<front>
<title abbrev="">Service Function Chaining Using MPLS-SPRING</title>
<author fullname="Xiaohu Xu" initials="X.X." surname="Xu">
<organization>Huawei</organization>
<address>
<!--
<postal>
<street></street>
-->
<!-- Reorder these if your country does things differently -->
<!--
<city>Soham</city>
<region></region>
<code></code>
<country>UK</country>
</postal>
<phone>+44 7889 488 335</phone>
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<email>xuxiaohu@huawei.com</email>
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</address>
</author>
<author fullname="Zhenbin Li" initials="Z.L." surname="Li">
<organization>Huawei</organization>
<address>
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<country>UK</country>
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<phone>+44 7889 488 335</phone>
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<email>lizhenbin@huawei.com</email>
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</address>
</author>
<author fullname="Himanshu Shah" initials="H.S." surname="Shah">
<organization>Ciena</organization>
<address>
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<email>hshah@ciena.com</email>
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</address>
</author>
<author fullname="Luis M. Contreras" initials="L.M." surname="Contreras">
<organization>Telefonica I+D</organization>
<address>
<postal>
<street>Ronda de la Comunicacion, s/n</street>
<street>Sur-3 building, 3rd floor</street>
<city>Madrid,</city>
<code>28050</code>
<country>Spain</country>
</postal>
<email>luismiguel.contrerasmurillo@telefonica.com</email>
<uri>http://people.tid.es/LuisM.Contreras/</uri>
</address>
</author>
<!--
-->
<date day="" month="" year="2014"/>
<abstract>
<t>Source Packet Routing in Networking (SPRING) WG specifies a special
source routing mechanism. Such source routing mechanism can be leveraged
to realize the service path layer functionality of the service function
chaining (i.e, steering traffic through a particular service function
path) by encoding the service function path or the service function
chain information as the explicit path information. This document
describes how to leverage the MPLS-based source routing mechanism as
developed by the SPRING WG to realize the service path layer
functionality of the service function chaining.</t>
</abstract>
</front>
<middle>
<section title="Introduction">
<t>When applying a particular Service Function Chain (SFC) <xref
target="I-D.ietf-sfc-architecture"/> to the traffic selected by a
service classifier, the traffic need to be steered through an ordered
set of Service Functions (SF) in the network. This ordered set of SFs in
the network indicates the Service Function Path (SFP) associated with
the above SFC. To steer the selected traffic through an ordered list of
SFs in the network, the traffic need to be attached by the service
classifier with the information about the SFP (i.e., specifying exactly
which Service Function Forwarders (SFFs) and which SFs are to be visited
by traffic), the SFC, or the partially specified SPF which is in between
the former two extremes. Source Packet Routing in Networking (SPRING) WG
specifies a special source routing mechanism which can be used to steer
traffic through an ordered set of routers (i.e., an explicit path). Such
source routing mechanism can be leveraged to realize the service path
layer functionality of the SFC (i.e., steering traffic through a
particular SFP) by encoding the SFP, the SFC or the partially specified
SFP information as the explicit path information contained in packets.
The source routing mechanism specified by the SPRING WG can be applied
to the MPLS data plane <xref target="I-D.gredler-spring-mpls"/> <xref
target="I-D.filsfils-spring-segment-routing-mpls"/> and IPv6 data plane.
This document only describes how to leverage the MPLS-based source
routing mechanisms to realize the service path layer functionality of
the service function chaining. How to leverage the IPv6-based source
routing mechanism will be described in a separate document. Furthermore,
how to carry metadata within MPLS packet would be described in a
separate document as well.</t>
<section 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>
</section>
</section>
<section anchor="Teminology" title="Terminology">
<t>This memo makes use of the terms defined in <xref
target="I-D.filsfils-spring-segment-routing"/> and <xref
target="I-D.ietf-sfc-architecture"/>.</t>
</section>
<section anchor="Advertising" title="Solution Description">
<t><figure>
<artwork align="center"><![CDATA[ +----------------------------------------------- ----+
| SPRING Netowrks |
| +---------+ +---------+ |
| | SF1 | | SF2 | |
| +----+----+ +----+----+ |
| | | |
| (1) | (2) | (3) |
+----+-----+ ---> +----+----+ ----> +----+----+ ---> +---+---+
|Classifier+------+ SFF1 +-------+ SFF2 +-------+ D |
+----------+ +---------+ +---------+ +---+---+
| |
+----------------------------------------------------+
Figure 1: Service Function Chaining in SPRING Networks]]></artwork>
</figure></t>
<t>As shown in Figure 1, assume SFF1 and SFF2 are two MPLS-SPRING-
capable nodes. They are also Service Function Forwarder (SFF) nodes to
which two SFs (i.e., SF1 and SF2) are attached respectively. In
addition, they have allocated and advertised Segment IDs (SID) for their
locally attached SFs. In the MPLS-SPRING context, SIDs are intercepted
as MPLS labels. For example, SFF1 allocates and advertises an SID (i.e.,
SID(SF1)) for SF1 while SFF2 allocates and advertises an SID ( i.e.,
SID(SF2)) for SF2. These SIDs which are used to indicate SFs are
referred to as SF SIDs. To encode the SFP information by an MPLS label
stack, those SF SIDs as mentioned above would be interpreted as local
MPLS labels. In contrast, to encode the SFC information by an MPLS label
stack, those SF SIDs MUST be interpreted as domain-wide unique MPLS
labels. In addition, assume node SIDs for SFF1 and SFF2 are SID(SFF1)
and SID(SFF2) respectively. To simplify the illustration in this
document, those node SIDs would be interpreted as domain-wide unique
MPLS labels as well. Now assume a given traffic flow destined for
destination D is selected by the service classifier to go through a
particular SFC (i.e., {SF1, SF2}) before reaching its final destination
D. Section 3.1 and 3.2 describe two approaches of leveraging the MPLS-
based source routing mechanisms to realize the service path
functionality of the service function chaining (i.e., by encoding the
SFP information within an MPLS label stack or by encoding the SFC
information within an MPLS label stack) respectively. Since the encoding
of the partially specified SFP is just a simple combination of the
encoding of the SFP and the encoding of the SFC, this document would not
describe how to encode the partially specified SFP anymore.</t>
<section title="Encoding SFP Information by an MPLS Label Stack">
<t>Since the selected packet needs to travel through an SFC {SF1,
SF2}, the service classifier would attach a segment list {SID(SFF1),
SID(SF1), SID(SFF2), SID(SF2)} which indicates the corresponding SFP
to the packet. This segment list is actually represented by a MPLS
label stack. When the encapsulated packet arrives at SFF1, SFF1 would
know which SF should be performed according to the current top label
(i.e., SID (SF1)). Before sending the packet to SF1, the remaining
MPLS label stack (i.e., a segment list {SID(SFF2), SID(SF2)}) MUST be
stripped. After receiving the packet returned from SF1, SFF1 would
reimpose the MPLS label stack which had been stripped before to the
packet and then send it to SFF2 according to the current top label
(i.e., SID (SFF2) ). When the encapsulated packet arrives at SFF2,
SFF2 would do the similar action as what has been done by SFF1.
Provided that there was no MPLS LSP tunnel towards the next node
segment (i.e., the next SFF node identified by the current top label),
the corresponding IP-based tunnel (e.g., MPLS-in-IP/GRE tunnel <xref
target="RFC4023"/>, MPLS-in-L2TPv3 tunnel <xref target="RFC4817"/> or
MPLS-in-UDP tunnel <xref target="I-D.ietf-mpls-in-udp"/>) towards the
next node segment could be used instead. For more details about this
special usage, please refer to <xref
target="I-D.xu-spring-islands-connection-over-ip"/>. This approach of
encoding the SFP information by an MPLS label stack is transport
independent since the transport (i.e., the underlay) protocol could be
IPv4, IPv6 or even MPLS. In other words, it fully meets the
requirement of transport independence for the SFC encapsulation as
mentioned in <xref target="I-D.ietf-sfc-architecture"/>.</t>
</section>
<section title="Encoding SFC Information by an MPLS Label Stack">
<t>Since the selected packet needs to travel through an SFC (i.e.,
{SF1, SF2}), the service classifier would attach a segment list
{SID(SF1), SID(SF2)} which indicates that SFC to the packet. This
segment list is actually represented by a MPLS label stack. Since it's
known to the service classifier that SFF1 is attached with an instance
of SF1, the service classifier would therefore send the encapsulated
packet through either an MPLS LSP tunnel or an IP-based tunnel towards
SFF1. When the encapsulated packet arrives at SFF1, SFF1 would know
which SF should be performed according to the current top label (i.e.,
SID (SF1)). Before sending the packet to SF1, the remaining MPLS label
stack (i.e., a segment list {SID(SF2)}) MUST be stripped. Upon
receiving the packet returned from SF1, SFF1 would re-impose the MPLS
label stack which had been stripped before to the packet, and then
send it to SFF2 through either an MPLS LSP tunnel or an IP-based
tunnel towards SFF2 since it's known to SFF1 that SFF2 is attached
with an instance of SF2. When the encapsulated packet arrives at SFF2,
SFF2 would do the similar action as what has been done by SFF1. This
approach of encoding the SFC information by an MPLS label stack is
transport independent since the transport (i.e., the underlay)
protocol could be IPv4, IPv6 or even MPLS. In other words, it fully
meets the requirement of transport independence for the SFC
encapsulation as mentioned in <xref
target="I-D.ietf-sfc-architecture"/>.</t>
</section>
</section>
<!---->
<section anchor="Acknowledgements" title="Acknowledgements">
<t>The authors would like to thank Loa Andersson and Andrew G. Malis for
their valuable comments and suggestions on the draft.</t>
<!---->
</section>
<section anchor="IANA" title="IANA Considerations">
<t>TBD.</t>
<!---->
</section>
<section anchor="Security" title="Security Considerations">
<t>TBD</t>
<!---->
</section>
</middle>
<back>
<references title="Normative References">
&RFC2119;
<?rfc include="reference.I-D.gredler-spring-mpls"?>
<?rfc include="reference.I-D.filsfils-spring-segment-routing-mpls"?>
<?rfc include="reference.I-D.xu-spring-islands-connection-over-ip"?>
<!---->
</references>
<references title="Informative References">
<!---->
<?rfc include="reference.I-D.filsfils-spring-segment-routing"?>
<?rfc include="reference.I-D.ietf-sfc-architecture"?>
<?rfc include="reference.RFC.4023"?>
<?rfc include="reference.RFC.4817"?>
<?rfc include="reference.I-D.ietf-mpls-in-udp"?>
</references>
</back>
</rfc>
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