Internet DRAFT - draft-ao-sfc-overlay
draft-ao-sfc-overlay
SFC WG T. Ao
Internet-Draft ZTE Corporation
Intended status: Standards Track G. Mirsky
Expires: January 3, 2018 ZTE Corp.
July 2, 2017
Interworking SFC network and Overlay network
draft-ao-sfc-overlay-02
Abstract
Service Function Chain (SFC) network presents a distinct network
layer. As such, it is carried over by an underlay network. The
document reviews two interworking scenarios between the SFC domain
and its underlay network - co-located and stand-alone. The document
also defines necessary interworking between stand-alone Network
Virtual Edge and Service Forwarding Function entities to ensure
proper handling of SFC traffic by the underlay network.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on January 3, 2018.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Requirements Language . . . . . . . . . . . . . . . . . . . . 3
4. Interworking Action . . . . . . . . . . . . . . . . . . . . . 3
4.1. Co-located NVE-SFF . . . . . . . . . . . . . . . . . . . 5
4.2. Stand-alone NVE-SFF . . . . . . . . . . . . . . . . . . . 5
4.2.1. Classifier-based Action . . . . . . . . . . . . . . . 5
4.2.2. SFF-based Action . . . . . . . . . . . . . . . . . . 5
4.2.3. NVE-based Action . . . . . . . . . . . . . . . . . . 6
5. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . 6
6. Security Considerations . . . . . . . . . . . . . . . . . . . 6
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
8.1. Normative References . . . . . . . . . . . . . . . . . . 6
8.2. Informative References . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
Service Function Chaining (SFC) is a technique for prescribing
differentiated traffic forwarding policies within the SFC domain.
SFC architecture has been defined in [RFC7665].
SFC traffic is transferred in overlay network, which is described in
SFC architecture document [RFC7665]. In an underlay network, Network
Virtualization Edge (NVE) maps the traffic to a tunnel according to
the inner destination address of the particular flow, then
encapsulates the packet into outer layer, specific to the underlay
network. In this document, we assume that the NVEs in overlay
network have already obtained the mapping information between NVE and
Service Functions (SFs), as described in NVO3 network framework
[RFC7365].
But the destination address of SFC traffic is the final destination
of the traffic, not the next hop of the SFC, so that NVE will not
tunnel the traffic to the next SF, but encapsulate the SFC traffic
with the NVE address connected to the destination station. So it's
important to coordinate SFC domain and corresponding underlay
network. Underlay network edge device NVE needs to know how to
forward SFC traffic, i.e., NVE should only encapsulate the SFC
traffic into the tunnel to the next hop of the SFC. This document
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analyzes how SFC domain can be coordinated with the underlay network
to ensure that SFC traffic can be forwarded properly.
2. Terminology
The document uses the terminology in defined in [RFC7665] and
[RFC7365].
NVE: Network Virtualization Edge
NSH: Network Service Header
SFC: Service Function Chain
SFF: Service Function Forwarder
SF: Service Function
SFP: Service Function Path
SFP ID: SFP Identifier
3. Requirements Language
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 BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
4. Interworking Action
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+--------------------------------------------------------------+
| |
| Transport Network |
| |
| +---------+ +---------+ +---------+ +---------+ |
+--| NVE4 |----| NVE1 +-----+ NVE2 +-----+ NVE3 +--+
+---+-----+ +----+----+ +----+----+ +----+----+
| |/ \ | |/ \ | |/ \ | |
\ /| | \ /| | \ /| | \ /|
+-----+----+ ===> +----+----+ ===> +----+----+ ===> +----+---+
|Classifier+------+ SFF1 +------+ SFF2 +------+ D |
+----------+ +----+----+ +----+----+ +----+---+
| |
+----+----+ ===> +----+----+
+ SF1 +------+ SF2 +
+----+----+ +----+----+
==> - path through overlay network
--> - path through underlay network
Figure 1: SFC and NVO Interworking
Figure 1 reflects how SFC traffic is transported by the underlay
network through Classifier, then to SF1 and SF2 to the destination at
D. Devices NVE1 through NVE4 are to encapsulate the SFC packets into
the underlay header, e.g., GENEVE [I-D.ietf-nvo3-geneve]. Once
packet addressed to the node D has been processed by Classifier it is
directed to the Service Function Path (SFP) following processing
takes place:
NVE4 encapsulates SFC packet and transports it over underlay
tunnel to NVE1;
NVE1 decapsulates the SFC packet and passes SFC packet to SFF1;
after being processed by SF1, SFC packet will be encapsulated by
NVE1 to be transported over the tunnel to NVE2;
consequently, NVE2 decapsulates the SFC packet and passes it to
SFF2;
after the packet processed by SF2, SFF2 terminates SFP and passes
user packet to NVE2;
NVE3, in turn, encapsulates the user payload packet once again and
sends over underlay tunnel to NVE3;
NVE3 is expected to decapsulate and pass the user payload to the
node D.
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In order for NVEs to transport the SFC traffic over the underlay
network through the right tunnel each NVE needs to know what's the
next hop of the SFC traffic. In the example presented in Figure 1
NVE1 needs to know that the traffic should be forwarded to SFF2 which
is the next hop of the SFC packet in this SFP. As we know, the SFC
traffic from Classifier has the destination address of D. So here is
a question, if the underlay network and SFC domain are independent,
NVE1 may tunnel the traffic to NVE3 according to the destination of
the user packet, which is D in this scenario, and then NVE3 will
forward the traffic to D, which is a wrong path for the SFC, as it
will miss the processing by the SF2. So there must be a way to
coordinate between overlay network and SFC domain, to make sure that
the transport path in the underlay network is correct.
4.1. Co-located NVE-SFF
When NVE and SFF nodes are co-located coordination between them can
be achieved through well-defined Application Programming Interface
(API). Control plane or SDN controller may signal to NVE and SFF
that SFF should notify the NVE what the next hop is, and NVE should
encapsulate the traffic to the next hop NVE according to the address
of the next hop once it finds that the next protocol is Network
Service Header (NSH).
4.2. Stand-alone NVE-SFF
In this scenario, NVE and SFF are physically separate. Hence the
coordination between NVE and SFF should be considered. Two possible
solutions are presented, one is from data plane aspect, and another
is from control plane aspect.
4.2.1. Classifier-based Action
Classifier receives traffic from the source device and classifies the
traffic, then encapsulates into NSH. When the Classifier forwards
the packet to SFF1 according to SFP ID in the SFC header, it should
identify the next hop of the SFC (SF1 for example), and before it
forwards the traffic to NVE4, the Classifier should change the
destination of the packet to be the next hop (SF1) and store the
actual destination address in the SFC header as a metadata.
4.2.2. SFF-based Action
Once SFF receives SFC packet from SF, before it forwards the SFC
traffic to NVE that the SFF is connected to, the SFF should find the
next hop with the SFP ID in the SFC header of the packet, then
replace the destination address to next hop, and store the actual
destination address in the metadata of the SFC header.
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Once SFF receives SFC traffic from NVE, before it forwards the SFC
packet to SF according to SFPID, the SFF should restore the
destination address back to the actual address that is stored in the
metadata of the SFC header.
The last SFF receives the SFC packet from SF, and finds that it is
the last hop of the SFC, and the next hop is the actual destination
address in the metadata, so it just restores the destination address
to the actual destination address.
4.2.3. NVE-based Action
NVE receives SFC packet from the Classifier and encapsulates it with
appropriate underlay network encapsulation, e.g.,GENEVE Header,
according to the destination address of the next hop. According to
the outer address header, the traffic is transmitted to the next NVE
where it is decapsulated so that it can be forwarded to the
corresponding SF. The NVE's action is the same as described in
[RFC7365]
5. Conclusions
As described above, for stand-alone deployment of SFC-NVE, SFF MUST
use destination of the next SFF in SFP when forwarding SFC packet to
NVE, SHOULD NOT use the destination address of the original user
packet.
6. Security Considerations
To be added later
7. IANA Considerations
TBD
8. References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <http://www.rfc-editor.org/info/rfc8174>.
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8.2. Informative References
[I-D.ietf-nvo3-geneve]
Gross, J., Ganga, I., and T. Sridhar, "Geneve: Generic
Network Virtualization Encapsulation", draft-ietf-
nvo3-geneve-04 (work in progress), March 2017.
[RFC7365] Lasserre, M., Balus, F., Morin, T., Bitar, N., and Y.
Rekhter, "Framework for Data Center (DC) Network
Virtualization", RFC 7365, DOI 10.17487/RFC7365, October
2014, <http://www.rfc-editor.org/info/rfc7365>.
[RFC7665] Halpern, J., Ed. and C. Pignataro, Ed., "Service Function
Chaining (SFC) Architecture", RFC 7665,
DOI 10.17487/RFC7665, October 2015,
<http://www.rfc-editor.org/info/rfc7665>.
Authors' Addresses
Ting Ao
ZTE Corporation
No.889, BiBo Road
Shanghai 201203
China
Phone: +86 21 68897642
Email: ao.ting@zte.com.cn
Greg Mirsky
ZTE Corp.
1900 McCarthy Blvd. #205
Milpitas, CA 95035
USA
Email: gregimirsky@gmail.com
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