Hybrid Hierarchical Multi-Domain Service Function chaining
draft-li-sfc-hhsfc-00
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| Authors | Guanglei Li , Guanwen Li , Taixin Li , Qi Xu , Hua-chun Zhou | ||
| Last updated | 2016-06-10 | ||
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draft-li-sfc-hhsfc-00
Service Function Chaining Guanglei Li
Guanwen Li
Taixin Li
Qi Xu
Huachun Zhou
Internet Draft Beijing Jiaotong University
Intended status: Informational June 11, 2016
Expires: December 2016
Hybrid Hierarchical Multi-Domain Service Function chaining
draft-li-sfc-hhsfc-00.txt
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Abstract
This document describes a Hybrid Hierarchical Multi-Domain Service
Function Chaining (hhSFC) architecture that extends Service Function
Chaining (SFC) to multiple domains with different technology,
administration or ownership.
The goals of Hybrid Hierarchical SFC are to reduce the complexity of
the control plane in a single domain and make the negotiation
between different domains possible.
Table of Contents
1. Introduction ................................................ 2
1.1. Scope .................................................. 3
1.2. Terminology ............................................ 4
1.3. Assumptions ............................................ 4
2. Hybrid Hierarchical Service Function Chaining ................5
2.1. Architecture ........................................... 5
2.2. Control plane .......................................... 5
2.2.1. Intra-domain .......................................5
2.2.2. Inter-domain .......................................6
2.3. Data plane ............................................. 8
2.3.1. Intra-domain .......................................8
2.3.2. Inter-domain .......................................8
3. SFC eXchange Platform ........................................8
4. Security Considerations ......................................9
5. References .................................................. 9
5.1. Normative References ....................................9
5.2. Informative References ..................................9
6. Acknowledgments ............................................ 10
1. Introduction
Service Function Chaining supports customer traffic passing through
an ordered list of functions as required.
The [I-D.ietf-sfc-nsh] creates a service plane via Network Service
Headers (NSH), which provide data-plane information to construct
service paths and transfer metadata.
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The document [I-D.ietf-sfc-control-plane] describes requirements for
conveying information between SFC control plane and data plane in a
SFC-enabled domain. The document [I-D.dolson-sfc-hierarchical]
proposes a hierarchical SFC for multiple domains, which are
controlled by a single organization and trusted by each other, and
focus on data plane. [I-D. unify-sfc-control-plane-exp] provides an
insight into a Service Function Chain (SFC) control and Network
Function Virtualization (NFV) orchestration proof of concept
implementation and experimentation in multi-domain/technology
environments, which adopts a recursive control plane, but does not
consider the business model between different virtual network
providers or infrastructure providers to support a SFC spanning
domains with different ownership.
In this document, we consider SFCs traversing different domains
owned by different organizations (e.g., ISPs) or by a single
organization with administration partitions (e.g., for purpose of
security isolation), which means an overarching orchestrator or
manager is infeasible for multi-domain SFC.
The Hybrid Hierarchical SFC combines flat distributed control plane
and centralized hierarchical control plane. A centralized recursive,
hierarchical control plane is recommended to be deployed into a
large administration domain consisting of smaller sub-domains and a
flat distributed control plane into multiple large administration
domains.
1.1. Scope
The "domain" discussed in this document is a logical concept. Domain
division depends on circumstances including but not limited to: geo-
location, technology, administration, security policy or ownership.
While a logical centralized control plane over multiple physical
domains might still be feasible with virtual network embedding, the
distributed control plane aims at those circumstances where a
centralized paradigm is inapplicable.
This document focus on control plan. [I-D.dolson-sfc-hierarchical]
gives many discussions about data plane, especially internal
boundary node (IBN) path configuration. The four methods to
manipulate NSH are still practicable in this document.
In a recursive hierarchical control plane, an upper level plane is
responsible to abstract a lower level plane's topologies and
services. A mapping element is also needed in every control plane
level. The control protocol, abstraction, mapping mechanism and
interfaces are out of this document's scope.
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In a flat distributed control plane, horizontal interfaces are used
to realize state sharing, context translation and policies
negotiation between domains. The protocol is out of this document's
scope.
1.2. Terminology
o Sub-domains: Smaller domains in a large administration/physical
domain.
o Multi-Domain Service Function Chaining A service function
chaining pass through multiple domains.
o SFC eXchange Platform: A logical entity that is used for the
negotiation between domains. It can be a trusted third-party
platform (e.g., deployed in future software defined IXP) or built
by a single owner between heterogeneous networks.
o Abstraction Element (AE) A logical entity that abstracts the
lower-level topology and services.
o Mapping Element (ME) A logical entity that map upper-level
instructions to lower-level control entities.
o Path Calculation Element (PCE): A logical entity that computes
service function paths (SFP).
o Information Base Element (IBE): A logical information base entity
that stores topology and service information acquired from the
abstraction element and provide them to the mapping element and
path calculation element.
1.3. Assumptions
We assume flexible and dynamic SFCs are based on Software Defined
Networking (SDN) and NFV that provide fine-grained packet forwarding
and decoupled network functions from hardware respectively.
Network virtualization and network function virtualization create
new business models such as service function as a service, e.g., a
third-part Software Defined IXP (SDX) between ISPs can provides a
negotiation platform to support Multi-domain SFC.
In this document, a domain consists of sub-domains, every sub-domain
has its own control plane. A single-level control plane is
impractical considering the scalability and complexity of control
plane.
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2. Hybrid Hierarchical Service Function Chaining
2.1. Architecture
Figure 1 shows an example of two-level and two-domain hybrid
hierarchical structure. In practice, there could be more levels and
domains. In every single domain, each control plane instance manages
a single level. Each control plane is agnostic about other levels of
hierarchy. Sub-domain control-planes are agnostic about control-
planes of other sub-domains. The expectations to control plane in
the document [draft-dolson-sfc-hierarchical] are satisfied.
+------------+ +------------+
| +->IBE-+ | | +->IBE-+ |
| | + v <----------------------> | + v |
| v v PCE | | v v PCE |
| AE ME<-+ | upper-level | AE ME<-+ |
+-^-+-----+-^+Control Plane +^-+------^--+
| | | | | | | |
| | | | | | | |
+---------v-+ +v----------+ +----------v+ +v----------+
| +->IBE-+ | | +->IBE-+ | | +->IBE-+ | | +->IBE-+ |
| | + v | | | + v | | | + v | | | + v |
| v v PCE | | v v PCE | | v v PCE | | v v PCE |
| AE ME<-+ | | AE ME<-+ | | AE ME<-+ | | AE ME<-+ |
+--+--------+ +---^-------+ +---^-------+ +---^-------+
^ | lower-level | |
| | Control Plane | |
+-----+-------+ +---v---------+ +----v--------+ +--v---------+
| Data Plane | | Data Plane | | Data Plane | | Data Plane|
| | | | | | | |
| Sub-Domain | | Sub-Domain | | Sub-Domain | | Sub-Domain|
+-------------+ +-------------+ +-------------+ +------------+
Figure 1: Architecture
2.2. Control plane
2.2.1. Intra-domain
Several important elements are required in every level control plane
to realize intra-domain global optimization.
Abstraction Elements abstracts lower-level topology, service and
resource. Each level control plane compute service function paths
according to the information it acquired. For an upper-level control
plane in a domain, the path computation should concern inter-
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subdomain optimization in a centralized way. For a lower-level
control plane, it only cares about the governed sub-domain.
Mapping Elements are responsible to translate the upper-level
instructions, which could contain abstracted services requirements,
service quality and overlay forwarding behaviors, to the lower-level
control instances.
Each level control plane has its own Information Base Elements.
Abstraction elements create, update or delete the information in
Information Base Elements. The information is utilized by Mapping
Elements and Path Calculation Elements.
2.2.2. Inter-domain
Horizontal interfaces should be deployed in the top level control
plane to realize inter-domain communication. State sharing, context
translation and policies negotiation are realized by horizontal
interfaces.
Considering the circumstance that domains owned by different ISPs
connected by the Internet eXchange Ports, which could be a datacenter
implemented SDN technology in the future, a SFC eXchange Platform
(SXP) was proposed to support rich business models between different
organizations. Their distributed, multi-domain nature makes it
possible to enable a highly customized multi-domains SFC.
Figure 2 shows a SFC eXchange Platform connecting three different
domains. Figure 3 shows an overview of layered domains and SFC
eXchange Platform. In a SaaS business model, inter-domain path
computation can be driven by service agreements. Horizontal
interfaces should be designed between domains and SFC eXchange
Platform. Figure 4 shows domains connected by distributed SFC
eXchange Platform. SFC eXchange Platforms server as brokers, which
orchestrate multi-domains SFC in a distributed way.
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+-------------------+
| +------+ +------+ |
| |Sub | |Sub | |
| |Domain| |Domain| |
| +------+ +------+ |
| Domain 2 |
+--------> +------+ +------+ |
+-------------------+ | | |Sub | |Sub | |
| +------+ +------+ | | | |Domain| |Domain| |
| |Sub | |Sub | | | | +------+ +------+ |
| |Domain| |Domain| | +------v--+ +-------------------+
| +------+ +------+ | |SFC |
| Domain 1 | |eXchange | +-------------------+
| +------+ +------+ <---->Platform | | +------+ +------+ |
| |Sub | |Sub | | | <-----> |Sub | |Sub | |
| |Domain| |Domain| | +---------+ | |Domain| |Domain| |
| +------+ +------+ | | +------+ +------+ |
+-------------------+ | Domain 3 |
| +------+ +------+ |
| |Sub | |Sub | |
| |Domain| |Domain| |
| +------+ +------+ |
+-------------------+
Figure 2: Multiple SFC domains connected by a SFC eXchange Platform
+-------------------+ +-------------------+
| Domain 1 | | Domain 2 |
| +---------------+ | | +---------------+ |
| | SFC <---+ +------------------+ +---> SFC | |
| |Control Plane | | | | SFC eX Platform | | | | Control Plane| |
| |Orchestrator | | | | +--------------+ | | | | Orchestrator | |
| |SDN Controler | | +---> Negotiation <---+ | | SDN Controler| |
| +---------------+ | | | Orchestrator | | | +---------------+ |
| | | +--------------+ | | |
| +---------------+ | | | | | | +---------------+ |
| | | | | |SDN Controller| | | | | |
| | Data Plane | | | +--------------+ | | | Data Plane| |
| | <-----> | Data Plane | <-----> | |
| +---------------+ | | +--------------+ | | +---------------+ |
+-------------------+ +------------------+ +-------------------+
Figure 3: Service Function Chaining Exchanging Platform
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+-------+ +-------+ +-------+
| | +--------+ | | +--------+ | |
| | | SFC | | | | SFC | | |
|Domains<--->eXchange<--->Domains<--->eXchange<--->Domains|
| | |Platform| | | |Platform| | |
+-------+ +--------+ +-------+ +--------+ +-------+
Figure 4: Distributed SFC eX Platforms
2.3. Data plane
2.3.1. Intra-domain
The discussion about SFC data plane components in top levels and
lower levels in the document [draft-dolson-sfc-hierarchical] can be
applied in the recursive hierarchical domain defined by this
document.
The document [draft-dolson-sfc-hierarchical] proposes four methods
to restore packets to original upper-level after exiting a path in
the sub-domain, including flow-stateful IBN, encoding upper-level
paths in metadata, using unique paths per upper-level path and
nesting upper-level NSH within lower-level NSH, which are also
feasible.
2.3.2. Inter-domain
When packets go out of a domain, the inter-domain NSH should be
added. Encoding inter-domain path in metadata or using unique path
is recommended to manipulate inter-domain NSH.
When domains are connected by SDN-enabled SFC eXchange Platforms,
which act as SFFs for Multi-domain SFC, the SFC eXchange Platforms
will forwarding traffics according to the inter-domain Service Path
Identifier (SPI).
3. SFC eXchange Platform
The inter-domain traffic classify rules should be negotiated and
decided by administrators of each domain with service agreements and
policies. Distributed SFC eXchange Platforms select the service
function location from multiple candidate domains and serves as
brokers orchestrating a Multi-Domain SFC.
As a trusted third-party platform, the SFC eXchange platform may not
orchestrate the Multi-Domain SFC directly. In other words, it only
exchanges and collect domains' service states and policies. Every
domain can decide their own multi-domain SFP according to the states
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and agreements. The SFC eXchange Platform also implements the
negotiation results and decisions for domains, such as flow-specific
peering.
Based on the SFC eXchange Platform, rich business models may appear,
such as competitive models for service functions. Service providers
may compete to provide high availability and bandwidth to attract
traffic and increase customer acquisition.
Dynamic and context aware Multi-domain SFC is also achievable
relaying on the exchange platform. For example, if a mobile user's
location is added in a context header at local SFC-enabled sub-
domain ingress node, when it moves to a new locations, a new Multi-
domain SFP with better delay performance can be applied according to
the new location.
4. Security Considerations
Authentication mechanism must be applied between intra-domain
control plane levels and inter-domain control elements. Lower-level
control plane elements must ignore any instructions from
authenticated upper-level control plane elements.
If SFC eXchange Platforms are implemented, the access to this
platform must be authenticated.
5. References
5.1. Normative References
[RFC7665] Halpern, J., Ed. and C. Pignataro, Ed., "Service Function
Chaining (SFC) Architecture", RFC 7665, DOI
10.17487/RFC7665, October 2015.
5.2. Informative References
[I-D.ietf-sfc-nsh] Quinn, P. and U. Elzur, "Network Service Header",
draft-ietf-sfc-nsh-04 (work in progress), March 2016.
[I-D.ietf-sfc-control-plane] Li, H., Wu, Q., Huang, O., Boucadair,
M., Jacquenet, C., Haeffner, W., Lee, S., Parker, R.,
Dunbar, L., Malis, A., Halpern, J., Reddy, T., and P.
Patil, "Service Function Chaining (SFC) Control Plane
Components & Requirements", draft-ietf-sfc-control-plane-
06 (work in progress), May 2016.
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[I-D.dolson-sfc-hierarchical] Dolson, D., Homma, S., Lopez, D.,
Boucadair, M., and D. Liu, "Hierarchical Service Function
Chaining", draft-dolson-sfc-hierarchical-05 (work in
progress), Mar 2016
[I-D.unify-sfc-control-plane-exp] Szabo, R. and B. Sonkoly, "SFC
Control Plane Experiment: UNIFYed Approach", draft-unify-
sfc-control-plane-exp-00, March 2016.
[Software Defined internet exchange] Gupta A, Vanbever L, Shahbaz M,
et al. Sdx: A software defined internet exchange. ACM
SIGCOMM Computer Communication Review, 2015.
[MD2-NFV] Rosa R V, Silva Santos M A, Esteve Rothenberg C. Md2-nfv:
The case for multi-domain distributed network functions
virtualization. Networked Systems (NetSys), 2015
International Conference and Workshops on.
6. Acknowledgments
The work in this document was supported by National High Technology
of China ("863 program") under Grant No.2015AA015702.
Authors' Addresses
Guanglei Li
Beijing Jiaotong University
Beijing, 100044, P.R. China
Email: 15111035@bjtu.edu.cn
Guanwen Li
Beijing Jiaotong University
Beijing, 100044, P.R. China
Email: 14120079@bjtu.edu.cn
Taixin Li
Beijing Jiaotong University
Beijing, 100044, P.R. China
Email: 14111040@bjtu.edu.cn
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Qi Xu
Beijing Jiaotong University
Beijing, 100044, P.R. China
Email: 15111046@bjtu.edu.cn
Huachun Zhou
Beijing Jiaotong University
Beijing, 100044, P.R. China
Email: hchzhou@bjtu.edu.cn
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