Internet Research Task Force (IRTF) S. Lee
Internet-Draft ETRI
Intended status: Informational S. Pack
Expires: November 19, 2015 KU
M-K. Shin
ETRI
E. Paik
KT
May 18, 2015
Resource Management in Service Chaining
draft-irtf-nfvrg-resource-management-service-chain-00
Abstract
This document specifies problem definition and use cases of NFV
resource management in service chaining for path optimization,
traffic optimization, failover, load balancing, etc. It further
describes design considerations and relevant framework for the
resource management capability that dynamically creates and updates
network forwarding paths (NFPs) considering resource constraints of
NFV infrastructure.
Status of This Memo
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This Internet-Draft will expire on November 19, 2015.
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document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Resource management in service chain . . . . . . . . . . . . 4
3.1. Use cases . . . . . . . . . . . . . . . . . . . . . . . . 4
3.2. Design considerations . . . . . . . . . . . . . . . . . . 6
3.3. Framework . . . . . . . . . . . . . . . . . . . . . . . . 7
4. Applicability to SFC . . . . . . . . . . . . . . . . . . . . 7
4.1. Related works in IETF SFC WG . . . . . . . . . . . . . . 7
4.2. Integration in SFC control-plane architecture . . . . . . 8
5. Security Considerations . . . . . . . . . . . . . . . . . . . 9
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
7.1. Normative References . . . . . . . . . . . . . . . . . . 9
7.2. Informative References . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction
Network Functions Virtualisation (NFV) [ETSI-NFV-WHITE] offers a new
way to design, deploy and manage network services. The network
service can be composed of one or more network functions and NFV
relocates the network functions from dedicated hardware appliances to
generic servers, so they can run in software. Using these
virtualized network functions (VNFs), one or more VNF forwarding
graph (VNF-FG) can be associated to the network service, each of
which describes a network connectivity topology, by referencing VNFs
and Virtual Links that connect them. One or more network forwarding
paths (NFPs) can be built on top of such a topology, each defining an
ordered sequence of VNFs and Virtual Links to be traversed by traffic
flows matching certain criteria.
The performance or state of the NFP depends on the ones of underlying
NFVI resources including VNF instances (VNF-Is) and VLs. For
example, if one of the VNF instances in a NFP gets failed, the whole
network service using the NFP also gets failed. Thus, the VNF
instances per NFP need to be carefully selected at VNF-FG
instantiation or dynamically replaced by other VNF instances at run-
time for better performance and resilience of the NFP.
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The resource placement problem in service chains matters not only to
the quality of NFPs but also to the optimized use of NFVI resources.
For example, if some of the VNF instances and VLs are selected to
constitute a NFP but the others are not, the processing and bandwidth
burden will converge on those VNF instances and VLs, which results in
scalability problem.
This document addresses resource management problem in service
chaining to optimize the NFP quality and resource usage. It provides
the relevant use cases of the resource management such as traffic
optimization, failover, load balancing and further describes design
considerations and relevant framework for the resource management
capability that dynamically creates and updates NFPs considering
resource state of VNF instances.
This document mainly focuses on the resource capability in the ETSI
NFV framework [ETSI-NFV-ARCH] but also studies its applicability to
the control plane of SFC architecture [I-D.ietf-sfc-architecture].
2. Terminology
This document uses the following terms and most of them were
reproduced from [ETSI-NFV-TERM].
o Network Functions (NF): A functional building block within a
network infrastructure, which has well-defined external interfaces
and a well-defined functional behavior.
o Network service: A composition of network functions and defined by
its functional and behavioural specification.
o NFV Framework: The totality of all entities, reference points,
information models and other constructs defined by the
specifications published by the ETSI ISG NFV.
o Virtualised Network Function (VNF): An implementation of an NF
that can be deployed on a Network Function Virtualisation
Infrastructure (NFVI).
o NFV Infrastructure (NFVI): The NFV-Infrastructure is the totality
of all hardware and software components which build up the
environment in which VNFs are deployed.
o NF Forwarding Graph: A graph of logical links connecting NF nodes
for the purpose of describing traffic flow between these network
functions.
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o VNF Forwarding Graph (VNF-FG): A NF forwarding graph where at
least one node is a VNF.
o Virtual Link: A set of connection points along with the
connectivity relationship between them and any associated target
performance metrics (e.g. bandwidth, latency, QoS). The Virtual
Link can interconnect two or more entities (VNF components, VNFs,
or PNFs).
o Scaling: Ability to dynamically extend/reduce resources granted to
the Virtual Network Function (VNF) as needed.
3. Resource management in service chain
The goal of the resource management is to optimize the quality of
network services and resource usage of NFVI. To meet this goal, NFPs
of the network services need to consider the state of NFV resources
(such as VNF instances or virtual links) at construction. The NFPs
also need to dynamically adapt to the changes of the resource state
at run-time, such as availability, load, and topological locations of
VNF instances; latency and bandwidth of virtual links. The
adaptation of NFPs can be executed by monitoring the resource state
of VNF instances and VLs and replacing the original VNF instances of
the NFP with new VNF instances that constitute a NFP with better
performance. This functionality can be a part of Orchestrator
functional building block in the NFV framework [ETSI-NFV-MANO] but it
needs further study.
3.1. Use cases
In this section, several (but not exhausted) use cases for resource
management in service chaining are provided: fail-over, path
optimization, traffic optimization, load balancing, and energy
efficiency.
Fail-over
When one of VNF instances in a NFP gets failed to run due to failure
of its VM or underlying network, the whole chain of network service
also gets failed. For service continuity, the failure of VNF
instance needs to be detected and the failed one needs to be replaced
with the other one which is available to use. Figure 1 presents an
example of the fail-over use case. A network service is defined as a
chain of VNF-A and VNF-B; and the service chain is instantiated with
VNF-A1 and VNF-B1 which are instances of VNF-A and VNF-B
respectively. In the meantime, failure of VNF-B1 is detected so that
VNF-B2 replaces the failed one for fail-over of the NFP.
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+--------+ +--------+
| VNF-B2 | #| VNF-B2 |###
+--------+ +--------+ +--------+ # +--------+
###| VNF-A1 | _|_ ###| VNF-A1 |# _|_
+--------+ (___) +--------+ (___)
___/ # / \ \ ___/ / \
(___)+---#------+ + ===} (___)+----------+ +
# \ ___ / / \ ___ /
# (___) (___)
# | |
# +--------+ +--------+
######| VNF-B1 |### (failure)--> | VNF-B1 |
+--------+ +--------+
### NFP
Figure 1: A fail-over use case
Path optimization
Traffic for a network service traverses all of the VNF instances and
the connecting VLs given by a NFP to reach a target end point. Thus,
quality of the network service depends on the resource constraints
(e.g., processing power, bandwidth, topological locations, latency)
of VNF instances and VLs. In order to optimize the path of the
network service, the resource constraints of VNF instances and VLs
need to be considered at constructing NFPs. Since the resource state
may vary in time during the service, NFPs also need to adapt to the
changes of resource constraints of the VNF instances and VLs by
monitoring and replacing them at run-time.
Traffic optimization
A network operator may provide multiple network services with
different VNF-FGs and different flows of traffic traverse between
source and destination end-points along the VNF-FGs. For efficiency
of network management resource usage, the NFPs need to be built as to
localize the traffic flows or as to avoid bottleneck links shared by
multiple traffic flows. In this case, multiple NFV instances of
different NFPs need to be considered together at constructing a new
NFP or adapting one.
Load balancing
A single VNF instances may be shared by multiple traffic flows of the
same of different network services. In order to avoid bottleneck
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points due to overloaded NFV instances, NFPs need to be constructed
or maintained to distribute workloads of the shared VNF instances.
Energy efficiency
Energy efficiency in the network is getting important to reduce
impact on the environment so that energy consumption of VNF instances
using VNFI resources (e.g., compute, storage, I/O) needs to be
considered at NFP construction or adaptation. For example, a NFP can
be constructed as to make traffic flows aggregated into a limited
number of VNF instances as much as its performance is preserved in a
certain level.
3.2. Design considerations
To support the aforementioned use cases, it is required to support
resource management capability which provides service chain (or NFP)
construction and adaptation by considering resource state or
constraints of VNF instances and virtual links among them. The
resource management operations for service chain construction and
adaptation can be divided into several sub-actions:
o Select a VNF instance
o Evaluate a VNF instance and a virtual link
o Replace a VNF instance to update a NFP
o Monitor state or resource constraints of a VNF instance and a
virtual link
o Migrate a VNF instance to another ones in different locations
Note: While scaling-in/out or -up/down of VNF instances is one of the
essential actions for NFV resource management, it is a different
approach with a finer granularity than service chain adaptation. The
scaling approach may be integrated together with the service chain
adaptation but it is still under study.
As listed above, VNF instances are selected or replaced according to
monitoring or evaluation results of performance metrics of the VNF
instances and virtual links. Studies about evaluation methodologies
and performance metrics for VNF instances and NFVI resources can be
found at [ETSI-NFV-PER001] [I-D.liu-bmwg-virtual-network-benchmark]
[I-D.morton-bmwg-virtual-net]. The performance metrics of VNF
instances and virtual links specific to service chain construction
and adaptation can be defined as follows:
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o availability (or failure) of a VNF instance and a virtual link
o a topological location of a VNF instance
o a utilization rate of a VNF instance
o a throughput of a VNF instance
o energy consumption of VNF instance
o bandwidth of a virtual link
o latency of a virtual link
3.3. Framework
The resource management functionality for dynamic service chain
adaptation takes role of NFV orchestration with support of VNF
manager and Virtualised Infrastructure Manager (VIM) in the NFV
framework [ETSI-NFV-ARCH]. Detailed functional building block and
interfaces are still under study.
4. Applicability to SFC
4.1. Related works in IETF SFC WG
IETF SFC WG provides a new service deployment model that delivers the
traffic along the predefined logical paths of service functions
(SFs), called service function chains (SFCs) with no regard of
network topologies or transport mechanisms. Basic concept of the
service function chaining is similar to VNF-FG where a network
service is composed of SFs and deployed by making traffic flows
traversed instances of the SFs in a pre-defined order.
There are several works in progress in IETF SFC WG for resource
management of service chaining. [I-D.ietf-sfc-architecture] defines
SFC control plane that selects specific SFs for a requested SFC,
either statically or dynamically but details are currently outside
the scope of the document. There are other works
[I-D.ww-sfc-control-plane] [I-D.lee-sfc-dynamic-instantiation]
[I-D.krishnan-sfc-oam-req-framework] [I-D.aldrin-sfc-oam-framework]
which define the control plane functionality for service function
chain construction and adaptation but details are still under study.
While [I-D.dunbar-sfc-fun-instances-restoration] and
[I-D.meng-sfc-chain-redundancy] provide detailed mechanisms of
service chain adaptation, they focus only on resilience or fail-over
of service function chains.
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4.2. Integration in SFC control-plane architecture
In SFC WG, [I-D.ww-sfc-control-plane] defines a generic architecture
of SFC control plane with well-defined functional building blocks and
interfaces as follows:
+-------------------------------------------------+
| SFC Control Plane |
| +---------------+ +---------------+ |
+-------| |Chain Management |Service Overlay| |
| | |Policy Control | |Topo Management| |
| | +---------------+ +---------------+ |
| | +---------------+ +---------------+ |
+---------|Chain Selection| | Chain Mapping | +----------+|
| | | Policy Control| | and Forwarding| |External SF|
| +---------------+ | Control | |Management||
| | +---------------+ +----------+|
C1 +------^-----------^-------------^----------------+
+---------------------|F----------|-------------|-------------+
| | +----+ | | |
| | | SF | |C2 |C2 |
| +----+ | | |
| +----V--- --+ | | | |
| | SFC | +----+ +-|--+ +----+ |
| |Classifier |---->|SFF |----->|SFF |------->|SFF | |
| | Node |<----| |<-----| |<-------| | |
| +-----------+ +----+ +----+ +----+ |
| | | | |
| |C2 ------- | |
| | | | +-----------+ F |
| V +----+ +----+ | SFC Proxy |--> |
| | SF | |SF | +-----------+ |
| +----+ +----+ |
| |F |F |
| SFC Data Plane Components V V |
| |
+-------------------------------------------------------------+
Figure 2: SFC control plane architecture
The service chain adaptation addressed in this document may be
integrated into the Chain Mapping and Forwarding Control functional
block and may use the C2 and F interfaces for monitoring or
collecting the resource constraints of VNF instances and VLs.
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Note that SFC does not assume that Service Functions are virtualized.
Thus, the parameters of resource constraints may differ, and it needs
further study for integration.
5. Security Considerations
TBD.
6. IANA Considerations
TBD.
7. References
7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
7.2. Informative References
[ETSI-NFV-ARCH]
ETSI, "ETSI NFV Architectural Framework v1.1.1", October
2013.
[ETSI-NFV-MANO]
ETSI, "Network Function Virtualization (NFV) Management
and Orchestration V0.6.3", October 2014.
[ETSI-NFV-PER001]
ETSI, "Network Function Virtualization: Performance and
Portability Best Practices v1.1.1", June 2014.
[ETSI-NFV-TERM]
ETSI, "NFV Terminology for Main Concepts in NFV", October
2013.
[ETSI-NFV-WHITE]
ETSI, "NFV Whitepaper 2", October 2013.
[I-D.aldrin-sfc-oam-framework]
Aldrin, S., Krishnan, R., Akiya, N., Pignataro, C., and A.
Ghanwani, "Service Function Chaining Operation,
Administration and Maintenance Framework", draft-aldrin-
sfc-oam-framework-01 (work in progress), October 2014.
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[I-D.dunbar-sfc-fun-instances-restoration]
Dunbar, L. and A. Malis, "Framework for Service Function
Instances Restoration", draft-dunbar-sfc-fun-instances-
restoration-00 (work in progress), April 2014.
[I-D.ietf-sfc-architecture]
Halpern, J. and C. Pignataro, "Service Function Chaining
(SFC) Architecture", draft-ietf-sfc-architecture-08 (work
in progress), May 2015.
[I-D.krishnan-sfc-oam-req-framework]
Krishnan, R., Ghanwani, A., Gutierrez, P., Lopez, D.,
Halpern, J., Kini, S., and A. Reid, "SFC OAM Requirements
and Framework", draft-krishnan-sfc-oam-req-framework-00
(work in progress), July 2014.
[I-D.lee-sfc-dynamic-instantiation]
Lee, S., Pack, S., Shin, M., and E. Paik, "SFC dynamic
instantiation", draft-lee-sfc-dynamic-instantiation-01
(work in progress), October 2014.
[I-D.liu-bmwg-virtual-network-benchmark]
Liu, V., Liu, D., Mandeville, B., Hickman, B., and G.
Zhang, "Benchmarking Methodology for Virtualization
Network Performance", draft-liu-bmwg-virtual-network-
benchmark-00 (work in progress), July 2014.
[I-D.meng-sfc-chain-redundancy]
Wu, C., Meng, W., and C. Wang, "Redundancy Mechanism for
Service Function Chains", draft-meng-sfc-chain-
redundancy-01 (work in progress), December 2014.
[I-D.morton-bmwg-virtual-net]
Morton, A., "Considerations for Benchmarking Virtual
Network Functions and Their Infrastructure", draft-morton-
bmwg-virtual-net-03 (work in progress), February 2015.
[I-D.ww-sfc-control-plane]
Li, H., Wu, Q., Boucadair, M., Jacquenet, C., Haeffner,
W., Lee, S., and R. Parker, "Service Function Chaining
(SFC) Control Plane Achitecture", draft-ww-sfc-control-
plane-04 (work in progress), March 2015.
Authors' Addresses
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Seungik Lee
ETRI
218 Gajeong-ro Yuseung-Gu
Daejeon 305-700
Korea
Phone: +82 42 860 1483
Email: seungiklee@etri.re.kr
Sangheon Pack
Korea University
145 Anam-ro, Seongbuk-gu
Seoul 136-701
Korea
Phone: +82 2 3290 4825
Email: shpack@korea.ac.kr
Myung-Ki Shin
ETRI
218 Gajeong-ro Yuseung-Gu
Daejeon 305-700
Korea
Phone: +82 42 860 4847
Email: mkshin@etri.re.kr
EunKyoung Paik
KT
17 Woomyeon-dong, Seocho-gu
Seoul 137-792
Korea
Phone: +82 2 526 5233
Email: eun.paik@kt.com
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