Internet DRAFT - draft-zhang-computing-aware-sfc-usecase
draft-zhang-computing-aware-sfc-usecase
Network Working Group S. Zhang
Internet-Draft China Unicom
Intended status: Informational X. Chen
Expires: 26 January 2023 Huawei Technologies
25 July 2022
Use Cases of Computing-aware Service Function Chaining (SFC)
draft-zhang-computing-aware-sfc-usecase-01
Abstract
Multiple occurrences of the same service function(SF) can exist in
the same administrative domain and each occurrence of SF is called SF
instance. A Service Function Path(SFP) is determined by composing
selected SF instances and overlay links. The SF instances are
selected according to the computing power of SFs in addition to the
network information and this is defined as the computing-aware SFC in
this document.
This document describes the use cases for computing-aware Service
Function Chaining(SFC).
Requirements Language
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 RFC 2119 [RFC2119].
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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Internet-Drafts are draft documents valid for a maximum of six months
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on 26 January 2023.
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Copyright Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Use Cases of Computing-aware SFC . . . . . . . . . . . . . . 3
2.1. Computing-aware SFC in multiple data centers(DCs) . . . . 3
3. Security Considerations . . . . . . . . . . . . . . . . . . . 5
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
5. Normative References . . . . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
[RFC7665]defines the architecture for SFC and mentions load-balancing
considerations of the scenario that is same service function may be
reachable through multiple SFFs.The selection of which SFF to use to
reach SF may be made by the control logic in defining the SFP, or may
be left to the SFFs themselves, depending upon policy, solution, and
deployment constraints.
[I-D.ietf-sfc-control-plane] indicates that implementing a
(logically) centralized path computation engine requires information
to be dynamically communicated to the central SFC Control Element,
such as the list of available SF instances, SFF locators, load
status, SFP availability, etc. SF load update information such as
the performance threshold or stress level of SF can be exchanged
between an SF and the SFC control plane to establish or adjust an
SFP.
In this document the computing power of SF includes computing
resources and computing load of SF. For example, the compute
resource can be the vCPUs allocated to SF, and the compute load can
be the CPU utilization of SF or the ratio of the number of SFPs
currently using SF to the maximum number of SFPs supported by SF.
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Multiple instances of the same service function(SF) can exist in the
same administrative domain. A Service Function Path(SFP) is
determined by composing selected SF instances and overlay links.The
SF instances can be selected according to the computing power of SFs
in addition to the network information and this is defined as the
computing-aware SFC.
This document describes the use cases for computing-aware Service
Function Chaining(SFC).
2. Use Cases of Computing-aware SFC
2.1. Computing-aware SFC in multiple data centers(DCs)
In carrier networks, operators may deploy multiple data centers or
computing resource pools dispersed geographically. These data
centers can host diverse types of value-added services(VASes) such as
FW(Firewall), IPS(Intrusion Prevention System), WOC(Web Optimization
Control) and VO(Video Optimizer) shared by the enterprise leased line
services, internet services etc.
Each data center may have different types of service functions. For
example, high usage service functions are deployed in edge or
regional data centers while other low usage service functions are
deployed in global or central data centers. So SFCs with different
types of service functions may span multiple data centers.
The same service function can be deployed in multiple data centers.
In such deployments the SF in one data center is called a SF
instance. SFPs are constructed with the ordered chain of SFs each of
which is from specific data center.
The path computation of SFP should consider the computing load of SFs
and the cost or latency of network paths between the DCs hosting the
SFs in order to get the good service experience of SFs and the
optimal end to end network path.
In Figure 1, A enterprise tenant orders SFC with a chain of two
value-added services for its access to internet service. The
sequenced services of SFC are FW and VO.
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+------+ +------+ +------+
|DC1 | |DC2 | |DC3 |
| | | | | |
| FW | | FW | | VO |
+------+ +------+ +------+
| | |
+ + +
+----+ +----+ +----+ +----+
CPE+--->| R1 |+--->| R2 |+--->| R3 |+--->| R4 |+-->internet
+----+ +----+ +----+ +----+
Figure 1: Illustration of Computing-aware SFC
The current computing load status of the FW SFs in DC1 and DC2 is as
follows: each SF uses 6 vCPUs. The load of DC1 is 50%. The load of
DC2 is 20%. Considering lightly loaded SF the computed SFP is
represented as: DC2 FW -> DC3 VO. Traffic follows the path: CPE ->
R1 -> R2 -> DC2 FW -> R2 -> R3 ->DC3 VO -> R3 -> R4 -> internet
The procedures for SFP creation according to computing power of SFs
and network topology may be handled by the control plane as follows:
1.Collect computing power which are computing resources and computing
load of of SFs in DCs
2.Associate the DC location and computing power of the available SFs
with topological information of network connecting all the data
centers to allow control plane to construct the overall map
The following potential solutions could be considered:
* Collect the SF's location and computing power by BGP-LS or Netconf
from the router connecting the data centers and dynamically get
the association relationship.
* Independently collect the SF location and computing power by other
means and statically configure the association with the network on
the control plane.
3.Compute the actual sequence of specific routers and selected SFs in
the network for SFP
If the same SF is deployed in multiple data centers the control plane
selects one SF instance for SFP considering the computing load of SF
and the cost or latency of network paths between the DCs hosting the
SFs.
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4.Deliver the actual computed path called Rendered Service Path (RSP)
[RFC7665] to the routers to steer the traffic from classifier to
destination
In some cases SFP adjustments can be handled. For example, a SF in
the selected DC fails, the load of the same SF in each DC varies
greatly, and the delay is caused among routers connected to the DC.
3. Security Considerations
TBD
4. IANA Considerations
There are no IANA considerations in this document.
5. Normative References
[I-D.ietf-sfc-control-plane]
Boucadair, M., "Service Function Chaining (SFC) Control
Plane Components & Requirements", Work in Progress,
Internet-Draft, draft-ietf-sfc-control-plane-08, 23
October 2016, <https://www.ietf.org/archive/id/draft-ietf-
sfc-control-plane-08.txt>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", DOI 10.17487/RFC2119, BCP 14,
RFC 2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC7665] Halpern, J., Ed. and C. Pignataro, Ed., "Service Function
Chaining (SFC) Architecture", RFC 7665,
DOI 10.17487/RFC7665, October 2015,
<https://www.rfc-editor.org/info/rfc7665>.
Authors' Addresses
Shuai Zhang
China Unicom
Beijing
China
Email: zhangs366@chinaunicom.cn
Xia Chen
Huawei Technologies
Beijing
China
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Email: jescia.chenxia@huawei.com
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