Internet DRAFT - draft-gu-sfc-ps-vlb
draft-gu-sfc-ps-vlb
Network Working Group Rong Gu
Vic Liu
Internet Draft China Mobile
Intended status: Informational
Expires: January 2015 July 4, 2014
Problem statements of Virtual Load Balancers
draft-gu-sfc-ps-vlb-00.txt
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Abstract
This document describes the development of virtual load balancer
with a recent test in function and performance of virtual load
balancer shared. Several problems of deploying virtual load balancer
practically are presented. And requirements of further work in
virtual load balancer are suggested with internet community.
Table of Contents
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1. Introduction ................................................ 3
2. Test overview ............................................... 4
3. Problem statement ........................................... 4
4. Summary and requirement...................................... 6
5. Security Considerations...................................... 6
6. IANA Considerations ......................................... 6
7. References .................................................. 6
7.1. Normative References.................................... 6
7.2. Informative References.................................. 7
8. Acknowledgments ............................................. 7
1. Introduction
According to the network operators, Network Functions Virtualization
(NFV) brings many benefits such as equipment cost reduction, power
consumption reduction, optimization of network configuration and
automated network installation. Virtual load balancer (VLB) is a
piece of software acting as a reverse proxy to distribute network or
application traffic over different servers. Instead of the form of
hardware, VLB is a virtual machine (VM) which is a part of NFV
performing application-level optimization by distributing the
workload across multiple servers.
VLB can be realized by some OSS (open-source software) such as LVS,
Nginx and HA Proxy. Besides, many vendors launch virtual load
balancers as commercial products as well as their hardware load
balancers (LBs). Either the open-source software or the commercial
software can perform the basic function of the Layer 4-7 server load
balancing. The open-source software limits the features with
additional function needing to be further developed. The commercial
software load balancer acts almost the same as hardware load
balancer with the function of IPv4/IPv6 server load balancing,
powerful application scripting, SSL offload, high availability,
prevention from attacks and so on.
Because of the form of software, the VLB has superiority in the
application scenarios of elasticity, flexibility and agility such as
cloud computing and IDC (Internet Data Center).
a. The software load balancer performs great flexibility and saves
your space.
b. Virtual load balancer is a program which can be deployed
anywhere, such as very close to the servers that need to have the
information flow metered.
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c. Software load balancer has the advantage of agility which can be
moved and reconfigured quickly.
d. Software load balancer can be installed in several hypervisors
such as VMware ESX/ESXi and Linux KVM.
e. Software load balancer supports extensible management and
orchestration.
2. Test overview
Recently, we have tested several demos of VLB from different
vendors. The test mainly includes both the function and performance
of VLB. Results show that basic function of load balancing, health
monitoring and persistence are well supported by commercial VLB
products and partly supported by VLB of OSS. The performance of new
session, concurrent, and throughput of VLB is poorer than that of
hardware load balancer.
Test topology
-------- ------------ -----------
| Client |-----| VLB |-----| Server |
-------- ------------ -----------
3. Problem statement
The virtual load balancer shows vast potentialfor future development
of NFV. However, there are a number of challenges in deploying VLB
due to its immaturity.
a. The performance of VLB is an obvious disadvantage comparing with
the hardware load balancer, since software rather than chips
achieves the load balancing function. Reading from our exploratory
test, there is a huge gap of performance including new session,
concurrent session and throughput between VLB and the hardware LB.
According to our testing data, the number of new session of VLB can
be increased to ten thousand, the number of concurrent session can
reach up to several million, and the throughput can reach up to tens
Gbps. Performance of VLB after optimization still can't catch up
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with the hardware LB of low performance, as performance of the
software is subject to the physical server. And the performance of
VLB realized by OSS is much poorer than the commercial products of
VLB, several thousand of new session, tens thousand of concurrent
session and one Gbps in details, which shows that commercial
products do the performance optimization by their private
technology.
b. The VLB shows instability when operating in the network. VLB acts
as a VM coexisting with other VMs in the physical server. Other VMs
sometimes have an influence on VLB. Virtual bridge or virtual switch
takes the role of forwarding datagram in the physical server.In our
test, performance of server NIC and virtual bridge has an impact on
the operation of VLB which leads to unsuccessful request sometimes.
c. The VLB occupies the CPU and memory of the physical server
working as a VM. And VLBs of different vendors give variability in
large scale of the utilization rate of CPU and memory when
operating. And performances are influenced largely by the hardware
resources. Thus the utilization rate of CPU and memory of a physical
server should be taken into consideration in choosing the suitable
VLB, while the problem of bench mark exists in measuring VLB from
this aspect.
d. VLB shows problems of compatibility with various platforms of
VMware ESX/ESXi, Citrix Xenserver, Microwave Hypervisor,
RedHat/CentOS/Ubuntu Linux KVM and community Xen. From the result of
our study, VLB of different vendors support most of the platforms.
However, several platforms are not supported by VLB of some vendors
or some specific license of VLB of one vendor.
e. Some additional functions such as access control list (ACL) and
SSL acceleration are not fully supported by VLB of all the vendors
due to the progress of software development. Because of the
performance of software, functions like SSL acceleration prefer to
be achieved by hardware and ACL can be performed by other devices.
What's more, VLB realized by OSS only has basic functions by
default, with more functions added by specific modules which needs
to be developed and debugged.
f. Open APIs such as Openflow, OpenStack, OpenNaaS or OGF's are
partly supported by VLBs from different vendors, which may have an
impact on the management and data plane control.
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4. Summary and requirement
Network Functions Virtualization is already on the road. In order to
accelerate the progress of large-scale deployment of VLB, further
work should focus on responding to these challenges nowadays.
a. Compatibility with various platforms should be optimized. And
open APIs should be fully developed contributing to centralized
management.
b. Standard methods of measuring hardware resources such as the CPU
and memory of physical servers occupied should be set in making it
easier for horizontal comparison of different VLBs.
c. High availability of VLB as a VM should be ensured by either
virtual machine migration or master-standby with two VLBs. The
restoration time should be controlled when one VLB breaks down.
d. Performance of VLB should be further improved by advanced
techniques such as traffic migration.
5. Security Considerations
<Add any security considerations>
6. IANA Considerations
7. References
7.1. Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[2] Crocker, D. and Overell, P.(Editors), "Augmented BNF for
Syntax Specifications: ABNF", RFC 2234, Internet Mail
Consortium and Demon Internet Ltd., November 1997.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
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[RFC2234] Crocker, D. and Overell, P.(Editors), "Augmented BNF for
Syntax Specifications: ABNF", RFC 2234, Internet Mail
Consortium and Demon Internet Ltd., November 1997.
7.2. Informative References
[3] Faber, T., Touch, J. and W. Yue, "The TIME-WAIT state in TCP
and Its Effect on Busy Servers", Proc. Infocom 1999 pp. 1573-
1583.
[Fab1999] Faber, T., Touch, J. and W. Yue, "The TIME-WAIT state in
TCP and Its Effect on Busy Servers", Proc. Infocom 1999
pp. 1573-1583.
8. Acknowledgments
Authors' Addresses
Rong Gu
China Mobile
32 Xuanwumen West Ave, Beijing, China
Email: gurong@chinamobile.com
Vic Liu
China Mobile
32 Xuanwumen West Ave, Beijing, China
Email: liuzhiheng@chinamobile.com
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