Internet DRAFT - draft-li-v6ops-load-balancing-requirement
draft-li-v6ops-load-balancing-requirement
v6ops Z. Li
Internet-Draft China Mobile
Intended status: Informational Q. Zhao
Expires: May 3, 2012 X. Huang
Y. Ma
Beijing University of Posts and
Telecommunications
X. Xu
Huawei Technologies Co.,Ltd
October 31, 2011
Analysis on Load Balancing Requirement in IPv4/IPv6 Transition
draft-li-v6ops-load-balancing-requirement-02
Abstract
This document first analyzes the critical issues of bottlenecks in
existing tunneling and translation technologies, which can be solved
by proper load balancing mechanisms(e,g., scalability, availability,
and single point of failure). Then, several key factors in designing
a valid load balancing mechanism are described. Solutions to
specific load balancing requirements can be drawn out by considering
these factors. At last, current efforts about load balancing are
introduced.
Status of this Memo
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This Internet-Draft will expire on May 3, 2012.
Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 4
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Problems of Bottlenecks . . . . . . . . . . . . . . . . . . . 5
5. Keys To the Load-balancing Solutions . . . . . . . . . . . . . 6
5.1. Target Device . . . . . . . . . . . . . . . . . . . . . . 6
5.1.1. Tunnel End-Point . . . . . . . . . . . . . . . . . . . 6
5.1.2. Translation Gateway . . . . . . . . . . . . . . . . . 6
5.2. Selection Policy . . . . . . . . . . . . . . . . . . . . . 6
5.2.1. Anycast-Based Selection Policy . . . . . . . . . . . . 6
5.2.2. Source-Based Selection Policy . . . . . . . . . . . . 6
5.2.3. Destination-Based Selection Policy . . . . . . . . . . 7
5.2.4. Round-Robin Selection Policy . . . . . . . . . . . . . 7
5.2.5. Subscriber-Based Policy . . . . . . . . . . . . . . . 7
5.2.6. Dynamic Selection Policy . . . . . . . . . . . . . . . 7
5.3. Transport Protocol . . . . . . . . . . . . . . . . . . . . 7
5.3.1. DNS . . . . . . . . . . . . . . . . . . . . . . . . . 7
5.3.2. DHCP . . . . . . . . . . . . . . . . . . . . . . . . . 7
5.3.3. ICMPv6 . . . . . . . . . . . . . . . . . . . . . . . . 7
5.3.4. RADIUS . . . . . . . . . . . . . . . . . . . . . . . . 8
5.4. Load-balancer Location . . . . . . . . . . . . . . . . . . 8
5.4.1. Terminal/Host . . . . . . . . . . . . . . . . . . . . 8
5.4.2. Access Gateway . . . . . . . . . . . . . . . . . . . . 8
5.4.3. Network Servers . . . . . . . . . . . . . . . . . . . 8
6. Where Are We Now . . . . . . . . . . . . . . . . . . . . . . . 8
6.1. Work Done . . . . . . . . . . . . . . . . . . . . . . . . 8
6.1.1. 6RD . . . . . . . . . . . . . . . . . . . . . . . . . 8
6.1.2. BIH . . . . . . . . . . . . . . . . . . . . . . . . . 9
6.2. Work In Progress . . . . . . . . . . . . . . . . . . . . . 9
6.2.1. NAT64 . . . . . . . . . . . . . . . . . . . . . . . . 9
6.3. Work To Be Done . . . . . . . . . . . . . . . . . . . . . 9
6.3.1. IVI . . . . . . . . . . . . . . . . . . . . . . . . . 9
6.3.2. DS-Lite . . . . . . . . . . . . . . . . . . . . . . . 9
6.3.3. 4RD . . . . . . . . . . . . . . . . . . . . . . . . . 10
7. Security Considerations . . . . . . . . . . . . . . . . . . . 10
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
9. Other Authors and Contributors . . . . . . . . . . . . . . . . 10
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
10.1. Normative References . . . . . . . . . . . . . . . . . . . 11
10.2. Informative References . . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12
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1. Introduction
Since the depletion of IPv4 address, IPv6 is being introduced into
existing networks and IPv4 will be gradually replaced by IPv6.
The Current Internet is almost fully built on IPv4. IPv6 is
fundamentally incompatible with IPv4. The smooth and incremental
transition from IPv4 to IPv6 is vital to IPv6's success. IPv6
transition technologies are generally classified into three
catigories: dual stack, tunneling (e.g., 6RD[RFC5969], DS-
Lite[I-D.ietf-softwire-dual-stack-lite]) and translation (e.g. ,
NAT64[RFC6146], IVI[RFC6219], BIH[I-D.ietf-behave-v4v6-bih]).
Dual stack technology can gradually steer traffic from IPv4 network
to IPv6 network by using the address selection policy that generally
"IPv6 prior to IPv4", as specified in [RFC3484].
Both tunneling and translation technologies introduce traffic
concentration points, the tunnel end-point in tunneling technology
and the translation gateway in translation technology. When the
scope of IPv6 deployment continuously expands and the traffic of IPv6
business gradually grows, traffic concentration points usually bare
very heavy work load. These concentration points will become
bottlenecks and the sources of the single point of failure. To
address such issues,load balancing mechanism should be considered.
This document firstly analyzes these problems caused by the
centralized points imposed in the current tunneling and translation
solutions. These problems are expected to be solved by proper load
balancing mechanisms. Secondly, several key factors in designing
such load balancing mechanisms are analyzed. Finally, current
efforts about load balancing are analyzed and concluded.
2. 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 [RFC2119].
3. Terminology
The terminology used in this document is consistent with
6rd[RFC5969], NAT64[RFC6146], IVI[RFC6219], DS-
Lite[I-D.ietf-softwire-dual-stack-lite]. Besides, the following
terminology is defined.
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Load-balancer: A system which distributes users' workload across
multiple devices providing identical services.
Target Device: The device to which a load-balancer distributes
workload. That is the concentration points of the tunneling and
translation technologies.
Selection policy: The Policy by which the load-balancer selects
target device.
Transport protocol: The protocol the load balancer uses to delivery
information of selected target device to user.
4. Problems of Bottlenecks
During the coexistence of IPv4 and IPv6, more and more IPv6 traffic
will be carried on IPv4 network or IPv4 Internet in the form of 6in4
tunnel such as 6RD[RFC5969]. Similarly, more and more IPv4 traffic
will be guided to IPv6 network or IPv6 Internet in the form of 4in6
tunnel such as DS-Lite [I-D.ietf-softwire-dual-stack-lite]. Both DS-
Lite and 6RD concentrate all the tunnel traffic at the tunnel end-
points in the service provider network. These tunnel end-points are
traffic concentration points which are potential bottlenecks.
During the evolution from IPv4 to IPv6, IPv6 users will communicate
with IPv4 network or IPv4 Internet in the form of 6->4 translation
such as NAT64[RFC6146]. Similarly, some IPv4 users will visit IPv6
network or IPv6 Internet in the form of 4->6 translation such as
IVI[RFC6219]. Both NAT64 and IVI convert all the translation traffic
at the translation gateways in service provider network. These
translation gateways are traffic concentration points or potential
bottlenecks.
There are many problems about bottlenecks.
1. The performance of a single concentration point cannot satisfy
the increasing workload.
2. Drive traffic through roundabout path.
3. Involve a single point of failure.
In order to avoid becoming bottleneck, traffic concentration point
should be distributed to multiple parallel points. Each parallel
point performs the same operations. There must be some load-
balancing mechanisms to make parallel points collaborate with one
another stably, smartly and efficiently.
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5. Keys To the Load-balancing Solutions
In order to keep transition technology always available when traffic
growing from small to large scale, some load balancing approaches
should be applied at IPv4/IPv6 conjunction points. There are four
categories requirements for load balancing scheme. Different
solutions or mechanisms may be concluded when necessary to meet the
requirements of each. The four categories requirements are: Target
Device, Selection policy, Transport protocol and Load-balancer
location.
5.1. Target Device
As mentioned above, the target device can be tunnel end-point or
translation gateway in service provider network.
5.1.1. Tunnel End-Point
Tunnel End-Point can be stateful (like DS-Lite) or stateless (like
6RD). In DS-Lite, such device is AFTR (Address Family Transition
Router element) which is 4in6 tunnel concentration point and NAPT44
address port translator. In 6RD, such device is BR (Border Relay)
which is only a 6in4 tunnel concentration point.
5.1.2. Translation Gateway
Translation Gateway can be stateful (like NAT64) or stateless (like
IVI). Either MAY introduce Application Layer Gateway (ALG) into it.
In NAT64, such device is stateful NAT64 device which is IPv6 to IPv4
protocol address translator. In IVI, such device is stateless IVI
translator which is the mapping and translation gateway.
5.2. Selection Policy
[I-D.zhang-behave-nat64-load-balancing] has proposed some kinds of
prefix64 selection policies for NAT64 load balancing. Those policies
can also be applied to general load balancing selection policy in
addition to Subscriber-Based Policy.
5.2.1. Anycast-Based Selection Policy
It requires a load-balancer to select target device according to
whether target device and involved routers support anycast[RFC4291].
5.2.2. Source-Based Selection Policy
It requires a load-balancer to select target device according to the
IPv6 address of user device.
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5.2.3. Destination-Based Selection Policy
It requires a load-balancer to choose target device according to
e.g., the FQDN, the IPv4/IPv6 address, or other identifiers of
destination servers.
5.2.4. Round-Robin Selection Policy
It requires a load-balancer to select target device and destination
servers circularly according to the arrival request.
5.2.5. Subscriber-Based Policy
It requires a load-balancer to choose target device according to the
subscriber's information, which can be stored in AAA servers, for
example.
5.2.6. Dynamic Selection Policy
It requires a load-balancer to select target device according to the
real-time status of target device.
5.3. Transport Protocol
According to the selection policy, one or more target devices may be
chosen by load-balancer. There are different protocols can be used
to transport the results to user device.
5.3.1. DNS
DNS protocol carries response results to DNS queries. If result is
IPv6 address with network specific IPv6 prefix, traffic can be lead
to relevant translation gateway. If result is IPv6 address of tunnel
end-point in service provider network, traffic can be lead to
relevant tunnel concentration point.
5.3.2. DHCP
DHCPv4 or DHCPv6 protocol sends network configuration parameters to
user device. The parameters may contain network specific IPv6 prefix
or tunnel end-point address.
5.3.3. ICMPv6
ICMPv6 protocol can broadcast RA (Router Advertisement) message and
options to user device. The options may contain network specific
IPv6 prefix or tunnel end-point address.
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5.3.4. RADIUS
RADIUS protocol[RFC2865]] can transport subscriber's information to
network servers such as DHCP or DNS server. The subscriber's
information may contain selected network specific IPv6 prefix or
tunnel end-point address. The network servers then can distribute
the prefix or address to user device.
5.4. Load-balancer Location
The load-balancer can be implemented in different locations or
different devices.
5.4.1. Terminal/Host
Terminal/Host can be modified to balance the load to target devices.
The terminal/host should use the selection policy in 5.2 to choose a
target device and make its traffic go through it.
5.4.2. Access Gateway
Access gateway can be modified to balance the load on target devices.
The access gateway should use the selection policy in 5.2 to choose a
target device and make user traffic go through it.
5.4.3. Network Servers
Network servers include DHCP server, DNS server, RADIUS server and so
on. They should use the selection policy in 5.2 to choose a target
device. Then, they delivery the results to user device and user
device will make its traffic go through the target device.
6. Where Are We Now
At present, some transition technologies have specified their own
load balancing solutions, some transition technologies' load
balancing solutions are in discussion and the others' are still
waiting to be focused on.
6.1. Work Done
6.1.1. 6RD
Target Device is BR, the tunnel end-point.
Selection Policy is Anycast.
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Transport Protocol can be DNS, DHCPv4, PPP, or manual configuration
etc. DHCPv4 is recommended in [RFC5969].
Load-balancer Location is in network server. DHCPv4 server is
recommended in [RFC5969].
6.1.2. BIH
BIH is described in [I-D.ietf-behave-v4v6-bih].Since BIH is NOT
REOMMENDED to use together with a NAT64, there is no traffic
concentration point for the BIH per se. So BIH does not need any
load-balancing mechanism.
6.2. Work In Progress
6.2.1. NAT64
Target Device is the NAT64 translator.
[I-D.xu-behave-stateful-nat-standby] defines a framework for ensuring
redundancy for stateful Network Address Translators (NAT),including
NAT44, NAT64 and NAT46, which mainly tries to solve the single point
of failure problem. Three redundancy modes are described in the
document: the cold standby, the hot standby and the partial hot
standby modes.
[I-D.zhang-behave-nat64-load-balancing] is considering NAT64 load-
balancing mechanism. But no solution is recommended at present.
6.3. Work To Be Done
6.3.1. IVI
Target Device is the IVI translator.
The load-balancing mechanism is not mentioned in the specification of
IVI[RFC6219].
6.3.2. DS-Lite
Target Device is AFTR, the tunnel end-point.
Although the load-balancing of AFTR can be done by using the FQDN
option defined in [I-D.ietf-softwire-ds-lite-tunnel-option] and DNS,
this point is not explicitly described in the specification of DS-
lite [I-D.ietf-softwire-dual-stack-lite].
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6.3.3. 4RD
Target Device is BR, the tunnel end-point.
The load-balancing mechanism is not mentioned in the specification of
4RD [I-D.murakami-softwire-4rd].
7. Security Considerations
The potential security problem should be considered in the specific
load balancing mechanism designed for the specific transition
technology.
8. IANA Considerations
This document makes no request of IANA.
Note to RFC Editor: this section may be removed on publication as an
RFC.
9. Other Authors and Contributors
The following individuals have contributed to this document:
Gang Chen
China Mobile
Unit2, Dacheng Plaza, No. 28 Xuanwumenxi Ave, Xicheng District
Beijing 100053
P.R. China
Email: chengang@chinamobile.com
Dacheng Zhang
Huawei Technologies Co.,Ltd
KuiKe Building, No.9 Xinxi Rd.,Haidian District
Beijing 100085
P.R. China
Email: zhangdacheng@huawei.com
10. References
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10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
10.2. Informative References
[I-D.ietf-behave-v4v6-bih]
Huang, B., Deng, H., and T. Savolainen, "Dual Stack Hosts
Using "Bump-in-the-Host" (BIH)",
draft-ietf-behave-v4v6-bih-06 (work in progress),
August 2011.
[I-D.ietf-softwire-ds-lite-tunnel-option]
Hankins, D. and T. Mrugalski, "Dynamic Host Configuration
Protocol for IPv6 (DHCPv6) Option for Dual- Stack Lite",
draft-ietf-softwire-ds-lite-tunnel-option-10 (work in
progress), March 2011.
[I-D.ietf-softwire-dual-stack-lite]
Durand, A., Droms, R., Woodyatt, J., and Y. Lee, "Dual-
Stack Lite Broadband Deployments Following IPv4
Exhaustion", draft-ietf-softwire-dual-stack-lite-11 (work
in progress), May 2011.
[I-D.murakami-softwire-4rd]
Murakami, T., Troan, O., and S. Matsushima, "IPv4 Residual
Deployment on IPv6 infrastructure - protocol
specification", draft-murakami-softwire-4rd-01 (work in
progress), September 2011.
[I-D.xu-behave-stateful-nat-standby]
Xu, X., Boucadair, M., Lee, Y., and G. Chen, "Redundancy
Requirements and Framework for Stateful Network Address
Translators (NAT)",
draft-xu-behave-stateful-nat-standby-06 (work in
progress), October 2010.
[I-D.zhang-behave-nat64-load-balancing]
Zhang, D., Xu, X., and M. Boucadair, "Considerations on
NAT64 Load-Balancing",
draft-zhang-behave-nat64-load-balancing-03 (work in
progress), July 2011.
[RFC2865] Rigney, C., Willens, S., Rubens, A., and W. Simpson,
"Remote Authentication Dial In User Service (RADIUS)",
RFC 2865, June 2000.
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[RFC3484] Draves, R., "Default Address Selection for Internet
Protocol version 6 (IPv6)", RFC 3484, February 2003.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, February 2006.
[RFC5969] Townsley, W. and O. Troan, "IPv6 Rapid Deployment on IPv4
Infrastructures (6rd) -- Protocol Specification",
RFC 5969, August 2010.
[RFC6146] Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful
NAT64: Network Address and Protocol Translation from IPv6
Clients to IPv4 Servers", RFC 6146, April 2011.
[RFC6219] Li, X., Bao, C., Chen, M., Zhang, H., and J. Wu, "The
China Education and Research Network (CERNET) IVI
Translation Design and Deployment for the IPv4/IPv6
Coexistence and Transition", RFC 6219, May 2011.
Authors' Addresses
Zhenqiang Li
China Mobile
Unit2, Dacheng Plaza, No. 28 Xuanwumenxi Ave, Xicheng District
Beijing 100053
P.R. China
Email: lizhenqiang@chinamobile.com
Qin Zhao
Beijing University of Posts and Telecommunications
Information Network Center, No. 10 Xitucheng Road, Haidian District
Beijing 100876
P.R. China
Email: zhaoqin@bupt.edu.cn
Xiaohong Huang
Beijing University of Posts and Telecommunications
Information Network Center, No. 10 Xitucheng Road, Haidian District
Beijing 100876
P.R. China
Email: huangxh@bupt.edu.cn
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Yan Ma
Beijing University of Posts and Telecommunications
Information Network Center, No. 10 Xitucheng Road, Haidian District
Beijing 100876
P.R. China
Email: mayan@bupt.edu.cn
Xiaohu Xu
Huawei Technologies Co.,Ltd
KuiKe Building, No.9 Xinxi Rd., Haidian District
Beijing 100085
P.R. China
Email: xuxiaohu@huawei.com
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