Internet DRAFT - draft-ma-v6ops-ipv6-address-assignment
draft-ma-v6ops-ipv6-address-assignment
Internet Engineering Task Force Q. Ma
Internet-Draft T. Yang
Intended status: Informational China Mobile
Expires: July 5, 2013 Jan 2013
Considerations on IPv6 Address Assignment
draft-ma-v6ops-ipv6-address-assignment-00
Abstract
This document discusses general principles and rules of IPv6 address
assignment and gives an example to illustrate.
Status of this Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. The General principles of IPv6 address assignment . . . . . . . 3
3. Prefix length assignment to end site . . . . . . . . . . . . . 3
4. IPv6 address pool assignment for network device . . . . . . . . 4
5. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
6. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . 6
7. Security Considerations . . . . . . . . . . . . . . . . . . . . 6
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
9. Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6
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1. Introduction
IPv6 address space available to each network operator is very large
compared with IPv4. Unreasonable IPv6 address assignment will result
in the rapid expansion of routing table. In order to improve the
utilization of IPv6 address and avoid wasting, The principle and
rules of IPv6 address assignment need to be researched.
There are three types of IPv6 addresses: unicast, multicast and
anycast address, what operators can assign is the 001 Global Unicast
Address. The document discusses the general principles and rules of
IPv6 address assignment, gives some specific recommendations and sets
an example to illustrate the principles and rules.
2. The General principles of IPv6 address assignment
(1)The requirement of route aggregation
- End sites should be assigned fixed prefix length, for example /48,
/56, /64, etc, for route aggregation and easy to manage
- It is recommended to contain the location information in the IPv6
address, and address space assigned to each area should be contiguous
as far as possible to improve route aggregation and reduce router
pressure
(2)Address continuity requirements
- Take into account the subscriber growth and service development, to
assign enough address space for each type of Business
(3)The needs of management
- Address assignment and management should be simple and convenient
- Allocation granularity to meet management requirements such as QoS,
ACL
(4)Meet the needs of business and subscribers development
- Under the premise of not dramatically affect the route aggregation,
meet some special address demands of subscriber
3. Prefix length assignment to end site
Reference to the existing Specifications, we recommend some rules:
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(1) A single PC or mobile phone , with no additional need to subnet,
should receive a /64 prefix[RFC3177]
(2) In the wireless network, user equipment can access through MiFi
device. As an access point, MiFi need to request an address space
and assign a /64 prefix for hosts through DHCP prefix delegation.
MiFi or mobile phone used as MiFi should receive a /60 prefix for
downstream interface, can address 2^4 hosts
(3) In the broadband network, CPE (Customer Premise Equipment) or
home gateway request an address space and assign a /64 prefix for
hosts through DHCP prefix delegation. Generally speaking, the number
of users and business address demand in the h ome broadband is larger
than in the wireless network, so the CPE should receive a /56 prefix
[RFC6177 and BBF TR-177] for downstream interface, can address 2^8
hosts
(4) For enterprise, the CE router should receive one or more /48
prefix [RFC3177], according to the number of hosts in the subnet
(5) When it is absolutely known that one and only one device is
connecting, the device, mainly refers to the network equipment,
should receive a /128 prefix as loopback interfaces
(6) The two interfaces of a link should configurate a /127
prefix[RFC6164, RFC6547]. This rule refer to not only routers,
switches and management equipment in the core network, but also
servers in the IDC, DNS system and service platform.
4. IPv6 address pool assignment for network device
For easy to route aggreation, The IPv6 address pool in the access
control device should be configurated according to the equipment
performance and user capacity. The size of the pool can be
calculated with the user cpicaty multiplied by the address space
assigned to one user.
Take the address pool in GGSN for example, assume that user capcity
configurated in a GGSN is One million, each UE need a / 64 address.
The size of the address pool is: 1,000,000*1=1,000,000, nearly 2^20,
so the address pool in GGSN should be configured to /44.
The calculation of address pool in BRAS is slightly more complicated.
In the broadband network, assume that user capcity configurated in a
BRAS is 30 thousand, Each CPE need a / 64 LAN interface address and a
/ 56 WAN interface address， equivalent to 257 /64 address. By
calculating, the size of the address pool is: 30,000*257=7,710,000,
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nearly 2^23, so the address pool in BRAS should be configured to /41.
5. Example
we set an example to illustrate the principle and rules of address
assignment described above.IPv6 address assignment cannot be
generalized. It should be taken on case to case basis and meet the
requirement of route aggregation.
| 64 bits | 64 bits |
+-------------------------------+---------------------------------+
| P0 | P1 | P2 | P3 | P4 | P5 | interface ID |
+-------------------------------+---------------------------------+
Figure 1: address assignment
The field of address is divided as shown above.
where,
- P0: Global routing prefix obtained from a local Internet registry.
- P1: Type flag, used to distinguish between the network address and
user address. The network address refers to the equipment Loopback
address and the interface address. The user address refers to the
dynamic or static address assigned to the hosts, including IP address
pool in the service control equipment, such as BRAS, AC, GGSN and PGW
etc.
- P2: Network flag, used to distinguish between different networks,
if there are several networks available. Different networks occupy
different address space, the address space in same network should be
continuous as far as possible.
- P3 and P4: Province flag and City flag, the location information in
the IPv6 address. Address assignment of the same region should be
continuous as far as possible.
- P5: The field is assigned in the city internally
In this example, the IPv6 address field is divided in detail, which
increase the complexity of the address assignment, but is beneficial
to route aggregation and address management. The length of each
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field is assigned according to the development of service and users.
Each field can be partially reserved according to the expansion
demands.
6. Conclusion
The document discussed the general principles and rules of IPv6
address assignment, give some specific recommendations and set an
example to illustrate the principles and rules. In fact, IPv6
address assignment cannot be generalized. It should be taken on case
to case basis and meet the requirement of route aggregation.
7. Security Considerations
It needs to be further identified.
8. IANA Considerations
TBD
9. Reference
[RFC3177] IAB and IESG, "IAB/IESG Recommendations on IPv6 Address
Allocations to Sites", RFC 3177, September 2001.
[RFC6177] T. Narten, G. Huston and L. Roberts, "IPv6 Address
Assignment to End Sites", RFC6177, March 2011
[RFC6164] M. Kohno,B. Nitzan,R. Bush, etc., "Using 127-Bit IPv6
Prefixes on Inter-Router Links", RFC6164,April 2011
[RFC6547] W. George, "RFC 3627 to Historic Status", RFC6547, December
2011
[BBF TR-177] "IPv6 in the context of TR-101", BBF TR-177, November
2010
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Authors' Addresses
Ma Qiongfang
China Mobile
32, Xuanwumenxi Ave.
Xicheng District, Beijing 01719
China
Email: maqiongfang@chinamobile.com
Yang Tianle
China Mobile
32, Xuanwumenxi Ave.
Xicheng District, Beijing 01719
China
Email: yangtianle@chinamobile.com
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