Internet DRAFT - draft-chen-v6ops-nat64-cpe
draft-chen-v6ops-nat64-cpe
Internet Engineering Task Force G. Chen
Internet-Draft China Mobile
Intended status: Informational Oct 2011
Expires: April 3, 2012
NAT64 Operational Considerations
draft-chen-v6ops-nat64-cpe-03
Abstract
The document has summarized NAT64 usages on different modes, in which
NAT64 may serve for a large-scale network or would give enterprise or
residential service opportunities to be accessed by IPv6 remote
subscribers. The document has described different operations for
each usage and proposed operational considerations for each
particular NAT64-mode.
Status of this Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. NAT64-CGN Deployment . . . . . . . . . . . . . . . . . . . . . 3
2.1. Deployment in IDC . . . . . . . . . . . . . . . . . . . . . 3
2.2. Connecting with IPv4 Internet . . . . . . . . . . . . . . . 4
2.3. NAT64-CGN Mode Requirements . . . . . . . . . . . . . . . . 5
3. NAT64-CE Mode . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.1. NAT64 at Enterprise Network Edge . . . . . . . . . . . . . 6
3.2. NAT64 at Residential Network Edge . . . . . . . . . . . . . 7
4. Security Considerations . . . . . . . . . . . . . . . . . . . . 7
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
6. Normative References . . . . . . . . . . . . . . . . . . . . . 8
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 8
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1. Introduction
With fast developments of global Internet, the demands for IP address
are rapidly increasing at present.This year, IANA announced that the
global free pool of IPv4 depleted on 3 February. IPv6 is the only
real option on the table. Operators have to accelerate the process
of deploying IPv6 networks in order to address IP address
strains.IPv6 deployment normally involves a step-wise approach where
parts of the network should properly updated gradually. As IPv6
deployment progresses it may be simpler for operators and ICP/ISP to
employ NAT64[RFC6146] functionalities at edge of IPv4 and IPv6
networks, since a significant part of network will still stay in IPv4
for long time. Especially, NAT64 could facilitate large ICP/ISP IPv6
transition process by eliminating upgrations of tremendous legacy
IPv4 servers. Therefore, it's quite popular to deploy NAT64 at the
front of IDC to shift the entire service to be IPv6-enable.
Depending on different usage, NAT64 could be deployed on different
places. The document has summarized NAT64 usages on different modes.
Considering the existing deployment approaches, the memo has proposed
different operational consideration for each particular NAT64-mode.
2. NAT64-CGN Deployment
2.1. Deployment in IDC
NAT has widely used in data center environments whenever IDC have to
make your IPv4-only content available to IPv6 clients.
Figure 1 illustrates the usage where an IPv6-only host would like to
initiate communications with IDC in IPv4 domain through NAT64. The
NAT64 would accept IPv6 incoming session and distribute them to
multiple IPv4 servers.
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+----------------------+ +------------------------------+
| IPv6-only network | | IPv4 IDC |
| | | |
| | | |
| | | +----------+ |
| +----+ +---------+ | | |
| | H1 |-----------| NAT64 |-------------| Servers | |
| +----+ +---------+ | | |
| v6 only / | | \ +----------+ |
| Host / | | \ IPv4-only |
| +------+ | | +-----+ |
| |DNS64 | | | | DNS | |
| +------+ | | +-----+ |
+----------------------+ +------------------------------+
Figure 1: NAT64-CGN Mode Usage
NAT64 device in IDC may also take responsibilities of load balancer,
which can accept incoming TCP/UDP sessions on a single virtual IPv6
interface or multiple IPv6 interfaces. Afterwards, it distributes
them according to a specific algorithm it uses to multiple IPv4
servers. Ideally you could have a mix of IPv4 and IPv6 servers
sitting behind the virtual IPv6 address.
Therein, NAT64 has to pick a new source IPv4 address and associated
port number from local IPv4 address pool. DNS64 is a logical
function that synthesizes DNS resource records(e.g., AAAA records
containing IPv6 addresses) from DNS resource records actually
contained in the DNS (e.g., A records containing IPv4 addresses).
2.2. Connecting with IPv4 Internet
NAT64 may also be used to connecting IPv6 users with IPv4 Internet.
In this cases, NAT64 could colocated with BNG or Core Router to map
legacy IPv4 servers into a NAT64 prefix and performs 6-to-4 address.
Therein, NAT64 would perform protocol translation mechanism and
address translation mechanism. Protocol translation from an IPv4
packet header to an IPv6 packet header and vice versa is performed
according to the IP/ICMP Translation Algorithm [RFC6145]. Address
translation maps IPv6 transport addresses to IPv4 transport addresses
and vice versa.
Following illustrates normal process for this usage.
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o Step1: IPv6-only host performs an AAAA DNS query to DNS64 for the
IPv6 address of the Pv4-only sever.
o Step2: DNS64 could not find the IPv6 address of the IPv4-only
sever. So it tries to get the IPv4 address of the Pv4-only sever
by sending A DNS query to DNS4.
o Step3: DNS4 return the A record to the DNS64.
o Step4: DNS64 map the IPv4 address to IPv6 address and send a
synthetic AAAA record which is translated from A record to IPv6-
only host.
o Step5: IPv6-only host send the IPv6 packet to the NAT64. NAT64
translates the IPv6 packet to IPv4 packet and send it to IPv4-only
server.
2.3. NAT64-CGN Mode Requirements
According to above description for NAT64-CGN, the NAT64-CGN
requirements are listed as following.
NAT64-CGN-R1: Each NAT64 device MUST have at least one unicast IPv6
prefix assigned to it, denoted Pref64::/n.
NAT64-CGN-R2:A NAT64 MUST have one or more unicast IPv4 addresses
assigned to it.
NAT64-CGN-R3:Irrespective of the transport protocol used, the NAT64
MUST silently discard all incoming IPv6 packets containing a source
address that contains the Pref64::/n.
NAT64-CGN-R4:The NAT64 MUST only process incoming IPv6 packets that
contain a destination address that contains Pref64::/n. Likewise,
the NAT64 MUST only process incoming IPv4 packets that contain a
destination address that belongs to the IPv4 pool assigned to the
NAT64.
NAT64-CGN-R5:NAT64 MUST support the algorithm for generating IPv6
representations of IPv4 addresses defined in RFC6052 as Address
Translation Algorithms.
NAT64-CGN-R6:For incoming packets carrying TCP or UDP fragments with
a non-zero checksum, NAT64 MAY elect to queue the fragments as they
arrive and translate all fragments at the same time.
NAT64-CGN-R7: For incoming IPv4 packets carrying UDP packets with a
zero checksum, if the NAT64 has enough resources, the NAT64 MUST
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reassemble the packets and MUST calculate the checksum. If the NAT64
does not have enough resources, then it MUST silently discard the
packets.
NAT64-CGN-R8: The NAT64 MAY require that the UDP, TCP, or ICMP header
be completely contained within the fragment that contains fragment
offset equal to zero.
NAT64-CGN-R9:The NAT64 MUST limit the amount of resources devoted to
the storage of fragmented packets in order to protect from DoS
attacks.
NAT64-CGN-R10:The NAT64 MUST make fragmentation process when MTU of
incoming IPv4 traffic exceed maximum MTU on IPv6 side.
NAT64-CGN-R11:The NAT64 MAY let hosts and applications know IPv6
prefix used by the NAT64 and DNS64 so as to hosts have knowledge
whether synthetic IPv6 address is targeted.
NAT64-CGN-R12:The NAT64 MAY decouple with DNS64 in order to establish
communication with IPv4-only servers.
NAT64-CGN-R13:The NAT64 MAY take load-balancing functionalities
incorporating with DNS64.
3. NAT64-CE Mode
NAT64-CE mode represents usages where there NAT64 is closed to
customer edges, like enterprise network edge or residential network
edge.
3.1. NAT64 at Enterprise Network Edge
Some enterprise would like to offers their employees with IPv6
access. However, the service may still stay in IPv4 domain. NAT64
useges in enterprise network could help shift all enterprise service
to be IPv6 enable.
Figure 2 illustrates a network usage where an IPv6-only client
attached to a dual-stack network, but the destination server is
running on a private site where there is NAT64-CE numbered with
public IPv6 addresses and private IPv4 addresses.
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+----------------------+ +------------------------------+
| Dual Stack Internet | | IPv4 Private site (Net 10) |
| | | |
| | | |
| | | +----------+ |
| +----+ +---------+ | | |
| | H1 |-----------|NAT64-CE |-------------| Server | |
| +----+ +---------+ | | |
| v6 only / | | +----------+ |
| Host / | | IPv4-only |
| +-----+ | | etc. 10.1.1.1 |
| | DNS | | | |
| +-----+ | | |
+----------------------+ +------------------------------+
Figure 2: NAT64-CPE Mode Usage
3.2. NAT64 at Residential Network Edge
Residential servers are usually going beyond the operator's
management. They may not able to IPv6-enable due to limitations of
application supporting. In this case, ISP is still assigning private
IPv4 address to servers. However, The nature of private IPv4 would
block the end-to-end bi-directional communications. On the other
hand, IPv6 will bring end-to-end benefits to operators. NAT64-CPE
mode could let IPv6 users to access such IPv6-disable services in
residential areas.
This scenario may appears in ISP network for several cases. As the
instances, visitors go through distant network to take care of family
affairs, like monitoring house security via residential camera,
manipulating household appliances remotely prior to comeback home.
4. Security Considerations
Essentially, there are strong demands to have thorough security
mechanism to prevent privacy invasion in NAT64-CPE scenario. The
detailed considerations need to be further identified.
5. IANA Considerations
This memo includes no request to IANA.
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6. Normative References
[RFC6145] Li, X., Bao, C., and F. Baker, "IP/ICMP Translation
Algorithm", RFC 6145, April 2011.
[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.
[RFC6147] Bagnulo, M., Sullivan, A., Matthews, P., and I. van
Beijnum, "DNS64: DNS Extensions for Network Address
Translation from IPv6 Clients to IPv4 Servers", RFC 6147,
April 2011.
[RFC6204] Singh, H., Beebee, W., Donley, C., Stark, B., and O.
Troan, "Basic Requirements for IPv6 Customer Edge
Routers", RFC 6204, April 2011.
Author's Address
Gang Chen
China Mobile
53A,Xibianmennei Ave.,
Xuanwu District,
Beijing 100053
China
Email: chengang@chinamobile.com
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