Network Working Group K. Nishizuka
Internet-Draft NTT Communications
Intended status: Informational D. Natsume
Expires: April 1, 2014 NTT Neomeit
Sep 28, 2013
Carrier-Grade-NAT (CGN) Deployment Considerations.
draft-nishizuka-cgn-deployment-considerations-01
Abstract
This document provides deployment considerations for Carrier-Grade-
NAT (CGN). Due to emerging new web technologies such as Websocket,
SPDY and HTTP2.0, the trend of the Internet traffic has been
changing. The number of sessions of commonly-used applications were
investigated to estimate the efficiency of IPv4 address sharing of
CGN. Based on the result of the average number of sessions of
subscribers, the verification of CGN was conducted in the large scale
network experiment environment with one million emulated subscribers.
It revealed that CGN can be used in more centralized location of a
provider's network and it arose many considerations.
Status of this Memo
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This Internet-Draft will expire on April 1, 2014.
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document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions used in this document . . . . . . . . . . . . . . 3
3. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. The number of sessions of applications . . . . . . . . . . . . 4
5. Feasibility of port assignment methods . . . . . . . . . . . . 6
5.1. Port assignment methods . . . . . . . . . . . . . . . . . 6
5.2. Efficiency of address saving . . . . . . . . . . . . . . . 6
5.3. Logging design . . . . . . . . . . . . . . . . . . . . . . 7
5.3.1. Amount of the NAT log . . . . . . . . . . . . . . . . 7
5.3.2. Necessity for destination information . . . . . . . . 9
6. Scalability of CGN . . . . . . . . . . . . . . . . . . . . . . 9
6.1. Performance of CGN . . . . . . . . . . . . . . . . . . . . 9
6.2. Redundancy features of CGN . . . . . . . . . . . . . . . . 11
6.3. DNS query traffic considerations . . . . . . . . . . . . . 12
6.4. Separation of traffic . . . . . . . . . . . . . . . . . . 13
7. Tested web sites and applications (Excerpts) . . . . . . . . . 13
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
9. Security Considerations . . . . . . . . . . . . . . . . . . . 14
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 14
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15
11.1. Normative References . . . . . . . . . . . . . . . . . . . 15
11.2. Informative References . . . . . . . . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16
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1. Introduction
IP address sharing is tentative technic to deal with the shortage of
IPv4 addresses. As described in [RFC6269], IP address sharing causes
many issues such as application failures and security
vulnerabilities. A part of these issues is based on the assigned
number of sessions per user and port allocation method of CGN. How
many sessions are sufficient for users is one of the important
considerations. Moreover, the efficiency of CGN is based on the
average number of sessions of subscribers. To answer to these
points, this document lists the number of port consumption of major
application and web sites.
This document also describes the deployment considerations of CGN to
specify the optimum place according to CGN performance. CGN
performance was experimentally-verified with realistic traffic
generated by amount of emulated users.
The growth of IPv6 is continual solution of the shortage of IPv4
addresses and frees these issues. By adopting the combination of the
IPv4 shared address and native IPv6, the duty of CGN will decrease
and as the result, the bad effect on applications which are caused by
the limitation of available ports and address translation itself and
security vulnerability will be resolved. The most effective way of
deploying CGN is examined in this document. Further discussion about
the integration of CGN into the existing network is studied in
[I-D.ietf-opsawg-lsn-deployment].
2. Conventions used in this document
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. Motivation
With a progressive exhaustion of IPv4 addresses, the demands for
sharing IPv4 addresses with multiple customers are rapidly rising,
thus many proposals are getting much attention include Carrier Grade
NAT (CGN, or LSN for Large Scale NAT) [RFC6888], Dual-Stack Lite
[RFC6333], NAT64 [RFC6146], Address+Port (A+P) [RFC6346], 464XLAT
[RFC6877] and MAP [I-D.ietf-softwire-map]. The practical
configuration of these method is based on the same considerations as
follows:
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- Stateful or Stateless
- Centralized or Distributed
- Dynamic port assignment or Static port assignment
- Log reduction strategy
- Security considerations
The best practice about these considerations should be derived from
realistic experiment because there are pros and cons. Though we
tested them in NAT444 environment, the result is applicable for other
approaches. The investigation of number of sessions is described in
this document and it can be also helpful for all of them.
4. The number of sessions of applications
The number of concurrent sessions of applications is important factor
of designing of CGN because there is trade-off between the efficiency
of IPv4 address saving and the availability of those applications.
In addition, for security and fairness, we should limit the number of
sessions per user. As described in [RFC6269], infected devices could
rapidly exhaust the available ports of global pool addresses, hence
all the rest of users could not through the CGN anymore. In order to
place the CGN to existing network, we should know how many sessions
are sufficient for every user. Here is a list of applications and
their average sessions. We selected and tested 50 sites from the
list of top sites and remarkable applications. For web browsing, We
used Chrome and Firefox which are capable of SPDY.
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+-------------------------+----------+--------+--------+--------+
| Application | Total | TCP | TCP | UDP |
| | sessions | port80 | port443| port53 |
+-------------------------+----------+--------+--------+--------+
| Web mail | 65 | 35 | 30 | 20 |
| | | | | |
| Video | 83 | 77 | 6 | 20 |
| | | | | |
| Portal site | 47 | 47 | 0 | 13 |
| | | | | |
| EC site | 45 | 43 | 2 | 11 |
| | | | | |
| blog | 61 | 59 | 2 | 17 |
| | | | | |
| Search Engine | 8 | 8 | 0 | 4 |
| | | | | |
| Online Banking | 20 | 2 | 18 | 4 |
| | | | | |
| Cloud Service | 29 | 23 | 6 | 6 |
| | | | | |
| iTunes | 20 | 1 | 19 | 7 |
| | | | | |
| Twitter | 33 | 1 | 32 | 12 |
| | | | | |
| Twitter(mobile) | 14 | 2 | 11 | 3 |
| | | | | |
| facebook | 51 | 40 | 11 | 18 |
| | | | | |
| facebook(mobile) | 18 | 11 | 7 | 10 |
| | | | | |
| Game | 95 | 86 | 9 | 19 |
| | | | | |
+-------------------------+----------+--------+--------+--------+
Figure 1: The number of sessions of applications.
Figure 1
The number of sessions of these applications are up to 100 sessions.
There are no longer high-consumption applications. This observation
implies that modern applications such as facebook have changed to use
multiplexed requests. Previously, web technologies for achieving
high-performance access consumed many HTTP sessions. Now, current
cutting edge technologies such as WebSocket, SPDY and HTTP2.0 avoid
such an abusing. Basically, all the requests are multiplexed into
one TCP connection. However, a kind of game applications still
consume many sessions.
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The last factor of the estimation of number of sessions is how many
applications are used simultaneously within a single CPE (Customer
Premises Equipment) which includes non-PC devices like gaming
devices. Our investigation shows that the average number of session
of active subscriber is 400. We daresay the limitation of 1000
sessions per user would not affect the most of users while preventing
the severe abuse from certain users.
5. Feasibility of port assignment methods
Basing on the investigation of the number of sessions of
applications, the realistic parameter of each port assignment method
was estimated by the verification.
5.1. Port assignment methods
The efficiency of IPv4 saving by CGN is highly depending on how to
allocate the ports of pool addresses to each users. There are 2
major methods: dynamic assignment and static assignment
[I-D.chen-sunset4-cgn-port-allocation]. There are combined problem
involving efficiency of address saving and logging information
reduction. Typical IP Network Address Translator (NAT)
[RFC2663][RFC2993] implementation uses dynamic assignment, so NAT444,
NAT64, DS-lite and 464XLAT are originally dynamic assignment
approach. To avoid the huge amount of information needed to be
recorded, those approaches have variations of static assignment
[I-D.donley-behave-deterministic-cgn] and MAP is inherently static
assignment approach. For taking advantage of both methods, the
hybrid method that is dynamic assignment of port ranges has been
implemented in some CGN. The merits of the port block assignment
have been referred in [RFC6346],
[I-D.donley-behave-deterministic-cgn] and
[I-D.chen-sunset4-cgn-port-allocation].
5.2. Efficiency of address saving
In the dynamic assignment, the ports of pool address are allocated
randomly for active users. This method can use pool addresses and
ports most effectively. The average number of port consumption (N)
per active subscriber is the key value for dynamic assignment. In
the verification, the average number of port consumption (N) was
estimated to be 400. At the same time, user-quota of 1000 sessions
was set to avoid the abuse. The percentage of the active subscribers
(a) was estimated to be 25% at the value during the busy hour of
traffic (21:00 pm to 1:00am). In this time, "active" subscriber
means who create a new session in certain period of time. Then, when
a CGN adopt the dynamic assignment, the required number of the pool
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address is as follows:
# of pool address (P) = # of Subscriber (S) * a * N / (65536 - R)
Here, (R) is reserved TCP/UDP port list referred in
[I-D.donley-behave-deterministic-cgn]. CGN should eliminate the
wellknown ports (0-1023 for TCP and UDP) to avoid the bad
interpretation from destination servers. It is natural to translate
source port of outgoing packet to ephemeral ports. Using the
equation, 1550 pool addresses are sufficient for 1,000,000
subscribers.
On the other hand, in static assignment, the ports are allocated a
priori for every users. The pool addresses and ports are reserved to
every users, so most of them could be a dead stock because there are
light users and heavy users in aspect of port consumption. The max
number of port consumption in all subscribers is the key value for
static assignment. The true peak number of the session by a heavy
user could be over 10,000 sessions. However it can be assumed that
such a severe consumption of ports to be an abuse, so the number of
statically assigned port (M) is controllable parameter by each
providers. In the static assignment, the required number of the pool
address is as follows:
# of pool address (P) = # of Subscriber (S) * M / (65536 - R)
Taking account into the investigation of number of sessions of
applications, the desirable value of (M) is over 1,000. As the
result, no less than 15,501 pool addresses are needed for 1,000,000
subscribers. The compression ratio is one tenth of the case of
dynamic assignment.
The feasibility of dynamic and static assignment configuration was
confirmed in the verification.
5.3. Logging design
5.3.1. Amount of the NAT log
The size of the log is important consideration of dynamic assignment
because it demands a huge scale of logging ecosystem for CGN. There
is a case that providers must identify a user to respond abuse or
public safety requests. Conventionally, source IP address and a
timestamp are needed. It was possible to identify a user by
comparing IP address with authentication logs of the exact time.
However, when IP address is shared by the CGN, it is necessary to
compare the translated address and port information which are given
by the destination host with the NAT log to identify the untranslated
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IP address. According to the [RFC6888], following information is
recommended to log (for NAT444):
- Transport Protocol - 1 byte
- Source IP address:port - 6 byte
- Source IP address:port after translation - 6 byte
- Timestamp - 8 byte
In addition, the indicator of the allocation and deallocation are
needed because it assures that the identified subscriber certainly
had been using the translated IP address and port. Plus, some
identifier like the index or hostname of the CGN is needed to
identify to which realm an address belongs.
- Add/Delete - 1 byte
- CGN device ID - 4 byte
As the result, the minimum size of NAT log is 26 bytes in binary. In
ASCII format, the average size of NAT log is about 120 byte . Every
active subscriber generate 400 sessions in average for a certain
amount of time. It is assumed that the event happens every 5 minute
in the most severe condition. The size of the log (L) for time frame
(T) can be estimated as follows (for ASCII format):
The size of log (L) = # of Subscriber (S) * a * N * 120byte * 2 * (
Time frame(T) / 5 min. )
It should be noted that the log is generated at the timing of NAT
table creation and freeing. As the result, for 1,000,000 users, the
size of log is piled up to 6.4 terabytes per day. The verification
result confirm the existing estimation referred in
[I-D.donley-behave-deterministic-cgn].
The size of the log can be reduced without loss of information.
Compact format is the technique of reducing the amount of log by
using a notational change (hexadecimal number). It was confirmed by
verification that the compact format can reduce amount of log to
about 80% as compared with ASCII format. Though it was not tested,
theoretically binary format is the smallest notation and amount of
log can be reduced to 22%.
In static allocation, the amount of log is dramatically reduced even
to zero because the untranslated IP address and the translated IP
address / port range are mapped a priori.
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5.3.2. Necessity for destination information
In [RFC6269], it is pointed out that only providing information about
the external address to a service provider is no longer sufficient to
identify customers unambiguously . One of the solutions is the
method of recording the source port information (and exact time
stamp) additionally by the destination server or FW, which is
demanded in [RFC6302]. The other solution is the method of recording
destination IP address and port information by CGN of service
provider. The both solutions are imperfect. In
[I-D.tsou-behave-natx4-log-reduction], it is noted that source port
recording is not supported by every application. Thus, to increase
the certainty, additional logging of destination address and port is
effective measure to deal with the legal request from servers which
are not compliant with [RFC6302]. In dynamic assignment, to log
destination address is additional. It is confirmed by the
verification that by logging destination address, only 4% of amount
of log is increased in ASCII format. On the other hand, in static
assignment, logging of every session is newly required and it has the
same amount of log as the dynamic assignment. It completely breaks
the merit of the static assignment.
6. Scalability of CGN
The estimation of efficiency of address saving and the logging design
are depending on the number of subscribers accommodated with a CGN.
The scalability of the current CGN was verified by the measurement of
the performance.
6.1. Performance of CGN
According to the experimental results, there are three base
capacities to indicate CGN performance as follows:
- Through put
- MCS: Max Concurrent Sessions
- CPS: Connections per Sec
These capacities are not independent of each other, but become mixed
load for CGN. Each load will be combined in real network traffic,
thus using subscriber emulated traffic is important for measuring the
performance in realistic way.
Through put is forwarding performance of CGN. Currently CGN
equipments with an IF of 1GigabitEthernet and 10GigabitEthernet are
flagship models of the manufactures, but CGN has an upper limit
internally because the performance depends on internal devices such
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as CPUs. By ON / OFF of ALGs (Application Level Gateway), the
forwarding performance will be affected because the traffic process
is possibly changed to the path through CPU.
MCS shows an upper limit of the number of records kept in NAT table.
The number of holding sessions depends on retention time of NAT
table. That is because, even after the end of data transmission, the
NAT table is held in a certain period of time to guarantee the
behavior of an application. As described in [RFC6888] REQ-8, if the
CGN tracks TCP sessions, NAT tables may be released when RST or FIN
of TCP has been observed. In case of TCP session where RST or FIN
session has not been observed, and UDP and ICMP communication, NAT
table should retain a certain amount of time. Also, in case of Full
Cone NAT, a table of Full Cone NAT also should retain a certain time
to await communication from outside for a certain period of time. It
is effective to shorten the time-out value in order to suppress the
overflowing NAT table, but it is needed to be careful not to inhibit
the behavior of the application. It is desirable that retention time
of NAT table is configurable as time-out value. In the experiment,
the time-out values are as follows:
+------------------+---------+--------+--------+--------+--------+
| Protocols | TCP | TCP | UDP | DNS | ICMP |
| | | SYN | |(port53)| |
+------------------+---------+--------+--------+--------+--------+
| Time-out Value | 300 | 60 | 300 | 3 | 2 |
+------------------+---------+--------+--------+--------+--------+
Figure 2: The time-out values (sec) in the experiment.
Figure 2
These settings didn't break the behavior of applications we tested.
It is very difficult to estimate maximum number of concurrent
sessions in the network where traffic already exists. By our
assumption, maximum number of concurrent sessions was estimated to be
1M sessions per 10,000 users as follows:
Max Concurrent Sessions (MCS) = # of Subscriber (S) * a * N
As the result, it is verified that tested current CGN is able to have
16M sessions for 160,000 subscribers with the capability of the
dynamic assignment and logging. It means that introducing CGN up to
about 15G traffic section is capable, which implies that CGN can be
placed to more centralized position of the network. In summary, the
settings and the performance result are as follows:
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+----------------------------------------------+
| | Assumed |
| | Values |
+---------------------------------+------------+
| average # of sessions(N) | 400 |
+---------------------------------+------------+
| % of the active subscribers (a) | 25 |
+---------------------------------+------------+
| | Verified |
| | Values |
+---------------------------------+------------+
| # of Subscriber (S) | 160,000 |
+---------------------------------+------------+
| Max Concurrent Sessions(MCS) | 16,000,000 |
+---------------------------------+------------+
| Connection Per Sec(CPS) | 30,000 |
+---------------------------------+------------+
| # of pool address (P) | 4,000 |
+---------------------------------+------------+
| size of log (L) (in 10min) | 7.0GB |
+---------------------------------+------------+
Figure 3: The performance results of tested CGN.
Figure 3
In the verification, session arrival rate by emulated subscribers was
not so high because the load of concurrent sessions is noticeable in
the equipment used in the experiment. There were no problems in weak
load of about 30,000 CPS. In case that traffic flows suddenly change
to standby equipment in redundant network, CPS performance becomes
rate-limiting, so CPS performance is also important factor to
minimize the effect of failures.
6.2. Redundancy features of CGN
It is often referred that introduction of CGN could create Single
Point of Failure(SPOF) (ex. in [RFC6269]). CGN is stateful, in
contrast to stateless BR of MAP, so the redundant configuration must
be achieved by the synchronization of the NAT table between redundant
equipments. Moreover, introduction of CGN creates layer 3 boundary
to NATed traffic, so the redundancy features may work with routers
via dynamic routing. Nevertheless, it is verified that current CGN
can be configured and introduced to service providers network with
the redundancy features. In the verification, CGN was able to switch
to another CGN with sub-sec loss of traffic even in the situation
that they holds 16M concurrent sessions.
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6.3. DNS query traffic considerations
How to deal with the DNS query traffic is unignorable concern for
deployment of CGN. In the test scenario, a control experiment was
conducted to reveal the impact of the huge amount of DNS queries.
Access Node CGN
Emulated +-----------+
Subscribers +-------+ +-------+ | |
+----+ | | | | | |
| --+-----+ R +---------+ CGN +------+ |
+----+ | | | | | Core |
+---+---+ +-------+ | Network |
| | |
| | |
| +-------+ | +-------+ |
| | | | | | |
+-------------+ DNS +------+ | DNS | |
| | | | | |
+-------+ | +-------+ |
+-----------+
DNS Forwarder
Figure 4: Bypassing of DNS queries using DNS forwarder.
In the first case, the original DNS server IP address in the service
provider network is distributed to the subscribers. The emulated
subscribers use the DNS server to get host IP address by name, so all
query packets go through the CGN. The generated DNS query is 12M at
the speed of 10k query per sec. In the second case, IP address of a
DNS server placed in the bypassing position of CGN is distributed to
users. The second DNS server works as a forwarder, so all queries
are forwarded to the first DNS server. Therefore, all DNS queries
are bypassed from the CGN while data traffic is still going through
the CGN.
As the result, it was shown that DNS query almost does not affect the
performance of the CGN. The max concurrent sessions of DNS packet
was only 40k. NAT table of DNS (udp/53,tcp/53) timeouts in 3
seconds, thus It saves the consumption of NAT tables. However NAT
log was generated for every query and it doubled the total amount of
the log. It would be rare that the NAT log of DNS is needed to react
to a legal request. The impact of the DNS query traffic is
relatively small if DNS timeout is adjusted.
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6.4. Separation of traffic
In the existing network, IPv4 communication and IPv6 communication
may already be mixed in the dual stack. In this case, by introducing
CGN which can route IPv6 and existing IPv4 aside from NAT function,
the influence for the network architecture could be suppressed and so
a flexible design is possible. However, though current CGN is
scalable enough to be deployed in core of the service providers
network, the feature of routing is insufficient to replace the
exsisting routers. Such a CGN is desirable, otherwise the design
which makes IPv6 traffic and traditional IPv4 traffic bypass from CGN
is effective choice for providers. In dividing NAT flows and non-NAT
flows routers, VRF (Virtual Routing and Forwarding) and PBR (policy
based routing) are needed at routers in front of CGN. In that case
it is indispensable to configure routers so that the hairpining
communication between the NAT user and non-NAT user to be possible.
The considerations about the separation of traffic and effective
deployment configuration are discussed in detail in
[I-D.ietf-opsawg-lsn-deployment].
7. Tested web sites and applications (Excerpts)
- Web Mail
gmail
yahoo mail
hot mail
- Video
ustream
youtube
nicovideos
Hulu
dailymotion
daum
qq
fc2
xvideos
- Portal&EC site
yahoo
rakuten
amazon
apple
- Blog
livedoor blog
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ameba blog
- Search Engine
google
- Online Banking
mizuho bank
DC card
- Cloud Service
drop box
Evernote
- InstantMessenger & VoIP
skype
Line
- facebook
- twitter
- google map
- Online PC Game
aeria games
ameba pigg
nexon
hangame
- Consumer Game
Armored Core V (Play Station3)
Dark Souls 2 (Play Station3)
Gundam Extreme VS. (Play Station3)
Kinect adventure (XBox)
Persona 4 the ultimate in mayonaka arena (XBox)
Mingol 4 (WiiU)
Monster Hunter 3G (DS-lite)
Keri-hime sweets (iOS)
PuzzDra (iOS)
8. IANA Considerations
This document makes no request of IANA.
9. Security Considerations
TBD
10. Acknowledgments
This research and experiment are conducted under the great support of
Ministry of Internal Affairs and Communications of Japan. Many
thanks to MIC, JAIST members and Shin Miyakawa for their ideas and
feedback in documentation.
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11. References
11.1. Normative References
[I-D.donley-behave-deterministic-cgn]
Donley, C., Grundemann, C., Sarawat, V., Sundaresan, K.,
and O. Vautrin, "Deterministic Address Mapping to Reduce
Logging in Carrier Grade NAT Deployments",
draft-donley-behave-deterministic-cgn-06 (work in
progress), July 2013.
[I-D.ietf-opsawg-lsn-deployment]
Kuarsingh, V. and J. Cianfarani, "CGN Deployment with BGP/
MPLS IP VPNs", draft-ietf-opsawg-lsn-deployment-03 (work
in progress), June 2013.
[RFC2663] Srisuresh, P. and M. Holdrege, "IP Network Address
Translator (NAT) Terminology and Considerations",
RFC 2663, August 1999.
[RFC2993] Hain, T., "Architectural Implications of NAT", RFC 2993,
November 2000.
[RFC6269] Ford, M., Boucadair, M., Durand, A., Levis, P., and P.
Roberts, "Issues with IP Address Sharing", RFC 6269,
June 2011.
[RFC6888] Perreault, S., Yamagata, I., Miyakawa, S., Nakagawa, A.,
and H. Ashida, "Common Requirements for Carrier-Grade NATs
(CGNs)", BCP 127, RFC 6888, April 2013.
11.2. Informative References
[I-D.chen-sunset4-cgn-port-allocation]
Chen, G., "Analysis of NAT64 Port Allocation Method",
draft-chen-sunset4-cgn-port-allocation-02 (work in
progress), July 2013.
[I-D.ietf-softwire-map]
Troan, O., Dec, W., Li, X., Bao, C., Matsushima, S.,
Murakami, T., and T. Taylor, "Mapping of Address and Port
with Encapsulation (MAP)", draft-ietf-softwire-map-08
(work in progress), August 2013.
[I-D.tsou-behave-natx4-log-reduction]
Tsou, T., Li, W., Taylor, T., and J. Huang, "Port
Management To Reduce Logging In Large-Scale NATs",
draft-tsou-behave-natx4-log-reduction-04 (work in
Nishizuka & Natsume Expires April 1, 2014 [Page 15]
Internet-Draft CGN Deployment Considerations Sep 2013
progress), July 2013.
[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.
[RFC6302] Durand, A., Gashinsky, I., Lee, D., and S. Sheppard,
"Logging Recommendations for Internet-Facing Servers",
BCP 162, RFC 6302, June 2011.
[RFC6333] Durand, A., Droms, R., Woodyatt, J., and Y. Lee, "Dual-
Stack Lite Broadband Deployments Following IPv4
Exhaustion", RFC 6333, August 2011.
[RFC6346] Bush, R., "The Address plus Port (A+P) Approach to the
IPv4 Address Shortage", RFC 6346, August 2011.
[RFC6877] Mawatari, M., Kawashima, M., and C. Byrne, "464XLAT:
Combination of Stateful and Stateless Translation",
RFC 6877, April 2013.
Authors' Addresses
Kaname Nishizuka
NTT Communications Corporation
Granpark Tower
3-4-1 Shibaura, Minato-ku
Tokyo 108-8118
Japan
Email: kaname@nttv6.jp
Daigo Natsume
NTT-Neomeit Corporation
3-15 Babacho, Chuo-ku, Osaka-shi
Osaka 540-8511
Japan
Email: daigo.natsume@ntt-neo.co.jp
Nishizuka & Natsume Expires April 1, 2014 [Page 16]