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+Independent Submission                                    C. Donley, Ed.
+Request for Comments: 7021                                     CableLabs
+Category: Informational                                        L. Howard
+ISSN: 2070-1721                                        Time Warner Cable
+                                                            V. Kuarsingh
+                                                   Rogers Communications
+                                                                 J. Berg
+                                                               CableLabs
+                                                                J. Doshi
+                                                        Juniper Networks
+                                                          September 2013
+
+
+   Assessing the Impact of Carrier-Grade NAT on Network Applications
+
+Abstract
+
+   NAT444 is an IPv4 extension technology being considered by Service
+   Providers as a means to continue offering IPv4 service to customers
+   while transitioning to IPv6.  This technology adds an extra Carrier-
+   Grade NAT (CGN) in the Service Provider network, often resulting in
+   two NATs.  CableLabs, Time Warner Cable, and Rogers Communications
+   independently tested the impacts of NAT444 on many popular Internet
+   services using a variety of test scenarios, network topologies, and
+   vendor equipment.  This document identifies areas where adding a
+   second layer of NAT disrupts the communication channel for common
+   Internet applications.  This document was updated to include the
+   Dual-Stack Lite (DS-Lite) impacts also.
+
+Status of This Memo
+
+   This document is not an Internet Standards Track specification; it is
+   published for informational purposes.
+
+   This is a contribution to the RFC Series, independently of any other
+   RFC stream.  The RFC Editor has chosen to publish this document at
+   its discretion and makes no statement about its value for
+   implementation or deployment.  Documents approved for publication by
+   the RFC Editor are not a candidate for any level of Internet
+   Standard; see Section 2 of RFC 5741.
+
+   Information about the current status of this document, any errata,
+   and how to provide feedback on it may be obtained at
+   http://www.rfc-editor.org/info/rfc7021.
+
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+Donley, et al.                Informational                     [Page 1]
+
+RFC 7021                     NAT444 Impacts               September 2013
+
+
+Copyright Notice
+
+   Copyright (c) 2013 IETF Trust and the persons identified as the
+   document authors.  All rights reserved.
+
+   This document is subject to BCP 78 and the IETF Trust's Legal
+   Provisions Relating to IETF Documents
+   (http://trustee.ietf.org/license-info) in effect on the date of
+   publication of this document.  Please review these documents
+   carefully, as they describe your rights and restrictions with respect
+   to this document.
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+Donley, et al.                Informational                     [Page 2]
+
+RFC 7021                     NAT444 Impacts               September 2013
+
+
+Table of Contents
+
+   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
+   2.  Testing Scope  . . . . . . . . . . . . . . . . . . . . . . . .  5
+     2.1.  Test Cases . . . . . . . . . . . . . . . . . . . . . . . .  5
+       2.1.1.  Case 1: Single Client, Single Home Network, Single
+               Service Provider . . . . . . . . . . . . . . . . . . .  5
+       2.1.2.  Case 2: Two Clients, Single Home Network, Single
+               Service Provider . . . . . . . . . . . . . . . . . . .  6
+       2.1.3.  Case 3: Two Clients, Two Home Networks, Single
+               Service Provider . . . . . . . . . . . . . . . . . . .  7
+       2.1.4.  Case 4: Two Clients, Two Home Networks, Two
+               Service Providers Cross ISP  . . . . . . . . . . . . .  8
+     2.2.  General Test Environment . . . . . . . . . . . . . . . . .  8
+     2.3.  Test Metrics . . . . . . . . . . . . . . . . . . . . . . . 10
+     2.4.  Test Scenarios Executed  . . . . . . . . . . . . . . . . . 11
+     2.5.  General Test Methodologies . . . . . . . . . . . . . . . . 11
+   3.  Observed CGN Impacts . . . . . . . . . . . . . . . . . . . . . 12
+     3.1.  Dropped Services . . . . . . . . . . . . . . . . . . . . . 13
+     3.2.  Performance Impacted Services  . . . . . . . . . . . . . . 14
+     3.3.  Improvements since 2010  . . . . . . . . . . . . . . . . . 15
+     3.4.  Additional CGN Challenges  . . . . . . . . . . . . . . . . 16
+   4.  2011 Summary of Results  . . . . . . . . . . . . . . . . . . . 17
+     4.1.  NAT444 . . . . . . . . . . . . . . . . . . . . . . . . . . 17
+     4.2.  DS-Lite  . . . . . . . . . . . . . . . . . . . . . . . . . 19
+   5.  2010 Summary of Results  . . . . . . . . . . . . . . . . . . . 22
+     5.1.  Case 1: Single Client, Single Home Network, Single
+           Service Provider . . . . . . . . . . . . . . . . . . . . . 22
+     5.2.  Case 2: Two Clients, Single Home Network, Single
+           Service Provider . . . . . . . . . . . . . . . . . . . . . 24
+     5.3.  Case 3: Two Clients, Two Home Networks, Single Service
+           Provider . . . . . . . . . . . . . . . . . . . . . . . . . 24
+     5.4.  Case 4: Two Clients, Two Home Networks, Two Service
+           Providers Cross ISP  . . . . . . . . . . . . . . . . . . . 25
+   6.  CGN Mitigation . . . . . . . . . . . . . . . . . . . . . . . . 25
+   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 26
+   8.  Informative References . . . . . . . . . . . . . . . . . . . . 26
+   Appendix A.  Acknowledgements  . . . . . . . . . . . . . . . . . . 28
+
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+Donley, et al.                Informational                     [Page 3]
+
+RFC 7021                     NAT444 Impacts               September 2013
+
+
+1.  Introduction
+
+   IANA, APNIC, and RIPE NCC exhausted their IPv4 address space in 2011-
+   2012.  Current projections suggest that ARIN may exhaust its free
+   pool of IPv4 addresses in 2013.  IPv6 is the solution to the IPv4
+   depletion problem; however, the transition to IPv6 will not be
+   completed prior to IPv4 exhaustion.  NAT444 [NAT444] and Dual-Stack
+   Lite [RFC6333] are transition mechanisms that will allow Service
+   Providers to multiplex customers behind a single IPv4 address, which
+   will allow many legacy devices and applications some IPv4
+   connectivity.  While both NAT444 and Dual-Stack Lite provide basic
+   IPv4 connectivity, they impact a number of advanced applications.
+   This document describes suboptimal behaviors of NAT444 and DS-Lite
+   found in our test environments.
+
+   From July through August 2010, CableLabs, Time Warner Cable, and
+   Rogers Communications tested the impact of NAT444 on common
+   applications using Carrier-Grade NAT (CGN) devices.  This testing was
+   focused on a wide array of real-time usage scenarios designed to
+   evaluate the user experience over the public Internet using NAT444 in
+   both single and dual ISP environments.  The purpose of this testing
+   was to identify applications where the technology either breaks or
+   significantly impacts the user experience.  The testing revealed that
+   applications, such as video streaming, video gaming, and peer-to-peer
+   file sharing, are impacted by NAT444.
+
+   From June through October 2011, CableLabs conducted additional
+   testing of CGN technologies, including both NAT444 and Dual-Stack
+   Lite.  The testing focused on working with several vendors including
+   A10, Alcatel-Lucent, and Juniper to optimize the performance of those
+   applications that experienced negative impacts during earlier CGN
+   testing and to expand the testing to DS-Lite.
+
+   Applications that were tested included, but were not necessarily
+   limited to, the following:
+
+   1.  Video/Audio streaming, e.g., Silverlight-based applications,
+       Netflix, YouTube, Pandora 2
+
+   2.  Peer-to-peer applications, e.g., video gaming, uTorrent
+
+   3.  Online gaming, e.g., Xbox
+
+   4.  Large file transfers using File Transfer Protocol (FTP)
+
+   5.  Session Initiation Protocol (SIP) calls via X-Lite, Skype
+
+
+
+
+
+Donley, et al.                Informational                     [Page 4]
+
+RFC 7021                     NAT444 Impacts               September 2013
+
+
+   6.  Social Networking, e.g., Facebook, Webkinz
+
+   7.  Video chat, e.g., Skype
+
+   8.  Web conferencing
+
+2.  Testing Scope
+
+2.1.  Test Cases
+
+   The diagrams below depict the general network architecture used for
+   testing NAT444 and Dual-Stack Lite coexistence technologies at
+   CableLabs.
+
+2.1.1.  Case 1: Single Client, Single Home Network, Single Service
+        Provider
+
+                                  ^^^^^^^^
+                                 (Internet)
+                                  vvvvvvvv
+                                     |
+                                     |
+                              +---------------+
+                              |      CGN      |
+                              +---------------+
+                                   |
+                              +---------------+
+                              |      CMTS     |
+                              +---------------+
+                                    |
+                              +---------------+
+                              |      CM       |
+                              +---------------+
+                                    |
+                             +-------------------------+
+                             |      Home Router        |
+                             +-------------------------+
+                                    |
+                             +---------------+
+                             |      Client   |
+                             +---------------+
+
+   This is a typical case for a client accessing content on the
+   Internet.  For this case, we focused on basic web browsing, voice and
+   video chat, instant messaging, video streaming (using YouTube, Google
+   Videos, etc.), torrent leeching and seeding, FTP, and gaming.
+
+
+
+
+
+Donley, et al.                Informational                     [Page 5]
+
+RFC 7021                     NAT444 Impacts               September 2013
+
+
+2.1.2.  Case 2: Two Clients, Single Home Network, Single Service
+        Provider
+
+                                  ^^^^^^^^
+                                 (Internet)
+                                  vvvvvvvv
+                                    |
+                                    |
+                             +---------------+
+                             |      CGN      |
+                             +---------------+
+                                    |
+                             +---------------+
+                             |      CMTS     |
+                             +---------------+
+                                   |
+                             +---------------+
+                             |      CM       |
+                             +---------------+
+                                   |
+                            +-------------------------+
+                            |      Home Router        |
+                            +-------------------------+
+                                   |                |
+                     +---------------+   +---------------+
+                     |      Client   |   |      Client   |
+                     +---------------+   +---------------+
+
+   This is similar to Case 1, except that two clients are behind the
+   same Large-Scale NAT (LSN) and in the same home network.  This test
+   case was conducted to observe any change in speed in basic web
+   browsing and video streaming.
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+Donley, et al.                Informational                     [Page 6]
+
+RFC 7021                     NAT444 Impacts               September 2013
+
+
+2.1.3.  Case 3: Two Clients, Two Home Networks, Single Service Provider
+
+                                 ^^^^^^^^
+                                (Internet)
+                                 vvvvvvvv
+                                    |
+                                    |
+                             +---------------+
+                             |      CGN      |
+                             +---------------+
+                                     |
+                             +---------------+
+                             |      CMTS     |
+                             +---------------+
+                                     |
+           ----------------------------------------
+                       |                     |
+           +---------------+         +---------------+
+           |      CM       |         |      CM       |
+           +---------------+         +---------------+
+                   |                     |
+   +-------------------------+ +-------------------------+
+   |      Home Router        | |      Home Router        |
+   +-------------------------+ +-------------------------+
+                   |                     |
+     +---------------+         +---------------+
+     |      Client   |         |      Client   |
+     +---------------+         +---------------+
+
+   In this scenario, the two clients are under the same LSN but behind
+   two different gateways.  This simulates connectivity between two
+   residential subscribers on the same ISP.  We tested peer-to-peer
+   applications.
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+Donley, et al.                Informational                     [Page 7]
+
+RFC 7021                     NAT444 Impacts               September 2013
+
+
+2.1.4.  Case 4: Two Clients, Two Home Networks, Two Service Providers
+        Cross ISP
+
+            ^^^^^^^^                    ^^^^^^^^
+           ( ISP A )                   ( ISP B  )
+            Vvvvvvvv                    vvvvvvvv
+             |                           |
+           +---------------+         +---------------+
+           |      LSN      |         |      LSN      |
+           +---------------+         +---------------+
+               |                         |
+           +---------------+         +---------------+
+           |      CMTS     |         |      CMTS     |
+           +---------------+         +---------------+
+              |                          |
+           +---------------+         +---------------+
+           |      CM       |         |      CM       |
+           +---------------+         +---------------+
+                 |                         |
+   +-------------------------+ +-------------------------+
+   |      Home Router        | |      Home Router        |
+   +-------------------------+ +-------------------------+
+                  |                        |
+     +---------------+         +---------------+
+     |      Client   |         |      Client   |
+     +---------------+         +---------------+
+
+   This test case is similar to Case 1 but with the addition of another
+   identical ISP.  This topology allows us to test traffic between two
+   residential customers connected across the Internet.  We focused on
+   client-to-client applications such as IM and peer-to-peer.
+
+2.2.  General Test Environment
+
+   The lab environment was intended to emulate multiple Service Provider
+   networks with a CGN deployed and with connectivity to the public IPv4
+   or IPv6 Internet (as dictated by the coexistence technology under
+   test).  This was accomplished by configuring a CGN behind multiple
+   cable modem termination systems (CMTSs) and setting up multiple home
+   networks for each ISP.  Testing involved sending traffic to and from
+   the public Internet in both single and dual ISP environments, using
+   both single and multiple home networks.  The following equipment was
+   used for testing:
+
+   o  CGN
+
+   o  CMTS
+
+
+
+
+Donley, et al.                Informational                     [Page 8]
+
+RFC 7021                     NAT444 Impacts               September 2013
+
+
+   o  Cable Modem (CM)
+
+   o  IP sniffer
+
+   o  RF (radio frequency) sniffer
+
+   o  Metrics tools (for network performance)
+
+   o  CPE (Customer Premises Equipment) gateway devices
+
+   o  Laptop or desktop computers (multiple OSs used)
+
+   o  Gaming consoles
+
+   o  iPad or tablet devices
+
+   o  other Customer Edge (CE) equipment, e.g., Blu-ray players
+      supporting miscellaneous applications
+
+   One or more CPE gateway devices were configured in the home network.
+   One or more host devices behind the gateways were also configured in
+   order to test conditions, such as multiple users on multiple home
+   networks in the CGN architecture, both in single and dual ISP
+   environments.
+
+   The scope of testing was honed down to the specific types of
+   applications and network conditions that demonstrated a high
+   probability of diminishing user experience based on prior testing.
+   The following use cases were tested:
+
+   1.   Video streaming over Netflix
+
+   2.   Video streaming over YouTube
+
+   3.   Video streaming over Joost
+
+   4.   Online gaming with Xbox (one user)
+
+   5.   Peer-to-peer gaming with Xbox (two users)
+
+   6.   BitTorrent/uTorrent file seeding/leeching
+
+   7.   Pandora Internet Radio
+
+   8.   FTP server
+
+   9.   Web conferencing GoToMeeting (GTM), WebEx
+
+
+
+
+Donley, et al.                Informational                     [Page 9]
+
+RFC 7021                     NAT444 Impacts               September 2013
+
+
+   10.  Social Networking -- Facebook, Webkinz (chat, YouTube, file
+        transfer)
+
+   11.  Internet Archive -- Video and Audio streaming; large file
+        downloads
+
+   12.  Video streaming using iClips
+
+   13.  SIP Calls -- X-Lite, Skype, PJSIP
+
+   14.  Microsoft Smooth Streaming (Silverlight)
+
+   15.  Video chat -- Skype, ooVoo
+
+   The following CPE devices were used for testing these applications on
+   one or more home networks:
+
+   1.  Windows 7, XP, and Vista-based laptops
+
+   2.  Mac OS X laptop
+
+   3.  iPad
+
+   4.  Xbox gaming consoles
+
+   5.  iPhone and Android smartphones
+
+   6.  LG Blu-ray player (test applications such as Netflix, Vudu, etc.)
+
+   7.  Home routers -- Netgear, Linksys, D-Link, Cisco, Apple
+
+2.3.  Test Metrics
+
+   Metrics data that were collected during the course of testing were
+   related to throughput, latency, and jitter.  These metrics were
+   evaluated under three conditions:
+
+   1.  Initial finding on the CGN configuration used for testing
+
+   2.  Retest of the same test scenario with the CGN removed from the
+       network
+
+   3.  Retest with a new configuration (optimized) on the CGN (when
+       possible)
+
+   In our testing, we found only slight differences with respect to
+   latency or jitter when the CGN was in the network versus when it was
+   not present in the network.  It should be noted that we did not
+
+
+
+Donley, et al.                Informational                    [Page 10]
+
+RFC 7021                     NAT444 Impacts               September 2013
+
+
+   conduct any performance testing and metrics gathered were limited to
+   single session scenarios.  Also, bandwidth was not restricted on the
+   Data Over Cable Service Interface Specification (DOCSIS) network.
+   Simulated homes shared a single DOCSIS upstream and downstream
+   channel. (In the following table, "us" stands for microsecond.)
+
+   +---------+---------+---------+---------+-----------------+---------+
+   | Case    | Avg     | Min     | Max     | [RFC4689]       | Max     |
+   |         | Latency | Latency | Latency | Absolute Avg    | Jitter  |
+   |         |         |         |         | Jitter          |         |
+   +---------+---------+---------+---------+-----------------+---------+
+   | With    | 240.32  | 233.77  | 428.40  | 1.86 us         | 191.22  |
+   | CGN     | us      | us      | us      |                 | us      |
+   +---------+---------+---------+---------+-----------------+---------+
+   | Without | 211.88  | 190.39  | 402.69  | 0.07 us         | 176.16  |
+   | CGN     | us      | us      | us      |                 | us      |
+   +---------+---------+---------+---------+-----------------+---------+
+
+                              CGN Performance
+
+   Note: Performance testing as defined by CableLabs includes load
+   testing, induction of impairments on the network, etc.  This type of
+   testing was out of scope for CGN testing.
+
+2.4.  Test Scenarios Executed
+
+   The following test scenarios were executed using the aforementioned
+   applications and test equipment:
+
+   1.  Single ISP, Single Home Network, with Single User
+
+   2.  Single ISP, Two Home Networks, with One User on Each Network
+
+   3.  Dual ISPs, Single Home Network, with Single User on Each ISP
+
+   4.  Dual ISPs, One Home Network, with One User connected to ISP-A;
+       Two Home Networks, with One User on Each connected to ISP-B
+
+   These test scenarios were executed for both NAT444 and DS-Lite
+   technologies.
+
+2.5.  General Test Methodologies
+
+   The CGN was configured for the optimal setting for the specific test
+   being executed for NAT444 or DS-Lite.  Individual vendors provided
+   validation of the configuration used for the coexistence technology
+   under test prior to the start of testing.  Some NAT444 testing used
+   private [RFC1918] IPv4 space between the CGN and CPE router; other
+
+
+
+Donley, et al.                Informational                    [Page 11]
+
+RFC 7021                     NAT444 Impacts               September 2013
+
+
+   tests used public (non-[RFC1918]) IPv4 space between the CGN and CPE
+   router.  With the exception of 6to4 [RFC3056] traffic, we observed no
+   difference in test results whether private or public address space
+   was used. 6to4 failed when public space was used between the CGN and
+   the CPE router was public, but CPE routers did not initiate 6to4 when
+   private space was used.
+
+   CPE gateways and client devices were configured with IPv4 or IPv6
+   addresses using DHCP or manual configuration, as required by each of
+   the devices used in the test.
+
+   All devices were brought to operational state.  Connectivity of CPE
+   devices to provider network and public Internet was verified prior to
+   the start of each test.
+
+   IP sniffers and metrics tools were configured as required before
+   starting tests.  IP capture and metrics data was collected for all
+   failed test scenarios.  Sniffing was configured behind the home
+   routers, north and south of the CMTS, and north and south of the CGN.
+
+   The test technician executed test scenarios listed above, for single
+   and dual ISP environments, testing multiple users on multiple home
+   networks, using the applications described above where applicable to
+   the each specific test scenario.  Results and checklists were
+   compiled for all tests executed and for each combination of devices
+   tested.
+
+3.  Observed CGN Impacts
+
+   CGN testing revealed that basic services such as email and web
+   browsing worked normally and as expected.  However, there were some
+   service-affecting issues noted for applications that fall into two
+   categories: dropped service and performance impacted service.  In
+   addition, for some specific applications in which the performance was
+   impacted, throughput, latency, and jitter measurements were taken.
+   We observed that performance often differs from vendor to vendor and
+   from test environment to test environment, and the results are
+   somewhat difficult to predict.  So as to not become a comparison
+   between different vendor implementations, these results are presented
+   in summary form.  When issues were identified, we worked with the
+   vendors involved to confirm the specific issues and explore
+   workarounds.  Except where noted, impacts to NAT444 and DS-Lite were
+   similar.
+
+   In 2010 testing, we identified that IPv6 transition technologies such
+   as 6to4 [RFC3056] and Teredo [RFC4380] fail outright or are subject
+   to severe service degradation.  We did not repeat transition
+   technology testing in 2011.
+
+
+
+Donley, et al.                Informational                    [Page 12]
+
+RFC 7021                     NAT444 Impacts               September 2013
+
+
+   Note: While email and web browsing operated as expected within our
+   environment, there have been reports that anti-spam/anti-abuse
+   measures limiting the number of connections from a single address can
+   cause problems in a CGN environment by improperly interpreting
+   address sharing as too many connections from a single device.  Care
+   should be taken when deploying CGNs to mitigate the impact of address
+   sharing when configuring anti-spam/anti-abuse measures.  See Section
+   3.4.
+
+3.1.  Dropped Services
+
+   Several peer-to-peer applications, specifically peer-to-peer gaming
+   using Xbox and peer-to-peer SIP calls using the PJSIP client, failed
+   in both the NAT444 and Dual-Stack Lite environments.  Many CGN
+   devices use "full cone" NAT so that once the CGN maps a port for
+   outbound services, it will accept incoming connections to that port.
+   However, some applications did not first send outgoing traffic and
+   hence did not open an incoming port through the CGN.  Other
+   applications try to open a particular fixed port through the CGN;
+   while service will work for a single subscriber behind the CGN, it
+   fails when multiple subscribers try to use that port.
+
+   PJSIP and other SIP software worked when clients used a registration
+   server to initiate calls, provided that the client inside the CGN
+   initiated the traffic first and that only one SIP user was active
+   behind a single IPv4 address at any given time.  However, in our
+   testing, we observed that when making a direct client-to-client SIP
+   call across two home networks on a single ISP, or when calling from a
+   single home network across dual ISPs, calls could neither be
+   initiated nor received.
+
+   In the case of peer-to-peer gaming between two Xbox 360 users in
+   different home networks on the same ISP, the game could not be
+   connected between the two users.  Both users shared an outside IP
+   address and tried to connect to the same port, causing a connection
+   failure.  There are some interesting nuances to this problem.  In the
+   case where two users are in the same home network and the scenario is
+   through a single ISP, when the Xbox tries to register with the Xbox
+   server, the server sees that both Xboxes are coming through the same
+   public IP address and directs the devices to connect using their
+   internal IP addresses.  So, the connection ultimately gets
+   established directly between both Xboxes via the home gateway, rather
+   than the Xbox server.  In the case where there are two Xbox users on
+   two different home networks using a single ISP and the CGN is
+   configured with only one public IPv4 address, this scenario will not
+   work because the route between the two users cannot be determined.
+   However, if the CGN is configured with two public NAT IP addresses,
+   this scenario will work because now there is a unique IP address with
+
+
+
+Donley, et al.                Informational                    [Page 13]
+
+RFC 7021                     NAT444 Impacts               September 2013
+
+
+   which to communicate.  This is not an ideal solution, however,
+   because it means that there is a one-to-one relationship between IP
+   addresses in the public NAT and the number of Xbox users on each
+   network.
+
+   Update: in December 2011, Microsoft released an update for Xbox.
+   While we did not conduct thorough testing using the new release,
+   preliminary testing indicates that Xboxes that upgraded to the latest
+   version can play head-to-head behind a CGN, at least for some games.
+
+   Other peer-to-peer applications that were noted to fail were seeding
+   sessions initiated on BitTorrent and uTorrent.  In our test, torrent
+   seeding was initiated on a client inside the CGN.  Leeching was
+   initiated using a client on the public Internet.  It was observed
+   that direct peer-to-peer seeding did not work.  However, the torrent
+   session typically redirected the leeching client to a proxy server,
+   in which case the torrent session was set up successfully.
+   Additionally, with the proxy in the network, re-seeding via
+   additional leech clients worked as would be expected for a typical
+   torrent session.  Finally, uTorrent tries to use Session Traversal
+   Utilities for NAT (STUN) to identify its outside address.  In working
+   with vendors, we learned that increasing the STUN timeout to 4
+   minutes improved uTorrent seeding performance behind a CGN, resulting
+   in the ability for the uTorrent client to open a port and
+   successfully seed content.
+
+   FTP sessions to servers located inside the home (e.g., behind two
+   layers of NAT) failed.  When the CGN was bypassed and traffic only
+   needed to flow through one layer of NAT, clients were able to
+   connect.  Finally, multicast traffic was not forwarded through the
+   CGN.
+
+3.2.  Performance Impacted Services
+
+   Large size file transfers and multiple video streaming sessions
+   initiated on a single client on the same home network behind the CGN
+   experienced reduced performance in our environment.  We measured
+   these variations in user experience against a baseline IPv4
+   environment where NAT is not deployed.
+
+   In our testing, we tried large file transfers from several FTP sites,
+   as well as downloading sizable audio and video files (750 MB to 1.4
+   GB) from the Internet Archive.  We observed that when Dual-Stack Lite
+   was implemented for some specific home router and client
+   combinations, the transfer rate was markedly slower.  For example,
+   PC1 using one operating system behind the same home router as PC2
+   using a different operating system yielded a transfer rate of 120
+   kbps for PC1, versus 250 kbps for PC2.  Our conclusion is that
+
+
+
+Donley, et al.                Informational                    [Page 14]
+
+RFC 7021                     NAT444 Impacts               September 2013
+
+
+   varying combinations of home routers and CE-client devices may result
+   in a user experience that is less than what the user would expect for
+   typical applications.  It is also difficult to predict which
+   combinations of CPE routers and CE devices will produce a reduced
+   experience for the user.  We did not analyze the root cause of the
+   divergence in performance across CE devices, as this was beyond the
+   scope of our testing.  However, as this issue was specific to Dual-
+   Stack Lite, we suspect that it is related to the MTU.
+
+   While video streaming sessions for a single user generally performed
+   well, testing revealed that video streaming sessions such as
+   Microsoft Smooth Streaming technology (i.e., Silverlight) or Netflix
+   might also exhibit some service impacting behavior.  In particular,
+   this was observed on one older, yet popular and well-known CPE router
+   where the first session was severely degraded when a second session
+   was initiated in the same home network.  Traffic from the first
+   session ceased for 8 s once the second session was initiated.  While
+   we are tempted to write this off as a problematic home router, its
+   popularity suggests that home router interactions may cause issues in
+   NAT444 deployments (newer routers that support DS-Lite were not
+   observed to experience this condition).  Overall, longer buffering
+   times for video sessions were noted for most client devices behind
+   all types of home routers.  However, once the initial buffering was
+   complete, the video streams were consistently smooth.  In addition,
+   there were varying degrees as to how well multiple video sessions
+   were displayed on various client devices across the CPE routers
+   tested.  Some video playback devices performed better than others.
+
+3.3.  Improvements since 2010
+
+   Since CableLabs completed initial CGN testing in 2010, there have
+   been quantifiable improvements in performance over CGN since that
+   time.  These improvements may be categorized as follows:
+
+   o  Content provider updates
+
+   o  Application updates
+
+   o  Improvements on the CGNs themselves
+
+   In terms of content provider updates, we have noted improvements in
+   the overall performance of streaming applications in the CGN
+   environment.  Whereas applications such as streaming video were very
+   problematic a year ago with regard to jitter and latency, our most
+   recent testing revealed that there is less of an issue with these
+   conditions, except in some cases when multiple video streaming
+
+
+
+
+
+Donley, et al.                Informational                    [Page 15]
+
+RFC 7021                     NAT444 Impacts               September 2013
+
+
+   sessions were initiated on the same client using specific types of
+   home routers.  Applications such as MS Smooth Streaming appear to
+   have addressed these issues to some degree.
+
+   As far as application updates, use of STUN and/or proxy servers to
+   offset some of the limitations of NAT and tunneling in the network
+   are more evident as workarounds to the peer-to-peer issues.
+   Applications appear to have incorporated other mechanisms for
+   delivering content faster, even if buffering times are somewhat
+   slower and the content is not rendered as quickly.
+
+   CGN vendors have also upgraded their devices to mitigate several
+   known issues with specific applications.  With regard to addressing
+   peer-to-peer SIP call applications, port reservations appear to be a
+   workaround to the problem.  However, this approach has limitations
+   because there are limited numbers of users that can have port
+   reservations at any given time.  For example, one CGN implementation
+   allowed a port reservation to be made on port 5060 (default SIP
+   port), but this was the only port that could be configured for the
+   SIP client.  This means that only one user can be granted the port
+   reservation.
+
+3.4.  Additional CGN Challenges
+
+   There are other challenges that arise when using shared IPv4 address
+   space, as with NAT444.  Some of these challenges include:
+
+   o  Loss of geolocation information - Often, translation zones will
+      cross traditional geographic boundaries.  Since the source
+      addresses of packets traversing an LSN are set to the external
+      address of the LSN, it is difficult for external entities to
+      associate IP/Port information to specific locations/areas.
+
+   o  Lawful Intercept/Abuse Response - Due to the nature of NAT444
+      address sharing, it will be hard to determine the customer/
+      endpoint responsible for initiating a specific IPv4 flow based on
+      source IP address alone.  Content providers, Service Providers,
+      and law enforcement agencies will need to use new mechanisms
+      (e.g., logging source port and timestamp in addition to source IP
+      address) to potentially mitigate this new problem.  This may
+      impact the timely response to various identification requests.
+      See [RFC6269].
+
+   o  Anti-spoofing - Multiplexing users behind a single IP address can
+      lead to situations where traffic from that address triggers anti-
+      spoofing/DDoS-protection mechanisms, resulting in unintentional
+      loss of connectivity for some users.  We have received reports of
+
+
+
+
+Donley, et al.                Informational                    [Page 16]
+
+RFC 7021                     NAT444 Impacts               September 2013
+
+
+      such anti-spoofing/DDoS mechanisms affecting email and web
+      services in some instances, but did not experience them in our
+      environment.
+
+4.  2011 Summary of Results
+
+4.1.  NAT444
+
+ +---------------------+--------+--------+--------+----------+---------+
+ | Test Scenario       | Single | Single | Dual   | Dual     | Notes   |
+ | (per Test Plan)     | ISP,   | ISP,   | ISP,   | ISP, One |         |
+ |                     | Single | Two    | One HN | HN+One   |         |
+ |                     | HN,    | HN,    | with   | User on  |         |
+ |                     | Single | Single | One    | ISP-A,   |         |
+ |                     | User   | User   | User   | Two HN   |         |
+ |                     |        | on     | on     | with One |         |
+ |                     |        | Each   | Each   | User on  |         |
+ |                     |        |        | ISP    | Each on  |         |
+ |                     |        |        |        | ISP-B    |         |
+ +---------------------+--------+--------+--------+----------+---------+
+ | Video streaming     | Pass   | Pass   | Pass   | Pass     | fails   |
+ | over Netflix        |        |        |        |          | behind  |
+ |                     |        |        |        |          | one     |
+ |                     |        |        |        |          | router  |
+ +---------------------+--------+--------+--------+----------+---------+
+ | Video streaming     | Pass   | Pass   | Pass   | Pass     |         |
+ | over YouTube        |        |        |        |          |         |
+ +---------------------+--------+--------+--------+----------+---------+
+ | Video streaming     | Pass   | Pass   | Pass   | Pass     |         |
+ | over Joost          |        |        |        |          |         |
+ +---------------------+--------+--------+--------+----------+---------+
+ | Online gaming with  | Pass   | Pass   | Pass   | NT       |         |
+ | one user            |        |        |        |          |         |
+ +---------------------+--------+--------+--------+----------+---------+
+ | Peer-to-peer gaming | Pass   | Fail   | Pass   | NT       | fails   |
+ | with two users      |        |        |        |          | when    |
+ |                     |        |        |        |          | both    |
+ |                     |        |        |        |          | users   |
+ |                     |        |        |        |          | NAT to  |
+ |                     |        |        |        |          | same    |
+ |                     |        |        |        |          | address |
+ +---------------------+--------+--------+--------+----------+---------+
+ | BitTorrent/uTorrent | Fail   | Fail   | Fail   | Fail     |         |
+ | file seeding        |        |        |        |          |         |
+ +---------------------+--------+--------+--------+----------+---------+
+
+
+
+
+
+
+Donley, et al.                Informational                    [Page 17]
+
+RFC 7021                     NAT444 Impacts               September 2013
+
+
+ (continued)
+ +---------------------+--------+--------+--------+----------+---------+
+ | BitTorrent/uTorrent | Pass   | Pass   | Pass   | Pass     |         |
+ | file leeching       |        |        |        |          |         |
+ +---------------------+--------+--------+--------+----------+---------+
+ | Pandora Internet    | Pass   | Pass   | Pass   | Pass     |         |
+ | Radio               |        |        |        |          |         |
+ +---------------------+--------+--------+--------+----------+---------+
+ | FTP server          | Pass   | Pass   | Pass   | Pass     |         |
+ +---------------------+--------+--------+--------+----------+---------+
+ | Web conferencing    | Pass   | Pass   | Pass   | Pass     |         |
+ | GTM                 |        |        |        |          |         |
+ +---------------------+--------+--------+--------+----------+---------+
+ | Social Networking   | Pass   | Pass   | Pass   | Pass     |         |
+ | Facebook            |        |        |        |          |         |
+ +---------------------+--------+--------+--------+----------+---------+
+ | Social Networking   | Pass   | Pass   | Pass   | Pass     |         |
+ | Webkinz             |        |        |        |          |         |
+ +---------------------+--------+--------+--------+----------+---------+
+ | X-Lite for SIP      | Pass   | Pass   | Pass   | Pass     |         |
+ | calls with proxy    |        |        |        |          |         |
+ +---------------------+--------+--------+--------+----------+---------+
+ | X-Lite for SIP      | Fail   | Fail   | Fail   | Fail     |         |
+ | calls no proxy      |        |        |        |          |         |
+ +---------------------+--------+--------+--------+----------+---------+
+ | Skype text chat     | Pass   | Pass   | Pass   | Pass     |         |
+ +---------------------+--------+--------+--------+----------+---------+
+ | Skype video chat    | Pass   | Pass   | Pass   | Pass     |         |
+ +---------------------+--------+--------+--------+----------+---------+
+ | ooVoo               | Pass   | Pass   | Pass   | Pass     |         |
+ +---------------------+--------+--------+--------+----------+---------+
+ | MS Smooth streaming | Pass   | Pass   | Pass   | Pass     |         |
+ +---------------------+--------+--------+--------+----------+---------+
+ | Internet Archive    | Pass   | Pass   | Pass   | Pass     |         |
+ | video streaming     |        |        |        |          |         |
+ +---------------------+--------+--------+--------+----------+---------+
+ | Internet Archive    | Pass   | Pass   | Pass   | Pass     |         |
+ | audio streaming     |        |        |        |          |         |
+ +---------------------+--------+--------+--------+----------+---------+
+ | Internet Archive    | Pass   | Pass   | Pass   | Pass     |         |
+ | file download       |        |        |        |          |         |
+ +---------------------+--------+--------+--------+----------+---------+
+ | iClips              | Pass   | Pass   | Pass   | Pass     |         |
+ +---------------------+--------+--------+--------+----------+---------+
+
+                                  NAT444
+
+
+
+
+
+Donley, et al.                Informational                    [Page 18]
+
+RFC 7021                     NAT444 Impacts               September 2013
+
+
+4.2.  DS-Lite
+
+  +--------------+---------+-----------+---------------+---------------+
+  | Test         | DS-Lite | Duration  | Description   | General       |
+  | Scenario     | Test    | of Test   | of Test       | Observations  |
+  | (per Test    | Results | Performed | Execution     | and Notes     |
+  | Plan)        |         |           |               |               |
+  +--------------+---------+-----------+---------------+---------------+
+  | Video        | Pass    | 15 min.   |               |               |
+  | streaming    |         |           |               |               |
+  | over Netflix |         |           |               |               |
+  +--------------+---------+-----------+---------------+---------------+
+  | Video        | Pass    | 10 min.   |               |               |
+  | streaming    |         |           |               |               |
+  | over YouTube |         |           |               |               |
+  +--------------+---------+-----------+---------------+---------------+
+  | Video        | Pass    | 10 min.   |               |               |
+  | streaming    |         |           |               |               |
+  | over Joost   |         |           |               |               |
+  +--------------+---------+-----------+---------------+---------------+
+  | Online       | Pass    | 15 min.   |               |               |
+  | gaming with  |         |           |               |               |
+  | one user     |         |           |               |               |
+  +--------------+---------+-----------+---------------+---------------+
+  | Peer-to-peer | Fail    | NA        | user inside   | Users inside  |
+  | gaming with  |         |           | HN1 playing   | both HN are   |
+  | two users    |         |           | game against  | not able to   |
+  |              |         |           | user inside   | connect.  The |
+  |              |         |           | HN2           | error shown   |
+  |              |         |           |               | on console,   |
+  |              |         |           |               | "The game     |
+  |              |         |           |               | session is no |
+  |              |         |           |               | longer        |
+  |              |         |           |               | available"    |
+  +--------------+---------+-----------+---------------+---------------+
+  | BitTorrent   | Fail    | 12 min.   | user on the   |               |
+  | or uTorrent  |         |           | Internet is   |               |
+  | file seeding |         |           | able to       |               |
+  |              |         |           | download file |               |
+  |              |         |           | using proxy   |               |
+  |              |         |           | server and    |               |
+  |              |         |           | not           |               |
+  |              |         |           | peer-to-peer  |               |
+  +--------------+---------+-----------+---------------+---------------+
+
+
+
+
+
+
+
+Donley, et al.                Informational                    [Page 19]
+
+RFC 7021                     NAT444 Impacts               September 2013
+
+
+  (continued)
+  +--------------+---------+-----------+---------------+---------------+
+  | BitTorrent   | Pass    | 10 min.   |               |               |
+  | or uTorrent  |         |           |               |               |
+  | file         |         |           |               |               |
+  | leeching     |         |           |               |               |
+  +--------------+---------+-----------+---------------+---------------+
+  | Pandora      | Pass    | 10 min.   |               |               |
+  | Internet     |         |           |               |               |
+  | Radio        |         |           |               |               |
+  +--------------+---------+-----------+---------------+---------------+
+  | FTP server   | Pass    | 700 Mb    |               |               |
+  +--------------+---------+-----------+---------------+---------------+
+  | Web          | Pass    | 10 min.   |               |               |
+  | conferencing |         |           |               |               |
+  | (GTM)        |         |           |               |               |
+  +--------------+---------+-----------+---------------+---------------+
+  | Social       | Pass    | NA        |               |               |
+  | Networking   |         |           |               |               |
+  | Facebook     |         |           |               |               |
+  +--------------+---------+-----------+---------------+---------------+
+  | Social       | Pass    | NA        |               |               |
+  | Networking   |         |           |               |               |
+  | Webkinz      |         |           |               |               |
+  +--------------+---------+-----------+---------------+---------------+
+  | X-Lite for   | Pass    | 10 min.   |               |               |
+  | SIP calls    |         |           |               |               |
+  | with proxy   |         |           |               |               |
+  | given        |         |           |               |               |
+  +--------------+---------+-----------+---------------+---------------+
+  | X-Lite for   | Fail    | NA        |               |               |
+  | SIP calls no |         |           |               |               |
+  | proxy        |         |           |               |               |
+  +--------------+---------+-----------+---------------+---------------+
+  | Skype text   | Pass    | NA        |               |               |
+  | chat         |         |           |               |               |
+  +--------------+---------+-----------+---------------+---------------+
+  | Skype video  | Pass    | 20 min.   |               |               |
+  | chat         |         |           |               |               |
+  +--------------+---------+-----------+---------------+---------------+
+  | ooVoo        | Pass    | 15 min.   |               |               |
+  +--------------+---------+-----------+---------------+---------------+
+  | MS Smooth    | Pass    | 10 min.   |               |               |
+  | streaming    |         |           |               |               |
+  +--------------+---------+-----------+---------------+---------------+
+
+
+
+
+
+
+Donley, et al.                Informational                    [Page 20]
+
+RFC 7021                     NAT444 Impacts               September 2013
+
+
+  (continued)
+  +--------------+---------+-----------+---------------+---------------+
+  | Internet     | Pass    | 10 min.   |               |               |
+  | Archive      |         |           |               |               |
+  | video        |         |           |               |               |
+  | streaming    |         |           |               |               |
+  +--------------+---------+-----------+---------------+---------------+
+  | Internet     | Pass    | 5 min.    |               |               |
+  | Archive      |         |           |               |               |
+  | audio        |         |           |               |               |
+  | streaming    |         |           |               |               |
+  +--------------+---------+-----------+---------------+---------------+
+  | Internet     | Pass    | 80 Mb     |               |               |
+  | Archive file |         |           |               |               |
+  | download     |         |           |               |               |
+  +--------------+---------+-----------+---------------+---------------+
+  | iClips       | Pass    | 10 min.   |               |               |
+  +--------------+---------+-----------+---------------+---------------+
+
+                                  DS-Lite
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Donley, et al.                Informational                    [Page 21]
+
+RFC 7021                     NAT444 Impacts               September 2013
+
+
+5.  2010 Summary of Results
+
+   The tables below summarize results from the 2010 NAT444 testing at
+   CableLabs, Time Warner Cable, and Rogers Communications.  They are
+   included for comparison with 2011 results, documented above.
+
+5.1.  Case 1: Single Client, Single Home Network, Single Service
+      Provider
+
+   +--------------+-------------+--------------------------------------+
+   | Test Case    | Results     | Notes                                |
+   +--------------+-------------+--------------------------------------+
+   | Web browsing | pass        |                                      |
+   +--------------+-------------+--------------------------------------+
+   | Email        | pass        |                                      |
+   +--------------+-------------+--------------------------------------+
+   | FTP download | pass        | performance degraded on very large   |
+   |              |             | downloads                            |
+   +--------------+-------------+--------------------------------------+
+   | BitTorrent   | pass        |                                      |
+   | leeching     |             |                                      |
+   +--------------+-------------+--------------------------------------+
+   | BitTorrent   | fail        |                                      |
+   | seeding      |             |                                      |
+   +--------------+-------------+--------------------------------------+
+   | Video        | pass        |                                      |
+   | streaming    |             |                                      |
+   +--------------+-------------+--------------------------------------+
+   | Voice chat   | pass        |                                      |
+   +--------------+-------------+--------------------------------------+
+   | Netflix      | pass        |                                      |
+   | streaming    |             |                                      |
+   +--------------+-------------+--------------------------------------+
+   | Instant      | pass        |                                      |
+   | Messaging    |             |                                      |
+   +--------------+-------------+--------------------------------------+
+   | Ping         | pass        |                                      |
+   +--------------+-------------+--------------------------------------+
+   | Traceroute   | pass        |                                      |
+   +--------------+-------------+--------------------------------------+
+   | Remote       | pass        |                                      |
+   | desktop      |             |                                      |
+   +--------------+-------------+--------------------------------------+
+   | VPN          | pass        |                                      |
+   +--------------+-------------+--------------------------------------+
+   | Xbox Live    | pass        |                                      |
+   +--------------+-------------+--------------------------------------+
+
+
+
+
+Donley, et al.                Informational                    [Page 22]
+
+RFC 7021                     NAT444 Impacts               September 2013
+
+
+   (continued)
+   +--------------+-------------+--------------------------------------+
+   | Xbox online  | pass        | Blocked by some LSNs.                |
+   +--------------+-------------+--------------------------------------+
+   | Xbox network | fail        | Your NAT type is moderate.  For best |
+   | test         |             | online experience you need an open   |
+   |              |             | NAT configuration.  You should enable|
+   |              |             | Universal Plug and Play (UPnP) on    |
+   |              |             | the router.                          |
+   +--------------+-------------+--------------------------------------+
+   | Nintendo Wii | pass behind |                                      |
+   |              | one LSN,    |                                      |
+   |              | fail behind |                                      |
+   |              | another     |                                      |
+   +--------------+-------------+--------------------------------------+
+   | PlayStation  | pass        |                                      |
+   | 3            |             |                                      |
+   +--------------+-------------+--------------------------------------+
+   | Team         | fail        | pass behind one LSN, but performance |
+   | Fortress 2   |             | degraded                             |
+   +--------------+-------------+--------------------------------------+
+   | StarCraft II | pass        |                                      |
+   +--------------+-------------+--------------------------------------+
+   | World of     | pass        |                                      |
+   | Warcraft     |             |                                      |
+   +--------------+-------------+--------------------------------------+
+   | Call of Duty | pass        | performance degraded behind one LSN  |
+   +--------------+-------------+--------------------------------------+
+   | SlingCatcher | fail        |                                      |
+   +--------------+-------------+--------------------------------------+
+   | Netflix      | fail        | pass behind one LSN                  |
+   | Party (Xbox) |             |                                      |
+   +--------------+-------------+--------------------------------------+
+   | Hulu         | pass        | performance degraded behind one LSN  |
+   +--------------+-------------+--------------------------------------+
+   | AIM File     | pass        | performance degraded                 |
+   | Transfer     |             |                                      |
+   +--------------+-------------+--------------------------------------+
+   | Webcam       | fail        |                                      |
+   +--------------+-------------+--------------------------------------+
+   | 6to4         | fail        |                                      |
+   +--------------+-------------+--------------------------------------+
+   | Teredo       | fail        |                                      |
+   +--------------+-------------+--------------------------------------+
+
+                                  Case 1
+
+
+
+
+
+Donley, et al.                Informational                    [Page 23]
+
+RFC 7021                     NAT444 Impacts               September 2013
+
+
+5.2.  Case 2: Two Clients, Single Home Network, Single Service Provider
+
+   +-----------------+---------+---------------------------------------+
+   | Test Case       | Results | Notes                                 |
+   +-----------------+---------+---------------------------------------+
+   | BitTorrent      | pass    |                                       |
+   | leeching        |         |                                       |
+   +-----------------+---------+---------------------------------------+
+   | BitTorrent      | fail    |                                       |
+   | seeding         |         |                                       |
+   +-----------------+---------+---------------------------------------+
+   | Video streaming | fail    |                                       |
+   +-----------------+---------+---------------------------------------+
+   | Voice chat      | pass    |                                       |
+   +-----------------+---------+---------------------------------------+
+   | Netflix         | pass    | performance severely impacted,        |
+   | streaming       |         | eventually failed                     |
+   +-----------------+---------+---------------------------------------+
+   | IM              | pass    |                                       |
+   +-----------------+---------+---------------------------------------+
+   | Limewire        | pass    |                                       |
+   | leeching        |         |                                       |
+   +-----------------+---------+---------------------------------------+
+   | Limewire        | fail    |                                       |
+   | seeding         |         |                                       |
+   +-----------------+---------+---------------------------------------+
+
+                                  Case 2
+
+5.3.  Case 3: Two Clients, Two Home Networks, Single Service Provider
+
+                  +-------------------+---------+-------+
+                  | Test Case         | Results | Notes |
+                  +-------------------+---------+-------+
+                  | Limewire leeching | pass    |       |
+                  +-------------------+---------+-------+
+                  | Limewire seeding  | fail    |       |
+                  +-------------------+---------+-------+
+                  | uTorrent leeching | pass    |       |
+                  +-------------------+---------+-------+
+                  | uTorrent seeding  | fail    |       |
+                  +-------------------+---------+-------+
+
+                                  Case 3
+
+
+
+
+
+
+
+Donley, et al.                Informational                    [Page 24]
+
+RFC 7021                     NAT444 Impacts               September 2013
+
+
+5.4.  Case 4: Two Clients, Two Home Networks, Two Service Providers
+      Cross ISP
+
+                  +------------------+---------+-------+
+                  | Test Case        | Results | Notes |
+                  +------------------+---------+-------+
+                  | Skype voice call | pass    |       |
+                  +------------------+---------+-------+
+                  | IM               | pass    |       |
+                  +------------------+---------+-------+
+                  | FTP              | fail    |       |
+                  +------------------+---------+-------+
+                  | Facebook chat    | pass    |       |
+                  +------------------+---------+-------+
+                  | Skype video      | pass    |       |
+                  +------------------+---------+-------+
+
+                                  Case 4
+
+6.  CGN Mitigation
+
+   Our testing did not focus on mitigating the impact of Carrier-Grade
+   NAT, as described above.  As such, mitigation is not the focus of
+   this document.  However, there are several approaches that could
+   lessen the impacts described above.
+
+   +-----------------------+-------------------------------------------+
+   | Challenge             | Potential Workaround(s)                   |
+   +-----------------------+-------------------------------------------+
+   | Peer-to-peer          | Use a proxy server; [RFC6887]             |
+   +-----------------------+-------------------------------------------+
+   | Gaming                | [RFC6887]                                 |
+   +-----------------------+-------------------------------------------+
+   | Negative impact to    | Deploy CGN close to the edge of the       |
+   | geolocation services  | network; use regional IP and port         |
+   |                       | assignments                               |
+   +-----------------------+-------------------------------------------+
+   | Logging requirements  | Deterministic Logging [DETERMINE]; data   |
+   | for lawful intercept  | compression [NAT-LOG]; bulk port logging  |
+   +-----------------------+-------------------------------------------+
+
+                              CGN Mitigation
+
+   Other mitigation techniques that are currently being researched, such
+   as [STATELESS], may also improve performance.
+
+
+
+
+
+
+Donley, et al.                Informational                    [Page 25]
+
+RFC 7021                     NAT444 Impacts               September 2013
+
+
+7.  Security Considerations
+
+   Security considerations are described in [RFC6264] and [RFC6269].
+
+   In general, since a CGN device shares a single IPv4 address with
+   multiple subscribers, CGN devices may provide an attractive target
+   for denial-of-service attacks.  In addition, as described in
+   [DETERMINE], abuse attribution is more challenging with CGN and
+   requires content providers to log IP address, source port, and time
+   to correlate with Service Provider CGN logs.  Also, if a CGN public
+   IP address is added to a blacklist (e.g., for SPAM) or if a server
+   limits the number of connections per IP address, it could negatively
+   impact legitimate users.
+
+8.  Informative References
+
+   [DETERMINE]  Donley, C., Grundemann, C., Sarawat, V., Sundaresan, K.,
+                and O. Vautrin, "Deterministic Address Mapping to Reduce
+                Logging in Carrier Grade NAT Deployments", Work in
+                Progress, July 2013.
+
+   [NAT-LOG]    Sivakumar, S. and R. Penno, "IPFIX Information Elements
+                for logging NAT Events", Work in Progress, August 2013.
+
+   [NAT444]     Yamagata, I., Shirasaki, Y., Nakagawa, A., Yamaguchi,
+                J., and H. Ashida, "NAT444", Work in Progress,
+                July 2012.
+
+   [RFC1918]    Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G.,
+                and E. Lear, "Address Allocation for Private Internets",
+                BCP 5, RFC 1918, February 1996.
+
+   [RFC3056]    Carpenter, B. and K. Moore, "Connection of IPv6 Domains
+                via IPv4 Clouds", RFC 3056, February 2001.
+
+   [RFC4380]    Huitema, C., "Teredo: Tunneling IPv6 over UDP through
+                Network Address Translations (NATs)", RFC 4380,
+                February 2006.
+
+   [RFC4689]    Poretsky, S., Perser, J., Erramilli, S., and S. Khurana,
+                "Terminology for Benchmarking Network-layer Traffic
+                Control Mechanisms", RFC 4689, October 2006.
+
+   [RFC6264]    Jiang, S., Guo, D., and B. Carpenter, "An Incremental
+                Carrier-Grade NAT (CGN) for IPv6 Transition", RFC 6264,
+                June 2011.
+
+
+
+
+
+Donley, et al.                Informational                    [Page 26]
+
+RFC 7021                     NAT444 Impacts               September 2013
+
+
+   [RFC6269]    Ford, M., Boucadair, M., Durand, A., Levis, P., and P.
+                Roberts, "Issues with IP Address Sharing", RFC 6269,
+                June 2011.
+
+   [RFC6333]    Durand, A., Droms, R., Woodyatt, J., and Y. Lee, "Dual-
+                Stack Lite Broadband Deployments Following IPv4
+                Exhaustion", RFC 6333, August 2011.
+
+   [RFC6887]    Wing, D., Cheshire, S., Boucadair, M., Penno, R., and P.
+                Selkirk, "Port Control Protocol (PCP)", RFC 6887,
+                April 2013.
+
+   [STATELESS]  Tsou, T., Liu, W., Perreault, S., Penno, R., and M.
+                Chen, "Stateless IPv4 Network Address Translation", Work
+                in Progress, October 2012.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Donley, et al.                Informational                    [Page 27]
+
+RFC 7021                     NAT444 Impacts               September 2013
+
+
+Appendix A.  Acknowledgements
+
+   Thanks to the following people for their testing, guidance, and
+   feedback:
+
+      Paul Eldridge
+
+      Abishek Chandrasekaran
+
+      Vivek Ganti
+
+      Joey Padden
+
+      Lane Johnson
+
+   Also, thanks to Noel Chiappa for his comments.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Donley, et al.                Informational                    [Page 28]
+
+RFC 7021                     NAT444 Impacts               September 2013
+
+
+Authors' Addresses
+
+   Chris Donley (editor)
+   CableLabs
+   858 Coal Creek Circle
+   Louisville, CO  80027
+   USA
+
+   EMail: c.donley@cablelabs.com
+
+
+   Lee Howard
+   Time Warner Cable
+   13241 Woodland Park Rd
+   Herndon, VA  20171
+   USA
+
+   EMail: william.howard@twcable.com
+
+
+   Victor Kuarsingh
+   Rogers Communications
+   8200 Dixie Road
+   Brampton, ON  L6T 0C1
+   Canada
+
+   EMail: victor@jvknet.com
+
+
+   John Berg
+   CableLabs
+   858 Coal Creek Circle
+   Louisville, CO  80027
+   USA
+
+   EMail: j.berg@cablelabs.com
+
+
+   Jinesh Doshi
+   Juniper Networks
+   1194 N. Mathilda Ave
+   Sunnyvale, CA  94089
+   USA
+
+   EMail: jineshd@juniper.net
+
+
+
+
+
+
+Donley, et al.                Informational                    [Page 29]
+