[Docs] [txt|pdf] [Tracker] [Email] [Diff1] [Diff2] [Nits] [IPR]

Versions: 00 01 02 03 04 draft-ietf-tsvwg-behave-requirements-update

Port Control Protocol                                           R. Penno
Internet-Draft                                                     Cisco
Intended status: BCP                                        S. Perreault
Expires: July 11, 2013                                          Viagenie
                                                              S. Kamiset
                                                              Consultant
                                                            M. Boucadair
                                                          France Telecom
                                                                K. Naito
                                                                     NTT
                                                        January 07, 2013


   Network Address Translation (NAT) Behavioral Requirements Updates
              draft-penno-behave-rfc4787-5382-5508-bis-04

Abstract

   This document clarifies and updates several requirements of RFC4787,
   RFC5382 and RFC5508 based on operational and development experience.
   The focus of this document is NAPT44.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on July 11, 2013.

Copyright Notice

   Copyright (c) 2013 IETF Trust and the persons identified as the



Penno, et al.             Expires July 11, 2013                 [Page 1]


Internet-Draft  draft-penno-behave-rfc4787-5382-5508-bis    January 2013


   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.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.


Table of Contents

   1.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     2.1.  Scope  . . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.  TCP Session Tracking . . . . . . . . . . . . . . . . . . . . .  3
     3.1.  TCP Transitory Connection Idle-Timeout . . . . . . . . . .  4
       3.1.1.  Port resources limited case  . . . . . . . . . . . . .  5
       3.1.2.  Proposal: Apply RFC6191 and PAWS to NAT  . . . . . . .  6
     3.2.  TCP RST  . . . . . . . . . . . . . . . . . . . . . . . . .  9
   4.  Port Overlapping behavior  . . . . . . . . . . . . . . . . . .  9
   5.  Address Pooling Paired (APP) . . . . . . . . . . . . . . . . . 10
   6.  EIF Security . . . . . . . . . . . . . . . . . . . . . . . . . 10
   7.  EIF Protocol Independence  . . . . . . . . . . . . . . . . . . 10
   8.  EIF Mapping Refresh  . . . . . . . . . . . . . . . . . . . . . 10
     8.1.  Outbound Mapping Refresh and Error Packets . . . . . . . . 11
   9.  EIM Protocol Independence  . . . . . . . . . . . . . . . . . . 11
   10. Port Parity  . . . . . . . . . . . . . . . . . . . . . . . . . 11
   11. Port Randomization . . . . . . . . . . . . . . . . . . . . . . 11
   12. IP Identification (IP ID)  . . . . . . . . . . . . . . . . . . 12
   13. ICMP Query Mappings Timeout  . . . . . . . . . . . . . . . . . 12
   14. Hairpinning Support for ICMP Packets . . . . . . . . . . . . . 12
   15. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 12
   16. Security Considerations  . . . . . . . . . . . . . . . . . . . 12
   17. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13
   18. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13
     18.1. Normative References . . . . . . . . . . . . . . . . . . . 13
     18.2. Informative References . . . . . . . . . . . . . . . . . . 14
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14









Penno, et al.             Expires July 11, 2013                 [Page 2]


Internet-Draft  draft-penno-behave-rfc4787-5382-5508-bis    January 2013


1.  Terminology

   The reader should be familiar with all terms defined in RFC2663
   [RFC2663],RFC4787 [RFC4787],RFC5382 [RFC5382],RFC5508 [RFC5508]


2.  Introduction

   [RFC4787], [RFC5382] and [RFC5508] greatly advanced NAT
   interoperability and conformance.  But with widespread deployment and
   evolution of NAT more development and operational experience was
   acquired some areas of the original documents need further
   clarification or updates.  This documents provides such
   clarifications and updates.

2.1.  Scope

   This document focuses solely on NAPT44 and its goal is to clarify,
   fill gaps or update requirements of [RFC4787], [RFC5382] and
   [RFC5508].  It is out of the scope of this document the creation of
   completely new requirements not associated with the documents cited
   above.  New requirements would be better served elsewhere and if they
   are CGN specific in [I-D.ietf-behave-lsn-requirements]


3.  TCP Session Tracking

   [RFC5382] specifies TCP timers associated with various connection
   states but does not specify the TCP state machine a NAPT44 should use
   as a basis to apply such timers.  The TCP state machine below,
   adapted from [RFC6146], provides guidance on how TCP session tracking
   could be implemented - it is non-normative.



















Penno, et al.             Expires July 11, 2013                 [Page 3]


Internet-Draft  draft-penno-behave-rfc4787-5382-5508-bis    January 2013


                                      +-----------------------------+
                                      |                             |
                                      V                             |
                                +------+     CV4                    |
                                |CLOSED|-----SYN------+             |
                                +------+              |             |
                                   ^                  |             |
                                   |TCP_TRANS T.O.    |             |
                                   |                  V             |
                                +-------+          +-------+        |
                                | TRANS |          |V4 INIT|        |
                                +-------+          +-------+        |
                                 |    ^               |             |
                           data pkt   |               |             |
                                 |  V4 or V4 RST      |             |
                                 |  TCP_EST T.O.      |             |
                                 V    |              SV4 SYN        |
                            +--------------+          |             |
                            | ESTABLISHED  |<---------+             |
                            +--------------+                        |
                              |           |                         |
                         CV4 FIN      SV4 FIN                       |
                              |           |                         |
                              V           V                         |
                      +---------+       +----------+                |
                      |CV4 FIN  |       | SV4 FIN  |                |
                      |   RCV   |       |    RCV   |                |
                      +---------+       +----------+                |
                              |           |                         |
                         SV4 FIN      CV4 FIN                  TCP_TRANS
                              |           |                        T.O.
                              V           V                         |
                        +----------------------+                    |
                        | CV4 FIN + SV4 FIN RCV|--------------------+
                        +----------------------+
   (postamble)

3.1.  TCP Transitory Connection Idle-Timeout

   [RFC5382]:REQ-5 The transitory connection idle-timeout is defined as
   the minimum time a TCP connection in the partially open or closing
   phases must remain idle before the NAT considers the associated
   session a candidate for removal.  But the document does not clearly
   states if these can be configured separately.  This document
   clarifies that a NAT device SHOULD provide different knobs for
   configuring the open and closing idle timeouts.  This document
   further acknowledges that most TCP flows are very short (less than 10
   seconds) [FLOWRATE][TCPWILD] and therefore a partially open timeout



Penno, et al.             Expires July 11, 2013                 [Page 4]


Internet-Draft  draft-penno-behave-rfc4787-5382-5508-bis    January 2013


   of 4 minutes might be excessive if security is a concern.  Therefore
   it MAY be configured to be less than 4 minutes in such cases.  There
   also may be a case that timeout of 4 minutes might be excessive.  The
   case and the solution are written below.

3.1.1.  Port resources limited case

   After IPv4 addresses run out, IPv4 address resources will be further
   restricted site-by-site.  If global IPv4 address are shared between
   several clients, assignable port resources at each client will be
   limited.

   NAT is a tool that is widely used to deal with this IPv4 address
   shortage problem.  However, the demand for resources to provide
   Internet access to users and devices will continue to increase.  IPv6
   is a fundamental solution to this problem, but the deployment of IPv6
   will take time.

   In some cases, e.g. browsing a dynamic web page for a map service, a
   lot of sessions are used by the browser, and a number of ports are
   eaten up in a short time.  What is worse is that when a NAT is
   between a PC and a server, TIME_WAIT state of each TCP connection is
   kept for certain period, typically for four minutes, which consumes
   port resources.  Therefore, new connections cannot be established.

   This problem is caused or worsened by the following behavior.

      TIME_WAIT state assigned for a TCP connection remains active for
      2MSL after the last ACK to the last FIN is transferred.

   To reuse resources effectively, reducing TIME_WAIT without making any
   bad effect is important.  To reduce TIME_WAIT, [RFC6191] is proposed
   for clients and remote hosts.  To prevent bad effects, there is a
   PAWS mechanism, which prevent the old duplicate problem.  We propose
   mechanisms adopting to NAT, to change the TIME_WAIT behavior that
   make it possible to save addresses and ports resources.

3.1.1.1.   RFC6191 Reducing the TIME-WAIT State Using TCP Timestamps

   [RFC6191] defines a mechanism for reducing the TIME_WAIT state using
   TCP timestamps and sequence numbers.  When a connection request is
   received with a four-tuple that is in the TIME-WAIT state, the
   connection request may be accepted if the sequence number or the
   timestamp of the incoming SYN segment is greater than the last
   sequence number seen on the previous incarnation of the connection






Penno, et al.             Expires July 11, 2013                 [Page 5]


Internet-Draft  draft-penno-behave-rfc4787-5382-5508-bis    January 2013


3.1.1.2.   TCP TIME_WAIT

   The TCP TIME_WAIT state is described in [RFC0793].  The TCP TIME_WAIT
   state needs to be kept for 2MSL before a connection is CLOSED, for
   the reasons below.

   1: In the event that packets from a session are delayed in the in-
      between network, and delivered to the end relatively later, we
      should prevent the packets from being transferred and interpreted
      as a packet that belongs to a new session.

   2: If the remote TCP has not received the acknowledgment of its
      connection termination request, it will re-send the FIN packet
      several times.

   These points are important for the TCP to work without problems.

3.1.1.3.   Protect Against Wrapped Sequence numbers (PAWS)

   The TCP sequence number wraps frequently especially in a high
   bandwidth session.  PAWS is used to prevent old duplicate packets
   that occurred in a previous session from being transferred to the new
   session whose valid TCP sequence numbers happen to overlap with the
   old duplicate packets.  This is implemented by introducing TCP
   timestamp option, and checking the timestamp option value of each
   packet.  PAWS is described in [RFC1323].

3.1.2.   Proposal: Apply RFC6191 and PAWS to NAT

   This section proposes to apply [RFC6191] mechanism at NAT.  This
   mechanism MAY be adopted for both clients' and remote hosts' TCP
   active close.



















Penno, et al.             Expires July 11, 2013                 [Page 6]


Internet-Draft  draft-penno-behave-rfc4787-5382-5508-bis    January 2013


            client                     NAT                  remote host
              |                         |                         |
              |          FIN            |          FIN            |
              |------------------------>|------------------------>|
              |                         |                         |
              |          ACK            |          ACK            |
              |<------------------------|<------------------------|
              |          FIN            |          FIN            |
              |<------------------------|<------------------------|
              |                         |                         |
              |        ACK(TSval=A)     |          ACK            |
              |------------------------>|------------------------>|
              |                         |  -                      |
              |                         |  |                      |
              |                         |  |                      |
              |                         |  |                      |
              |                         |  | TIME_WAIT            |
              |                         |  |  ->assassinated at x |
              |                         |  |                      |
              |                         |  |                      |
              |                         |  |                      |
              |        SYN(TSval>A)     |  x      SYN             |
              |------------------------>|------------------------>|
              |                         |  -                      |
              |                         |  |                      |
              |                         |  | SYN_SENT             |
              |                         |  |                      |
              |                         |  |                      |
   (postamble)

   Also, PAWS works to discard old duplicate packets at NAT.  A packet
   can be discarded as an old duplicate if it is received with a
   timestamp or sequence number value less than a value recently
   received on the connection.

   To make these mechanisms work, we should concern the case that there
   are several clients with nonsuccessive timestamp or sequence number
   values are connected to a NAT device (i.e. not monotonically
   increasing among clients).  Two mechanisms to solve this mechanism
   and applying [RFC6191] and PAWS to NAT are described below.  These
   mechanisms are optional.

3.1.2.1.   Rewrite timestamp and sequence number values at NAT

   Rewrite timestamp and sequence number values of outgoings packets at
   NAT to be monotonically increasing.  This can be done by adopting
   following mechanisms at NAT.




Penno, et al.             Expires July 11, 2013                 [Page 7]


Internet-Draft  draft-penno-behave-rfc4787-5382-5508-bis    January 2013


   A: Store the newest rewritten value of timestamp and sequence number
      as the "max value at the time".

   B: NAT rewrite timestamp and sequence number values of incoming
      packets to be monotonically increasing.


   When packets come back as replies from remote hosts, NAT rewrite
   again the timestamp and sequence number values to be the original
   values.  This can be done by adopting following mechanisms at NAT.


   C: Store the values of original timestamp and sequence number of
      packets, and rewritten values of those.

3.1.2.2.   Split an assignable number of port space to each client

   Adopt following mechanisms at NAT.


   A: Choose clients that can be assigned ports.

   B: Split assignable port numbers between clients.


   Packets from other clients which are not chosen by these mechanisms
   are rejected at NAT, unless there is unassigned port left.

3.1.2.3.   Resend the last ACK to the resended FIN

   We should concern another case to make RFC6191 work at NAT.  In case
   the remote TCP could not receive the acknowledgment of its connection
   termination request, NAT, on behalf of clients. resends the last ACK
   packet when it receives an FIN packet of the previous connection, and
   when the state of the previous connection is deleted from the NAT.
   This mechanism MAY be used when clients starts closing process, and
   the remote host could not receive the last ACK.

3.1.2.4.   Remote host behavior of several implementations

   To solve the port shortage problem on the client side, the behavior
   of remote host should be compliant to [RFC6191] or the mechanism
   written in 4.2.2.13 of [RFC1122], since NAT may reuse the same 5
   tuple for a new connection.We have investigated behaviors of OSes
   (e.g., Linux, FreeBSD, Windows, MacOS), and found that they
   implemented the server side behavior of the above two.





Penno, et al.             Expires July 11, 2013                 [Page 8]


Internet-Draft  draft-penno-behave-rfc4787-5382-5508-bis    January 2013


3.2.   TCP RST

   [RFC5382] leaves the handling of TCP RST packets unspecified.  This
   document does not try standardize such behavior but clarifies based
   on operational experience that a NAT that receives a TCP RST for an
   active mapping and performs session tracking MAY immediately delete
   the sessions and remove any state associated with it.  If the NAT
   device that performs TCP session tracking receives a TCP RST for the
   first session that created a mapping, it MAY remove the session and
   the mapping immediately.


4.  Port Overlapping behavior

   There may be another solution to the address resource restricted
   environment written in 3.1.1.  Also NAT are required to be maped
   endpoint-independent in [RFC4787] and [RFC5382] REQ-1, the mechanism
   below MAY be one optional implement to NAT.

   If destination addresses and ports are different for outgoing
   connections started by local clients, NAT MAY assign the same
   external port as the source ports for the connections.  The port
   overlapping mechanism manages mappings between external packets and
   internal packets by looking at and storing the 5-tuple (protocol,
   source address, source port, destination address, destination port)
   of them.  This enables concurrent use of a single NAT external port
   for multiple transport sessions, which enables NAT to work correctly
   in IP address resource limited network.

   Discussions:

   [RFC4787]and[FC5382] requires "endpoint-independent mapping" at NAT,
   and port overlapping NAT cannot meet the requirement.  This mechanism
   can degrade the transparency of NAT in that its mapping mechanism is
   endpoint-dependent and makes NAT traversal harder.  However, if a NAT
   adopts endpoint-independent mapping together with endpoint-dependent
   filtering, then the actual behavior of the NAT will be the same as
   port overlapping NAT.  It should also be noted that a lot of existing
   NAT devices(e.g., SEIL, FITELnet Series) adopted this port
   overlapping mechanism.


   A: Reference URL for SEIL -> www.seil.jp

   B: Reference URL for FITELnet -> www.furukawa.co.jp/fitelnet


   The netfilter, which is a popular packet filtering mechanism for



Penno, et al.             Expires July 11, 2013                 [Page 9]


Internet-Draft  draft-penno-behave-rfc4787-5382-5508-bis    January 2013


   Linux, also adopts port overlapping behavior.


5.  Address Pooling Paired (APP)

   [RFC4787]: REQ-2 [RFC5382]:ND Address Pooling Paired behavior for NAT
   is recommended in previous documents but behavior when a public IPv4
   run out of ports is left undefined.  This document clarifies that if
   APP is enabled new sessions from a subscriber that already has a
   mapping associated with a public IP that ran out of ports SHOULD be
   dropped.  The administrator MAY provide a knob that allows a NAT
   device to starting using ports from another public IP when the one
   that anchored the APP mapping ran out of ports.  This is trade-off
   between subscriber service continuity and APP strict enforcement.
   (NE: It is sometimes referred as 'soft-APP')


6.  EIF Security

   [RFC4787]:REQ-8 and [RFC5382]:REQ-3 End-point independent filtering
   could potentially result in security attacks from the public realm.
   In order to handle this, when possible there MUST be strict filtering
   checks in the inbound direction.  A knob SHOULD be provided to limit
   the number of inbound sessions and a knob SHOULD be provided to
   enable or disable EIF on a per application basis.  This is specially
   important in the case of Mobile networks where such attacks can
   consume radio resources and count against the user quota.


7.  EIF Protocol Independence

   [RFC4787]:REQ-8 and[RFC5382]: REQ-3 Current RFCs do not specify
   whether EIF mappings are protocol independent.  In other words, if a
   outbound TCP SYN creates a mapping it is left undefined whether
   inbound UDP packets create sessions and are forwarded.  EIF mappings
   SHOULD be protocol independent in order allow inbound packets for
   protocols that multiplex TCP and UDP over the same IP: port through
   the NAT and maintain compatibility with stateful NAT64 RFC6146
   [RFC6146].  But the administrator MAY provide a configuration knob to
   make it protocol dependent.


8.  EIF Mapping Refresh

   [RFC4787]: REQ-6 [RFC5382]: ND The NAT mapping Refresh direction MAY
   have a "NAT Inbound refresh behavior" of "True" but it does not
   clarifies how this applies to EIF mappings.  The issue in question is
   whether inbound packets that match an EIF mapping but do not create a



Penno, et al.             Expires July 11, 2013                [Page 10]


Internet-Draft  draft-penno-behave-rfc4787-5382-5508-bis    January 2013


   new session due to a security policy should refresh the mapping
   timer.  This document clarifies that even when a NAT device has a
   inbound refresh behavior of TRUE, that such packets SHOULD NOT
   refresh the mapping.  Otherwise a simple attack of a packet every 2
   minutes can keep the mapping indefinitely.

8.1.  Outbound Mapping Refresh and Error Packets

   In the case of NAT outbound refresh behavior there might be certain
   types of packets that should not refresh the mapping.  For example,
   if the mapping is kept alive by ICMP Error or TCP RST outbound
   packets sent as response to inbound packets, these SHOULD NOT refresh
   the mapping.


9.  EIM Protocol Independence

   [RFC4787] [RFC5382]: REQ-1 Current RFCs do not specify whether EIM
   are protocol independent.  In other words, if a outbound TCP SYN
   creates a mapping it is left undefined whether outbound UDP can reuse
   such mapping and create session.  On the other hand, Stateful NAT64
   [RFC6146] clearly specifies three binding information bases (TCP,
   UDP, ICMP).  This document clarifies that EIM mappings SHOULD be
   protocol dependent .  A knob MAY be provided in order allow protocols
   that multiplex TCP and UDP over the same source IP and port to use a
   single mapping.


10.  Port Parity

   A NAT devices MAY disable port parity preservation for dynamic
   mappings.  Nevertheless, A NAT SHOULD support means to explicitly
   request to preserve port parity (e.g., [I-D.boucadair-pcp-rtp-rtcp]).


11.  Port Randomization

   A NAT SHOULD follow the recommendations specified in Section 4 of
   [RFC6056] especially: "A NAPT that does not implement port
   preservation [RFC4787] [RFC5382] SHOULD obfuscate selection of the
   ephemeral port of a packet when it is changed during translation of
   that packet.  A NAPT that does implement port preservation SHOULD
   obfuscate the ephemeral port of a packet only if the port must be
   changed as a result of the port being already in use for some other
   session.  A NAPT that performs parity preservation and that must
   change the ephemeral port during translation of a packet SHOULD
   obfuscate the ephemeral ports.  The algorithms described in this
   document could be easily adapted such that the parity is preserved



Penno, et al.             Expires July 11, 2013                [Page 11]


Internet-Draft  draft-penno-behave-rfc4787-5382-5508-bis    January 2013


   (i.e., force the lowest order bit of the resulting port number to 0
   or 1 according to whether even or odd parity is desired)."


12.  IP Identification (IP ID)

   A NAT SHOULD handle the Identification field of translated IPv4
   packets as specified in Section 9 of [I-D.ietf-intarea-ipv4-id-
   update].


13.  ICMP Query Mappings Timeout

   Section 3.1 of [RFC5508] says that ICMP Query Mappings are to be
   maintained by NAT device.  However, RFC doesn't discuss about the
   Query Mapping timeout values.  Section 3.2 of that RFC only discusses
   about ICMP Query Session Timeouts.  ICMP Query Mappings MAY be
   deleted once the last the session using the mapping is deleted.


14.  Hairpinning Support for ICMP Packets

   [RFC5508]:REQ-7 This requirement specifies that NAT devices enforcing
   Basic NAT MUST support traversal of hairpinned ICMP Query sessions.
   This implicitly means that address mappings from external address to
   internal address (similar to Endpoint Independent Filters) MUST be
   maintained to allow inbound ICMP Query sessions.  If an ICMP Query is
   received on an external address, NAT device can then translate to an
   internal IP.  [RFC5508]:REQ-7 This requirement specifies that all NAT
   devices (i.e., Basic NAT as well as NAPT devices) MUST support the
   traversal of hairpinned ICMP Error messages.  This too requires NAT
   devices to maintain address mappings from external IP address to
   internal IP address in addition to the ICMP Query Mappings described
   in section 3.1 of that RFC.


15.  IANA Considerations

   TBD


16.  Security Considerations

   In the case of EIF mappings due to high risk of resource crunch, a
   NAT device MAY provide a knob to limit the number of inbound sessions
   spawned from a EIF mapping.

   [TCP-Security] contains a detailed discussion of the security



Penno, et al.             Expires July 11, 2013                [Page 12]


Internet-Draft  draft-penno-behave-rfc4787-5382-5508-bis    January 2013


   implications of TCP Timestamps and of different timestamp generation
   algorithms.


17.  Acknowledgements

   Thanks to Dan Wing, Suresh Kumar, Mayuresh Bakshi, Rajesh Mohan and
   Senthil Sivamular for review and discussions


18.  References

18.1.  Normative References

   [I-D.ietf-pcp-base]
              Wing, D., Cheshire, S., Boucadair, M., Penno, R., and P.
              Selkirk, "Port Control Protocol (PCP)",
              draft-ietf-pcp-base-29 (work in progress), November 2012.

   [RFC0793]  Postel, J., "Transmission Control Protocol", STD 7,
              RFC 793, September 1981.

   [RFC1122]  Braden, R., "Requirements for Internet Hosts -
              Communication Layers", STD 3, RFC 1122, October 1989.

   [RFC1323]  Jacobson, V., Braden, B., and D. Borman, "TCP Extensions
              for High Performance", RFC 1323, May 1992.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2663]  Srisuresh, P. and M. Holdrege, "IP Network Address
              Translator (NAT) Terminology and Considerations",
              RFC 2663, August 1999.

   [RFC3605]  Huitema, C., "Real Time Control Protocol (RTCP) attribute
              in Session Description Protocol (SDP)", RFC 3605,
              October 2003.

   [RFC4787]  Audet, F. and C. Jennings, "Network Address Translation
              (NAT) Behavioral Requirements for Unicast UDP", BCP 127,
              RFC 4787, January 2007.

   [RFC5382]  Guha, S., Biswas, K., Ford, B., Sivakumar, S., and P.
              Srisuresh, "NAT Behavioral Requirements for TCP", BCP 142,
              RFC 5382, October 2008.

   [RFC5508]  Srisuresh, P., Ford, B., Sivakumar, S., and S. Guha, "NAT



Penno, et al.             Expires July 11, 2013                [Page 13]


Internet-Draft  draft-penno-behave-rfc4787-5382-5508-bis    January 2013


              Behavioral Requirements for ICMP", BCP 148, RFC 5508,
              April 2009.

   [RFC6056]  Larsen, M. and F. Gont, "Recommendations for Transport-
              Protocol Port Randomization", BCP 156, RFC 6056,
              January 2011.

   [RFC6146]  Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful
              NAT64: Network Address and Protocol Translation from IPv6
              Clients to IPv4 Servers", RFC 6146, April 2011.

   [RFC6191]  Gont, F., "Reducing the TIME-WAIT State Using TCP
              Timestamps", BCP 159, RFC 6191, April 2011.

18.2.  Informative References

   [FLOWRATE]
              Zhang, Y., Breslau, L., Paxson, V., and S. Shenker, "On
              the Characteristics and Origins of Internet Flow Rates".

   [I-D.boucadair-pcp-rtp-rtcp]
              Boucadair, M. and S. Sivakumar, "Reserving N and N+1 Ports
              with PCP", draft-boucadair-pcp-rtp-rtcp-05 (work in
              progress), October 2012.

   [I-D.ietf-behave-lsn-requirements]
              Perreault, S., Yamagata, I., Miyakawa, S., Nakagawa, A.,
              and H. Ashida, "Common requirements for Carrier Grade NATs
              (CGNs)", draft-ietf-behave-lsn-requirements-10 (work in
              progress), December 2012.

   [I-D.naito-nat-resource-optimizing-extension]
              Kengo, K. and A. Matsumoto, "NAT TIME_WAIT reduction",
              draft-naito-nat-resource-optimizing-extension-02 (work in
              progress), July 2012.

   [TCPWILD]  Qian, F., Subhabrata, S., Spatscheck, O., Morley Mao, Z.,
              and W. Willinger, "TCP Revisited: A Fresh Look at TCP in
              the Wild".












Penno, et al.             Expires July 11, 2013                [Page 14]


Internet-Draft  draft-penno-behave-rfc4787-5382-5508-bis    January 2013


Authors' Addresses

   Reinaldo Penno
   Cisco Systems, Inc.
   170 West Tasman Drive
   San Jose, California  95134
   USA

   Email: repenno@cisco.com


   Simon Perreault
   Viagenie
   2875 boul. Laurier, suite D2-630
   Quebec, QC  G1V 2M2
   Canada

   Email: simon.perreault@viagenie.ca


   Sarat Kamiset
   Consultant
   California

   Phone:
   Fax:


   Mohamed Boucadair
   France Telecom
   Rennes,   35000
   France

   Email: mohamed.boucadair@orange.com


   Kengo Naito
   NTT
   Tokyo
   Japan

   Email: kengo@lab.ntt.co.jp









Penno, et al.             Expires July 11, 2013                [Page 15]


Html markup produced by rfcmarkup 1.121, available from https://tools.ietf.org/tools/rfcmarkup/