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Versions: 00                                                            
Network Working Group                                          Louis Chan
INTERNET-DRAFT
Intended status: Standard Track                                Juniper Networks
Expires: Aug 21, 2022                                          Feb 21, 2022



                   Enhanced Port Forwarding functions with CGNAT
                       draft-chan-tsvwg-eipf-cgnat-00.txt


Abstract

   There is a need for peer-to-peer (P2P) communication under the use of CGNAT in
   service providers. With the combination of home gateway, this becomes NAT444.

   In RFC5128, methods of using UDP hole punching solves the problem partially when
   EIM (Endpoint-Independent Mapping) is supported in NAT device in the path, and
   there exists a common rendezvous server.

   The success rate of UDP hole punching is high, but not TCP hole punching in
   practical world. Also, the P2P solution requires a common server in the public
   internet to exchange the IP and port information.

   In this draft, a method is described to achieve incoming TCP or UDP session without
   a common rendezvous server in NAT444 situation.



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-
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   http://datatracker.ietf.org/drafts/current/.

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   inappropriate to use Internet-Drafts as reference material or to cite them other
   than as "work in progress."

   This Internet-Draft will expire on Aug 21, 2022.

Copyright Notice

   Copyright (c) 2017 IETF Trust and the persons identified as the document authors.
   All rights reserved.






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   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
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   warranty as described in the Simplified BSD License.



Table of Contents


   1. Introduction ......................................................... 2
   2. Conventions used in this document..................................... 3
   3. Port acquiring procedure in Application............................... 3
   4. Endpoint Independent port forwarding (EIPF) Enhancement .............. 4
      4.1. When this feature enabled in CGNAT with EIM...................... 4
      4.2. When this feature is enabled in CGNAT with both EIM and EIF ..... 4
   5. Retrieval of IP and port information via HTTP......................... 5
      5.1. IP and port - URI /ipport/ ...................................... 5
      5.2. IP and port range - URI /ipportrange/............................ 5
   6. Compatibility ........................................................ 6
   7. Security Considerations .............................................. 6
   8. References ........................................................... 6
      8.1. Normative References ............................................ 6
      8.2. Informative References .......................................... 6
   9. Acknowledgments....................................................... 7

1. Introduction

   The purpose of this document is to describe to a way to allow incoming TCP or UDP
   sessions under NAT444 situation.

   The success rate of TCP and UDP session would be guaranteed under this proposal.

   There would be two sections in the draft.

   - The first section describes a procedure for an application in end device to
     detect and allocate TCP or UDP port for its use for incoming session. The
     required tools are STUN [RFC5389] and UPNP [RFC6970].

   - The second section describes a method for residential gateway RG to discover the
     usable port range under a CGNAT deployment with port-block-allocation. In turn,
     the home gateway could allocate TCP or UDP to the end devices via UPNP, NAT-PMP
     [RFC6886] or PCP [RFC6887].






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2. Conventions used in this document

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

   In this document, these words will appear with that interpretation only when in ALL
   CAPS. Lower case uses of these words are not to be interpreted as carrying
   significance described in RFC 2119.



3. Port acquiring procedure in Application


        PC1-----RG-------CGNAT------Internet------PC2
                                       |
                                       +-----STUN server


   - Private network: PC1: 192.168.1.10, RG: 192.168.1.1
   - WAN: RG: 10.1.1.20, CGNAT: 10.1.1.1
   - CGNAT: public IP 100.1.1.1
   - PC2: public IP 201.1.1.10



   Here is an example of step to acquire a TCP or UDP port

   -  Application in PC1 sends a STUN request to STUN servers in public internet. The
      STUN server would reply the XOR-mapped-address. E.g.

         100.1.1.1:1024                      ;public ip is 100.1.1.1 with port 1024

     This detects both public IP address and the UDP port available. This assumes the
     same TCP port is also available since most CGNAT implementations allocate the
     same port number for both TCP and UDP with EIM enabled.

     The application will then send UPNP request to residential gateway RG,
     192.168.1.1, for port forward TCP port 1024 to the local device IP,
     192.168.1.10.


   - CGNAT, due to PBA allocation and a special setting enabled, TCP traffic sent to
     100.1.1.1:1024 as destination would be forwarded to RG 10.1.1.20:1024 without
     changing port value. Then, RG would pass the TCP traffic to PC1 with
     192.168.10.1:1024 as destination due to the registration of UPNP. In this case,
     PC2 could initiate a direct TCP session to PC1 via 100.1.1.1:1024.

   - UDP would work in the same way. Any host in the internet could create TCP or UDP
     session directly with the application in PC1

   The above procedure assumes both RG and CGNAT have EIM capability enabled.

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   The application in PC1, optionally, could release the UPNP mapping after finishing
   the session.



4. Endpoint Independent Port Forwarding (EIPF) Enhancement

4.1. When this feature enabled in CGNAT with EIM

   - the associated TCP or UDP port is UNCHANGED for the inbound traffic if there is
     no matching session in the NAT table.
   - only the IP address is going through NAT process. That is changing the public IP
     to a private IP
   - It is working like port forward function in a NAT44
   - In the example, any IP source address, 202.1.1.1 or 222.1.1.1, sending traffic
     to 100.1.1.1:1024. CGNAT would translate the traffic as 10.1.1.20:1024 as
     destination.
   - UDP hole punching would be compatible if the UDP session is still in RG and
     CGNAT session table. Port 1024 would follow the translation.

4.2. When this feature is enabled in CGNAT with both EIM and EIF

   - EIF (Endpoint-Independent Filtering), described in RFC5128, will happen only if
     the external host already has a session through EIM.
   - The TCP or UDP port is kept UNCHANGED for any other external hosts sending
     inbound traffic.
   - For example, there is a session originated from PC1 to PC3, 201.1.1.20

         PC1-----------RG----------CGNAT-----------Internet---------PC3
                                                       |
                                                       +---------------------PC4

     Src: 192.168.1.10:3333    10.1.1.20:4444           100.1.1.1:1033

     Dst: 201.1.1.20:5555      201.1.1.20:5555          201.1.1.20:5555



     When PC3 sends traffic with different source port, 201.1.1.20:6666 and
     destination 100.1.1.1:1033, CGNAT should honor the EIF behavior. It would be
     translated back to 10.1.1.20:4444.

     When other host without any session established through EIM, and it sends
     traffic with destination port 1033, the port 1033 should not be changed at
     CGNAT.

     When PC4 send traffic to 100.1.1.1:1033, the port 1033 is kept UNCHANGED. PC4
     has no previous established sessions with PC1.

     This behavior is an optional implementation with EIF enabled. Another option is
     to make EIPF and EIF exclusive.



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5. Retrieval of IP and port information via HTTP

   The internet service provider host a HTTP web server for the enquiry of IP and port
   information. Two URIs are suggested

5.1. IP and port - URI /ipport/

   With the URI /ipport/, the HTTP response is clear text with IP:PORT, where IP is
   the external public IP address and the PORT is external port as seen.

   For example, the response is

   100.1.1.1:1040

   The HTTP response should be human readable with a web browser.

   Although TCP port 1040 is seen here, it is assumed that UDP port 1040 is also
   available from CGNAT for incoming mapping.

5.2. IP and port range - URI /ipportrange/

   With the URI /ipportrange/, the HTTP response is clear text with

   IP:PORT_START:PORT_END<LF>

   IP:PORT_START:PORT_END<LF>

   IP:PORT_START

   Where <LF> is ASCII character for line feed.

   The response is a human readable format in a normal web browser.

   For examples, here are valid responses

   a) Single line

   100.1.1.1:1024:1031

   Port range 1024 to 1031 assigned for both TCP and UDP.

   b) Two lines

   100.1.1.1:1024:1031

   100.1.1.1:1064:1071

   Port ranges 1024 to 1031 and range 1064 and 1071 are assigned for both TCP and UDP.



   It is possible to have multiple port block allocated to the same private IP address
   from CGNAT perspective.

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   If the RG device or application could not support multiple entries of IP and port
   range, it should take one of the lines, preferably the first line.

   Human user or RG could use this information to plan for incoming services. For
   example, when PC1 requests a TCP 8888 port forward from RG via UPNP [RFC6970], NAT-
   PMP [RFC6886] or PCP [RFC6887], RG would counter offer another TCP port 1031.





6. Compatibility

   TBD



7. Security Considerations

   TBD



8. References

8.1. Normative References

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

8.2. Informative References

   [RFC5128] Srisuresh, P., Ford, B., and D. Kegel, "State of Peer-to-
             Peer (P2P) Communication across Network Address
             Translators (NATs)", March 2008.


   [RFC5389] Rosenberg, J., Mahy, R., Matthews, P., and D. Wing,
              "Session Traversal Utilities for NAT (STUN)", October 2008.


   [RFC6886] S. Cheshire and M. Krochmal. NAT Port Mapping Protocol (NAT-PMP),
             April 2013.

   [RFC6887] Wing, D., Cheshire, S., Boucadair, M., Penno, R., and P.
             Selkirk, "Port Control Protocol (PCP)", April 2013.


   [RFC6970] Boucadair, M., Penno, R., and D. Wing, "Universal Plug and
             Play (UPnP) Internet Gateway Device - Port Control
             Protocol Interworking Function (IGD-PCP IWF)", July 2013




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9. Acknowledgments


        The following people have contributed to this document:






     Author Address

     Louis Chan (editor)
        Juniper Networks
        2604, Cityplaza One, 1111 King's Road
        Taikoo Shing
        Hong Kong

        Phone: +852-25876659
        Email: louisc@juniper.net
































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