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Network Working Group                                        M. Blanchet
Internet-Draft                                                  Viagenie
Intended status: Informational                             July 31, 2013
Expires: February 01, 2014


    Implications of Blocking Outgoing Ports Except Ports 80 and 443
             draft-blanchet-iab-internetoverport443-02.txt

Abstract

   Users are often connected to Internet with very few outgoing ports
   available, such as only port 80 and 443 over TCP.  This situation has
   many implications on designing, deploying and using IETF protocols,
   such as encaspulating protocols within HTTP, difficulty to do traffic
   engineering, quality of service, peer-to-peer, multi-channel
   protocols or deploying new transport protocols.  This document
   describes the situation and its implications.

Status of This Memo

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   This Internet-Draft will expire on February 01, 2014.

Copyright Notice

   Copyright (c) 2013 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Implications  . . . . . . . . . . . . . . . . . . . . . . . .   3
     3.1.  IETF Guidance . . . . . . . . . . . . . . . . . . . . . .   3
     3.2.  Trafic Policing . . . . . . . . . . . . . . . . . . . . .   3
     3.3.  Deploying New Protocols . . . . . . . . . . . . . . . . .   4
     3.4.  Overloading HTTP  . . . . . . . . . . . . . . . . . . . .   4
     3.5.  Increasing the rate of usage of IP addresses  . . . . . .   4
     3.6.  More Complex Operations . . . . . . . . . . . . . . . . .   4
     3.7.  Inability to Deploy Applications and Protocols  . . . . .   5
     3.8.  Applications Become Only HTTP-based . . . . . . . . . . .   5
     3.9.  Applications Need to Become Very Smart for Opening
           Connection  . . . . . . . . . . . . . . . . . . . . . . .   5
     3.10. Internet Transport  . . . . . . . . . . . . . . . . . . .   5
     3.11. Should IETF Protocols Only Use HTTP Encapsulation . . . .   5
   4.  Mitigation  . . . . . . . . . . . . . . . . . . . . . . . . .   6
   5.  Recommendations . . . . . . . . . . . . . . . . . . . . . . .   6
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   7
   9.  Informative References  . . . . . . . . . . . . . . . . . . .   7
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   A trend started many years ago has been to provide Internet access to
   end-users with limited outgoing ports.  The most constraint but
   common case is to only have outgoing TCP port 80 and port 443 opened.
   Port 80 is expected to carry HTTP and some middleboxes in the network
   may block non-HTTP traffic on that port.  Port 443 is often less
   policed than port 80 based on the assumption that it is carrying
   encrypted traffic.  However, enterprise firewalls sometimes verify
   the use of TLS/SSL on port 443.

   A consequence of this trend is that Internet statistics show
   [Labovitz] that a majority of the Internet traffic is over port 80
   and 443.  And the concentration on these ports are further increasing
   every year.

   While the purpose of this document is not to find or judge the
   reasons why providers (in the large sense of providing) are blocking
   all outgoing ports except very few, a few known reasons can be
   listed, while no opinion on the validity is expressed:



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   o  Users only need HTTP anyway.  Now email and chat is over HTTP.

   o  Less number of ports means easier control over shadow traffic.

   o  Provider wants to control, verify, police all outgoing traffic.

   A consequence for the enterprise or non-HTTP application service
   provider is that there are very few ways to offer a service to its
   end-users.  For example, an application (VoIP, ssh, jabber, ftp, ...)
   provider need to use an additional IP address and to bind its
   application server to the port 443 to make sure its users can reach
   it whatever the characteristics of the access network the nomadic
   users are attaching to.  The other way is to build a tunnel such as
   VPN to the service infrastructure and then tunnel all application
   traffic to that tunnel.  Obviously for the same reason, the tunnel
   server itself has to be bound on port 443.

   From the application developer point of view, HTTP framework is often
   chosenfor its own benefits with or without the limited outgoing ports
   deployment considerations, as discussed in
   [I-D.tschofenig-post-standardization].

2.  Terminology

   This document uses the term provider in a large sense of some
   organization offering the Internet access to users.  For example, a
   provider in this document includes coffee shop wifi access, guest
   access in various public places and networks, hotel networks,
   enterprise guest access networks, as well as traditional providers
   such as broadband, mobile and wifi network established large
   providers.

3.  Implications

3.1.  IETF Guidance

   IETF provided guidance about the use of HTTP and port 80.  For
   example, [RFC3205] recommended to use different ports than 80 for new
   services, even when HTTP encapsulation was used.  This guidance may
   need to be revisited.

   This situation further complicates the Internet transparency, end-to-
   end and hourglass model, as discussed in [RFC2775],[RFC3234] and
   [RFC4924].

3.2.  Trafic Policing





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   If all traffic goes over one or two ports, then it is more difficult
   to differentiate delay sensitive traffic to bulk traffic while
   applying policies on forwarding engines at the transport level.  The
   policing nodes on the network haveto open the application payload.
   For example, for Motion-JPEG over http, parsing the HTTP headers is
   needed to discover that this data is streaming.

3.3.  Deploying New Protocols

   If port 80 and 443 are the only ports opened, then given that
   middleboxes in networks are inspecting packets and validate HTTP
   traffic, then a new protocol not based on HTTP and requiring a
   different transport port or protocol is difficult, while impossible,
   to deploy as is.

3.4.  Overloading HTTP

   Another consequence of this situation is that protocols and data go
   over HTTP.  HTTP is defined with a specific set of requirements and
   is implemented in a solution set that is far from the IP layer.  It
   uses TCP transport, has multiple ascii headers in the payload to be
   parsed, has state, etc.  However, the HTTP protocol is being revised
   [RFC6455][httpbis] related to some of these new requirements.

3.5.  Increasing the rate of usage of IP addresses

   If an organization has N different services where each one takes a
   different port, then, in the context of its users only able to use
   outgoing port 80/443, the organization has to use N IP addresses, one
   for each service and bind the service on port 443 (or 80) on that IP
   address.  Therefore, the organization increases the rate of its usage
   of IP addresses.  Since IPv4 addresses are almost exhausted, this
   situation adds pain to the IPv4 address exhaustion.  IPv6 addresses
   are almost limitless to this issue, but having too many IPv6
   addresses on the same server to support the services add complexity
   to the operations.

3.6.  More Complex Operations

   As a network operator likes to monitor traffic to engineer and
   troubleshoot the network, it cannot do anymore by only looking at the
   ports used by the traffic.  For example, a peak traffic from a source
   node that always uses a single outgoing port for all its traffic, may
   be a video call or video streaming or file copy or a virus related
   traffic or torrent or ... Therefore, the network operations is blind
   to what the traffic is, unless the monitoring is at done within the
   application payload.




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3.7.  Inability to Deploy Applications and Protocols

   A good example of limitations to deploy applications and protocols
   are IP cameras.  These devices send video streams to outside.  While
   a typical protocol stack would use RTP/RTSP for this purpose, often
   the only way to successfully send the stream in all cases is to
   encapsulate it over HTTP using Motion JPEG or other coding over HTTP.
   Similar issues also happen for interactive applications.  The
   constraint of the transport protocol to use may have an important
   impact on the application design and behavior.

3.8.  Applications Become Only HTTP-based

   From the application developer point of view, the most garanteed way
   to get its outgoing traffic from the client host to the Internet
   (servers) is to carry its application data and protocols over HTTP
   over port 80 and/or 443.  This is, whatever the type of traffic, such
   as gaming, voice, video, file transfer, augmented reality, 3D, ...,
   with a wide set of different characteristics.  Within the HTTP
   framework, the Websocket Protocol[RFC6455] is one way to support the
   variety of applications over HTTP.

3.9.  Applications Need to Become Very Smart for Opening Connection

   Skype is a good illustration of a deployable application that works
   in most cases.  Analysis of Skype behavior [ColumbiaSkype] shows
   Skype is trying to open outgoing ports, and when not possible,
   defaults to port 80 or 443 as last resort.  Therefore, this
   illustrates that a successful deployable application should use
   similar techniques with the last resort being port 80 or 443.  That
   also means the other peer of the communication must be bound to the
   same 80 or 443 port.  This application behavior may require to have
   standardized ways of handling encapsulation over 80/443 for realtime
   applications.

3.10.  Internet Transport

   Written differently, this situation can be described as the Internet
   can only run with a single transport protocol(TCP) and two transport
   ports(80,443).  Given that some deployments have HTTP-aware
   middleboxes on those ports, then the Internet can only run "reliably"
   over a single transport protocol (HTTP) and a single transport port
   (443).

3.11.  Should IETF Protocols Only Use HTTP Encapsulation






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   Given above, should the IETF only design protocols over HTTP?  Should
   all current protocols be redesigned to be carried over HTTP? (more a
   question to debate than an affirmation...)

   For example, 3GPP and MPEG produced the Dynamic Adaptive Streaming
   over HTTP(DASH) protocol[DASH] where one of the reasons is related to
   firewalls and NAT traversal.  This new protocol is intended to
   replace the RTSP [RFC2326] protocol.

   Websockets[RFC6455] is a standardized way to encapsulate subprotocols
   within HTTP and therefore multiplexing the various application
   protocols within HTTP.

   [I-D.tschofenig-post-standardization] also discuss about this issue.

4.  Mitigation

   IPv6 could be seen as a way to mitigate that problem.  As discussed
   above, the reasons why access providers or enterprises are limiting
   outgoing ports are not related to IPv4 address exhaustion or IPv4
   itself.

   However, on the server side of the connections, given the large IPv6
   address space available per server, IPv6 could be used to partly
   mitigate the problem by having, on a single server, each service
   bound to a different IPv6 address while using the same transport port
   80.

   It should be noted that some IPv6 access providers are not blocking
   any port, helping restoring the Internet transparency.

5.  Recommendations

   A new network protocol that would likely be used and deployed in an
   environment described above, should:

   o  consider the issues listed and identify how the protocol
      specification will mitigate the issues.  For example, what happens
      if only port 80 and/or 443 over TCP are available for the end user
      to start its connection with that protocol?  What happens if HTTP
      protocol inspection is done on those ports by an intermediate
      node?

   o  consider, for the "transport" of the protocol, using the HTTP
      protocol, or enhancements of HTTP such as the RESTFUL or
      Websockets[RFC6455] methods.





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   The access network providers, including small organisations such as
   Internet cafes, should consider opening their outbound ports to
   mitigate the issues raised above and to enable a full Internet user
   experience.  There is an opportunity to implement these no-outgoing-
   ports blocking policies for the new IPv6 deployments.

6.  Security Considerations

   This document does not specify a new protocol.  However, it does
   highlight security impacts of the current Internet access.

7.  IANA Considerations

   This document has no actions for IANA.

8.  Acknowledgements

   Dave Thaler, Hannes Tschofenig, Brian Carpenter, Bernard Adoba, Joel
   Halpern, Cameron Byrne have provided input and suggestions to this
   document.

9.  Informative References

   [ColumbiaSkype]
              Baset, S. and H. Schulzrinne, "An Analysis of the Skype
              Peer-to-Peer Internet Telephony Protocol", , <http://
              www.cs.columbia.edu/~salman/publications/skype1_4.pdf>.

   [DASH]     , "ISO/IEC 23009-1:2012 Information technology -- Dynamic
              adaptive streaming over HTTP (DASH) -- Part 1: Media
              presentation description and segment formats", , <http://
              www.iso.org/iso/iso_catalogue/catalogue_tc/
              catalogue_detail.htm?csnumber=57623>.

   [I-D.tschofenig-post-standardization]
              Tschofenig, H., Aboba, B., Peterson, J., and D. McPherson,
              "Trends in Web Applications and the Implications on
              Standardization", draft-tschofenig-post-standardization-02
              (work in progress), May 2012.

   [Labovitz]
              Labovitz, C., "Internet Traffic and Content
              Consolidation", March 2010, <http://www.ietf.org/
              proceedings/77/slides/plenaryt-4.pdf>.

   [RFC2326]  Schulzrinne, H., Rao, A., and R. Lanphier, "Real Time
              Streaming Protocol (RTSP)", RFC 2326, April 1998.




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   [RFC2775]  Carpenter, B., "Internet Transparency", RFC 2775, February
              2000.

   [RFC3205]  Moore, K., "On the use of HTTP as a Substrate", BCP 56,
              RFC 3205, February 2002.

   [RFC3234]  Carpenter, B. and S. Brim, "Middleboxes: Taxonomy and
              Issues", RFC 3234, February 2002.

   [RFC4924]  Aboba, B. and E. Davies, "Reflections on Internet
              Transparency", RFC 4924, July 2007.

   [RFC6455]  Fette, I. and A. Melnikov, "The WebSocket Protocol", RFC
              6455, December 2011.

   [httpbis]  , "Hypertext Transfer Protocol Bis (httpbis)", ,
              <http://datatracker.ietf.org/wg/httpbis/charter>.

Author's Address

   Marc Blanchet
   Viagenie
   246 Aberdeen
   Quebec, QC  G1R 2E1
   Canada

   Email: Marc.Blanchet@viagenie.ca
   URI:   http://viagenie.ca























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