Internet DRAFT - draft-blanchet-iab-internetoverport443
draft-blanchet-iab-internetoverport443
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
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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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