Editing End-to-end principle (section)

==Limitations==
The most important limitation of the end-to-end principle is that its basic premise, placing functions in the application endpoints rather than in the intermediary nodes, is not trivial to implement. 

An example of the limitations of the end-to-end principle exists in mobile devices with [[mobile IPv6]].<ref>{{Cite IETF|rfc=3724|author1=J. Kempf|author2=R. Austein|date=March 2004|title=The Rise of the Middle and the Future of End-to-End: Reflections on the Evolution of the Internet Archichecture|publisher=Network Working Group, [[IETF]]}}</ref> Pushing service-specific complexity to the endpoints can cause issues with mobile devices if the device has unreliable access to network channels.<ref>{{Cite web|url=http://www.winlab.rutgers.edu/docs/focus/CNF/protocol%20architecture.html|title=CNF Protocol Architecture|website=Focus Projects|publisher=Winlab, Rutgers University|access-date=May 23, 2016|archive-date=June 23, 2016|archive-url=https://web.archive.org/web/20160623210856/http://www.winlab.rutgers.edu/docs/focus/CNF/protocol%20architecture.html|url-status=dead}}</ref>

Further problems can be seen with a decrease in network transparency from the addition of [[network address translation]] (NAT), which [[IPv4]] relies on to combat [[IPv4 address exhaustion|address exhaustion]].<ref>{{Cite news|url=https://www.bbc.com/news/technology-19600718|title=Europe hits old internet address limits|last=Ward|first=Mark|date=2012-09-14|work=BBC News|access-date=2017-02-28|language=en-GB}}</ref> With the introduction of [[IPv6]], users once again have unique identifiers, allowing for true end-to-end connectivity. Unique identifiers may be based on a [[MAC address|physical address]], or can be generated randomly by the host.<ref>{{Cite web|url=http://ftp.cuhk.edu.hk/pub/doc/ipng/html/ipv6-address-privacy.html|title=Statement on IPv6 Address Privacy|last=Steve Deering & Bob Hinden|first=Co-Chairs of the IETF's IP Next Generation Working Group|date=November 6, 1999|access-date=2017-02-28}}</ref>

The end-to-end principle advocates pushing coordination-related functionality ever higher, ultimately into the application layer. The premise is that application-level information enables flexible coordination between the application endpoints and yields better performance because the coordination would be exactly what is needed.  This leads to the idea of modeling each application via its own application-specific protocol that supports the desired coordination between its endpoints while assuming only a simple lower-layer communication service.  Broadly, this idea is known as application semantics (meaning).

Multiagent systems offers approaches based on application semantics that enable conveniently implementing distributed applications without requiring message ordering and delivery guarantees from the underlying communication services.  A basic idea in these approaches is to model the coordination between application endpoints via an information protocol<ref>{{cite web|title= Information-Driven Interaction-Oriented Programming: BSPL, the Blindingly Simple Protocol Language|url=http://www.csc.ncsu.edu/faculty/mpsingh/papers/mas/AAMAS-11-IBIOP.pdf |first1=Munindar P. |last1=Singh |publisher=Department of Computer Science, North Carolina State University |accessdate=24 April 2013 |url-status=dead |archive-url=https://web.archive.org/web/20150607040221/http://www.csc.ncsu.edu/faculty/mpsingh/papers/mas/AAMAS-11-IBIOP.pdf |archive-date= Jun 7, 2015 }}</ref> and then implement the endpoints (agents) based on the protocol.  Information protocols can be enacted over lossy, unordered communication services. A middleware based on information protocols and the associated programming model abstracts away message receptions from the underlying network and enables endpoint programmers to focus on the business logic for sending messages.