## 2 Comparing the Telco Approach to Internet Approach
### Internet Approach, the Evolution of Data Communication  
The internet [2,3] as we know it today has evolved from the original interconnection of local networks sponsored by DARPA research. The Internet Engineering Task Force (IETF), which hascovered internet related standards, targeted the layer approach. Each layer of the protocol stack should provide only necessary functionality on this layer, and as efficiently as possible. All other functionalities not implemented on that particular layer, or on any underlying layer, should be implemented separately.  
_Design goals/principles of the original internet (1970s):_  
* Connection of existing networks
* Survivability
* Support of multiple types of services
* Accommodation of a variety of physical networks
* To allow distributed management
* Cost-effectiveness
* Ease of use (host attachment)
* Resource accountability  
The scope of the internet protocol was defined as follows in RFC 791 [4]:  
_\"The internet protocol is specifically limited in scope to provide the functions necessary to deliver a package of bits (an internet datagram) from a source to a destination over an interconnected system of networks. There are no mechanisms to augment end-to-end data reliability, flow control, sequencing, or other services commonly found in host-to-host protocols. The internet protocol can capitalize on the services of its supporting networks to provide various types and qualities of service.\"_  
This approach was highly successful and yielded in the internet protocol using the stacking system still known today. The core of the internet is the famous Internet Protocol (IP). Under the IP protocol layer, there are device- and physical-transmission-medium-specific layers.  
_Internet protocol principles_:  
* Layering (ISO OSI, TCP/IP)
* Packet switching (universal packet format: IP)
* Network of collaborating networks
* Intelligent end-systems (\"dumb\" core network performing only packet routing)  
Typically, physical transmission of IP packets is over the Ethernet but many other layer-1 and layer-2 protocols may be used. The IP protocol was originally designed only to provide best effort services, but later \"managed IP networks\" have been developed with an operator/provider controlled infrastructure. Additionally the MultiProtocol Label Switching (MPLS) introduced Quality of Service (QoS) and a circuit switched service notion to the IP world. Above the IP protocol layer, there are usually connection-less datagram services using the User Datagram Protocol (UDP), or connection-oriented transport using the Transmission Control Protocol (TCP). On this layer, several other protocols have been designed, like Stream Control Transmission Protocol (SCTP), but mainly UDP and TCP are used.  
The internet is basically a packet transport and routing infrastructure. However, it allows new technologies to be introduced; is independent from the physical layer; and enables the use of open protocols on the application layer. It was new technologies that enabled the significant increase of traffic and number of subscribers to volumes comparable with the traffic provided by classical telecommunication networks, that made the suppliers of technologies, operators and standardization organizations and consortia, think seriously about convergence of the seemingly vastly different worlds of telecommunications and the internet.