Multiplex communications – Pathfinding or routing – Combined circuit switching and packet switching
Reexamination Certificate
1999-03-30
2003-07-01
Vu, Huy D. (Department: 2665)
Multiplex communications
Pathfinding or routing
Combined circuit switching and packet switching
C370S392000, C370S409000, C370S420000, C455S426100, C455S450000
Reexamination Certificate
active
06587457
ABSTRACT:
The present invention relates to a method as set forth in the preamble of the appended claim 1 for connecting data flows in wireless communication according to the Internet protocol, a system as set forth in the preamble of the appended claim 6, and an access point as set forth in the preamble of the appended claim 8.
The International Standardisation Organisation ISO has developed an open system interconnection (OSI) model for describing the distribution of data transmission in different layers. The layers are, listed from top downwards, an application layer (layer
7
), a presentation layer (layer
6
), a session layer (layer
5
), a transport layer (layer
4
), a network layer (layer
3
), a data link layer (layer
2
), and a physical layer (layer
1
). In view of the present specification, the most essential layers are the physical layer, the data link layer, the network layer, and the application layer.
The term “Internet” is commonly used to describe an information resource from which information can be retrieved from a data processor, such as a personal computer (PC). The data processor communicates via a modem with a telecommunication network. This information resource is distributed world-wide, comprising several storage locations which also communicate with the telecommunication network. The Internet is made operable by defining certain data communication standards and protocols, such as TCP (transmission control protocol), UPD (user datagram protocol), and IP (Internet protocol), which are used for controlling data transmission between numerous parts of the Internet. The TPC and the UDP are involved with preventing and correcting data transmission errors in the data transmitted in the Internet; the IP is involved with data structure and routing. The currently used versions of the Internet protocol are IPv
4
and IPv
6
.
Thanks to the growing popularity of open data systems, the Transmission Control Protocol/Internet Protocol (TCP/IP) communication protocol has become a generally used protocol whereby computers of different sizes and brands can communicate with each other. TCP/IP support is currently available for almost all operating systems. The network layer protocol of TCP/IP, the Internet Protocol IP, is intended to be routed by gateways, i.e. routers. The routing is conducted by means of IP addresses and routing tables.
In the Internet, each device has its own individual IP address. In the Internet protocol version IPv
4
, the IP address consists of 32 bits, i.e. it is a digit of four bytes which is divided in two parts: an organisation-specific network address and a network-specific device address. In the more recent Internet protocol version IPv
6
, the length of address fields has been added to 128 bits, which means in practice that an individual address can be reserved for all devices that are connected with the Internet network.
FIG. 1
shows in IPv
6
the blocks of the data packet in Internet messages.
The header block consists of the following elements:
Version IP version of 4 bits (=6),
Prio. priority of 4 bits,
Flow label 24 bit label for identifying the connection in the application layer,
Payload length 16 bit integer indicating the length of the payload, i.e. the length of the packet after the header in bytes,
Next header data of 8 bits determining the header immediately following the IPv
6
header,
Hop limit integer counter of 8 bits which is reduced by one at the each device (node) which transmits the packet further; the packet is rejected if the value is reduced to zero,
Source address the 128 bit address of the sender of the original packet,
Destination address the 128 bit address of the intended recipient.
The header is followed by the payload block, i.e. the actual information to be transmitted.
Physically, the Internet consists of communication networks arranged in a hierarchy, for example local area networks (LAN), regional telecommunication networks and international telecommunication networks. These communication networks are coupled internally and externally with routers which transmit information from the transmitting terminal equipment or from the preceding router in the chain of data transmission, and route the information to the receiving terminal equipment or to the next router in the chain of data transmission.
Below in this specification, the transmitting terminal equipment and receiving terminal equipment will also be called by the common term Internet host. The Internet hosts can be typically used either as the source host SH and the destination host DH. In the present specification, the Internet hosts connected in a wireless manner with the Internet network are called a wireless terminal.
An Internet host, coupled to the Internet network via a local area network LAN, is either provided with a permanently defined Internet address or the address is a dynamic address generated by the server of the local area network (for example by using a dynamic host configuration protocol DHCP). In case the Internet host is coupled by a modem to a telecommunication network, the telecommunication terminal must ask for an Internet address from an Internet service provider to which the Internet host is registered. This is conducted e.g. according to a point-to-point protocol (PPP) formed above the Internet protocol layer. In both cases, the information to be transmitted in the Internet is routed to the Internet host possibly via several communication networks and routers from a remote host by using a determined Internet address.
The IP defines the transmission of the communication in packets (datagrams). The packet data transmission is one reason for the popularity of the Internet, because it allows transmission in bursts which does not require constant on-line connection and makes it possible that several Internet hosts are coupled in the same telephone connection. When a router receives a packet containing a destination address, the router routes the packet forward, if there is free capacity in the buffer memory of the router and at least one open telephone line. If there is not sufficiently memory space or no open telephone line available at the moment, the packet is rejected and the source host or the preceding router must try retransmission later. In general, the Internet does not support time-critical data transmission, and the method of best effort offered by the Internet protocol is sufficient.
In the transmission of packets according to the Internet protocol, the packets can be transmitted directly to the receiver only when the network elements of the addresses of both the host and the destination are the same. In other cases, the packets are transmitted to a router which takes care of transmitting the packets further, either to the next router or to the destination, if the recipient is in the network of the router. In each router, each packet entering the router is transferred from the data link layer according to the OSI model to the network layer, where the header of the packets is examined, and on the basis of the address data therein, a decision is made where the packet is to be transmitted. For transmission, the packets are transferred back to packets of the data link layer. The packets running the same path constitute a so-called communication stream. Because the Internet protocol has the character of a connectionless protocol, the above-mentioned operations must be conducted for each packet entering the router. If the communication layer is fast, for example in accordance with the asynchronous transfer mode ATM, the processing of the packets takes a significant part of the time used for transmission. Thus, the whole transmission capacity of the transfer line cannot be utilised effectively. For correcting this situation, e.g. Internet Engineering Task Force (IETF) has developed a solution in which an attempt is made to accelerate the routing of communication streams. In this solution, which is called Layer
3
/Layer
2
switching (L
3
/L
2
switching) or Multi Protocol Label Switching (MPLS), an attempt is made to switch th
Nokia Mobile Phones Ltd.
Perman & Green LLP
Phan M.
Vu Huy D.
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