Multiplex communications – Pathfinding or routing – Combined circuit switching and packet switching
Reexamination Certificate
1998-05-26
2002-06-04
Cangialosi, Salvatore (Department: 2661)
Multiplex communications
Pathfinding or routing
Combined circuit switching and packet switching
C370S398000
Reexamination Certificate
active
06400712
ABSTRACT:
BACKGROUND OF THE INVENTION
I. Field of the Invention
The present invention relates to communication systems. More particularly, the present invention relates to the transmission of packetized data over circuit switched frame based data communication systems.
II. Description of the Related Art
Data Networks
Networks for interconnecting information processing entities are presently in widespread use. In general, networks provide for the communication of digital data between two or more data terminals or processing devices. Internetworks are essentially groups of individual networks coupled together so as to allow data interchange therebetween. The largest and most commonly known digital data network is the Internet.
Typical networks operate based on the transfer of discrete, quantized units of data called packets or frames. Thus, an entire file of data, such as an e-mail message, is segmented into a series of frames for transmission over the network. The actual data in each frame is attached to a series of headers associated with a set of protocol layers, described in additional detail below. Each protocol layer is devoted to handling one or more tasks involved with the transportation of data between terminals.
Most digital networks are comprised of many nodes or branch points. On its journey through the network, a frame may pass through a series of network nodes. The nodes may be generally categorized as repeaters, bridges, routers, switches or gateways based largely on 1) the highest protocol layer which is examined by the node, and 2) whether the node transforms the data between transport protocols. The nodes may be connected using a variety of different physical media referred to as links.
Network Protocols
An industry standard model describing seven protocol layers ranging from the physical layer to the application layer is defined by the Open Systems Interconnection (OSI) model. The layers are related hierarchically by level of abstraction with the physical layer being the lowest and the application layer being the highest. For instance, RS-232 is a physical layer protocol defining the electrical signal interface between terminals, whereas Simple Mail Transfer Protocol (SMTP) is a commonly used application layer protocol for sending e-mail over a network. A similar model, Transport Control Protocol/Internet Protocol (TCP/IP), is presently in widespread commercial and military use in data networking applications. The TCP/IP protocol suite (also known as a “stack”, due to the aforementioned layered construction) uses application, transport, internetwork, and network access layers. Overall, the TCP/IP suite provides a number of functions, including remote file transfer and copy, remote login capability, gateway and router support, electronic mail (STMP), and serial line communications via other existing protocols such as PPP or SLIP (described further below).
Generally speaking, Internetwork Protocol (IP) is implemented in all end systems and routers; it acts to relay or move a block of data on an internetwork from one host to another via one or more routers. Hence, it facilitates the delivery of data message packets (typically called “datagrams”; see discussion of packet switching below) from two devices not directly connected. TCP is typically resident only in end systems; it essentially functions to track and deliver data to the appropriate application layer entity. Specifically, TCP avoids loss, damage, duplication, or misordering of datagrams that may result from the application of IP by way of checksums, sequence numbers in the TCP header, and other means. Additionally, security and access limitations may be applied via TCP. In the generic TCP/IP suite, the network layer uses existing network protocols (such as Ethernet, IEEE Standard 802, or X.25), and encompasses those protocols necessary to effectuate physical communication with other network nodes or entities.
FIG. 1
illustrates the basic OSI and TCP/IP protocol suite models. IETF RFC 793 and 791 provide additional information on TCP and IP protocols, respectively.
Two levels of addressing are typically used in protocol suites such as TCP/IP. The first specifies the global internetwork (IP) address of a given host on a network, typically a 32-bit word. The second is unique within the host; i.e., it allows the host-to-host protocol (such as TCP) to deliver data to the proper application within a given host entity. This second address is commonly known as a port. Systems running TCP/IP typically have what is known as a kemal or internet routing table consisting of a series of entries, each entry containing multiple data fields. These fields include the destination IP address, a network mask, network “hopping” address (i.e., the next machine which knows how to reach the ultimate destination of the data message), and the identity of the network interface device through which the datagram(s) must be sent to reach the next hop. Routing “daemons” initialize and dynamically update the kernal routing table by communicating with comparable entities in other systems to exchange routing information.
The Point-to-Point Protocol (PPP) is a link protocol which provides for the use of network applications within the TCP/IP suite over serial line interfaces (such as dial-up Internet connections) by linking the serial line(s) to the IP protocol driver. The PPP stack typically consists of multiple components, including an asynchronous high level data link control (HDLC) protocol, a link control protocol (LCP), an network control protocol (NCP), and authorization protocols. The HDLC layer is typically the lowest layer of the stack, and functions to provide framing for data packets, error detection, and frame identification for high level protocols. The LCP sits above the HDLC and dynamically determines transmission link characteristics (MRU and ACCM) and integrity. The NCP (for example, Internet Protocol Control Protocol {IPCP} for IP suites) carries out addressing functions relating to the PPP link. Note that multiple NCPs can run on the same PPP link. RFC 1661 and 1332 provide additional information on PPP and IPCP protocols, respectively.
The PPP operates generally as follows. In order to establish a point-to-point link, each end of the PPP link must first send LCP packets to configure and test the data link. After the link has been established and transmission features negotiated, PPP sends NCP packets to select and configure the operable NCPs. Once each of the chosen NCPs is configured, datagrams from each NCP can be sent over the link.
Wireless Link to a Data Network
With the advent of wireless communication techniques, data networks now provide the terminal user with greatly increased mobility. For example, a lap top computer may utilize a cellular telephone transceiver to connect to digital networks such as the internet without a wired connection to a physical data port. Numerous other data network applications over wireless links are possible, as described below.
FIG. 2
is a representation of a terrestrial wireless communication system
10
. The system illustrated in
FIG. 2
may use code division multiple access (CDMA), time division multiple access (TDMA), a combination of frequency hopping and TDMA (such as the Global System for Mobile Communications, or GSM) or other modulation and access techniques.
FIG. 2
shows two remote units
10
,
12
, and two base station antenna
14
. In reality wireless communication systems may have hundreds of thousands of remote units and many hundreds of base stations. In
FIG. 2
, the remote unit
10
is shown as a mobile telephone unit with a laptop computer
11
connected thereto.
FIG. 2
also shows the personal digital assistant
12
in a standard cellular system. In the most general embodiment, the remote units may be any type of communication unit. For example, the remote units may be hand-held personal communication system (PCS) units, portable data units, or fixed location data units such as meter reading equipment.
FIG. 2
shows a single wireless link
16
between t
Baker Kent D.
Cangialosi Salvatore
Edmonston Brian S.
Qualcomm Incorporated
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