Multiplex communications – Communication techniques for information carried in plural... – Adaptive
Reexamination Certificate
1998-04-09
2002-01-29
Olms, Douglas (Department: 2661)
Multiplex communications
Communication techniques for information carried in plural...
Adaptive
C370S395500, C370S392000
Reexamination Certificate
active
06343083
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to techniques for carrying messages of one protocol over networks of a different protocol. More particularly, the invention involves a technique for carrying messages of a connectionless protocol, such as IP over Ethernet, over a connection-oriented network, such as an ATM network.
2. Description of Related Art
The various nodes or network elements (NE's) of a computer data network communicate with each other via commonly agreed upon communication protocols. These protocols have different layers or levels, each defining a different aspect of the protocol. Each different layer can be thought of as a sub-protocol of the overall protocol, but can also be thought of as a protocol in itself. All of the sub-protocols which together define an overall protocol are often referred to as a “protocol stack”. The interface between the different layers of a stack are well-defined, so different alternative sub-protocols can be substituted for other sub-protocols at the same layer in the stack.
One very common protocol used for computer networking is the so-called Internetworking Protocol (IP). IP is a network layer service and includes provisions for addressing, type-of-service specification, fragmentation and reassembly, and security information. It is defined- in a series of documents maintained by the Internet Engineering Task Force (IETF), most notably, J. Postel, “Internet Protocol,” STD0005 (September 1981) (including RFC0791, RFC0950, RFC0919, RFC0922, RFC792, RFC1112), incorporated herein by reference. IP defines a protocol to be used at one layer of the overall communication protocol, specifically the “network” protocol layer. Several common alternative network-level protocols are IPX (defined in Novell, Inc., “Advanced NetWare V2.1 Internetwork Packet Exchange Protocol (IPX) with Asynchronous Event Scheduler (AES)”, October 1986, incorporated by reference herein); DECnet; and Xerox PUP. Many modern local area networks (LANs) use an Ethernet protocol as the next layer below IP. Ethernet includes a Media Access Control (MAC) layer protocol, and is defined in IEEE, “IEEE Standards for Local Area Networks: Carrier Sense Multiple Access with Collision Detection (CSMA/CD) Access Method and Physical Layer Specifications” (IEEE Standard No. 802.3) (1985), incorporated herein by reference. When IP and Ethernet are used together in a protocol stack, the combined protocol is sometimes referred to herein as “IP over Ethernet”. Similarly, when IPX, DECnet or Xerox PUP are carried over Ethernet, the combined stack is sometimes referred to herein as “IPX over Ethernet”, “DECnet over Ethernet” and “PUP over Ethernet”, respectively.
The basic unit of data at the network layer is often referred to as a “datagram” (e.g. an “IP datagram”), whereas the basic unit of data at the MAC level is often referred to as a “packet” (as in “Ethernet packet”). Datagrams must be “encapsulated” according to the MAC level protocol in order to be transmitted, which may involve breaking them up into multiple packets. Similarly, the recipient node must extract and re-assemble the datagram from one or more MAC level packets in order to make use of it. Also as used herein, a “message” is a logical data unit that is not intended to imply any particular encapsulation. Some messages are bigger than a datagram, in which case they need to be divided up into multiple datagrams (and then multiple packets) in order to be transmitted. Other messages consist of a single packet, such as an ARP Request packet.
Wide Area Networks (WANs) typically take advantage of existing communications media for carrying messages over great distances. In particular, usually, the different nodes of a WAN communicate with each other via existing telephony networks such as Integrated Services Digital Networks (ISDN) or Broadband ISDN (B-ISDN). Very often, the telephony network is used to connect a subscriber's data network to an Internet Service Provider (ISP), or a subscriber's home office network to his or her central office network. ISDN and B-ISDN networks have their own protocols for transmitting messages, and when two computer networks need to communicate with each other via a telephony communications path, adapters are usually necessary on both ends of the telephony network to convert messages from a computer networking protocol to an ISDN or B-ISDN protocol and vice-versa.
Telephony protocols, having been designed historically for voice traffic (i.e., telephone calls), are usually connection-oriented protocols. That is, they proceed first with a set-up phase, in which a calling party specifies the “address” (e.g., phone number) of a called party, and the network establishes a “connection” between them. All subsequent communication between the two parties then takes place via the established connection, and no further addressing is needed. At the conclusion of the conversation, the connection is released, or “torn down”, releasing the telephony network resources for other connections. Connection-oriented networks and protocols are most cost effective in situations where it is expected that one node will communicate with a second node for a fairly lengthy period of time. Such protocols assume that it is less expensive to take the time and resources for a connection set-up phase than it would cost to examine and properly forward individually addressed message units which, at least for voice traffic, are all likely to be addressed to the same destination for a long period of time.
Computer data communication protocols, on the other hand, are often connectionless protocols, at least at the lowest levels. That is, no “connection” is established between the two communicating nodes at these protocol levels; rather, each message unit contains the address of its destination. Each node that receives packets examines the destination address of the packet in order to determine whether to take or ignore the packet. Connectionless protocols, sometimes also called packet-switched protocols, are most cost effective in computer data networks because traffic in such networks typically consists of numerous messages directed to many different destinations, with a lengthy communication to a single destination taking place only rarely.
Note that a given protocol stack can be connection-oriented or connectionless at different levels. It is even possible for a protocol stack to be connection-oriented at two different layers and connectionless at an intermediate layer, or vice versa. IP and IPX over Ethernet are both connectionless, for example, although higher levels in the stack might well be connection-oriented.
One commonly used connection-oriented protocol is known as ATM (Asynchronous Transfer Mode), defined in a number of specifications published by the ATM Forum, including: ATM Forum, “ATM User-Network Interface Specification Version 3.1,” ATM Forum, Mountain View, California (September, 1994) (“UNI 3.1”); ATM Forum, “ATM User-Network Interface (UNI) Signaling Specification Version 4.0,” ATM Forum, Mountain View, California (July 1996) (“UNI 4.0”); and International Telecommunication Union, “Broadband Integrated Services Digital Network (B-ISDN)—Digital Subscribers Signaling System No. 2 (DSS 2)—User-Network Interface (UNI) Layer 3 Specification for Basic Call/Connection Control,” ITU-T recommendation Q.2931 (February 1995) (“Q.2931”), all incorporated by reference herein. The term “ATM network,” as used herein, refers to a network that conforms to these documents in all relevant respects, whether or not it also conforms to more recent or other specifications as well.
When two parties wish to communicate over a connection-oriented network such as an ATM network, the network establishes a connection from the “point of presence” (or “endpoint”) on the connection-oriented-network, through which a first device (e.g. a telephone or a host computer) reaches the network, to the “point of presence” (or “endpoint”) on the connection-oriented network through which the second or des
Donahue Michael J.
Maranhao Marcus A.
Mendelson Jeffrey B.
Midani Mowaffak T.
Roiger Wayne R.
Alcatel USA Sourcing L.P.
Jackson Walker L.L.P.
Olms Douglas
Vanderpuye Ken
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