Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Patent
1997-12-22
2000-10-24
Patel, Ajit
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
370404, 370432, H04L 1256
Patent
active
061377996
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention is directed to a method for the transmission of information packets between a source LAN emulation client LEC of a first ELAN and an LAN emulation client of a second ELAN.
ELAN stands for emulated LAN as described, in particular, in the specification 94-0035R9, "LAN Emulation Over ATM: Version 1.0" of the LAN Emulation SWG Drafting Group of the ATM Forum of Jan. 6, 1995, Bill Ellington, editor. This is thereby an approach of the ATM Forum to the migration of current LANs to ATM networks. ATM thereby means "Asynchronous Transfer Mode", i.e. asynchronous data or, respectively, information transmission methods. LAN is an abbreviation of "Local Area Network". LANs are datagram-oriented local networks that are described in, among other references, the article by David D. Clark, Kenneth D. Program and David P. Reed, "An Introduction to Local Area Networks" in Proceedings of the IEEE, Vol. 66, No. 11, November 1978, pages 1497 through 1517. LANs are also described in ISO/IEC TR 8802-1, "Overview of LAN-Standards". LANs offer a connectionless service, what is referred to as the MAC service. MAC thereby stands for "Media Access Control". By contrast to this connectionless service, ATM technology is connection-oriented. When the protocols of the higher layers developed for LANs are to be used in emulated LANs on the basis of an ATM network, the properties of the connectionless MAC service must be produced in this ATM network. The LAN emulation according to the aforementioned specification realizes the MAC service in the local ATM network and thus defines a single emulated LAN, called ELAN below. The standard LAN protocols such as LLC, TCP/IP, SPX/IPX or TP/CLNP can be used in this ELAN.
The LAN emulation supports the two most frequently employed LAN standards, namely Ethernet according to IEEE 802.3 and Token Ring according to IEEE 802.5, whereby three frame lengths are supported given token ring. The addressing of every LAN station ensues on the basis of a destination MAC address that is unambiguous worldwide. For the transmission of information between LANs, the addresses are handed over from a high layer are. For the description of the information path, token ring LANs employ what are referred to as route descriptors in the frame header in addition to MAC addresses. The frame can be conveyed to the destination within token ring LANs on the basis of such a descriptor.
Only MAC addresses shall be mentioned below.
For emulation of an LAN in an ATM network, the LAN emulation must, among other things, resolve destination MAC address into destination ATM addresses, realize multicast and broadcast, i.e. a distribution of information to as plurality of or to all subscribers, as well as assure the transmission of LAN emulation frames in the proper sequence. The LAN emulation has a client-server configuration. The client side is called LAN emulation client LEC and the server side is called LAN emulation service. The LAN emulation service is composed of LAN emulation server LES, broadcast-and-unknown server BUS and LAN emulation configuration server LECS. The LAN emulation client receives the destination MAC address from a higher-ranking layer, for example the LLC layer, and must find the corresponding ATM address, in order to subsequently initiate the setup of a direct ATM connection to the destination by signaling. The signaling can thereby ensue, for example, according to the ITU-T Recommendation Q.2831/Q.2971. An LAN emulation client can be realized in the software or in the hardware of the stations that participate in the LAN emulation.
An LAN emulation server LES maintains a table with all MAC addresses that are reported in the emulated LAN, for example in the framework of a configuration, and with the corresponding ATM addresses. The communication between the LAN emulation clients and the LAN emulation client ensues according to an LAN emulation address resolution protocol that, conforming to the English designation LAN Emulation Address Resolution Protocol, is referred to a
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Fromm Ingrid
Karapetkov Stefan
Petri Bernhard
Nguyen Brian
Patel Ajit
Siemens Aktiengesellschaft
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