Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1997-12-23
2003-08-05
Rao, Seema S. (Department: 2666)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S396000, C370S410000, C370S522000, C379S221130
Reexamination Certificate
active
06603764
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to systems and methods for addressing, signaling and communicating in a communications network. Particularly, this invention relates to systems and methods for addressing, signaling and communicating in communications networks using scoped addressing.
BACKGROUND OF THE INVENTION
Conventional communications networks require procedures and products that dynamically establish and maintain connections between devices attached to the network through signaling. It is important for such signaling to be, among other things, flexible and responsive to the needs of the network and the customers of that network. Addressing plays an important role in signaling, and provides the means for structure and order in conventional networks and the signaling that is carried out therein.
Asynchronous Transfer Mode (“ATM”) is an increasingly popular standard for high-speed communication. An information stream, whether it be data, voice, video or other type of information, is divided into packets called “ATM cells.” Each ATM cell is fifty-three (53) bytes in length. An ATM cell comprises two main sections, a header, which is five bytes in length, and a payload, which is forty-eight bytes in length. The payload includes or corresponds to at least part of the subject information stream. The header includes information corresponding to a path to a desired destination, or endpoint, for the cell.
An ATM System typically comprises three architecture layers. An “Adaptation layer” divides information that it receives, whether it be data, voice, video or other type of information, into one or more (as needed) forty-eight byte payloads. An “ATM layer” adds a five-byte header comprising addressing information to each forty-eight byte payload. Once joined together, the five-byte header and the forty-eight byte payload comprise an ATM cell. A “Physical layer” converts the ATM cell to appropriate electrical, optical, or other format for physical transport.
The header comprises a virtual path identifier (VPI) and a virtual channel identifier (VCI). Within a typical ATM system, virtual connections are established between system elements as needed according to the VPI and VCI contained in the header. The header provides information which facilitates virtual connections between network elements.
For an introduction to ATM, see David E. McDysan & Darren L. Spohn,
ATM Theory and Application
(McGraw-Hill, Inc. 1995), the disclosure of which is incorporated herein by reference. For a further introduction to ATM and a description of various standards and specifications related to ATM, see The ATM Forum Technical Committee,
User
-
Network Interface
(
UNI
)
Specification Version
3.1 (1994), the disclosure of which is incorporated herein by reference.
In a conventional ATM network, each ATM connected endpoint, or point of attachment, which can be a device such as a telephone, computer, or video monitor, for instance, has an address. In one embodiment of such a network, when a first ATM device wishes to establish a connection with a second ATM device, the first ATM device sends a SETUP message to the ATM switch connected to it (“first ATM switch”). This message includes addressing information, in digital form, including the ATM address of the second ATM device. This first ATM switch examines the SETUP message. In particular, this first ATM switch examines the included address of the second ATM device. This first switch determines which switch in the network the SETUP message should be sent to next (assuming that the first switch is not directly connected to the second ATM device) and forwards the message to a second switch. Similarly, the second switch examines the SETUP message and determines which switch in the network the message should be send to next (same assumption) and forwards the packet to a third switch. This process continues until the SETUP message arrives at the second ATM device (or “endpoint”).
When the SETUP message arrives at the second ATM device, and if the device can support the desired connection, the second ATM device returns a CONNECT message to the first ATM device. As the CONNECT messages returns through the network switches back to the first ATM device, the switches set up a virtual connection, or virtual circuit, between the first ATM device and the second ATM device. In a conventional network, a CONNECT message includes the VPI/VCI values that the first ATM device should use for ATM cells that it wishes to send to the second ATM device. These VPI/VCI values are integrated into the ATM cells at the first ATM device.
Several ATM address formats have been developed. The references cited above describe these ATM End System Addresses (AESAs) in detail. Conventional public addresses are based upon the ITU-T E.164 format (or “native E.164” format). This format is generally an Integrated Services Digital Network (ISDN) telephone number. For example, a native E.164 address for a telephone in the Atlanta, Ga. area might be 14045551212. This number, by its 404 numbering plan area (or “NPA”) designation, is a geographic address indicating the Atlanta, Ga. area. The native E.164 address is based on the geographical location of the user. The digits of such an address generally includes the area code and, for international calls, the country code. The length of a native E.164 address is variable, depending upon, for example, whether the call made is an international call.
Conventional private ATM addresses are known as ATM End System Addresses (AESAs). AESAs are fixed in length at twenty (20) bytes. The ATM Forum supports at least three conventional AESA formats: E.164 AESA, Data Country Code (or “DCC”) AESA, and International Code Designator (or “ICD”) AESA. These formats are discussed herein as they relate to, and are used in, the United States.
In all three formats, the first thirteen (13) bytes are called the “network prefix” and the second seven (7) bytes are called the “user part.” In all three formats, the first byte of the network prefix (also the first byte of the AESA) is used for an authority and format identifier (or “AFI”). The AFI identifies which addressing scheme is found in the subsequent nineteen bytes. The E.164 AESA is identified by an AFI value of 45 (hex), the DCC AESA is identified by an AFI value of 39 (hex), and the ICD AESA is identified by an AFI value of 47 (hex).
Also, in all three formats the last seven (7) bytes of the twenty (20) byte address comprises a six (6) byte end system identifier (or “ESI”) and an one (1) byte selector (or “SEL”). Conventionally, the ESI is an IEEE 802 Media Access Control (or “MAC”) address. Incorporation of the MAC address into the AESA often simplifies the task of mapping AESAs into existing local area networks (or “LANs”). In a typical ATM system, the ESI of an end system is unique for a particular network prefix and is found in the ATM adapter card of the end system. The ESI and the network prefix combine to form a unique nineteen (19) byte address in the network.
In the DCC and ICD formats, the first two (2) bytes following the AFI comprise the initial domain identifier (or “IDI”). The IDI specifies the authority responsible for allocating the subsequent portion of the AESA. In the DCC and ICD formats, the last seventeen (17) bytes is called the domain specific part (or “DSP”) in order to indicate that that portion of the AESA is the portion structured by the authority indicated in the IDI.
The E.164 AESA is based upon the native E.164 format. After the AFI, the next eight (8) bytes comprise a native E.164 address, which is typically an ISDN telephone number. For example, the eight bytes referred to may be comprised of “000014045551212F”. In conventional telecommunications networks using the E.164 AESA, the service provider administers the native E.164 address portion of the E.164 AESA.
The DCC AESA is independent of the native E.164 format. In DCC AESAs, the IDI comprises a two (2) byte data country code. As mentioned above, the DCC AESA and other formats are discussed herein as they relate to, an
BellSouth Intellectual Property Corp.
Jagannathan Melanie
Rao Seema S.
Thomas Kayden Horstemeyer & Risley LLP
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