Electrical computers and digital processing systems: multicomput – Computer-to-computer protocol implementing – Computer-to-computer data framing
Reexamination Certificate
1996-09-27
2002-10-08
Maung, Zarni (Department: 2152)
Electrical computers and digital processing systems: multicomput
Computer-to-computer protocol implementing
Computer-to-computer data framing
C709S230000, C709S224000
Reexamination Certificate
active
06463477
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention pertains to data communication network services using Frame Relay (FR) and/or Asynchronous Transfer Mode (ATM) data communication protocols. The present invention relates to FR/ATM service interworking used to couple virtual connections that are provisioned between FR and ATM networks.
2. Related Art
The Frame Relay Forum and ATM Forum developed a joint implementation agreement which specified a method to provide permanent virtual connection (PVC) interworking between Frame Relay networks and ATM networks. This Implementation Agreement was formalized by the Frame Relay Forum and is known as FRF.8. See, “Frame Relay/ATM PVC Service Interworking Implementation Agreement,” The Frame Relay Forum, Document Number FRF.8, Apr. 14, 1995 (incorporated herein by reference).
The FRF.8 Agreement defines a protocol translation process known as a FR/ATM service interworking function or FR/ATM Service IWF. The service interworking function maps Frame Relay frames of data to ATM (ATM Adaptation Layer 5) AAL5 frames of data and vice versa. The service IWF can be implemented in a Frame Relay switch, ATM switch, and/or other separate processor devices.
FRF.8 specifies two modes of operation for each virtual connection regarding multiprotocol encapsulation, and in particular, upper layer user protocol encapsulation. The two modes of operation are called Translation Mode and Transparent Mode. Translation Mode is used to translate between different types of multiprotocol encapsulation on a virtual connection. Multiprotocol encapsulation is used to carry multiple protocols within a single virtual connection. Transparent Mode is used when a virtual connection is not transporting multiple protocols.
According to this industry standard, a FR or ATM virtual connection could support traffic in one of two mode types for multiprotocol encapsulation, either a Translation Mode or a Transparent Mode. The mode type had to be specified during the provisioning process used to establish FR and ATM virtual connections. The FR/ATM service interworking function was then preconfigured to either the Translation mode or the Transparent mode to match the mode type used by FR and ATM customer premise equipment for the virtual connections.
The customer premise equipment configuration, however, is likely to be modified as a result of application requirements, equipment change, software upgrade, repair or other type of servicing. Thus, customer premise equipment can require a different multiprotocol encapsulation mode type with or without making corresponding changes to preconfigured FR/ATM service interworking function connections. Indeed, FR/ATM service IWF modules are often under the control of a network service provider or other independent entity. CPE reconfiguration could result in failure of the Interworking Function to properly map a payload between the Frame Relay network and the ATM network. Failure to properly map the payload would result in the customer placing an order to change the multiprotocol encapsulation mode type. The mode type would then need to be re-provisioned for each impacted virtual connection, i.e., each impacted Frame Relay Permanent Virtual Connection (PVC) and ATM Virtual Channel Connection (VCC).
The conventional requirement that a multiprotocol encapsulation mode type be preset during the provisioning of virtual connections needs to be eliminated. What is needed is FR/ATM Service Interworking functionality which can transfer data over virtual connections between FR and ATM networks regardless of which multiprotocol encapsulation mode type (Translation Mode or Transparent Mode) is required by customer equipment.
SUMMARY OF THE INVENTION
The present invention is an enhancement to conventional FR/ATM service interworking that eliminates the need to specify interworking multiprotocol encapsulation mode type during preconfiguration of a FR/ATM virtual connection. The present invention provides a method, system and computer program product which automatically detects the presence of multiprotocol encapsulation. The FR/ATM service interworking function then operates in translation mode or transparent mode depending upon the presence or absence of multiprotocol encapsulation.
In a preferred embodiment, a multiprotocol encapsulation detection module first reads a control field value in a received protocol data unit (PDU). The control field value is then compared to a predetermined value representative of the presence of multiprotocol encapsulation in the PDU. An indication of the detected presence of multiprotocol encapsulation in the PDU is then provided when the control field value equals the predetermined value. An FR/ATM service interworking function module is then operated in Translation mode when multiprotocol encapsulation has been detected and indicated. Otherwise, the FR/ATM service interworking function module is operated in Transparent mode when multiprotocol encapsulation has not been detected.
According to another preferred embodiment of the present invention which is compatible with FR/ATM industry standards defined by the FRF.8 Agreement, a multiprotocol encapsulation detection module first reads a control field value in a Frame Relay or ATM AAL5 protocol data unit (PDU). The control field value is then compared to a predetermined value 0x03 representative of the presence of multiprotocol encapsulation for Layer 2 and Layer 3 protocols in FR and ATM AAL5 PDUs. An indication of the detected presence of multiprotocol encapsulation in the PDU is provided when the control field value equals the predetermined value 0x03, that is, “03” in hexadecimal or 00000011 in binary. A FR/ATM service interworking function module is then operated in Translation mode when multiprotocol encapsulation has been detected and indicated. Otherwise, the FR/ATM service interworking function module is operated in Transparent mode when multiprotocol encapsulation has not been detected.
For example, when multiprotocol encapsulation is used in the FR to ATM direction, the first octet after the Frame Relay header contains the Q.922 Control Field. The Q.922 Control Field is the first octet of the multiprotocol encapsulation header, as defined, in the RFC 1490, FRF.3, and FRF.3.1 standards. For a FR PDU, the multiprotocol encapsulation detection module compares the Q.922 Control field value to a predetermined value equivalent to 0x03, that is, “03” in hexadecimal or 00000011 in binary. When the Control field value is 0x03, the multiprotocol encapsulation detection module indicates that multiprotocol encapsulation has been detected. When multiprotocol encapsulation is detected, a FR/ATM Service IWF module operates in Translation Mode to translate the encapsulation type from Frame Relay RFC 1490, FRF.3 or FRF.3.1 multiprotocol encapsulation to ATM RFC 1483 multiprotocol encapsulation. Otherwise, when multiprotocol encapsulation is not detected, the FR/ATM Service IWF module operates in Transparent mode to de-encapsulate the FR PDU to a FR payload and then directly encapsulate the FR payload into an ATM AAL5 PDU.
In the ATM to FR direction where ATM AAL5 PDUs are received, when multiprotocol encapsulation is used the third octet of an ATM AAL5 multiprotocol encapsulation header, as defined in RFC 1483, is the IEEE 802.2 LLC Control Field. For an ATM AAL5 PDU, the multiprotocol encapsulation module compares the LLC Control field value to a predetermined value equivalent to 0x03, that is, “03” in hexadecimal or 00000011 in binary. When the Control field value is 0x03, the multiprotocol encapsulation detection module indicates that multiprotocol encapsulation has been detected. When multiprotocol encapsulation is detected, a FR/ATM Service IWF module operates in Translation Mode to translate the encapsulation type from ATM RFC 1483 multiprotocol encapsulation to Frame Relay RFC 1490, FRF.3 or FRF.3.1 multiprotocol encapsulation. Otherwise, when multiprotocol encapsulation is not detected, the FR/ATM Service IWF module operates in Transparent mode to
Cardone Jason D.
Maung Zarni
MCI Communications Corporation
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