Layer manager

Description of equivalent WO 02082774 A2

LAYER MANAGER

FIELD OF THE INVENTION

0003The present invention relates to networks, and more particularly to protocol stacks for networks.

BACKGROUND OF THE INVENTION

0005The Bluetooth™ networking protocol is well known in the art. Figure 1 illustrates a

0006standard Bluetooth protocol stack. The stack 100 includes a Host Controller Interface (HCI) layer 106, a Logical Link Control and Adaptation Protocol (L2CAP) layer 108, a Telephony

0007Control Protocol Specification (TCS) layer 110, a Service Discovery Protocol (SDP) layer

0008112, and a RFCOMM protocol layer 114.

0009The HCI layer 106 provides a command interface which accepts communications over the physical bus (not shown). The L2CAP layer 108 supports higher level protocol

0010multiplexing, packet segmentation and reassembly, and the conveying of quality of service

0011information. The TCS layer 110 provides call control and signaling of voice channels. The

0012RFCOMM protocol layer 114 provides emulation of serial ports over the L2CAP layer 108.

0013The SDP layer 112 provides a means for applications to discover which services are

0014provided by or available through a device. A Bluetooth device may act as an SDP client querying services, an SDP server providing services, or both. Each service registers with the

0015SDP server, and information concerning each service is cataloged in service records.

0016Through the SDP layer 112, a client may send a request to the SDP server to ask what services a remote device provides. The SDP server responds with service records of the services provided by the remote device. Part of each service record is a protocol descriptor list (PDL). The PDL comprises a list of layers of the protocol stack 100 through which to route a packet for the particular service. However, because the stack layers 106-114 have well defined upper and lower edges, each of the layers 106-114 require intimate knowledge of the stack layer "above" and "below" it in the protocol stack 100. For each path of a packet through the stack 100, the stack layers 106-114 must be specifically coded to talk to the stack layer above and below. Thus, when a new path is to be supported, one or more of the stack layers 106-114 must be modified. In addition, when a stack layer is to be added between two of the layers 106-114, one or more of the stack layers 106-114 must also be modified. For example, assume that a layer is to be added between the RFCOMM layer 114 and the L2CAP layer 108. The RFCOMM layer 114 must be modified to talk down stream to the new layer instead of the L2CAP layer 108, and the L2CAP layer 108 must be modified to talk upstream to the new • layer instead of the RFCOMM layer 114. This is burdensome and leads to considerable complexity in the protocol stack 100.

0017Accordingly, there exists a need for an improved protocol stack for a network. The present invention addresses such a need.

SUMMARY OF THE INVENTION

0019The present invention provides an improved method and system for controlling packet flow through a protocol stack. The system comprises the layer manager which interfaces with each stack layer. The layer manager handles the packet flow to the stack layers. For a new packet path to be supported, only the Layer Manager needs to be modified, not the stack layers. This makes the implementation of the layers in the protocol stack

0020easier. In an alternative embodiment, the layer manager comprises a plurality of protocol descriptor lists for supported services and uses these lists to route a packet to the appropriate stack layer. With this alternative embodiment, new stack layers may be inserted into the

0021protocol stack without the need to modify the existing stack layers.

BRIEF DESCRIPTION OF THE FIGURES

0023Figure 1 illustrates a standard Bluetooth protocol stack. Figure 2 illustrates a preferred embodiment of a protocol stack in accordance with

0024the present invention.

0025Figure 3 illustrates the preferred embodiment of the protocol stack with a Layer

0026Manager comprising protocol descriptor lists in accordance with the present invention. Figure 4 is a flowchart illustrating a preferred embodiment of a method for

0027controlling packet flow through the protocol stack in accordance with the present invention.

0028Figure 5 is a flowchart illustrating a preferred embodiment of a method for providing

0029stack component instrumentation in accordance with the present invention.

0030Figure 6 illustrates a preferred embodiment of a protocol stack which utilizes the

0031method for providing access control within the protocol stack in accordance with the present

0032invention.

0033Figure 7 is a flowchart illustrating the method for providing access control as utilized

0034by the preferred embodiment of the protocol stack in accordance with the present invention. DETAILED DESCRIPTION

0035The present invention provides an improved protocol stack for a network. The following description is presented to enable one of ordinary skill in the art to make and use the invention and is provided in the context of a patent application and its requirements. Various modifications to the preferred embodiment will be readily apparent to those skilled in the art and the generic principles herein may be applied to other embodiments. Thus, the present invention is not intended to be limited to the embodiment shown but is to be accorded the widest scope consistent with the principles and features described herein.

0036To more particularly describe the features of the present invention, please refer to Figures 2 through 7 in conjunction with the discussion below.

0037Figure 2 illustrates a preferred embodiment of a protocol stack in accordance with the present invention. The protocol stack 200, in addition to the stack layers 106-114 described in conjunction with Fig. 1, comprises a Layer Manager 202 which interfaces with each stack layer 106-114. The Layer Manager 202 handles the packet flow to the stack layers 106-114. The Layer Manager 202 allows each stack layer 106- 114 to process the packet without the need to have knowledge of which stack layers reside directly above and below them. Each stack layer concerns itself only with whether the packet is to travel "up" or "down" the stack 200. Each stack layer receives its packet from the Layer Manager 202, and when it is done processing the packet, it gives the packet back to the Layer Manager 202. The Layer Manager 202 then routes the packet to the next stack layer.

0038In the preferred embodiment, the packet flow is controlled by hard-coding the paths into the Layer Manager 202. Thus, for a new packet path to be supported, only the Layer Manager 202 need to be modified. The stack layers 106-114 do not. An alternate method of controlling the packet flow through the stack 200 is for the Layer Manager 202 to comprise a plurality of protocol descriptor lists (PDL). Figure 3 illustrates the preferred embodiment of the protocol stack 200 with a Layer Manager 202 comprising PDL 302 in accordance with the present invention. In the preferred embodiment, when a service is registered with a SDP server, as described above, the SDP server notifies the Layer Manager 202 and provides a copy of the PDL for that service. Also, the Layer Manager 202 contains a set of predefined PDL's for services provided by the clients. For example, for the RFCOMM service, the list is the HCI layer 106, the L2CAP layer 108, and the RFCOMM layer 114. If the packet is traveling up the stack 200, then the order is the HCI layer 106, the L2CAP layer 108, and the RFCOMM layer 114. If the packet is traveling down the stack 200, then the order is the RFCOMM layer 114, the L2CAP layer 108, and then the HCI layer 106. By using the PDL 302 for a particular service, the Layer Manager 202 knows to which layers of the stack 200 the packet should be routed.

0039Although the present invention is described with the Layer Manager receiving the PDL' s in the above manner, other methods of obtaining the PDL can be used without departing from the spirit and scope of the present invention.

0040Figure 4 is a flowchart illustrating a preferred embodiment of a method for controlling packet flow through the protocol stack in accordance with the present invention. First, the Layer Manager 202 receives a packet, via step 402. Next, the Layer Manager 202

0041determines a service associated with the packet, via step 404. In the preferred embodiment, this determination is based on the protocol/service multiplexer (PSM) field. The PSM is 16-

0042bit field occurring after the header in the packet which indicates the upper-level protocol the packet originated from. The PSM field references the PDL 302 to be used for the packet. The Layer Manager 202 accesses the PDL 302 for the service, via step 406. The PDL 302

0043comprises a list of layers of the protocol stack 200 for the service. Then, the Layer Manager

0044202 routes the packet to a layer of the protocol stack 200 according to the list, via step 408. For example, assume a packet is to be sent up through the stack 200 for the RFCOMM service. The packet is received by the Layer Manager 202, via step 402.

0045Through the packet's PSM field, the Layer Manager 202 determines that the RFCOMM

0046service is associated with the packet, via step 404. The Layer Manager 202 then accesses a

0047PDL for the RFCOMM service, via step 406. The RFCOMM service's PDL includes the

0048HCI layer 106, the L2CAP layer 108, and the RFCOMM layer 114. The Layer Manager 202

0049then routes the packet to the HCI layer 106, via step 408. The HCI layer 106 processes the

0050packet and returns it to the Layer Manager 202.

0051The Layer Manager 202 receives the packet from the HCI layer 106, via step 402.

0052Again, through the packet's PSM field, it determines that the RFCOMM service is associated with the packet, via step 404, and accesses the PDL for the RFCOMM service, via step 406. The Layer Manager 202 knows that the packet was received from the HCI

0053layer 106, and thus routes it to the next layer on the PDL, the L2CAP layer 108, via step 408.

0054The L2CAP layer 108 process the packet and returns it to the Layer Manager 202. .

0055The Layer Manager 202 receives the packet from the L2CAP layer 108, via step 402.

0056It determines that the RFCOMM service is associated with the packet, via step 404, and

0057accesses the PDL for the RFCOMM service, via step 406. The Layer Manager 202 knows

0058that the packet was received from the L2CAP layer 108, and thus routes it to the next layer

0059on the PDL, the RFCOMM layer 112, via step 408.

0060In this manner, each stack layer 106-114 communicates with the Layer Manager 202 and not with each other. The stack layers 106-114 thus need not have knowledge of the other layers or of the proper routing of the packet. This alternate method of controlling the packet flow has the added advantage of allowing easier insertion of new stack layers into the stack 200. When a new layer is to be added to the stack 200, the new layer is implemented so that it interfaces with the Layer Manager 202 in the same way as the other stack layers

0061106-114. None of the existing stack layers 106-114 need to be modified. This makes the modification of the protocol stack 200 easier.

0062With the protocol stack 200 comprising the Layer Manager 202, other advantages may be realized. For example, the instrumentation of stack components is considerably simplified with use of the Layer Manager 202. A "stack component", as used in this specification, is software which implements a layer of the protocol stack 200. Instrumentation of the stack components 106-114 is desirable to enable measurement of a stimulus received by a stack component and/or a response of the stack component to a stimulus. The instrumentation provides information which aid in fixing problems, optimizing performance and behavior, gathering utilization statistics, etc.

0063To instrument the stack components 106-114 in the conventional protocol stack 100, code must be added to the stack components 106-114 wherever data is available or where information can be gathered. Since the stack components 106-114 communicate with each other through private and unique interfaces, each stack component 106-114 must be instrumented separately. This often results in repetitive, and possibly incompatible, work being done on each interface. The data acquired at each interface may be dissimilar,

0064requiring more processing before analysis.

0065However, with the protocol stack 200 in accordance with the present invention, because the Layer Manager 202 is responsible for the routing of packets between stack components 106-114, it also is aware of the stimulus and response of each stack component 106-114. Thus, to instrument the protocol stack 200, the Layer Manager 202 is instrumented without the need to instrument the stack components 1Q6-114. Since the Layer Manager 202 provides a single interface through which all stimuli and responses are passed, the packet is captured at a single point and is similar in format. This reduces the amount of code required to capture and analyze the data in the packet.

0066Figure 5 is a flowchart illustrating a preferred embodiment of a method for providing stack component instrumentation in accordance with the present invention. First, the Layer Manager 202 receives data in a packet from a first stack component in the protocol stack

0067200, via step 502. Next, the Layer Manager 202 analyzes the data for instrumentation information, via step 504. Then, the Layer Manager 202 routes the data to a second stack component, either below or above it, in the protocol stack 200, via step 506.

0068Another advantage which may be realized with the protocol stack 200 comprising the Layer Manager 202 is the ability to provide access control within the protocol stack 200.

0069Conventionally, security mechanisms provide access control at the packet level. "Firewalls" are examples of such a security mechanism. Firewalls filter packets based on their addresses and port numbers. All packets with the address and the port number are blocked. However, these mechanisms do not provide access control within a protocol stack, i.e., between the layers of the protocol stack. They are not able to authenticate users at the stack layer level.

0070However, the protocol stack 200 in accordance with the present invention can

0071provide access control within a protocol stack through an Access Mediator in the Layer

0072Manager 202. The Access Mediator is a software which enforces the rules of a predetermined security policy. In the preferred embodiment, the security policy is subject (people) based. The rules of the security policy determines which subjects can have access to which objects (data) to perform a requested operation (e.g. read/write).

0073Figure 6 illustrates a preferred embodiment of a protocol stack which utilizes the method for providing access control within the protocol stack in accordance with the present invention. The protocol stack 2Q0, in addition to the layers 106-114 and the Layer Manager 202, described in conjunction with Fig. 2, comprises the Access Mediator 602 implemented in the Layer Manager 202. In this manner, the advantages provided by the Layer Manager 202 is realized in providing access control within the stack 200. Figure 7 is a flowchart illustrating the method for providing access control as utilized by the preferred embodiment of the protocol stack in accordance with the present invention.

0074First, the Layer Manager 202 receives a request from a layer of the protocol stack 200 to perform an operation at the layer, via step 702. In this embodiment, the operation is to be performed on an object by a particular subject. The Layer Manager 202 then calls the Access Mediator 602, via step 704. In calling the Access Mediator 602, the Layer Manager 202 passes the subject's identity, the object's identity, and the requested operation. The Access Mediator 602 determines whether the request is to be granted based upon a predetermined security policy, via step 706. Then, the Access Mediator 602 returns the determination to the Layer Manager 202, via step 708. If the Access Mediator 602 determines that the subject can access the object to perform the requested operation, then the operation is allowed to be

0075performed at the layer. If the Access Mediator 602 determines that the subject cannot access

0076the object to perform the requested operation, then the operation is blocked.

0077By implementing the Access Mediator 602 in the Layer Manager 202, the stack layers 106-114 need not be aware of the Access Mediator 602, or even that there is a security

0078policy at all. Awareness of the Access Mediator 602 is only required of the Layer Manager 202. Since the stack layers 106-114 need not be aware of the Access Mediator 602, they

0079also do not disrupt the Access Mediator 602, resulting in a more secure protocol stack. Although the present invention is described in the context of the Bluetooth protocol

0080stack, it may be applied to other protocol stacks without departing from the spirit and scope of the present invention.

0081An improved method and system for controlling packet flow through a protocol stack

0082has been disclosed. The system comprises a layer manager which interfaces .with each stack layer. The layer manager handles the packet flow to the stack layers. For a new packet path

0083to be supported, only the Layer Manager needs to be modified, not the stack layers. This

0084makes the implementation of the layers in the protocol stack easier. In an alternative embodiment, the layer manager comprises a plurality of protocol descriptor lists for

0085supported services and uses these lists to route a packet to the appropriate stack layer. With

0086this alternative embodiment, new stack layers may be inserted into the protocol stack

0087without the need to modify the existing stack layers. Other advantages, such as increased

0088ease in instrumenting the stack layers and in providing access control within the protocol

0089stack, may be realized using the protocol stack comprising the layer manager.

0090Although the present invention has been described in accordance with the

0091embodiments shown, one of ordinary skill in the art will readily recognize that there could

0092be variations to the embodiments and those variations would be within the spirit and scope

0093of the present invention. Accordingly, many modifications may be made by one of ordinary

0094skill in the art without departing from the spirit and scope of the appended claims.