Patent Grant
RE44211
1. Field of the Invention
The present invention relates to a mechanism to provide constant bit rate upstream data transport in a two way communication system (e.g., a cable TV system) that has a known contention based upstream data transport mechanism. In particular, the invention relates to a mechanism to provide the constant bit rate upstream data transport, such as for a telephone voice channel, in a way that is compatible with known contention based available bit rate upstream data transport mechanisms so that jitter requirements of the constant bit rate transmission are fulfilled while not adversely effecting the latency of the available bit rate upstream data transport.
2. Description of Related Art
The upstream channel of a cable system is expected to carry a variety of services ranging from CBR (Constant Bit Rate) to ABR (Available Bit Rate) as defined by the ATM Forum (Asynchronous Transfer Mode Forum). These two services have unique sets of quality of service requirements such as jitter. For the CBR services, bounded jitter is required but not for the ABR services. ABR performance is measured on the system response time where the access delay plays a key roll CBR and ABR data are also different on the prospects of the traffic patterns. CBR sources produce data in a constant rate fashion while the ABR sources are usually in the burst mode. In the shared upstream channel of the cable television (CATV) environment, the services can not be optimized by a single Medium Access Control (MAC) protocol due to the above differences. The contention based Medium Access Control algorithm has been shown as an appropriate protocol for the local area network (LAN) traffic to provide instant access but it can not provide a guaranteed access environment for CBR sources to achieve bounded jitter.
One family of the contention algorithms, Distributed Queue Random Access Protocol (DQRAP), which uses a separate field (other than the data field) for resolving collisions while the user data transmission is taking place at the same time has been proposed to optimize the system throughput for ABR traffic. DQRAP has shown 85% of utilization with reasonable average access delay. It falls short of providing guaranteed access in order to support CBR services.
What is needed is a priority preempt mechanism to support guaranteed access in a contention based media access protocol in order to optimize these two services in the same system.
Historically, guaranteed access is provided via a TDMA (time division multiple access) arrangement. However, the TDMA approach can only provide services of an integer multiplier of a base rate. For example, these services are possible, 16 Kbps, 32 Kbps, 48 Kbps, etc., if the base rate is 16 kbps. Any request between two layers results in bandwidth waste.
TDMA is based on a cyclic framing structure. Access to the media is usually restricted until the start of the next cycle. It can be a long time if the frame is large or the transmission rate is low.
Another scheme often employed for guaranteed performance is when a station is polled periodically and the station can indicate if there is information to send. Performance of the source data can be guaranteed but at a significant waste of bandwidth because of the need to send the poll to a station and the bandwidth wasted when the station has nothing to send.
A media access control mechanism such as DQRAP uses a separated fields called Control Mini-Slots (CMS) to resolve collided transmissions while actual data transmission occurs at the data slot. Several CMSs associated with a data slot form the basic transmission unit. A station with packets ready for transmission choose one of the CMSs randomly to gain the right to transmit. Those stations that have already obtained the transmission rights are scheduled in a virtual queue called TQ (each station knows the total number of waiting members and its position among them). The requesting stations are informed of the success of the access requests by feedback sent by the Central Controller on the downstream channel with what is called contention grants. DQRAP has shown good performance in terms of Utilization vs. Access Delays. It is difficult and expensive to implement a priority scheme during the contention phase without priority protection. DQRAP can not guarantee bounded jitter which is required in order to support CBR services.
XDQRAP (Extended Distributed Queue Random Access Protocol) is a Medium Access Control (MAC) protocol designed to satisfy a wide range of performances required by the services that the IEEE 802 14 network is expected to provide. It is a contention-based protocol that provides LAN type of traffic an instant access environment. With a central feedback mechanism that is a natural result of the tree-and-branch network topology, it seamlessly marries a reservation scheme to offer deterministic access for the Constant Bit Rate (CBR) services. The MAC was presented in the paper. A proposal to Use XDQRAP for the IEEE 802 14 (IEEE 802 14/95-068) incorporated herein by reference. Simulation results of the basic XDQRAP were presented in the paper Simulation of the Performance of XDQRAP under a Range of Conditions (IEEE 802 14/95-049) incorporated herein by reference.
In the XDQRAP model, the channel time is partitioned into a sequence of fixed-sized time slots. Each unit consists of a data field where the actual data transmissions takes place and a control field used for requesting data slots. The request field consists of two areas called Control Mini Slots (CMS) Stations with data to transmit follow a set of rules to put the transmission requests in one of the control mini slots. The contention resolution algorithm is a tree based approach since there are potentially more than one request in the same control mini slot. By taking advantage of the central feedback, XDQRAP keeps the newly arrived packets out of contention to achieve fast-coverage resolution cycle.
The status of the control mini-slots and the data slots are constantly monitored at the headend. Based on the information, the global queuing information is fed back to the network via the common downstream channel. An individual station, therefore, adjusts its local state-machine accordingly. The contention winning stations position themselves in the global transmission sequence. Stations that lose in the contention retry at the next scheduled time.
Voice and some video conferencing data streams require that data arrives at the receiver within a narrow window of time (i.e., minimum jitter). Having contention for data slots is thus not a good mechanism to use for Constant Bit Rate (CBR) data streams. What is needed is a mechanism whereby a station can be guaranteed to send data at fixed intervals without having to use the control mini-slots to request data slots.
It is an object to the present invention to provide a priority preempt mechanism to support guaranteed access in a contention based media access protocol. It is a further object of the present invention to provide a mechanism for constant bit rate upstream data transport, such as for a telephone voice channel, in a way that is compatible with known contention based available bit rate upstream data transport mechanisms so that jitter requirements of the constant bit rate transmission are fulfilled while not adversely effecting the latency of the available bit rate upstream data transport.
These and other objects are achieved in a method of granting rights for upstream data transmission from user terminals that includes processing contention requests to generate contention grants and maintaining a list of connections, each connection having specified a predetermined bit rate. The method is practiced in a two way cable system that includes a controller and a plurality of the user terminals. The controller sends a downstream data stream to the user terminals and receives an upstream data stream from the user terminals. The downstream data stream includes a plurality of grant fields, and the upstream data stream includes upstream data slots and upstream control slots. The method further includes scheduling preemptive grants for upstream data slots using selected fields of the plurality of,grant fields so as to provide preemptive grants for upstream data transport at a bit rate specified for each connection, sending to the user terminals a data transmission grant in a grant field of the plurality of grant fields for which a preemptive grant is scheduled, and sending to the user terminals a data transmission grant in a grant field of the plurality of grant fields in which a contention grant is pending and no preemptive grant is scheduled.
The invention will be described in detail in the following description of preferred embodiments with reference to the following figures wherein:
The preemptive grant mechanism can be used on top of DQRAP so that CBR sources can use access mechanisms such as DQRAP to obtain guaranteed access. The preemptive grant is issued by the Central Controller without a request from the station and bypasses the contention at the control mini-slot.
The preemptive grant mechanism is briefly described by the following:
The central controller operation is briefly described as follows:
For example, a feedback data field in the downstream channel from the controller to a user terminal will include a station or terminal ID and a transmission right type. The transmission right type may be encoded as:
Since the contention grants and preemptive grant share the control fields on the downstream channel, the Central Controller will try to minimize the impacts of the regular contention operation by choosing the feedback data field based on the following order: no request, then collision, then contention grant.
When a preemptive grant is generated by the scheduler, the Central Controller scans through the incoming control mini-slot field and chooses a feedback data field based on the above criteria. It also overwrites the ID field by the CBR connection ID and the feedback field by ‘11’.
The user terminal (station) operation is briefly described as follows. The basic idea is to treat a preemptive grant as if it were a collision indication.
The station having newly arrived messages.
The stations treat it as TQ>0 cases once they see FB=11.
The stations holding TQ positions.
The station holding the first position will be preempted and not transmit on the current slot. The stations holding the positions other than the first will not have an effect since the TQ value broadcasted by the Central Controller is not changed.
The station in the contention process.
The stations putting their request in the control mini-slot overwritten by the Central Controller treat it as a collision; it is equivalent to FB=‘10’. Those stations using a different mini-slot are not impacted.
The CBR station
Transmit the cell on the current slot. Essentially, the station which requests a CBR service needs to maintain two queues: the TQ and a CBR queue. XDQRAP does an excellent job of handling bursty computer data by providing immediate access for data transmission during light loads and high utilization through fast contention resolution during heavy loads. To summarize XDQRAP protocol:
1. A station randomly chooses one of the Control Mini-Slots (CMS) to put on the connection ID and it indicates the number of cells it wishes to transmit (reservation mode). With modifications to XDQRAP, the number of control mini-slots may be dynamically varied.
Many stations vie for usage for the data slots and it is possible for delays to occur as stations resolve the contention for these data slots. As seen by the receiver of this data, there could be variation of arrival times even if the information was sent on a periodic basis. For data streams that require minimal buffering, trying to accommodate this variation in arrival time is unacceptable. Embodiment of present invention to handle Continuous Bit Rate (CBR) data streams are described as follows.
For available bit rate traffic (ABR traffic), the headend broadcast upstream control slot (e.g., control mini-slot) assignment data to the user terminals. The user terminals store this assignment data and use it to locate where requests may be placed in the upstream data stream.
When a user terminal has ABR data to send to the head-end, the user terminal sends a request in an assigned control slot to request an allocation of upstream data slots to carry the ABR data. Then the head-end acknowledges receipt of the request for allocation.
For constant bit rate (CBR) and variable but rate (VBR) traffic, the user terminals communicate with the head-end to establish a connection. The connection is good until cancelled. It does not have to be renewed with each quantum of data to be transferred. The communication channel may be over the cable network or outside of the cable network (e.g., via telephone line).
The head-end schedules upstream data slots to carry data for all CBR and VBR connections and then schedules upstream data slots to carry data for the pending ABR requests. The head-end then broadcasts grants to the user terminals that give data transmission rights to specifically identified station IDs to carry data upstream in specifically identified upstream data slots based on the above described schedule. In this way CBR and VBR jitter requirements can be fulfilled in systems with ABR contention based mechanisms.
The user terminal responds to a grant by sending the specified data (e.g., defined by station ID) upstream in the specified data slot. Receipt of the upstream data transmission is then acknowledged by the head-end.
The downstream data frame (e.g.,
In the cable environment there needs to be some centralized control (e.g., at the headend) to allow for authorizing stations to use the network, providing security, and statistics gathering for billing. Generically, this function is called network control and there is at least one element responsible for network resources. The entity responsible for the network resources is called the network control element.
Prior to transmitting data, a station must request a connection be setup by the network. As part of the connection setup process, it informs the network about the characteristics of the path. One of the ways to define the characteristics is called Q.2931, an ITU standard incorporated herein by reference. The process of sending and receiving information about the connection is called signaling. In our environment the signaling information is sent to a network control element located at the head-end.
Q.2931 signaling information consists of the bandwidth, delay and jitter requirements for this connection. CBR data streams would request a specific data rate, maximum end-to-end delay and jitter tolerance. ABR traffic would have the CBR parameters plus minimum bandwidth and burst size information. Several network entities may be involved in the connection such as a switch, intermediate controllers and the destination. Each of these entities can accept, modify or reject the various parameters of the signaling information. This ensures that the network resources exist to support the type of connection required for a particular data stream.
The CMS and data slot can be viewed as a single entity and part of an infinitely long time domain multiplex (TDM) frame starting at number 1 and going on indefinitely (see
When a station initiates a CBR connection, the head-end begins to allocate a ‘TDM slot’ periodically at a rate equal to the requested data rate. It can do this because it knows what information rate has been requested and the amount of jitter the connection requires. From the first frame, the head-end is able to calculate the slot number for every data transmission for that connection. Because its centralized control can have other stations transmit data on data slots not previously reserved by CBR connections. This mechanism for providing a station a data slot (TQ) number without the station having to request it via a Control Mini-Slot is called a preemptive grant.
As an example, assume a station wants to request a connection having a bandwidth of 64 Kb/s and minimal jitter. The network control element calculates that the connection requires 167 ATM cells (64 Kb/sec)/(8 bits /byte)/(48 bytes/ATM cell)) to be available in the upstream direction every second. For an upstream QPSK signal of 1 MHz, a 1.544 Mb/s data rate is possible. Our ‘TDM slot’ consists of 82 bytes and this translates into 2,353 ((1.5 Mb/sec)/(8 bits/byte)/(82 bytes/frame)) available frames in a second. The network controller will allocate every 14th (167/2,353) ‘TDM slot’ to the station requesting the 64 Kb/sec CBR connection.
As an example,
The controller received Station B's request and will issue a starting frame of 548 in response to Station B's request. Because the controller knows that Station A's frame will occur in the middle of the 5 frames, the controller will only allow Station B to have 3 ATM cells transmitted Station B can issue an immediate request for another 2 ATM cells and have that resolved before the completion of the CBR Frame and transmit the remaining 2 ATM cells starting at frame 552.
In order to make the CBR connections work and to maintain the quality of service for the stations, the network controller must receive the desired network service level from the originating station. As mentioned before, an existing standard from the International Telecommunications Union (ITU) known as Q.2931 may be a useful mechanism to convey the connection characteristics to the network. A subset of this standard (Q.931, 0.932, Q.933) is used in ISDN, Frame Relay and ATM signaling.
Multiple connections from a modem can be multiplexed over the same physical link. Each connection can have a different class of service such as CBR, VBR, ABR and UBR. The network also guarantees the amount of maximum delay the packet will incur through the network and the amount of variation in arrival time (packet arrival jitter).
The quality of the connection between the source and destination modems is determined by the source modem specifying the characteristics of the connection. The quality of service parameters are negotiated during the connection setup phase. If the modem does not specify a value for a particular parameter, then the default value is assumed. Default values may be network specific or may be established at connection set-up time.
There are three phases of a connection: connection establishment, data transfer, and termination. Connection established is the process of establishing a path through the network that has the characteristics specified. After establishing the connection, the information flows may commence data transfer. After the information has been transferred, the source is required to notify the network to terminate the connection. This termination notification is in the form of a disconnect sequence, and it is required to allow the network to reclaim network resources dedicated to this connection.
Messages are packets that flow between the source modem to the network in order to perform a desired function. The network may return the information requested or request information from devices outside the network.
As discussed above, there is a need to establish parameters that the headend controller will use when the scheduling algorithm. As a useful mechanism for relaying the connection requirements, ITU standard Q.2931 may be employed.
Each packet in a message contains one or more fields called ‘Information Elements’. Information elements contain the logical parameters associated with that element. For example, the information element for the ‘End-to-End Transit Delay’ contains the initiator's requested transit delay and the maximum transit delay that would be accepted. The main Information Elements are listed in Table 1. Some of the connection control messages are described in Table 2.
Generically, these messages are called connection control messages. A typical connection control packet would include a Protocol Discriminator, a Connection Reference, a Message Type and one or more Information Elements.
A particular message may contain more information than a particular network needs or can understand. All equipment should be able to ignore any extra information present in a message that is not required for the proper operation of that equipment. For example, the source may ignore the source address during the CONNECT message since it should be its own address.
The purpose of the Protocol Discriminator is to distinguish messages for network connection control from other messages within Q.931. It also distinguishes messages of Q.931 from OSI network layer protocol units that are coded to other ITU Recommendations and other standards.
The value for this field should be x‘08’ (hexadecimal 08) which is the value for the Q.931/(I 451) user-network call control messages specified in section 4.2 of Recommendation Q.931.
The purpose of the Connection Reference is to identify the connection to which the particular message applies. The Connection Reference does not have end-end significance across the network. Sec section 4.3 of Recommendation Q.931.
Connection Reference values are assigned by the originating side of the interface for a connection. These values are unique to the originating side only within a particular network port link. The Connection Reference value is assigned at the beginning of a connection and remains fixed for the lifetime of a connection. After a connection ends, the associated Connection Reference value may be reassigned to a later connection. Two identical Connection Reference values on the same connection may be used when each value pertains to a connection originated at opposite ends of the link.
Information Element identifiers (IE) are logical groupings of parameters needed to convey information. The Information Element has its own unique identifier, length field and parameters. Each Information Element remains the same regardless of the Message Type. Usually a particular information element may be present only once in a given message.
Having described preferred embodiments of a novel constant bit rate mechanism in a contention based medium access control (which are intended to be illustrative and not limiting), it is noted that modifications and variations can be made by persons skilled in the art in light of the above teachings. It is therefore to be understood that changes may be made in the particular embodiments of the invention disclosed which are within the scope and spirit of the invention as defined by the appended claims.
Having thus described the invention with the details and particularity required by the patent laws, what is claimed and desired protected by letters patent is set forth in the appended claims
This application is a continuation of U.S. Application No. 08/732,668, filed October 16, 1996, now U.S. Patent No. 5,966,163, which claims the benefit of the priority of U.S. Provisional Application No. 60/005,747, filed October 20, 1995.
| Number | Name | Date | Kind |
|---|---|---|---|
| 4186380 | Edwin et al. | Jan 1980 | A |
| 4207431 | McVoy | Jun 1980 | A |
| 4361851 | Asip et al. | Nov 1982 | A |
| 4429383 | Finick et al. | Jan 1984 | A |
| 4475123 | Dumbauld et al. | Oct 1984 | A |
| 4491983 | Pinnow et al. | Jan 1985 | A |
| 4528589 | Block et al. | Jul 1985 | A |
| 4536791 | Campbell et al. | Aug 1985 | A |
| 4550398 | Belforte et al. | Oct 1985 | A |
| 4577224 | Ost | Mar 1986 | A |
| 4601028 | Huffman et al. | Jul 1986 | A |
| 4672533 | Noble et al. | Jun 1987 | A |
| 4771391 | Blasbalg | Sep 1988 | A |
| 4804248 | Bhagavatula | Feb 1989 | A |
| 4823386 | Dumbauld et al. | Apr 1989 | A |
| 4858224 | Nakano et al. | Aug 1989 | A |
| 4912721 | Pidgeon, Jr. et al. | Mar 1990 | A |
| 5014125 | Pocock et al. | May 1991 | A |
| 5047928 | Wiedemer | Sep 1991 | A |
| 5050213 | Shear | Sep 1991 | A |
| 5113499 | Ankney et al. | May 1992 | A |
| 5131041 | Brunner et al. | Jul 1992 | A |
| 5136690 | Becker et al. | Aug 1992 | A |
| 5142690 | McMullan, Jr. et al. | Aug 1992 | A |
| 5155590 | Beyers, II et al. | Oct 1992 | A |
| 5159592 | Perkins | Oct 1992 | A |
| 5166930 | Braff et al. | Nov 1992 | A |
| 5166931 | Riddle | Nov 1992 | A |
| 5181107 | Rhoades | Jan 1993 | A |
| 5185860 | Wu | Feb 1993 | A |
| 5195092 | Wilson et al. | Mar 1993 | A |
| 5197094 | Tillery et al. | Mar 1993 | A |
| 5208665 | McCalley et al. | May 1993 | A |
| 5214390 | Montreuil | May 1993 | A |
| 5226120 | Brown et al. | Jul 1993 | A |
| 5235619 | Beyers, II et al. | Aug 1993 | A |
| 5239540 | Rovira et al. | Aug 1993 | A |
| 5251324 | McMullan, Jr. | Oct 1993 | A |
| 5261044 | Dev et al. | Nov 1993 | A |
| 5271041 | Montreuil | Dec 1993 | A |
| 5276789 | Besaw et al. | Jan 1994 | A |
| 5287351 | Wall, Jr. | Feb 1994 | A |
| 5295244 | Dev et al. | Mar 1994 | A |
| 5327554 | Palazzi, III et al. | Jul 1994 | A |
| 5333183 | Herbert | Jul 1994 | A |
| 5347304 | Moura et al. | Sep 1994 | A |
| 5361259 | Hunt et al. | Nov 1994 | A |
| 5384777 | Ahmadi et al. | Jan 1995 | A |
| 5404505 | Levinson | Apr 1995 | A |
| 5423003 | Berteau | Jun 1995 | A |
| 5423006 | Brown et al. | Jun 1995 | A |
| 5436909 | Dev et al. | Jul 1995 | A |
| 5471399 | Tanaka et al. | Nov 1995 | A |
| 5473599 | Li et al. | Dec 1995 | A |
| 5481542 | Logston et al. | Jan 1996 | A |
| 5483631 | Nagai et al. | Jan 1996 | A |
| 5504921 | Dev et al. | Apr 1996 | A |
| 5515361 | Li et al. | May 1996 | A |
| 5515418 | Yamaguchi et al. | May 1996 | A |
| 5517488 | Miyazaki et al. | May 1996 | A |
| 5517618 | Wada et al. | May 1996 | A |
| 5530695 | Dighe et al. | Jun 1996 | A |
| 5533108 | Harris et al. | Jul 1996 | A |
| 5534913 | Majeti et al. | Jul 1996 | A |
| 5535403 | Li et al. | Jul 1996 | A |
| 5553095 | Engdahl et al. | Sep 1996 | A |
| 5553287 | Bailey et al. | Sep 1996 | A |
| 5555244 | Gupta et al. | Sep 1996 | A |
| 5570355 | Dail et al. | Oct 1996 | A |
| 5572640 | Schettler | Nov 1996 | A |
| 5586121 | Moura et al. | Dec 1996 | A |
| 5594798 | Cox et al. | Jan 1997 | A |
| 5604528 | Edwards et al. | Feb 1997 | A |
| 5608446 | Carr et al. | Mar 1997 | A |
| 5610910 | Focsaneanu et al. | Mar 1997 | A |
| 5612959 | Takase et al. | Mar 1997 | A |
| 5638374 | Heath | Jun 1997 | A |
| 5644706 | Ruigrok et al. | Jul 1997 | A |
| 5650994 | Daley | Jul 1997 | A |
| 5654746 | McMullan, Jr. et al. | Aug 1997 | A |
| 5675732 | Majeti et al. | Oct 1997 | A |
| 5701465 | Baugher et al. | Dec 1997 | A |
| 5703795 | Mankovitz | Dec 1997 | A |
| 5706277 | Klink | Jan 1998 | A |
| 5708655 | Toth et al. | Jan 1998 | A |
| 5708961 | Hylton et al. | Jan 1998 | A |
| 5710884 | Dedrick | Jan 1998 | A |
| 5712897 | Ortel | Jan 1998 | A |
| 5720025 | Wilkes et al. | Feb 1998 | A |
| 5721780 | Ensor et al. | Feb 1998 | A |
| 5724492 | Matthews, III et al. | Mar 1998 | A |
| 5729682 | Marquis et al. | Mar 1998 | A |
| 5737311 | Wyld | Apr 1998 | A |
| 5737316 | Lee | Apr 1998 | A |
| 5751706 | Land et al. | May 1998 | A |
| 5751707 | Voit et al. | May 1998 | A |
| 5751971 | Dobbins et al. | May 1998 | A |
| 5761602 | Wagner et al. | Jun 1998 | A |
| 5768280 | Way | Jun 1998 | A |
| 5790548 | Sistanizadeh et al. | Aug 1998 | A |
| 5790806 | Koperda | Aug 1998 | A |
| 5793753 | Hershey et al. | Aug 1998 | A |
| 5796718 | Caterisano | Aug 1998 | A |
| 5799002 | Krishnan | Aug 1998 | A |
| 5799016 | Onweller | Aug 1998 | A |
| 5805591 | Naboulsi et al. | Sep 1998 | A |
| 5805596 | Kranzler et al. | Sep 1998 | A |
| 5808671 | Maycock et al. | Sep 1998 | A |
| 5808886 | Suzuki | Sep 1998 | A |
| 5812819 | Rodwin et al. | Sep 1998 | A |
| 5818845 | Moura et al. | Oct 1998 | A |
| 5822319 | Nagami et al. | Oct 1998 | A |
| 5828655 | Moura et al. | Oct 1998 | A |
| 5828666 | Focsaneanu et al. | Oct 1998 | A |
| 5835696 | Hess | Nov 1998 | A |
| 5835725 | Chiang et al. | Nov 1998 | A |
| 5841468 | Wright | Nov 1998 | A |
| 5845091 | Dunne et al. | Dec 1998 | A |
| 5850400 | Eames et al. | Dec 1998 | A |
| 5859852 | Moura et al. | Jan 1999 | A |
| 5881234 | Schwob | Mar 1999 | A |
| 5881243 | Zaumen et al. | Mar 1999 | A |
| 5883901 | Chiu et al. | Mar 1999 | A |
| 5884024 | Lim et al. | Mar 1999 | A |
| 5884284 | Peters et al. | Mar 1999 | A |
| 5892812 | Pester, III | Apr 1999 | A |
| 5894479 | Mohammed | Apr 1999 | A |
| 5898780 | Liu et al. | Apr 1999 | A |
| 5903572 | Wright et al. | May 1999 | A |
| 5905714 | Havansi | May 1999 | A |
| 5905736 | Ronen et al. | May 1999 | A |
| 5956391 | Melen et al. | Sep 1999 | A |
| 5959972 | Hamami | Sep 1999 | A |
| 5999970 | Krisbergh et al. | Dec 1999 | A |
| 6018767 | Fijolek et al. | Jan 2000 | A |
| 6028860 | Laubach et al. | Feb 2000 | A |
| 6032266 | Ichinohe et al. | Feb 2000 | A |
| 6049826 | Beser | Apr 2000 | A |
| 6052819 | Barker et al. | Apr 2000 | A |
| 6055224 | King | Apr 2000 | A |
| 6058421 | Fijolek et al. | May 2000 | A |
| 6065049 | Beser et al. | May 2000 | A |
| 6070246 | Beser | May 2000 | A |
| 6073178 | Wong et al. | Jun 2000 | A |
| 6178455 | Schutte et al. | Jan 2001 | B1 |
| 6208656 | Hrastar et al. | Mar 2001 | B1 |
| 6230203 | Koperda et al. | May 2001 | B1 |
| 6249523 | Hrastar et al. | Jun 2001 | B1 |
| 6272150 | Hrastar et al. | Aug 2001 | B1 |
| 6282208 | Bowcutt et al. | Aug 2001 | B1 |
| 6286058 | Hrastar et al. | Sep 2001 | B1 |
| 6295298 | Hrastar et al. | Sep 2001 | B1 |
| 6670577 | Hattori et al. | Apr 2002 | B2 |
| 6418148 | Kumar et al. | Jul 2002 | B1 |
| 6813277 | Edmon et al. | Nov 2004 | B2 |
| Entry |
|---|
| PPP Bridging Control Protocol (BCP); F. Baker et al.; Network Working Group Request for Comments, Jun. 1994; pp. 1-28. |
| Number | Date | Country | |
|---|---|---|---|
| 60005747 | Oct 1995 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 09294756 | Apr 1999 | US |
| Child | 10965711 | US |
