Electrical computers and digital processing systems: multicomput – Computer-to-computer protocol implementing – Computer-to-computer data transfer regulating
Reexamination Certificate
1999-08-02
2003-06-10
Maung, Zarni (Department: 2154)
Electrical computers and digital processing systems: multicomput
Computer-to-computer protocol implementing
Computer-to-computer data transfer regulating
C709S234000, C709S235000, C370S230000, C370S235000
Reexamination Certificate
active
06578082
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates in general to a distributed flow control system and method for General Packet Radio Service (GPRS) networks and in particular to a system and method for adapting a leaky bucket mechanism to a system having multiple traffic sources wherein the combined traffic from all sources must satisfy a single set of peak and average rate requirements.
2. Description of the Related Art
Wireless communication technologies require the use of various defined standards such as for voice and data communications. General Packet Radio Service (GPRS) is a relatively newer version standard that has been established for wireless data communications in Europe, and GPRS is able to be used anywhere in the world. A general prior art diagram of the topology of a GPRS network
10
is shown in FIG.
1
. The GPRS network
10
generally comprises a number of nodes. The GPRS network
10
comprises a mobile switching center (MSC), a visitor location register (VLR)
12
, a home location register (HLR), an authentication center (AuC)
14
, a gateway GPRS support node (GGSN)
20
, a serving GPRS support node (SGSN)
24
, a base station system (BSS) having an antenna
30
, and a packet control unit (PCU)
28
. The MSC/VLR provides voice communications for wireless or cellular telephones. The MSC/VLR
12
is in direct communications with the HLR/AuC
14
, the SGSN
24
, and the BSS/PCU
28
. The HLR/AuC
14
is in direct communications with SGSN
24
and GGSN
20
.
The GPRS network
10
is configured to support interfaces to and from outside packet data networks.
FIG. 1
shows that the GGSN
20
is coupled to and in communications with outside packet data networks that support the internet protocol (IP)
16
or the X.25 protocol
18
. In
FIG. 1
, data packets come in from the outside network (i.e. IP
16
or X.25 networks
18
) to the GGSN
20
, then to the SGSN
24
, and then to the BSS/PCU
28
. Thus, two way communications exist between the BSS/PCU
28
and the SGSN
24
, the GGSN
20
, and the outside network(s). One problem that exists for the data packet coming from the GGSN
20
(or outside) to the SGSN
24
and then to the BSS/PCU
28
is that the packet control unit (PCU) may have limited memory space. A long queue of incoming data may exist at the PCU, and the PCU may not be able to receive anymore data or information from the SGSN
24
. Therefore, a method for regulating traffic flow from the SGSN to the PCU is necessary.
FIG. 4
is a prior art block diagram of the protocol stack
55
between the BSS/PCU stack
56
for the BSS/PCU
28
and the SGSN stack
66
for the SGSN
24
in a GPRS network
10
. The BSS/PCU stack
56
comprises a relay
58
, a Base Station System GPRS protocol (BSSGP) layer
60
, a frame relay layer
62
, and a physical layer
64
. The SGSN stack
66
comprises a relay
66
, a SNDCP layer
70
, a Logical Link Control (LLC) layer
72
, a BSSGP layer
74
, a frame relay layer
76
, and a physical layer
78
. According to the GPRS standards, a frame relay network
63
couples the BSS/PCU
28
to the SGSN
24
. In the BSS/PCU stack
56
, BSSGP layer
60
is located immediately above the frame relay layer
62
. The operations of the BSSGP layer
60
include flow control and transmission of LLC frame
39
or data packet frame related information, such as routing and QoS requirements, between the SGSN
24
and the BSS/PCU
28
. The data streams transmitted from the SGSN
24
to a cell is grouped together to form a BSSGP virtual circuit (BVC). Flow control between the SGSN
24
and the BSS/PCU
28
is performed both on per BVC and per mobile station basis.
FIG. 2
shows a prior art diagram of the flow control between the SGSN
24
and the BSS/PCU
28
. Flow control parameters
32
are programmed and established from the BSS/PCU
28
. These flow control parameters
32
are directed from the BSS/PCU
28
to the SGSN
24
to control and regulate the flow of data from the SGSN
24
to the BSS/PCU
28
. Thus, regulated data flow exists from the SGSN
24
to the BSS/PCU
28
. The flow control mechanism implemented at the SGSN
24
is based on a leaky bucket flow control mechanism. The flow control parameters established by the BSS/PCU
28
are used to dimension the leaky bucket mechanism implemented at the SGSN
24
.
The leaky bucket flow control mechanism is a simple and effective system and method for regulating and controlling traffic flow. Each leaky bucket is dimensioned by two parameters: leak rate (R) and bucket size (maximum bucket size B
max
). These parameters together control the peak and the average rates of traffic departure from a traffic source. The leaky bucket flow control mechanism regulates the output bandwidth allocation to a traffic source such that traffic departing from the controlled source does not exceed the specified mean and peak rate values. The basic concept of this mechanism is to associate a bucket
40
with a traffic source at the SGSN
24
(see FIG.
3
). The bucket
40
has a finite number of bytes in size (i.e. maximum bucket size B
max
). When the traffic source at the SGSN
24
transmits traffic to the output link
80
, an equivalent number of bytes must be put into the bucket
40
. If the bucket
40
is full, transmission is not allowed. The available data
39
is either queued in the buffer
38
or discarded. Consequently, the traffic source at the SGSN
24
is not able to transmit more data
39
than the available capacity of the bucket
40
. At the same time, the bucket
40
“leaks”(i.e. the bucket level drops) at a given leak rate R such that the data departure is not totally confined to the finite bucket size. Based on the leaky bucket mechanism, the mean departure rate of the traffic source at the SGSN
24
cannot exceed the bucket leak rate R. At any time instant, the traffic source at the SGSN
24
is not able to send out more data
39
than the bucket size B
max
.
An application of the leaky bucket flow control mechanism
36
(see
FIG. 3
) is found in GPRS as specified in the European Telecommunications Standards Institute (ETSI) Global System for Mobile Communications (GSM) phase 2+ standards [1]. GPRS is the packet data extension of the circuit based GSM wireless communication standard. Details and applications of these standards and specifications are disclosed in ETSI, “Digital Cellular Telecommunications System (phase 2+); General Packet Radio Service (GPRS); Service Description; Stage 2,” ETSI GSM 03.60, Version 6.1.1, August 1998. These standards, specifications, and publications are incorporated by reference herein. Referring to FIG.
1
and as stated earlier, the GGSN node
20
is the interface between the GPRS network and the outside networks
16
or
18
. The GGSN
20
is responsible for forwarding data packets to the appropriate SGSN
24
and to provide mobility, security, and billing related operations. The SGSN
24
is responsible for the buffering and delivery of packet data and the handling of GPRS related signaling messages for subscribers residing in its assigned area. Each SGSN
24
is connected to one or more BSS/PCU
28
. The BSS/PCU
28
is responsible for interfacing with the mobile station or terminal
27
with antenna
29
through the GPRS air interface protocol.
FIG. 3
shows a prior art diagram of the leaky bucket flow control mechanism
36
. As a logical link control (LLC) frame of data
39
is forwarded from the data buffer
38
of the SGSN
24
to the BSS/PCU
28
via a BSSGP virtual circuit. A number of bytes equal to the length of the LLC frame must be placed in the bucket
40
. In other words, the same amount of data
39
that has been forwarded from the SGSN
24
to the BSS/PCU
28
needs to be placed into the bucket
40
. The data
39
collected in the bucket
40
leaks at the leak rate (R)
45
. The data
39
leaking from the bucket
40
operates to control the rate of data flow from the SGSN
24
to the BSS/PCU
28
by requiring that a sufficient amount of space (equal to the size of the next LLC frame to be trans
Hanson Mark Eric
Ho Joseph S.
Zhu Yixin
Bracewell & Patterson L.L.P.
Crane John D.
Lin Wen-Tai
Maung Zarni
Nortel Networks Limited
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