CN105578529A - An access point selection system and method - Google Patents

Abstract

The invention relates to an access point selection system and method. The system comprises a controller, a resource manager, a server, a workstation and multiple access points; the access point is used for sending request information of the workstation to the server, and the request information comprises signal strength information and user demand preference; the server is used for scheduling the resource manager according to the request information of the workstation to obtain network state information; the resource manager is used for scheduling a northern interface of the server to collect the network state information; in a small scale network, the resource manager is used for obtaining an optimal access point according to the network state information and the signal strength information, in combination with the user demand preference; and in a large scale network, the server is used for sending the obtained network state information to the workstation through the access point, thus allowing the workstation to obtain the optimal access point. According to the access point selection system provided by the invention, before accessing the network, the terminal obtains the network state information, the workstation selects the optimal access point according to the network condition, and the network load is more balanced.

Description

An access point selection system and method

technical field

The present invention relates to the technical field of wireless communication, in particular to a system and method for selecting an access point.

Background technique

Software Defined Network (Software Defined Network, referred to as SDN) (as shown in Figure 1) is a new type of network innovation architecture, based on OpenFlow technology to separate the control plane and data plane in the network, so as to realize the flexible control of data flow in the network, with Centralized network control and network can have features such as external program programming. The typical architecture of SDN is divided into three layers. The top layer is the application layer, which mainly includes network-related business and management applications; the middle layer is the control layer, which mainly has the controller to generate and issue flow tables to control the data forwarding of the network. At the same time, it can obtain the global view of the network and maintain network topology and status information; the bottom layer is the data layer, which is mainly composed of switches, and performs data processing, forwarding and information collection according to the flow table issued by the controller.

Wireless Local Area Network (WLAN for short) refers to a computer network using wireless channels as the transmission medium, providing users with network access services anytime and anywhere. Wireless local area networks based on the IEEE802.11 standard are widely used in society. In a wireless local area network, when a workstation (Station, terminal, referred to as STA) needs to access the network, it sends a broadcast probe frame, and the access point (AccessPoint, referred to as AP) responds to the probe frame, and then the STA can get the information of each AP. Signal strength value, select the AP with stronger signal for association. In the above process, the STA only selects according to the signal strength value, ignoring the channel interference and the load of the AP, which may affect the communication performance of the terminal and the load balance of the entire network. The reason is that, on the one hand, STAs cannot obtain much network information before association, and on the other hand, the distributed network architecture cannot collect global status information, even through the centralized There are also problems such as increased access delays in the way of controlling the network.

802.11u is an interoperability protocol between WLAN and external networks defined by the IEEE802.11 working group, which provides a Generic Advertisement Service (GAS for short), enabling STAs and APs to perform more data link layer information before association exchange. Access Network Query Protocol (Access Network Query Protocol, referred to as ANQP) standard is based on the protocol that provides network information query function based on GAS. The request sent by the STA to the AP can be responded by the AP according to all its own information, or forwarded to the corresponding ANQPServer for processing and processing. response. However, ANQP is mainly used for roaming switching between different operator networks, and cannot provide better AP selection. Some of the existing AP and network coordination solutions currently exist, or need to associate with an AP first for query and then switch, which increases the associated delay, or need to establish a tunnel, which requires a lot of development, and there is no standard support.

Contents of the invention

The technical problem to be solved by the present invention is: the existing terminal cannot obtain detailed network parameters before associating with the network, which leads to poor selection of access points and unbalanced network load.

In order to solve the above-mentioned technical problems, the present invention proposes an access point selection system on the one hand, and the system includes:

Controllers, resource managers, servers, workstations, multiple access points;

The access point is configured to send the request information of the workstation to the server, and the request information includes signal strength information;

The server is used to call the resource manager to obtain network status information according to the request information of the workstation;

The resource manager is used to call the northbound interface of the server to collect the network status information;

In a small-scale network, the resource manager is used to obtain an optimal access point according to the network status information, signal strength information, and user demand preference;

In a large-scale network, the server is used to send the obtained network status information to the workstation through the access point, so that the workstation obtains the optimal access point;

Wherein, the network status information includes the number of load users of the access point, the channel utilization rate, the retransmission rate, and the bottleneck bandwidth from the access point to the egress of the LAN;

The user demand preference is the sorting of the attribute value set based on the access point selection, and the attribute value set based on the access point selection includes: received signal strength indicator value, load user number of the access point, channel utilization rate , retransmission rate, and bottleneck bandwidth from the access point to the LAN egress.

Optionally, the server is specifically configured to call an API query protocol of the resource manager according to the request information of the workstation to obtain network status information.

Optionally, the resource manager is further configured to, when the network state information changes, send the changed network state information to the access point by calling an API of the server.

Optionally, the access point is further configured to, after receiving the changed network state information sent by the resource manager, forward the changed network state information to the workstation.

Optionally, at least one switch is also provided between the access point and the controller.

Another aspect of the present invention proposes a method for selecting an access point, the method comprising:

Before the workstation is associated with the access point, the signal strength of multiple access points is obtained, and the access point with the highest signal strength is determined as the query access point;

After receiving the workstation request information forwarded by the query access point, the server calls the resource manager to obtain network status information, and the request information includes signal strength information and user demand preferences;

In a small-scale network, the resource manager obtains the optimal access point according to the network status information and signal strength information combined with user demand preferences;

In a large-scale network, the server sends the obtained network status information to the workstation through the query access point, so that the workstation obtains the optimal access point;

The workstation is associated with the optimal access point;

Wherein, the network status information includes the number of load users of the access point, the channel utilization rate, the retransmission rate, and the bottleneck bandwidth from the access point to the egress of the LAN;

The user demand preference is the sorting of the attribute value set based on the access point selection, and the attribute value set based on the access point selection includes: received signal strength indicator value, load user number of the access point, channel utilization rate , retransmission rate, and bottleneck bandwidth from the access point to the LAN egress.

Optionally, the resource manager obtains the optimal access point according to the network status information, signal strength information and user demand preference, including:

The resource manager uses the AHP to construct a five-scale or nine-scale fuzzy matrix according to the network state information and signal strength information combined with user demand preferences, obtains the scores of each access point, and determines the access point with the highest score is the optimal access point.

Optionally, the server calls the resource manager to obtain network status information, including:

The server invokes the API query protocol of the resource manager to obtain network status information.

Optionally, the method also includes:

When the network status information changes, the resource manager sends the changed network status information to the access point by calling the API of the server.

Optionally, the method also includes:

After receiving the changed network state information sent by the resource manager, the access point forwards the changed network state information to the workstation.

The access point selection system and method provided by the present invention obtain network status information before the terminal accesses the network, realizes the optimal selection of the access point by the workstation according to the network status, and more effectively selects the access point, reducing the network load It is more balanced and improves the terminal communication performance.

Description of drawings

The features and advantages of the present invention will be more clearly understood by referring to the accompanying drawings, which are schematic and should not be construed as limiting the invention in any way. In the accompanying drawings:

FIG. 1 shows a schematic structural diagram of an access point selection system according to an embodiment of the present invention;

Fig. 2 shows a schematic diagram of a Beacon frame according to an embodiment of the present invention;

Fig. 3 shows a schematic diagram of a request frame according to an embodiment of the present invention;

Fig. 4 shows a schematic diagram of a response frame according to an embodiment of the present invention;

FIG. 5 shows a flow chart of an access point selection method according to an embodiment of the present invention;

Fig. 6 shows a signaling flowchart of an access point selection method according to an embodiment of the present invention.

detailed description

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

Fig. 1 shows a schematic structural diagram of an access point selection system according to an embodiment of the present invention. As shown in Figure 1, the access point selection system of this embodiment includes:

Controller 1, resource manager 2, server (Server) 3, workstation (STA) 4, multiple access points (AP) 5;

The access point 5 is used to send the request information of the workstation 4 to the server 3, and the request information includes signal strength information and user demand preferences;

The server 3 is used to call the resource manager 2 to obtain network status information according to the request information of the workstation 4;

The resource manager 2 is used to call the northbound interface of the server 3 to collect the network state information;

In a small-scale network, the resource manager 2 is used to obtain the optimal access point according to the network status information, signal strength information and user demand preference;

In a large-scale network, the server 3 is used to send the obtained network status information to the workstation 4 via the access point 5, so that the workstation obtains the optimal access point;

Wherein, the network status information includes the number of load users of the access point, the channel utilization rate, the retransmission rate, and the bottleneck bandwidth from the access point to the egress of the LAN;

The user demand preference is the sorting of the attribute value set based on the access point selection, and the attribute value set based on the access point selection includes: received signal strength indicator value, load user number of the access point, channel utilization rate , retransmission rate, and bottleneck bandwidth from the access point to the LAN egress.

It should be noted that the access point in this embodiment supports 802.11u and is controlled by a controller; the controller can be a professional SDN controller or a server running OpenFlow software; the network status information is collected periodically.

The access point selection system of this embodiment obtains network status information before the terminal accesses the network, realizes the optimal selection of the access point by the workstation according to the network condition, more effectively selects the access point, and makes the network load more balanced , improving the terminal communication performance.

In an optional implementation manner, the server is specifically configured to call an API query protocol of the resource manager according to the request information of the workstation to obtain network status information. The access point selection system realizes the organic combination of the two independent structures by providing RESTfulapi to each other through the server and the resource manager.

The resource manager is further configured to, when the network state information changes, send the changed network state information to the access point by calling the API of the server.

When the network status changes or the STA moves, the resource manager can call the API of the server to notify the STA and perform some actions.

The access point is further configured to, after receiving the changed network state information sent by the resource manager, forward the changed network state information to the workstation.

There is also at least one switch between the access point and the controller. In practice, the switch is an SDN switch that supports OpenFlow.

The access point selection system of this embodiment combines the system design scheme of 802.11u in the SDN wireless network, realizes the coordination mechanism between the network and the terminal, and provides the ability of the STA to actively query and passively notify without being associated with the AP.

It should be noted that the access point selection system in this embodiment is realized by using the Network Resource Query Protocol (NetworkResourceQueryProtocol) designed based on GAS. The NRQP is a redesigned protocol to solve the problem that the existing ANQP protocol is mainly used for roaming handover between different operator networks and cannot provide better AP selection. The following describes the NRQP protocol from the extension of the Beacon frame, the design of the request frame and the design of the response frame.

(1) FIG. 2 shows a schematic diagram of a Beacon frame according to an embodiment of the present invention. As shown in Figure 2, the first line is the field newly extended by 802.11u in the Beacon frame, and the Advertisement protocol field can carry the GAS protocol supported by the network. The second and third lines are the data format of the broadcast protocol field. The protocol number (AdvertisementProtocolID) has a total of 8 bits, which can support a total of 255 protocols from 0 to 255, and most of them are reserved. The present invention selects two reserved protocol numbers to represent NRQP of network decision-making and network query mode respectively. Network administrators can configure NRQP in different modes according to the network scale. In a large-scale network, use the network query mode to reduce the pressure on the server; quick response. The STA can request through the supported NRQP mode broadcasted by the AP.

(2) FIG. 3 shows a schematic diagram of a request frame according to an embodiment of the present invention. As shown in FIG. 3 , the first row in the figure shows the data format of the GAS request frame, AdvertisementProtocolElement contains the protocol number, and the present invention defines the Query Request (QueryRequest) field corresponding to NRQP. The second row in the figure is the data format of the request field, which includes two fields: user demand preference (UserSatisfy) and query AP list (QueryAPList). The third row in the figure is the data format of each item in the list, including the SSID (ServiceSetIdentifier, service set identifier) and BSSID (BasicServiceSetIdentifier, basic service set identifier) that can uniquely identify the AP, and an STA that needs to be carried in the network decision mode RSSI (ReceivedSignalStrengthIndication, received signal strength indication) value of the monitored access point, which is left blank in the network query mode.

The AdvertisementProtocolElement in the GAS request frame is the protocol number corresponding to the request, and the STA can set it according to the scanned NRQP protocol number. The present invention defines the query request (QueryRequest) field corresponding to NRQP, which mainly includes two fields: user demand preference (UserSatisfy) and query AP list (QueryAPList). User demand preference is the sorting of the attribute value set according to AP selection, and the attribute value set adopted in the present invention includes: (1) the RSSI value of the access point monitored by the STA (2) the number of loads of the AP (3) the channel utilization of the AP Rate (4) The retransmission rate of the AP (5) The bottleneck bandwidth from the AP to the LAN egress. These attributes can basically reflect the working conditions of the AP, and can be used as benchmark parameters for STA selection. The query AP list refers to the set of APs that the STA can monitor on the network and meet a certain RSSI threshold, and the information of each AP is an item in the list. The data format of each item in the AP list includes the SSID and BSSID that can uniquely identify the AP. There is also an RSSI value of the access point monitored by the STA that needs to be carried in the network decision mode, and left blank in the network query mode.

(3) FIG. 4 shows a schematic diagram of a response frame according to an embodiment of the present invention. As shown in Figure 4, the first row in the figure shows the data format of the GAS response frame. The AdvertisementProtocolElement in the number of GAS response frames is the protocol number of the corresponding request, and the NRQP server can perform the same setting according to the request frame. The present invention defines two query response (QueryResponse) fields corresponding to NRQP in two different modes. In the network decision-making mode, the data format of the query response field mainly includes two fields: the target AP (TargetAP) is calculated by the NRQP server based on the information returned by the resource manager and the user demand preference uploaded by the STA, which includes a unique identifier The SSID and BSSID of the AP; the Action field is determined by the server based on the current user status, including authentication, association, and switching. In the network query mode, the data format of the query response field includes a field: Response AP List (RespondAPList), which is the information obtained by querying all items corresponding to the query AP list in the STA request. The query information includes the AP load user number (Usernumber) , Channel utilization (Channelutilization), retransmission rate (RetryCount) and the bottleneck bandwidth (Bottleneckbandwidth) from the AP to the LAN egress.

FIG. 5 shows a flow chart of an access point selection method according to an embodiment of the present invention. The access point selection method of this embodiment is based on the above-mentioned access point selection system and utilizes the aforementioned NRQP protocol. As shown in Figure 5, the access point selection method of this embodiment includes:

S51: Before the workstation associates with the access point, acquire the signal strength of multiple access points, and determine the access point with the highest signal strength as the query access point;

S52: After receiving the workstation request information forwarded by the query access point, the server calls the resource manager to obtain network status information, and the request information includes signal strength information and user demand preferences;

S53: In a small-scale network, the resource manager obtains the optimal access point according to the network state information and signal strength information combined with user demand preferences; in a large-scale network, the server passes the acquired network state information through the Inquiring about the access point is sent to the workstation, so that the workstation obtains the optimal access point;

S54: The workstation associates with the optimal access point;

Wherein, the network status information includes the number of load users of the access point, the channel utilization rate, the retransmission rate, and the bottleneck bandwidth from the access point to the egress of the LAN;

The user demand preference is the sorting of the attribute value set based on the access point selection, and the attribute value set based on the access point selection includes: received signal strength indicator value, load user number of the access point, channel utilization rate , retransmission rate, and bottleneck bandwidth from the access point to the LAN egress.

The access point selection method provided in this embodiment obtains the network status information before the terminal accesses the network, realizes the optimal selection of the access point by the workstation according to the network condition, and more effectively selects the access point, making the network load more efficient. Balanced, improving the terminal communication performance.

In an optional implementation manner, the resource manager obtains the optimal access point according to the network status information and signal strength information combined with user demand preferences, including:

The resource manager uses the AHP to construct a five-scale or nine-scale fuzzy matrix according to the network state information and signal strength information combined with user demand preferences, obtains the scores of each access point, and determines the access point with the highest score is the optimal access point.

Specifically, the server calls the resource manager to obtain network status information, including:

The server invokes the API query protocol of the resource manager to obtain network status information.

In order to realize that after the STA is associated, the network person can notify the STA to perform some actions through the Ayong communication link, so as to optimize the overall performance, the method also includes:

When the network status information changes, the resource manager sends the changed network status information to the access point by calling the API of the server.

Further, the method also includes:

After receiving the changed network state information sent by the resource manager, the access point forwards the changed network state information to the workstation.

Fig. 6 shows a signaling flowchart of an access point selection method according to an embodiment of the present invention. The specific implementation process of an embodiment of the present invention is described below in conjunction with FIG. 6:

Step 1. The STA scans the Beacon frames broadcast by all APs in the current network, checks the NRQP modes it supports, takes the AP with the best signal strength as the query AP, and initiates a GAS request to the AP according to the user's configuration requirements and network support protocols.

Step 2: After receiving the request from the STA, the AP forwards it to the NRQP server according to the protocol number in the request.

Step 3: After receiving the request forwarded by the AP, the NRQP server invokes the API of the resource manager, usually an HTTP request, to query the attribute data of each item in the AP list to be checked (the four items involved in Figure 3).

In step 4, the resource manager obtains the data through the controller in a periodic collection manner. The number of users, the channel utilization rate and the retransmission rate of the AP can be read from the AP according to the Simple Network Management Protocol (SNMP for short), and stored and maintained. When the query API is called, the resource manager will query the last 3 sampling values <C ₃ , C ₂ , C ₁ > of each attribute of each AP according to the request, where C ₁ is the latest sampling value, according to the following The formula calculates the corresponding value C _r =0.2*C ₃ +0.3*C ₂ +0.5*C ₁ , which not only considers the current AP load, but also refers to the historical situation, making the attribute value more representative.

Step 5: The NRQP server performs calculations based on the return value and user demand preferences in the decision mode according to the set modes, and sends the resulting decision information to the STA, and directly forwards the return value to the STA in the query mode Make calculations and make decisions. The calculation process adopts the analytic hierarchy process, and according to the user's demand preference, the nine-division fuzzy matrix is constructed. The first row indicates the attribute with the highest ranking, and the matrix is as follows:

$\left(\begin{array}{ccccc}\mathrm{<span\; class="notranslate">\; 1</span>}& \mathrm{<span\; class="notranslate">\; 3</span>}& \mathrm{<span\; class="notranslate">\; 5</span>}& \mathrm{<span\; class="notranslate">\; 7</span>}& \mathrm{<span\; class="notranslate">\; 9</span>}\\ \mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 3</span>}& \mathrm{<span\; class="notranslate">\; 1</span>}& \mathrm{<span\; class="notranslate">\; 3</span>}& \mathrm{<span\; class="notranslate">\; 5</span>}& \mathrm{<span\; class="notranslate">\; 7</span>}\\ \mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 5</span>}& \mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 3</span>}& \mathrm{<span\; class="notranslate">\; 1</span>}& \mathrm{<span\; class="notranslate">\; 3</span>}& \mathrm{<span\; class="notranslate">\; 5</span>}\\ \mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 7</span>}& \mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 5</span>}& \mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 3</span>}& \mathrm{<span\; class="notranslate">\; 1</span>}& \mathrm{<span\; class="notranslate">\; 3</span>}\\ \mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 9</span>}& \mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 7</span>}& \mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 5</span>}& \mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 3</span>}& \mathrm{<span\; class="notranslate">\; 1</span>}\end{array}\right)$

Its maximum eigenvalue can be calculated as 5.2375, and the corresponding eigenvector as a weight vector is [0.863, 0.4401, 0.217, 0.1067, 0.0561] ^T , and its consistency verification is carried out. The calculated consistency index CI=0.0594, the same order random Consistency index RI＝1.12, random consistency ratio CR＝0.053＜0.1, indicating that the obtained weight value has satisfactory consistency. According to this weight value, calculate and sort the comprehensive score of AP for the normalized attributes to obtain the target AP.

In step 6, the STA determines the target AP according to the calculated result, and performs actions such as association or handover.

Step 7. When the network status changes or the STA moves, for example, the current AP load becomes heavy, and a user transmits a large amount of data, the resource manager can call the interface of the NRQP server to notify the STA to initiate a new query and reselect AP.

The access point selection system and method provided by the present invention obtain network status information before the terminal accesses the network, realizes the optimal selection of the access point by the workstation according to the network condition, and more effectively selects the access point, reducing the network load It is more balanced and improves the terminal communication performance.

Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present invention. within the bounds of the requirements.

Claims (10)

1. an access point selective system, is characterized in that, comprising: controller, explorer, server, work station, multiple access point;

Described access point is for sending the solicited message of work station to described server, and described request information comprises signal strength information and user's request preference;

Described server is used for calling explorer according to the solicited message of work station and obtains network state information;

Described explorer gathers described network state information for the northbound interface calling described server;

Under small scale network, described explorer is used for obtaining optimum access point according to described network state information and signal strength information in conjunction with user's request preference;

Under large scale network, described server is used for the network state information of acquisition to be sent to work station through access point, obtains optimum access point to make described work station;

Wherein, described network state information comprises the bottleneck bandwidth that the load demand number of access point, channel utilization, retransmission rate and access point export to local area network (LAN);

Described user's request preference be to access point selection according to the sequence of property value set, described to access point selection according to property value set comprise: the bottleneck bandwidth that the load demand number of received signal strength indicator value, access point, channel utilization, retransmission rate and access point export to local area network (LAN).

2. access point selective system according to claim 1, is characterized in that, described server obtains network state information specifically for the API vlan query protocol VLAN calling explorer according to the solicited message of work station.

3. the selective system of access point according to claim 1, is characterized in that, the network state information after change, also for when described network state information changes, is sent to access point by the API of invoking server by described explorer.

4. access point selective system according to claim 3, is characterized in that, described access point also for, receive explorer send change after network state information after, the network state information after described change is forwarded to work station.

5. access point selective system according to claim 1, is characterized in that, between described access point and controller, be also provided with at least one switch.

6. an access point system of selection, is characterized in that, comprising:

Before work station association access point, obtain the signal strength signal intensity of multiple access point, access point maximum for signal strength signal intensity is defined as inquire about access point;

After server receives the workstation requests information of described inquiry access point forwarding, call explorer and obtain network state information, described request information comprises signal strength information and user's request preference;

Under small scale network, explorer obtains optimum access point according to described network state information and signal strength information in conjunction with user's request preference;

Under large scale network, the network state information of acquisition is sent to work station through described inquiry access point by described server, obtains optimum access point to make described work station;

The described optimum access point of described work station association;

Wherein, described network state information comprises the bottleneck bandwidth that the load demand number of access point, channel utilization, retransmission rate and access point export to local area network (LAN);

Described user's request preference be to access point selection according to the sequence of property value set, described to access point selection according to property value set comprise: the bottleneck bandwidth that the load demand number of received signal strength indicator value, access point, channel utilization, retransmission rate and access point export to local area network (LAN).

7. access point system of selection according to claim 6, is characterized in that, described explorer obtains optimum access point according to described network state information and signal strength information in conjunction with user's request preference, comprising:

Described explorer adopts analytic hierarchy process (AHP) to construct five scales or nine scale fuzzy matrixes according to described network state information and signal strength information in conjunction with user's request preference, obtain the score of each access point, access point the highest for score is defined as optimum access point.

8. access point system of selection according to claim 6, is characterized in that, described server calls explorer obtains network state information, comprising:

The API vlan query protocol VLAN of described server calls explorer obtains network state information.

9. access point system of selection according to claim 6, is characterized in that, also comprise:

When described network state information changes, the network state information after change is sent to access point by the API calling described server by described explorer.

10. access point system of selection according to claim 9, is characterized in that, also comprise:

After the network state information of described access point after the change receiving explorer transmission, the network state information after described change is forwarded to work station.