WO2020108182A1

WO2020108182A1 - System and method for implementing zero proxy ip fast roaming

Info

Publication number: WO2020108182A1
Application number: PCT/CN2019/112847
Authority: WO
Inventors: 潘甦; 王亚利
Original assignee: 南京邮电大学
Priority date: 2018-11-30
Filing date: 2019-10-23
Publication date: 2020-06-04
Also published as: CN109413226A

Abstract

The present invention provides a system and method for implementing zero proxy IP fast roaming. The system comprises: a DHCP processing unit, used for receiving a DHCP request sent by a mobile terminal and making a DHCP ACK response; an ARP processing unit, used for receiving an ARP request from the mobile terminal; an DNS processing unit, used for receiving and analyzing an DNS request sent by the mobile terminal; and a static routing management unit, used for dynamically adding corresponding static routing entries according to a roaming access terminal, and periodically cleaning up expired static routing entries that are no longer used. The present invention can effectively solve the problems of data service interruption and data packet loss due to roaming handover delay, can shorten the network handover delay caused by re-acquisition of an IP address during the roaming process of the mobile terminal, and simplify the proxy configuration between subnets.

Description

A system and method for realizing zero-agent IP fast roaming

Technical field

The present invention relates to the field of wireless communication and mobile Internet, and in particular to a system and method for reducing the delay of IP address switching in a process in which a mobile terminal crosses different subnets in a wireless communication network.

Background technique

With the development of mobile communication, different networks such as WLAN and LTE are simultaneously providing services for terminals. When mobile terminals are moving, they often switch between different subnets. As shown in Figure 1, when a mobile terminal (STA) moves from subnet 1 to subnet 2, usually the mobile terminal uses different subnet IP addresses in different subnets, which is determined by the subnet deployment of.

Generally, there is a DHCP server in the wireless network to assign IP addresses to the accessed terminals, and the mobile terminal is the DHCP client. As shown in Figure 2, when the mobile terminal accesses another wireless network, the mobile terminal will initiate a DHCP Request. When the DHCP server responds to the NCK, the mobile terminal initiates DHCP Discovery, the DHCP server responds to the DHCP offer, the terminal sends a DHCP Request according to the DHCP offer, and the server returns DHCP to complete the IP acquisition.

Address Resolution Protocol (ARP) realizes to know its physical address through IP address. When the mobile terminal accesses the network, it will send out broadcast ARP packets after obtaining the IP address to achieve (1) determine other Whether the IP address of the host machine conflicts with the IP address of the machine. When other hosts receive the free ARP message, if they find that the IP address in the message is the same as their own IP address, an ARP response is returned to send the free ARP message The host of the document informs the host that the IP address used is in conflict. (2) When the host changes the MAC address, it notifies other hosts to update the ARP cache table by sending free ARP messages. Among them, the ARP cache table is used to store the IP address to MAC address mapping of each host and router in the network.

Network Address Translation (NAT) is used for private network hosts to initiate connection requests. Data packets are transferred to the next-level gateway through the gateway through NAT address translation. After multiple routes are sent to the public network server, the connection is established. The data can be transmitted in both directions in the future; the gateway is the main device that implements NAT technology. After the gateway converts the connection of the host in the LAN through NAT and records the related conversion information as a NAT entry, it converts the source address of the IP packet to the IP of the upstream port of the gateway The address communicates with the exit of the upper-level gateway. When receiving the upper-level gateway data, the gateway first queries the NAT table. If it can find the corresponding NAT information, it reverses the NAT conversion and sends it back to the host in the LAN. The host can complete two-way transmission with the public network server.

The gateway is an outlet and entrance device for the host in the LAN to communicate with the external network. The gateway has at least two IP addresses and corresponding physical communication ports. One of the external network IP is used to communicate with the superior gateway, and the other internal and external IP is connected to the local area network. Host communication. When the gateway wants to communicate with the local area network host, it determines the physical communication port to which the internal network host is connected by looking up the IP routing table. After finding the port, the data is handed over to the link layer for transmission.

DNS (Domain Name System) is the most important infrastructure for the operation of the Internet. Almost anything in the Internet is started with a DNS query. The main function of DNS is to convert human-recognized domain names into IP address. The DNS resolution process is a hierarchical recursive query. When the client accesses a web address, instead of directly searching for the root, (1) first check the hosts file; (2) if not, check the local DNS cache; (3) if not , Looking for the DNS server; now check the local DNS cache of the DNS server, if not, then query the DNS server's resolution library, none. DNS initiates a request to the root domain and starts iterative query. Until the IP address is found.

After receiving the IP address, the mobile terminal obtains that the IP is a private network IP address. The network can communicate normally, and the private network IP needs to be converted into a public network IP address that can be connected to the Internet.

NAT technology is used to initiate connection requests from hosts in the private network. Data packets are transferred to a higher-level gateway through a NAT address conversion via a gateway, and then sent to a public network server through multiple routes. After the connection is established, data can be transmitted in both directions; the gateway is NAT The main equipment of the technology, the gateway converts the connection of the host in the LAN through NAT and records the relevant conversion information as a NAT entry, then converts the source address of the IP packet to the IP address of the upstream port of the gateway and communicates with the upper gateway exit, and After receiving the data from the upper-level gateway, the gateway first queries the NAT table. If it can find the corresponding NAT information, it reverses the NAT conversion and sends it back to the host in the LAN. In this way, the host in the LAN can completely communicate with the public network server. Two-way transmission.

Static routing: It is a routing method. The routing items are manually configured and will not change, even if the network conditions have changed or are reconfigured. Generally speaking, static routing is added to the routing table item by item by the network management.

Mobile Internet Protocol (IP) mobile terminals switch freely from one network to another in various networks visited along its route. The MIP protocol describes those actions, that is, the mobile terminal is connected from one access router to another. The action of keeping the connection during the switch into the router. However, the typical handover of mobile terminals requires link layer and IP layer signaling. And during the handover, the mobile terminal cannot send or receive data packets. This period of time is called the switching delay. In many cases, when delay-sensitive network services come, they are unacceptable during handover. Therefore, for such services, seamless mobility management technology may be required.

For this delay, seamless switching can be achieved through fast switching and context transmission. However, the general fast switching mechanism only reduces the IP layer signaling delay and does not solve the link layer delay. But link layer assistance helps to eliminate or reduce the delay caused by link layer establishment.

Summary of the invention

In view of the above problems in the prior art, the object of the present invention is to provide a system and method for implementing fast roaming with zero proxy IP to solve the problems of data service interruption and data packet loss due to roaming switching delay.

To achieve the above objectives, the technical solutions adopted by the present invention are:

A system for implementing zero-agent IP fast roaming, including:

The DHCP processing unit, which is composed of a DHCP receiving module and a DHCP response module, is used to receive the DHCP request sent by the mobile terminal and perform a DHCP ACK response, so that the mobile terminal obtains the IP address again when accessing the new subnet;

The ARP processing unit is composed of an ARP receiving module and an ARP reply module. It is used to receive ARP requests from the mobile terminal. Regardless of whether the ARP request sent by the mobile terminal is the address of the subnet, the MAC address of the gateway of the subnet is used to respond;

The DNS processing unit is composed of a DNS receiving module and a DNS conversion module. It is used to receive and analyze the DNS request sent by the mobile terminal, convert the DNS request DNS server IP to the subnet DNS server IP, and forward it to the subnet DNS server. Parsing; the data returned by the DNS server in this subnet is then reverse converted by the DNS conversion module and then returned to the mobile terminal;

The static route management unit is used to dynamically add corresponding static route items according to the roaming access terminal, and periodically clean out the expired static route items that are no longer used.

A method for implementing zero-agent IP fast roaming includes the following steps:

(1) The mobile terminal switches from one subnet to another subnet. The mobile terminal does not need to change the original IP configuration. For DHCP requests, this subnet directly responds to ACK;

(2) When the subnet receives the DHCP request from the mobile terminal, it analyzes the DHCP request to determine whether it belongs to the network segment. If it is an IP request for the network segment, DHCP is normally allocated; if it is not, the steps are performed ( 3);

(3) The subnet responds to the ACK, and records the IP address of the DHCP request, add the IP address to the static reason table; and set a timer to check the static routing table regularly, if it is not received within the specified time When the terminal requests again, the record is deleted;

(4) After receiving the DHCP response, the mobile terminal issues an ARP request. When the ARP processing unit finds that the IP requested by the mobile terminal and its own are not in the same network segment, the ARP processing unit will send its own gateway address as a response, making the mobile The terminal communicates normally;

(5) After the DNS processing unit receives the DNS request, the mobile terminal is still the gateway of the original subnet. The gateway of the subnet judges whether the destination IP is the DNS of the home network. If it is, it responds normally. If it is not, the subnet light pipe replacement purpose IP is the DNS of this network and recorded in the DNS conversion table, and sent to the DNS of this subnet;

(6) After the above steps are processed, when responding to the mobile terminal, the mobile terminal judges whether there is a record in the conversion table according to the recorded DNS conversion table, if there is a record to reverse conversion, it is returned to the mobile terminal, if there is no record, then proceed Normal response.

In the step (1), no proxy association is required for the network that the mobile terminal last accessed, and there is no need to know the network that the terminal was connected to last time, and a complete proxy can be implemented for any gateway.

In the step (4), when the ARP processing unit receives the ARP request sent by the mobile terminal, the ARP processing unit processes the request, inquires whether the destination IP is the local subnet, and if so, responds normally; if not, uses The MAC address of the gateway and the requested IP address send a Response.

Beneficial effect: The system and method for realizing zero-agent IP fast roaming of the present invention, the adaptation of any IP without agents does not require any agent association for the last network of the mobile terminal, and the gateway adopting this method does not need to know the last connection of the terminal The network can realize full proxy for any gateway; when a new terminal accesses, the terminal does not need to change the original IP configuration, thereby greatly reducing the delay of IP switching. By analyzing the above problems, the present invention provides a simple method with simple principles, easy implementation, and easy operation. The invention can effectively solve data service interruption and data packet loss due to roaming switching delay. The invention can shorten the network switching delay caused by reacquiring the IP address during the roaming process of the mobile terminal, and simplify the proxy configuration between the subnets.

BRIEF DESCRIPTION

1 is a schematic diagram of a mobile terminal switching from one local area network to another local area network;

2 is a structural diagram of the system of the present invention;

3 is a schematic diagram of normal requests and responses when a mobile terminal enters a subnet;

Figure 4 is a schematic diagram of the DHCP processing flow;

Figure 5 is a schematic diagram of the ARP processing flow;

Figure 6 is a schematic diagram of the DNS processing flow.

detailed description

The present invention will be further explained below with reference to the drawings.

The system for realizing zero-agent IP fast roaming of the present invention includes:

The DHCP processing unit is composed of a DHCP receiving module and a DHCP response module, and is used to receive the DHCP request sent by the mobile terminal and perform a DHCP ACK response to enable the mobile terminal to reacquire an IP address when accessing a new subnet; when the mobile terminal (Referred to as STA) The process of switching from one subnet to another is shown in Figure 1. The IP address obtained by STA in subnet 1 is an IP address in 192.168.1.0/24; when the mobile node When subnet 1 is switched to another subnet 2, the terminal will first issue a DHCP request. Because the gateways of subnet 1 and subnet 2 are different, the IP requested by the mobile terminal is still the IP address obtained during subnet 1, and GW2 will send a NAK response. Then the mobile terminal will initiate DHCP Discovery, DHCP Server responds to the DHCP offer, the terminal sends out a DHCP Request according to the DHCP offer, and the server returns DHCP to complete the IP acquisition. In the present invention, no matter what IP address the mobile terminal uses to send the request, the gateway 2 (Gateway, GW2 for short) will make an ACK response. When the STA receives the ACK, it considers the configuration of the newly accessed subnet 2 and the subnet 1 The configuration is the same, no need to re-initiate the DHCP request.

The ARP processing unit is composed of an ARP receiving module and an ARP reply module. It is used to receive the ARP request of the mobile terminal. Regardless of whether the ARP request sent by the mobile terminal is the address of the subnet, the MAC address of the gateway of the subnet is used to respond; ARP receiving and The difference between the response unit and the normal ARP protocol is that when an ARP request from the mobile terminal is received, and then an ARP request is initiated to the gateway according to the ARP protocol, the request sent by the host broadcasts the ARP request containing the target IP address to the network. After all the hosts, GW2 receives the ARP request, it responds to the mobile terminal with the MAC address of GW2. At this time, the roaming mobile terminal has completed the network layer switching and established the communication link. After the mobile terminal completes the switching of the communication link, but still uses the IP configuration in subnet 1, in order to realize the roaming access STA can perform bidirectional communication in subnet 2, GW2 will roaming access STA in The IP address is added to the local routing table as a static route. The static route corresponds to the GW2 LAN port, so that GW2's routing process can automatically implement proxy for different network segments of the roaming terminal.

The DNS processing unit is composed of a DNS receiving module and a DNS conversion module. It is used to receive and analyze the DNS request sent by the mobile terminal, convert the DNS request DNS server IP to the subnet DNS server IP, and forward it to the subnet DNS server. Resolution; the data returned by the DNS server in this subnet is then reverse converted by the DNS conversion module and then returned to the mobile terminal; when the terminal needs to access the public website, it will first perform DNS resolution to obtain the corresponding IP address of the website, and GW2 receives the DNS of the STA When requesting, modify the destination IP of the DNS request to the DNS IP in subnet 2 and then forward it. At the same time, the DNS conversion table is established. When the DNS server returns a response, the information in the DNS conversion table is reverse converted, which makes STA can complete the DNS resolution process exactly as in Atomic Network 1.

The static route management unit is used to dynamically add the corresponding static route items according to the roaming access terminal, and regularly clean out the expired static route items that are no longer used.

(1) The mobile terminal switches from one subnet to another. The mobile terminal does not need to change the original IP configuration. For DHCP requests, this subnet directly responds to the ACK. Among them, it is not necessary for the network that the mobile terminal last accessed. Any proxy association, without the need to know the network that the terminal was connected to last time, can realize a complete proxy for any gateway;

(4) After receiving the DHCP response, the mobile terminal issues an ARP request. When the ARP processing unit finds that the IP requested by the mobile terminal and its own are not in the same network segment, the ARP processing unit will send its own gateway address as a response, making the mobile The terminal communicates normally; when the ARP processing unit receives the ARP request from the mobile terminal, the ARP processing unit processes the request, inquires whether the destination IP is the local subnet, and if so, responds normally; if not, uses the MAC of the gateway Address and requested IP address, send Response response.

In the present invention, this subnet refers to the subnet to which the mobile terminal is to be connected when switching from one subnet to another subnet, that is, as shown in FIG. 1, this subnet refers to the mobile terminal (STA) in the subnet 1 Subnet 2 in the process of moving to subnet 2.

Examples

As shown in FIG. 1, a general implementation process of a terminal switching from an access point in one local area network to an access point in another local area network is shown. When the mobile terminal moves from subnet 1 to subnet 2, the gateway (Gateway, GW2 for short) responds directly to the DHCP request sent by the mobile terminal. Under normal circumstances, the request sent by the mobile terminal will be as shown in Figure 3. The STA will initiate DHCP Discovery, DHCP Server responds to the DHCP offer, the terminal sends a DHCP Request according to the DHCP offer, and the server returns DHCP to complete the IP acquisition. This method proposes a proxy-free adaptation of any IP, which does not require any proxy association for the network that the mobile terminal last accessed. The gateway adopting this method does not need to know the network that the terminal was last connected to, and can be any gateway. A complete proxy is implemented; when a new terminal accesses, the terminal does not need to change the original IP configuration. For DHCP Request, GW2 directly responds to ACK. As shown in FIG. 4, when receiving the request from DHCP, GW2 analyzes the request to determine whether it belongs to the network segment. If it is an IP request to change the network segment, DHCP is normally allocated. If not, GW2 responds to the ACK and records the Request IP address and adds the IP address to the static reason table. And set a timer to check the static routing table regularly. If no further request is received from the terminal within the specified time, the record will be deleted.

After receiving the DHCP response, the STA issues an ARP request. When ARP finds that the IP requested by the mobile terminal is not on the same network segment as its own, ARP will send its own gateway address as a response, allowing the mobile terminal to communicate normally. The ARP proxy technology is used to replace hosts on different network segments to answer the host's ARP request. As shown in FIG. 5, when the mobile terminal receives the ARP request, the ARP processes the request and queries whether the destination IP is the local subnet. If yes, normal response processing; if not, use the MAC address of the gateway and the requested IP address to send a Response response.

As shown in Figure 6, after receiving the DNS request, the STA is still the gateway of the original subnet. GW2 determines whether the destination IP is the DNS of the home network, and if so, it responds normally. If not, GW2 replaces the destination IP with the local network DNS and records it in the DNS conversion table, and sends it to the local subnet DNS. After processing this process, when responding to the mobile terminal, GW2 judges whether there is a record in the conversion table according to the recorded DNS conversion table. If there is a record, perform the inverse conversion and return it to the mobile terminal. If there is no record, then respond normally.

In a specific implementation of the present invention, the present invention can be used as a software module of a gateway device, run in the gateway device, or can be an independent device connected to the gateway device in a serial manner.

The present invention greatly shortens the time delay during the roaming and switching process. Compared with the prior art, the present invention not only shortens the time delay caused by the switching, but also does not need to establish a tunnel communication between two subnets, and does not need to perform any Agent configuration greatly simplifies network management overhead.

The above is only the preferred embodiment of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principles of the present invention, several improvements and retouches can be made. These improvements and retouches also It should be regarded as the protection scope of the present invention.

Claims

A system for realizing zero-agent IP fast roaming, which is characterized by:

The DHCP processing unit, which is composed of a DHCP receiving module and a DHCP response module, is used to receive the DHCP request sent by the mobile terminal and perform a DHCP ACK response, so that the mobile terminal obtains the IP address again when accessing the new subnet;

The ARP processing unit is composed of an ARP receiving module and an ARP reply module. It is used to receive ARP requests from the mobile terminal. Regardless of whether the ARP request sent by the mobile terminal is the address of the subnet, the MAC address of the gateway of the subnet is used to respond;

The DNS processing unit is composed of a DNS receiving module and a DNS conversion module. It is used to receive and analyze the DNS request sent by the mobile terminal, convert the DNS request DNS server IP to the subnet DNS server IP, and forward it to the subnet DNS server. Parsing; the data returned by the DNS server in this subnet is then reverse converted by the DNS conversion module and then returned to the mobile terminal;

The static route management unit is used to dynamically add corresponding static route items according to the roaming access terminal, and periodically clean out the expired static route items that are no longer used.
A method for implementing zero-agent IP fast roaming, which is characterized by the following steps:

(1) The mobile terminal switches from one subnet to another subnet. The mobile terminal does not need to change the original IP configuration. For DHCP requests, this subnet directly responds to ACK;

(2) When the subnet receives the DHCP request from the mobile terminal, it analyzes the DHCP request to determine whether it belongs to the network segment. If it is an IP request for the network segment, DHCP is normally allocated; if it is not, the steps are performed ( 3);

(3) The subnet responds to the ACK, and records the IP address of the DHCP request, add the IP address to the static reason table; and set a timer to check the static routing table regularly, if it is not received within the specified time When the terminal requests again, the record is deleted;

(4) After receiving the DHCP response, the mobile terminal issues an ARP request. When the ARP processing unit finds that the IP requested by the mobile terminal and its own are not in the same network segment, the ARP processing unit will send its own gateway address as a response, making the mobile The terminal communicates normally;

(5) After the DNS processing unit receives the DNS request, the mobile terminal is still the gateway of the original subnet. The gateway of this subnet judges whether the destination IP is the DNS of this network. If it is, it responds normally. IP is the DNS of this network and recorded in the DNS conversion table, and sent to the DNS of this subnet;

(6) After the above steps are processed, when responding to the mobile terminal, the mobile terminal judges whether there is a record in the conversion table according to the recorded DNS conversion table. If there is a record, it reverses the conversion and returns to the mobile terminal. Normal response.
The method for implementing zero-agent IP fast roaming according to claim 2, characterized in that: in the step (1), no agent association is required for the network last accessed by the mobile terminal, and there is no need to know the terminal last time The connected network can realize complete proxy for any gateway.
The method for implementing zero-agent IP fast roaming according to claim 2, wherein in step (4), when the ARP processing unit receives the ARP request from the mobile terminal, the ARP processing unit processes the request, Inquire whether the destination IP is the subnet, if it is, then respond normally; if not, use the MAC address of the gateway and the requested IP address to send a Response.