CN1808998A - Method of detection and maintenance of PPP link - Google Patents

Abstract

This invention discloses one method to test and sustain point to point agreement PPP linkage, which comprises the following steps: a, customer end sends DNS demands to partner end through PPP interface; b, judging whether the partner end respond to the said DNS demands; if yes, then judging the PPP linkage is normal; if not, then judging PPP linkage is lost and starting re-linkage process.

Description

The method of a kind of detection and maintenance of PPP link

Technical field

The present invention relates to PPP (Point-to-Point Protocol peer-peer protocol is called for short PPP) link, relate in particular to the method for a kind of detection and maintenance of PPP link.

Background technology

PPP (Point-to-Point Protocol peer-peer protocol) is the link layer protocol of the so simple link design of transmits data packets between equal unit, and the data link that uses this kind link layer protocol to set up is called ppp link.This link provides full-duplex operation, and Data transmission bag in order, and main effect is to set up point-to-point connection and send data by dialing or private-line mode.At present, ppp link has become a kind of common solution that realizes simple connection between various main frames, bridge and the router, it has simply, possesses the user rs authentication ability, can solve advantages such as IP distribution, is one of most widely used agreement on the present wide area network.For example, family to dial up on the telephone be exactly to set up communication by ppp link between the access server of user side and operator (as China Netcom).In the application of broadband access, the form that ppp link is also derived and made new advances.For example, at ADSL (asymmetric data subscriber loop, AsymmetricalDigital Subscriber Loop) in the access way, adopt ppp protocol and other agreement to derive jointly and meet the new agreement that broadband access requires, as PPPoE (PPP over Ethernet), PPPoA (PPP over ATM).Above-mentioned variety of protocol also belongs to the ppp protocol of broad sense, and the link that uses above-mentioned agreement to set up also can be referred to as ppp link.The present invention uses the notion of ppp protocol and ppp link on broader terms.

Data link is seldom perfect.Because a variety of causes (buffer memory overflows or the like for line noise for example, equipment failure), the bag on the link may be lost or be destroyed, and this situation is referred to as " loss of link ".Under many circumstances, need accurately to grasp Link State, when loss of link takes place, take measures to rebulid link.Said process is called as " detection of link and maintenance ".

Under the prior art, in order to detect and maintenance of PPP link, can use the Echo Request (echo request) of ICMP (Internet control Message Protocol, Internet Control Message Protocol) or the LCP Echo Request (LCP echo request) of ppp protocol itself.Be that every certain interval of time just sends described Echo Request to server, and detect response.If do not receive response after sending the several times request, just can think that ppp link loses.

Described ICMP is used for fault processing and transmitting control information on Internet.One of its function is to get in touch with main frame, looks at whether operate as normal of main frame by sending " echo request " (Echo Request) packets of information.Prevailing ping utility has just used this function.

In the TPC/IP protocol stack, the priority ratio of application program that is used for processing IC MP Echo Request is higher, and therefore, this just causes server to be vulnerable to DOS (Deny of Service, denial of service) attacking.That is to say that if there is a large amount of ICMP Echo Request to arrive, server is busy with handling these requests, and other service can't be provided.

Therefore, provide the Virtual network operator of network connection service under attack, just refuse response IC MP Echo Request request for fear of server.So it is insecure utilizing ICMP Echo Request to safeguard and detect ppp link in client.

Owing to similar reason, utilize the LCP Echo Request of PPP self to safeguard and to detect ppp link unreliable too.

Summary of the invention

At above-mentioned defective, the technical problem that the present invention solves is, provide a kind of and detect and the method for maintenance of PPP link, this method can be owing to Virtual network operator is refused response IC MP Echo Request or LCP Echo Request and can't be detected the link connection status.

The method of detection provided by the invention and maintenance point end-to-end protocol (EEP) ppp link comprises:

11) client is sent the DNS request by the PPP interface to the opposite end;

12) judge whether to receive the opposite end to described DNS request responding; If judge that then ppp link is working properly; If not, judge that then ppp link loses, start the process that reconnects.

Preferably, after the step 11), wait for the some time, enter step 12) again.

Preferably, before the described step 11), detect the PPP interface and whether start,, then detect once more if do not start; If starting, the PPP interface then enters next step.

Preferably, if the testing result PPP interface whether described detection PPP interface starts starts, then detect the PPP interface and whether receive end data; If not, then enter step 11); If then detect the PPP interface again and whether start.

Preferably, pre-determined number M is set before the described step 11); Judge in the described step 12) that further the number of times of this kind situation appears in judgement continuously when not receiving the opposite end to described DNS request responding, if surpass M time, judge that ppp link loses, startup reconnects process; If surpass M time, then will describedly not receive and return step 11) after number of times that the opposite end responds adds 1, carry out DNS once more and ask; Described counting is receiving the DNS request response back zero clearing of opposite end.

Preferably, described carry out DNS request once more before, wait for short stand-by period.

Whether preferably, described judgement PPP interface does not start, or judges that the PPP interface starts when still receiving end data, waits for a long period, detect the PPP interface more again and start.

Preferably, after described one long period of wait, before whether detection PPP interface starts, will not receive the opposite end DNS request response counting zero clearing of the number of times of appearance continuously.

Preferably, judge ppp link in the described step 12) just often, then wait for a long period after, repeat above-mentioned ppp link again and detect and safeguard.

The DNS service that the present invention utilizes each network operation commercial city to provide realizes detection and maintenance to ppp link, compares with maintenance with the detection that prior art adopts Echo Request to carry out Lian Lu, and method provided by the invention has following advantages:

1, reliability height.The DNS that method provided by the invention is based upon operator must be provided serves on the basis, because operator can not close the DNS service, therefore, this kind mode is applicable to various ppp links.Use Echo Request then may close this function and can't carry out link detecting and maintenance owing to operator.

2, can avoid by malicious exploitation.Because DNS is a common service request, does not have high priority, therefore, can be used for attack server by the malice user.

3, need not to increase any expense.DNS request and service are the service requests that has had in the network, therefore, use DNS request detection and maintenance of PPP link not to need the increase expense.

Description of drawings

Fig. 1 is the flow chart of first embodiment of the invention.

Embodiment

The implication of DNS (Domain Name System) is the domain name supervising system, also can refer to domain name resolution server, and its effect provides the domain name mapping service.So-called domain name mapping service is that domain name is converted into the IP address that network can be discerned.For example: during online, input domain name www.sohu.com can be converted into IP address 61.135.132.6 automatically by DNS.The reason of using the domain name mapping service is to remember name because people are easier, as www.sohu.com, rather than IP address 61.135.132.6.Each provides the Virtual network operator of network insertion service all can provide the domain name analysis service by domain name resolution server, can abbreviate the DNS service as.

Because each Virtual network operator all can provide DNS service, can detect in the following way and maintenance of PPP link: every certain interval of time sends DNS and asks to dns server, and detect response.All the time do not receive response if send the several times request, judge that then ppp link loses.

Please, be the flow chart of first embodiment of the invention referring to Fig. 1.

Step S100, beginning.

In this step, comprise stand-by period t is set that wherein the time value of high latency is T1; Short latency value is T2.At first stand-by period t is set to high latency T1.

Described stand-by period t is to use blanking time of DNS request detection and maintenance link.When link condition just often, this blanking time can be longer, can use high latency T1; If link condition is unusual, then should shorten the time of DNS request, so that in time detect and maintenance link, at this moment use short stand-by period T2.

Step S101 is with counter zero setting.

Described counter is used to measure and sends the number of times that link detecting is carried out in the DNS request, before judging at first with this counter zero setting.

Step S102 waits for the stand-by period t that is provided with.

This section period t is the blanking time of carrying out link detecting and maintenance.

Step S103 judges whether the PPP interface starts; If then enter step S104; If not, then enter step S109.

The implication that described PPP interface starts is meant that this network interface is ready to, and can be used for receiving and sending data.

If the user is not activated the PPP interface, show that ppp link is not used, do not carry out necessity that ppp link detects and safeguards this moment.If the PPP interface starts, illustrating needs to use ppp link, therefore, is necessary to carry out subsequent step, carries out ppp link and detects and maintenance.

Step S104 judges whether the PPP interface receives end data; If then enter step S109; If not, then enter step S105.

If the PPP interface receives end data, illustrate that then ppp link is working properly, need not to carry out ppp link and detect.Otherwise the possibility that then exists ppp link to lose need be carried out ppp link and be detected.

Step S105 sends DNS request and wait-for-response.

Described DNS request, be exactly that client sends domain name by described PPP interface to the dns server of the Virtual network operator that the network insertion service is provided, dns server by Virtual network operator is asked according to the DNS that sends, produce corresponding IP address, and in response with this IP address, return client, when client PPP interface is received described response, illustrate that then ppp link is working properly.Because this DNS request and response mechanism are that each network operation commercial city must provide, and therefore, can effectively check the situation of link with this method.Simultaneously, described DNS request is common service request, does not have high priority, can be used for attack server by malicious user.

Be used to carry out the DNS request that ppp link detects and comprise some well-known domain names, to guarantee the validity of DNS request.

Step S106 judges whether the PPP interface receives the opposite end to described DNS request responding; If then enter step S109; If not, then enter step S107.

If the PPP interface receives the DNS response, promptly the IP address after the domain name mapping illustrates that then ppp link is working properly; Otherwise, illustrate that link work is undesired.

Step S107, counter adds 1, and the value of stand-by period t is set to short stand-by period T2.

Carry out link detecting the possibility of result that DNS request obtains and incorrect, this be owing to may be owing to dns server busy or other reason, and dns server is not in time responded, if make the detection conclusion, then may make mistakes according to situation this time.For avoiding this kind situation, private counter is set, the DNS request is not obtained the situation counting of response.

Because the situation that the DNS request does not obtain normal response occurs, therefore, ppp link might go wrong, and is necessary described stand-by period t is made as short stand-by period T2, to carry out more frequent DNS link detecting, so that in time find the situation of loss of link.

Step S108 judges that whether counter is greater than certain predetermined value M.If then enter step S110; If not, then return step S102.

Described predetermined value M is the threshold value of presetting, and when the DNS request that surpasses M time does not all obtain response, judges that then ppp link disconnects, and should enter correlation step and handle.Do not surpass M time as yet if carry out the number of times of DNS request, then should continue to adopt the DNS request mode to detect.

Step S109, stand-by period t are set to described high latency T1, and enter step S101.

Because the PPP interface do not start, perhaps information that receives recently or the detection of carrying out show that ppp link is working properly, then there is no need frequently to carry out ppp link and detect, therefore, can be set to described high latency the stand-by period after, return step S101.Restart the ppp link testing process of a new round.

Step S110 judges that ppp link disconnects, and starts to reconnect process or carry out other processing.

Owing to passed through the detection of several times, show that all the DNS service request of client does not obtain response, therefore, can judge that ppp link loses, need to start the process that reconnect, this process is used to rebulid the PPP link, thereby realizes the maintenance to ppp link.Certainly, also can send the warning message that ppp link loses or carry out other relevant treatment simultaneously.

The above only is a preferred implementation of the present invention; should be pointed out that for those skilled in the art, under the prerequisite that does not break away from the principle of the invention; can also make some improvements and modifications, these improvements and modifications also should be considered as protection scope of the present invention.

Claims (9)

1, the method for a kind of detection and maintenance point end-to-end protocol (EEP) ppp link is characterized in that, comprising:

11) client is sent the DNS request by the PPP interface to the opposite end;

12) judge whether to receive the opposite end to described DNS request responding; If judge that then ppp link is working properly; If not, judge that then ppp link loses, start the process that reconnects.

2, method according to claim 1 is characterized in that, after the step 11), waits for the some time, enters step 12) again.

Whether 3, method according to claim 2 is characterized in that, before the described step 11), detect the PPP interface and start, and if not, then detects once more; If then enter next step.

Whether 4, method according to claim 3 is characterized in that, if the testing result PPP interface whether described detection PPP interface starts starts, then detect the PPP interface and receive end data, if not, then enters step 11); If then detect the PPP interface again and whether start.

5, method according to claim 4 is characterized in that, pre-determined number M is set before the described step 11); Judge in the described step 12) that further the number of times of this kind situation appears in judgement continuously when not receiving the opposite end to described DNS request responding, if surpass M time, judge that ppp link loses, startup reconnects process; If surpass M time, then will describedly not receive and return step 11) after number of times that the opposite end responds adds 1, carry out DNS once more and ask; Described counting is receiving the DNS request response back zero clearing of opposite end.

6, method according to claim 5 is characterized in that, described carry out DNS request once more before, wait for short stand-by period.

Whether 7, method according to claim 6 is characterized in that, described judgement PPP interface does not start, or judges that the PPP interface starts when still receiving end data, waits for a long period, detect the PPP interface more again and start.

8, method according to claim 7 is characterized in that, after described one long period of wait, before whether detection PPP interface starts, will not receive the opposite end DNS request response counting zero clearing of the number of times of appearance continuously.

9, according to the described method of claim 1 to 8, it is characterized in that, judge ppp link in the described step 12) just often, then wait for a long period after, repeat above-mentioned ppp link again and detect and safeguard.