CN109379301A

CN109379301A - A method of communication path MTU is detected using CFM

Info

Publication number: CN109379301A
Application number: CN201811558184.8A
Authority: CN
Inventors: 张林华
Original assignee: Anhui Province Postal Communication Electricity Ltd Co
Current assignee: Anhui Province Postal Communication Electricity Ltd Co
Priority date: 2018-12-19
Filing date: 2018-12-19
Publication date: 2019-02-22

Abstract

A method of communication path MTU being detected using CFM, the technical issues of frament reassembling in network communication causes service disconnection or performance to decline can be solved.Include: S100, establish a CFM session end to end；The minimum length of Data TLV field and the detection parameters including maximum length of the LB of S200, order setting CFM simultaneously start LB path mtu detection function；Data TLV field length in the LBM request message of S300, LB does dichotomy according to the minimum length and maximum length of setting, on the basis of whether having successfully received LBR back message；S400, LB detection is repeated, maximum Data TLV field length when LBR back message can be had successfully received until finding；S500, the maximum Data TLV field length that can lead to according to LB, adjust the MTU of transmitting terminal.Compared with the LB function of existing CFM, newly-increased LB path mtu detection function can effectively detect the minimum MTU in entire communication path, so that transmitting terminal can choose suitable MTU to send data packet, avoid message and abandon in communication path or fragment.

Description

A method of communication path MTU is detected using CFM

Technical field

The present invention relates to network communication technology fields, and in particular to a method of communication path MTU is detected using CFM.

Background technique

With operation of more and more type business on Metropolitan Area Network (MAN) and wide area network, to the fault detection of carrier class network, Higher requirements are also raised for management etc., and operator may require that the switching equipment that device manufacturer provides, optical network device are necessary It supports OAM(Operation Administration Maintenance) to be also capable of providing the requirement of carrier class to guarantee Ethernet, including can degrade to some business and unsuccessfully etc. Network Abnormal mistake or abnormal problem are able to carry out detection in time, the function of restoring and manage.The connection of IEEE 802.1ag Fault management (CFM-Connectivity Fault Management) is just to provide the basic agreement of these OAM abilities.

CFM message is two layers of ether packet, and EtherType number is 0x8902.On the forwarding chip of receiving end, when being resolved to The EtherType of one message is 0x8902, then the message will carry out the process flow of CFM message.Common CFM PDU has following 3 It is a:

Detection of connectivity message (CCM, Connectivity Check Message): most important one in CFM message Message, the test side periodicity sending CMM message connectivity for detecting link；

Loopback (Loopback): detection port sends loopback information, is responded by opposite end, transmission similar to ping and returns It answers, including request message LBM and back message LBR, while LB detection can data with Data TLV field, as LBM message Load.

Link trace (Linktrace): link trace is initiated in detection port, is responded by opposite end, is similar to tracert order Transmission and response, including LTM and LTR.

Maximum transmission unit (Maximum Transmission Unit, MTU) refers on a kind of a certain layer of communication protocol The maximum data packet size that face can pass through (as unit of byte).This parameter of maximum transmission unit usually has with communication interface It closes (network interface card, serial ports etc.).By taking Ethernet transmits IPv4 message as an example.The length that MTU is indicated includes the length in the packet header IP, If the length for the data message that IP layers or more of protocol layer is sent has been more than MTU, the IP layer of sender will be to datagram Text carries out fragment, recombinates in the IP layer of recipient to the fragment received.

In network communication, need to avoid as far as possible that fragment and recombination occurs because frament reassembling on network performance influence compared with Greatly.Even when transmitting terminal does not support fragment or recombination, message will be simply discarded, and directly result in service disconnection.Therefore Data packet selects suitable MTU size necessary to communication performance is improved when sending.As shown in Figure 1, the communication of PC1 to PC2 R1, R2, R3, R4 are contained among path, and wherein the path mtu of R2 to R3 is 1000 bytes, remaining path mtu is all 1518 Byte will necessarily lead to PC1 to PC2 in the outlet discarding of R2 or fragment then PC1 issues the message of 1000 bytes or more Service disconnection or performance decline.

Summary of the invention

A kind of method using CFM detection communication path MTU proposed by the present invention, can solve the fragment weight in network communication The technical issues of group causes service disconnection or performance to decline.

To achieve the above object, the invention adopts the following technical scheme:

A method of communication path MTU is detected using CFM, comprising:

Establish a CFM session end to end；

The minimum length of the Data TLV field of the LB of order setting CFM: len_min and maximum length: including len_max Detection parameters and start LB path mtu detection function；

The TLV field length section Data of LB be array [len_min, len_max], determine array [len_min, Len_max] section middle position K, and Data TLV field length using array [k] as LB carries out LB detection；

If having successfully received LBM, len_min=k+1, len_max=len_max are reset, compares len_max and len_ Min size, if len_max >=len_min, then again with the middle position member in the section array [len_min, len_max] Plain array [k] carries out LB detection, and otherwise LB detection terminates, and feeds back array [k] value；

If not receiving LBM, len_min=len_min, len_max=k-1 are reset, compares len_max and len_ Min size, if len_max >=len_min, then again with the middle position member in the section array [len_min, len_max] Plain array [k] carries out LB detection, and otherwise LB detection terminates, and feedback LB detection is abnormal；

Above-mentioned two step executes and judges repeatedly, until LB path mtu detection function test feedback terminates；

According to final Data TLV field length, transmitting terminal selects suitable MTU to send data packet.

As shown from the above technical solution, compared with the LB function of existing CFM, newly-increased LB path mtu detection function can be with Effectively detect the minimum MTU in entire communication path, so that transmitting terminal can choose suitable MTU to send data packet, Message is avoided to abandon in communication path or fragment.

Detailed description of the invention

Fig. 1 is the introduction of usage scenario in the present invention；

Fig. 2 is method and step schematic diagram of the invention；

Fig. 3 is the method and process that CFM detects communication path MTU in the present invention.

Specific embodiment

In order to make the object, technical scheme and advantages of the embodiment of the invention clearer, below in conjunction with the embodiment of the present invention In attached drawing, technical scheme in the embodiment of the invention is clearly and completely described, it is clear that described embodiment is A part of the embodiment of the present invention, instead of all the embodiments.

As shown in Fig. 2, utilizing the method for CFM detection communication path MTU described in the present embodiment, comprising:

S100, a CFM session end to end is established；

The minimum length and the detection parameters including maximum length of the Data TLV field of the LB of S200, order setting CFM And start LB path mtu detection function；

Minimum length and maximum length of the Data TLV field length according to setting in the LBM request message of S300, LB Dichotomy is done, on the basis of whether having successfully received LBR back message；

S400, LB detection is repeated, maximum Data TLV word when LBR back message can be had successfully received until finding Segment length；

S500, the maximum Data TLV field length that can lead to according to LB, adjust the MTU of transmitting terminal.

Knot illustrates as shown in Figure 3 below, and Topology Discovery process includes: in the embodiment of the present invention

Open CFM session end to end；

The TLV field section Data of the LB of order setting CFM is array [len_min, len_max] and starts the path LB MTU detection function；

It takes array [len_min, len_max] neutral element array [k] as Data TLV field length, carries out LB survey Examination；

If receive LBM response, reset len_min=k+1, len_max=len_max, at the same compare len_max and Len_min size, if len_max >=len_min, then again with the interposition in the section array [len_min, len_max] It sets element array [k] and carries out LB detection, otherwise LB detection terminates, and feeds back array [k] value；

If do not receive LBM response, reset len_min=len_min, len_max=k-1, compare len_max and Len_min size, if len_max >=len_min, then again with the interposition in the section array [len_min, len_max] It sets element array [k] and carries out LB detection, otherwise LB detection terminates, and feedback LB detection is abnormal；

Above-mentioned two step executes and judges repeatedly, until LB path mtu detection function test feedback terminates.

Here is present example concrete application case:

CFM pattern configurations:

Cfm loopback min_size x max_sizte y: under some CFM example of // equipment, the Data of LB detection TLV field minimum length is x, and maximum length y, default situations min_size and max_size size is all 0；

If being configured with the min_size and max_size of loopback under a CFM example of equipment, then just defaulting LB path mtu detection function is opened, otherwise, the numerical value of min_size and max_size are just defaulted as 0, do not open the path LB MTU detection function is practical only to detect once.

To sum up, compared with the LB function of existing CFM, newly-increased LB path mtu detection function can have the embodiment of the present invention The minimum MTU of effect detected in entire communication path is kept away so that transmitting terminal can choose suitable MTU to send data packet Exempt from message to abandon in communication path or fragment.

The above embodiments are merely illustrative of the technical solutions of the present invention, rather than its limitations；Although with reference to the foregoing embodiments Invention is explained in detail, those skilled in the art should understand that: it still can be to aforementioned each implementation Technical solution documented by example is modified or equivalent replacement of some of the technical features；And these modification or Replacement, the spirit and scope for technical solution of various embodiments of the present invention that it does not separate the essence of the corresponding technical solution.

Claims

1. a kind of method using CFM detection communication path MTU, which is characterized in that

The following steps are included:

S100, a CFM session end to end is established；

The minimum length and detection parameters and starting including maximum length of the DataTLV field of the LB of S200, order setting CFM LB path mtu detection function；

DataTLV field length in the LBM request message of S300, LB does two points according to the minimum length and maximum length of setting Method, on the basis of whether having successfully received LBR back message；

S400, LB detection is repeated, maximum Data TLV field when can have successfully received LBR back message until finding is long Degree；

S500, the maximum DataTLV field length that can lead to according to LB, adjust the MTU of transmitting terminal.

2. the method according to claim 1 using CFM detection communication path MTU, it is characterised in that: the step S300 It specifically includes:

If the DataTLV field length section of LB is array [len_min, len_max], array [len_min, len_ are determined Max] section middle position K, and using array [k] as the DataTLV field length of LB carry out LB detection；

If having successfully received LBM, len_min=k+1, len_max=len_max are reset, compares len_max and len_min is big It is small, if len_max >=len_min, then again with the middle position element in the section array [len_min, len_max] Array [k] carries out LB detection, and otherwise LB detection terminates, and feeds back array [k] value；

If not receiving LBM, len_min=len_min, len_max=k-1 are reset, compares len_max and len_min is big It is small, if len_max >=len_min, then again with the middle position element in the section array [len_min, len_max] Array [k] carries out LB detection, and otherwise LB detection terminates, and feedback LB detection is abnormal.