CN100459576C - Method for detecting maximal transmission unit of path - Google Patents
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Abstract
The invention relates to a method for detecting the maximum transmission unit of path, which is characterized in that: each middle node of node chain from the force source node to the target node, should process the data report of maximum transmission unit of the detecting path sent from the source node to the target node; when the middle node receives the data report, to display the maximum transmission unit information in said data report; and when the target node receives the data report, sending the maximum transmission unit information to the source node; and the source node, based on received information, confirms the path maximum transmission unit of the chain from it to the target node. The invention can quickly and accurately confirm PMTU, to confirm the best throughout of network, and avoid loss and retransmission, to improve the network safety.
Description
Technical field
The present invention relates to the network communications technology field, be specifically related to a kind of method of detecting maximal transmission unit of path.
Background technology
Fast development along with Internet, IPv4 (Internet Protocol Version 4, network protocol version 4) the deficient problem in address is serious day by day, so IPv6 (Internet Protocol Version 6, network protocol version six) more and more causes people's attention, thereby become new focus.
IPv6 is the second generation standard agreement of network layer protocol, is also referred to as IPng (IP Next Generation, the IP next generation), and it is a cover standard of IETF (Internet engineering duty group) design, is the upgraded version of IPv4.The length of IP address is upgraded to 128 from 32 among the IPv6, efficiently solves the problem of IPv4 address scarcity.
IPv6 is except providing huge address space, also aspect a lot of, improve, wherein one is improved to: for improving the data forwarding efficient of router, IPv6 does not support the segment processing of intermediate node to the data message, the segmentation of big data message can only be carried out at source node, be that source node passes through PMTU (the Path Maximum Transmission Unit among the RFC1981, PMTU) discovery mechanism obtains the PMTU value of source node to destination node, source node utilizes this PMTU value to determine the data message length of its transmission, thereby, avoid intermediate node because data message length abandons the phenomenon of data message above its MTU value, improved data forwarding efficient.
At present, the realization principle of PMTU discovery mechanism is: source node with the MTU value of own outbound as the PMTU value, and send datagram to destination node according to the PMTU value, if intermediate router is when transmitting this data message, the length of finding this data message is during greater than the MTU value of its outgoing interface link, this intermediate router returns an ICMP Packet Too Big (Internet Control MessageProtocol to source node, the packet of Internet Control Message Protocol is oversize) error message, have the MTU value of this intermediate router outbound in this error message.After source node received this error message, modification PMTU value was the MTU value in the error message, and data message length is reduced to amended PMTU value, resend data message, received data message up to destination node.
Pass through said process, source node has been determined the PMTU value of the maximum data message that can transmit between itself and this destination node, when source node needs when this destination node sends datagram again, just uses this PMTU value, so that effectively utilize Internet resources, obtain best throughput.
Implementation method below in conjunction with 1 pair of PMTU discovery mechanism of accompanying drawing describes.
Among Fig. 1, set source node and destination node and be the PC terminal, be provided with 3 routers between source PC and the purpose PC, be router one, router two, router three, and the MTU value of source PC is 1500 bytes, the MTU value of router one outgoing interface link is 1500 bytes, and the MTU value of router two outgoing interface link is 1350 bytes, and the MTU value of router three outgoing interface link is 1400 bytes.
Source PC with oneself MTU value 1500 bytes as the PMTU value, sending length to purpose PC is the data message of 1500 bytes, when this data message is transmitted at the arrival router two, because router two is found MTU value 1350 bytes of length 1500 bytes of this data message greater than its outgoing interface link, so, router two is beamed back an ICMP Packet Too big error message to source PC, carries MTU value 1350 bytes of router two in this error message.
After source PC receives this ICMP Packet Too big error message, revise the PMTU value and be MTU value 1350 bytes in the error message, data message length is reduced into 1350 bytes, and resend data message to purpose PC once more, because the data message length of this moment is 1350 bytes, the MTU value of each router in the middle of being not more than, therefore, this data message can correctly arrive purpose PC.
After this, source PC needs when purpose PC sends datagram again, all with 1350 bytes as the PMTU value.
When the MTU value of router between source PC and the purpose PC during for the situation of successively decreasing, then source PC needs repeated multiple times to send datagram can to obtain correct PMTU value, and detailed process as shown in Figure 2.
Among Fig. 2, set source node and destination node and be the PC terminal, be provided with 3 routers between source PC and the purpose PC, be router one, router two, router three, and the MTU value of source PC is 1500 bytes, the MTU value of router one outgoing interface link is 1500 bytes, and the MTU value of router two outgoing interface link is 1400 bytes, and the MTU value of router three outgoing interface link is 1350 bytes.
Source PC with oneself MTU value 1500 bytes as the PMTU value, sending length to purpose PC is the data message of 1500 bytes, when this data message is transmitted at the arrival router two, because router two is found MTU value 1400 bytes of length 1500 bytes of this data message greater than its outgoing interface link, so, router two is beamed back an ICMP Packet Too big error message to source PC, carries MTU value 1400 bytes of router two in this error message.
After source PC receives this ICMP Packet Too big error message, revise the PMTU value and be MTU value 1400 bytes in the error message, data message length is reduced into 1400 bytes, and resend data message to purpose PC once more, when this data message is transmitted at the arrival router three, because router three is found MTU value 1350 bytes of length 1400 bytes of this data message greater than its outgoing interface link, so, router three is beamed back an ICMP Packet Too big error message to source PC, carries MTU value 1350 bytes of router three in this error message.
After source PC receives this ICMP Packet Too big error message, revise the PMTU value once more and be MTU value 1350 bytes in the error message, data message length is reduced into 1350 bytes, and resend data message to purpose PC for the third time, because this moment, this data message length was 1350 bytes, the MTU value of each router in the middle of being not more than, therefore, this data message can correctly arrive purpose PC.
After this, source PC needs when purpose PC transmits messages literary composition again, all with 1350 bytes as the PMTU value.
From top description as can be seen, at present, mainly there are following three problems in the implementation method of PMTU discovery mechanism:
Problem one, when the length of data message during greater than the MTU value of router outgoing interface link, router can abandon the data message of reality, thereby influences the quality of media streams such as real-time voice, video.These media streams are owing to relating to real-time decoding, so to the restriction that strictness is arranged the time of advent of message, packet loss and re-transmission all may have certain influence to the effect of final Media Stream.
Problem two, safety issue.When the network equipment needs self to generate message and sends, be unusual consumption network device handler resource.Malicious user is by sending the big message of MTU of a large amount of ratio network equipments, and, find that network equipment reply message is big, when requiring to reduce message that message size resends, malicious user can be taked not reduce message, repeat to send big message, and attack this network equipment together in conjunction with other frauds, make the network equipment have to handle a large amount of this ICMP response messages, thereby, a large amount of consumption network device resources influence the network equipment and transmit work normally.
Problem three, when there is the situation of successively decreasing in the MTU value of each router between source PC and the purpose PC or part router, present PMTU discovery mechanism needs source node repeatedly to send datagram repeatedly just can obtain correct PMTU value, makes the detection efficient of PMTU discovery mechanism low.
Summary of the invention
The objective of the invention is to, a kind of method of detecting maximal transmission unit of path is provided, make the source node can be after sending data message, accurately know the PMTU of link between itself and the destination node, to realize improving detecting maximal transmission unit of path efficient, improve internet security, improve the real-time multimedia effect, improve the purpose that IPv6 surveys PMTU mechanism.
For achieving the above object, the method for a kind of detecting maximal transmission unit of path provided by the invention comprises:
A, pressure source node all need source node is handled to the data message of the detecting maximal transmission unit of path of destination node transmission to each intermediate node in the destination node link;
After b, described each intermediate node receive described data message, all with the MTU message reflection of its corresponding transmission path in described data message;
After c, described destination node received described data message, the MTU information that this data message is carried was sent to described source node;
D, described source node determine the PMTU of itself and destination node link according to the MTU information of its reception.
The data message of detecting maximal transmission unit of path is among the described step a: the data message that is provided with the IPv6 hop-by-hop options header.
Option data is in the described IPv6 hop-by-hop options header: the MTU initial value, and the preceding dibit position of the high position of the option type of described IPv6 hop-by-hop options header is: 00, and the 3rd high-order bit is 1.
Described MTU initial value is: source node sends the MTU on the outgoing interface link of this message to destination node.
Described step a specifically comprises:
Source node is in that determine need be when destination node sends datagram and need to determine PMTU between detection source node and this destination node, judges the described length that needs the data message that sends and the length sum of IPv6 hop-by-hop options header that need increase and the size of predetermined bite;
If described sum surpasses predetermined bite, according to predetermined bite this data message is carried out burst and handle, and in first fragment data message, the IPv6 hop-by-hop options header is set, and send;
If described sum is no more than predetermined bite, the IPv6 hop-by-hop options header then directly is set in this data message, and sends.
Described predetermined bite is: 1280 bytes.
Source node need to determine the step of the PMTU between detection source node and this destination node specifically to comprise among the described step a:
Source node need to determine the PMTU between detection source node and this destination node for the first time when described destination node sends datagram; Or
Source node does not receive this source node that described destination node sends and the MTU information between the destination node and source node need be when described destination node sends datagram, and need to determine the PMTU between detection source node and this destination node; Or
Predetermined time interval is set;
After at interval overtime at the fixed time, source node need be when described destination node sends datagram, and need to determine the PMTU between detection source node and this destination node.
Described step b specifically comprises:
Source node is determined the outgoing interface link of data message correspondence of detecting maximal transmission unit of path of its reception and the MTU of this outgoing interface link to each intermediate node in the destination node link;
Described each intermediate node is judged the size of the MTU of carrying in the MTU of its outgoing interface link and the data message;
If the MTU of outgoing interface link is not less than the MTU of carrying in the data message, intermediate node is not revised the MTU of carrying in the IPv6 hop-by-hop options header of data message, and continues to send this data message;
If the MTU of outgoing interface link is less than the MTU of carrying in the data message, the MTU of carrying in the IPv6 hop-by-hop options header of intermediate node with data message is revised as the MTU of its outgoing interface link, and continues to send this data message.
Described step c specifically comprises:
Destination node is with source address in the data message of the detecting maximal transmission unit of path of its reception and destination address exchange, preceding 3 bits of the high position of the option type of IPv6 hop-by-hop options header are revised as 000, and after deleting payload data in this data message, send.
Described method also comprises:
Source node carries out the data message transmission according to its PMTU of determining and described destination node.
Description by technique scheme as can be known, the present invention all is reflected in its MTU separately in the data message of surveying PMTU by each intermediate node that makes link between source node and the destination node, make the source node can be after sending data message, accurately know the PMTU of link between itself and the destination node, when having avoided the MTU value of each intermediate node from the source node to the destination node to taper off state, source node need repeatedly send datagram, can accurately know the phenomenon of the PMTU of link between itself and the destination node, make the present invention when determining PMTU fast and accurately, guaranteed the optimal throughput of network; The present invention is by making full use of the hop-by-hop options header among the IPv6, and each intermediate node compares the MTU in its MTU and the option data, makes method of the present invention be easy to realize; By the PMTU probe messages that the normal data message of using the transmission of source node actual needs is constructed, make the present invention realize that in normal data message transmission course PMTU surveys, and reduce the influence of PMTU detection process to the normal data message transmissions; Each intermediate node does not need to generate and send the ICMP response message in the network among the present invention, has effectively avoided the network attack of malicious user; The present invention has avoided each node dropping packets in the network and has retransmitted the phenomenon of message, makes to access effective assurance the time of advent of real-time multimedia message; Thereby realized improving detection PMTU efficient by technical scheme provided by the invention, improved internet security, improved the real-time multimedia effect, improved the purpose of the detection PMTU mechanism of IPv6.
Description of drawings
Fig. 1 is the method schematic diagram one of the detection PMTU of prior art;
Fig. 2 is the method schematic diagram two of the detection PMTU of prior art;
Fig. 3 is the message format schematic diagram of detection PMTU data message of the present invention;
Fig. 4 is the message format schematic diagram of the back message using of detection PMTU data message of the present invention;
Fig. 5 is the method schematic diagram of detection PMTU of the present invention.
Embodiment
If source node is only by sending a data message, just can obtain the minimum value of the MTU in each intermediate node between itself and the destination node, then can be under the least possible situation about sending datagram, determine PMTU in itself and the destination node link fast and accurately, thereby, can effectively improve the detection efficient of PMTU discovery mechanism.
Therefore, core of the present invention is: force source node all to need source node is handled to the data message of the detecting maximal transmission unit of path of destination node transmission to each intermediate node in the destination node link, after described each intermediate node receives described data message, all with its MTU message reflection in described data message, after described destination node receives described data message, the MTU information of this data message carrying is sent to described source node, and described source node is determined the PMTU of itself and destination node link according to the MTU information of its reception.
Based on core concept of the present invention technical scheme provided by the invention is further described below.
Source node, then needs to send a data message of surveying PMTU to this destination node if determine that also not carrying out PMTU for this destination node surveys when destination node sends normal data message.The data message of detection PMTU can make full use of the above-mentioned normal data message of source node actual needs transmission and construct.
The structure of the data message of detection PMTU as shown in Figure 3.
Add blackboard among Fig. 3 and be divided into IPv6 hop-by-hop options header (Hop-by-Hop Options Header) that the present invention proposes, that add in the normal data message front that source node need send.The preceding dibit of the high position of the option type (option-type) of IPv6 option head is 00, expression is skipped this option when this option of network equipment nonrecognition processing, continue to handle follow-up heading, like this, guaranteed that effectively this data message can normally be transmitted; The 3rd high-order bit is 1, and each intermediate node on the intermediate path of expression from the source node to the destination node can be changed option data.The present invention to other bit in the option type without limits, option type that can IPv6 option head as the present invention is set to 37, promptly binary zero 0100101.
When source node sends this normal data message, option data in the data message is the MTU initial value, the MTU initial value can be set to the first MTU value of jumping of link between source node and destination node, and promptly source node sends the MTU on the outgoing interface link of this data message to destination node.This surveys the payload data Data that carries in the data message of PMTU is the normal data content of message that source node really will send.
The data message that is provided with IPv6 option head becomes the data message of surveying PMTU.
The present invention need guarantee that the size of the IPv6 data message of this detection PMTU is no more than i.e. 1280 bytes of minimum MTU value of the IPv6 link of IPv6 agreement defined, entire I Pv6 message length is not more than 1280 and just can be dropped on link, each router can not produce ICMPtoo big message at this data message of surveying PMTU promptly, thereby, make the data message of this detection PMTU can normally arrive destination node.
If the length sum of the length of the data message that source node need send and IPv6 option head surpasses 1280 bytes, can be MTU with 1280 bytes by source node, carry out the processing of data message burst, will add above-mentioned IPv6 hop-by-hop options header before first data message behind the burst.This first data message becomes the data message of surveying PMTU.Behind the data message burst, the length of each fragment message should not surpass 1280 bytes.
After each intermediate node between source node and destination node in the link receives the data message of this detection PMTU, because this data message has the IPv6 hop-by-hop options header, so each intermediate node need be handled this data message.
Intermediate node to the concrete processing method of the data message of this detection PMTU is: determine the MTU value on the outgoing interface link of destination address correspondence of this data message, and the MTU value in this MTU value and the data message option data compared, if the MTU value on the intermediate node outgoing interface link is less than the MTU value in this data message option data, then at first the MTU value in the data message option data is replaced with the MTU value on this intermediate node outgoing interface link, then, the outgoing interface link according to this data message destination address correspondence sends this data message; If the MTU value on the intermediate node outgoing interface link is not less than the MTU value in this data message option data, then the MTU value in this data message option data is not replaced modification, direct outgoing interface link according to this data message destination address correspondence sends this data message and gets final product.
Each intermediate node between source node and destination node in the link is all handled according to above-mentioned description when receiving the data message of surveying PMTU, arrives destination node up to this data message of surveying PMTU.
When destination node receives the data message of surveying PMTU, option data in this data message hop-by-hop options header be this data message the minimum value of MTU of each intermediate node on the link of process, promptly the option data in the hop-by-hop options header is the PMTU value that source node arrives link between destination node.In the payload data Data of destination node in handling this data message, need to generate the back message using of surveying the PMTU data message, and send this back message using to source node.
The message structure of back message using as shown in Figure 4.The IPv6 hop-by-hop options header that adds the back message using that black part proposes for the present invention, that destination node sends among Fig. 4.
The method that destination node is constructed this back message using is: the source address and the destination address of the detection PMTU data message that destination node is received are changed mutually, and preceding 3 bits of the high position in the option type in the IPv6 hop-by-hop options header are set to 000, and the expression destination node cannot be changed this option data to each intermediate node on the path of source node.The present invention is set to 5 as the option type of back message using to the value of other bit of the option type of back message using without limits.Destination node sends this back message using to source node after removing the payload data Data that surveys in the PMTU data message.
Source node obtains the MTU value from the option data of the hop-by-hop options header of this back message using after receiving the back message using of surveying the PMTU data message, this MTU value is the PMTU value of source node in the destination node link.
Like this, source node according to this PMTU value when above-mentioned destination node sends datagram, just situation that factor is dropped according to the length of message surpasses the MTU of certain intermediate node can not appear.
Do not receive the back message using of the detection PMTU data message that this destination node returns when source node, and this source node in addition need be when data message that this destination node sends, the method that source node can adopt above-mentioned transmission to survey the PMTU data message continues to send datagram, thereby, source node can receive the back message using of the detection PMTU data message that a plurality of destination nodes return successively, like this, source node is at every turn when this destination node sends datagram, can be with the MTU value in the option data of the hop-by-hop options header of the back message using of the up-to-date detection PMTU data message that receives as the PMTU value of source node in the destination node link, then, send datagram to destination node according to this PMTU value.
Because the path between from the source node to the destination node may change, PMTU value on the path may be changed, therefore, the present invention can be provided with an ageing time to each destination address, and ageing time carried out timing, after ageing time was overtime, if source node needs when the destination address of correspondence sends datagram again, the method that need reuse the detection PMTU that describes in the foregoing description was obtained the PMTU value between source node and destination node again.The time that ageing time is picked up counting can receive the time of the back message using that destination node returns for source node, also can send time of PMTU probe messages etc. for source node.
Intermediate node among the present invention comprises: routing device, and as router etc.
Method below in conjunction with 5 couples of detection PMTU that provide of the present invention of accompanying drawing describes.
In Fig. 5, set source node and destination node and be the PC terminal, be provided with 3 routers between source PC and the purpose PC, be router one, router two, router three, and the MTU value of source PC is 1500 bytes, the MTU value of router one outgoing interface link is 1500 bytes, and the MTU value of router two outgoing interface link is 1400 bytes, and the MTU value of router three outgoing interface link is 1350 bytes.
Need be when purpose PC sends datagram at source PC, if source PC determines also not survey PMTU between itself and the purpose PC or though source PC sent the data message of surveying PMTU, though but the back message using or the source PC that also do not receive the data message of the detection PMTU that purpose PC returns surveyed and had obtained the PMTU value from back message using, but, ageing time is overtime, then source PC needs the data message of structural exploration PMTU, promptly at its data message head that need send the IPv6 hop-by-hop options header is set.
Certainly, when if the length sum of the length of the data message that source PC need send and IPv6 hop-by-hop options header is 1280 bytes above predetermined bite, also need to carry out burst and handle, all be no more than 1280 bytes with the length of each data message of guaranteeing between source PC and purpose PC, to transmit according to the data message that 1280 bytes send its needs.
The IPv6 hop-by-hop options header option type of surveying the data message of PMTU can be set to 37, and option data is MTU value 1500 bytes of source node.The destination address of this data message is the address of purpose PC, and source address is the address of source PC.Source PC sends the data message of this detection PMTU.
This data message is when arriving router one, because this data message has the IPv6 hop-by-hop options header, so, router one must be handled this data message, router one finds that MTU value 1500 bytes of its outgoing interface link are not less than length 1500 bytes of this data message option data, so directly the outgoing interface link according to this data message destination address correspondence sends this data message.
This data message is when arriving router two, because this data message has the IPv6 hop-by-hop options header, so, router two must be handled this data message, router two is found length 1500 bytes of MTU value 1400 bytes of its outgoing interface link less than this data message option data, so, earlier the MTU value 1500 in the data message option data is replaced with the MTU value 1400 on its outgoing interface link, then, according to the outgoing interface link of this data message destination address correspondence this data message is sent again.
This data message is when arriving router three, because this data message has the IPv6 hop-by-hop options header, so, router three must be handled this data message, router three is found length 1400 bytes of MTU value 1350 bytes of its outgoing interface link less than this data message option data, so, earlier MTU value 1400 bytes in the data message option data are replaced with MTU value 1350 bytes on its outgoing interface link, then, according to the outgoing interface link of this data message destination address correspondence this data message is sent again.
This data message is when arriving purpose PC, in the payload data of purpose PC in handling this data message, the source address and the destination address of this data message are changed mutually, option type is set to 5, and remove the payload data of surveying in the PMTU data message, generate the back message using of surveying the PMTU data message, and send this back message using.
This back message using transfers to source PC through router three, router two, router one, because the option type of back message using is set to 5, so the MTU value that router three, router two, router one all do not carry in the option data to this back message using is made amendment.
Source PC obtains MTU value 1350 bytes from the option data of this back message using, determine that the PMTU of itself and purpose PC is 1350 bytes, and after this, source PC needs when purpose PC sends datagram again, and all carries out the data message transmission according to these PMTU value 1350 bytes.
By foregoing description as can be known, source node among the present invention can be behind data message of transmission, accurately know the PMTU of link between itself and the destination node, when having avoided the MTU value of each intermediate node from the source node to the destination node to taper off state, source node need repeatedly send datagram, can accurately know the phenomenon of the PMTU of link between itself and the destination node, make the present invention when determining PMTU fast and accurately, guarantee the optimal throughput of network.
The present invention is by making full use of the hop-by-hop options header among the IPv6, and each intermediate node compares the MTU in its MTU and the option data, makes method of the present invention be easy to realize.
Each intermediate node does not need to generate and send the ICMP response message in the network of the present invention, has effectively avoided the network attack of malicious user.
The present invention has avoided each node dropping packets in the network and has retransmitted the phenomenon of message, makes to access effective assurance the time of advent of real-time multimedia message.
The present invention constructs the PMTU probe messages by the normal data message of using the transmission of source node actual needs, make the present invention realize that in normal data message transmission course PMTU surveys, and has reduced the influence of PMTU detection process to the normal data message transmissions.
From foregoing description as can be known, the present invention has improved detection PMTU efficient, has improved internet security, has improved the real-time multimedia effect, the perfect detection PMTU mechanism of IPv6.
Though described the present invention by embodiment, those of ordinary skills know, the present invention has many distortion and variation and do not break away from spirit of the present invention, and the claim of application documents of the present invention comprises these distortion and variation.
Claims (8)
1, a kind of method of detecting maximal transmission unit of path is characterized in that, comprising:
A, source node be in that determine need be when destination node sends datagram and need to determine PMTU between detection source node and this destination node, judges the described length that needs the data message that sends and the length sum of IPv6 hop-by-hop options header that need increase and the size of predetermined bite; Described predetermined bite is the minimum MTU value of IPv6 link;
If described sum surpasses predetermined bite, according to predetermined bite this data message is carried out burst and handle, and in first fragment data message, the IPv6 hop-by-hop options header is set, and send;
If described sum is no more than predetermined bite, the IPv6 hop-by-hop options header then directly is set in this data message, and sends;
After b, described each intermediate node receive described data message, all with the MTU message reflection of its corresponding transmission path in described data message;
After c, described destination node received described data message, the MTU information that this data message is carried was sent to described source node;
D, described source node determine the PMTU of itself and destination node link according to the MTU information of its reception.
2, the method for a kind of detecting maximal transmission unit of path as claimed in claim 1, it is characterized in that, option data is in the described IPv6 hop-by-hop options header: the MTU initial value, and the preceding dibit position of the high position of the option type of described IPv6 hop-by-hop options header is: 00, and the 3rd high-order bit is 1.
3, the method for a kind of detecting maximal transmission unit of path as claimed in claim 2 is characterized in that, described MTU initial value is: source node sends the MTU on the outgoing interface link of this message to destination node.
4, the method for a kind of detecting maximal transmission unit of path as claimed in claim 1 is characterized in that, described predetermined bite is: 1280 bytes.
5, the method for a kind of detecting maximal transmission unit of path as claimed in claim 1 is characterized in that, source node need to determine the step of the PMTU between detection source node and this destination node specifically to comprise among the described step a:
Source node need to determine the PMTU between detection source node and this destination node for the first time when described destination node sends datagram; Or
Source node does not receive this source node that described destination node sends and the MTU information between the destination node and source node need be when described destination node sends datagram, and need to determine the PMTU between detection source node and this destination node; Or
Predetermined time interval is set;
After at interval overtime at the fixed time, source node need be when described destination node sends datagram, and need to determine the PMTU between detection source node and this destination node.
6, as the method for the described a kind of detecting maximal transmission unit of path of arbitrary claim in the claim 1 to 5, it is characterized in that described step b specifically comprises:
Source node is determined the outgoing interface link of data message correspondence of detecting maximal transmission unit of path of its reception and the MTU of this outgoing interface link to each intermediate node in the destination node link;
Described each intermediate node is judged the size of the MTU of carrying in the MTU of its outgoing interface link and the data message;
If the MTU of outgoing interface link is not less than the MTU of carrying in the data message, intermediate node is not revised the MTU of carrying in the IPv6 hop-by-hop options header of data message, and continues to send this data message;
If the MTU of outgoing interface link is less than the MTU of carrying in the data message, the MTU of carrying in the IPv6 hop-by-hop options header of intermediate node with data message is revised as the MTU of its outgoing interface link, and continues to send this data message.
7, as the method for the described a kind of detecting maximal transmission unit of path of arbitrary claim in the claim 2 to 5, it is characterized in that described step c specifically comprises:
Destination node is with source address in the data message of the detecting maximal transmission unit of path of its reception and destination address exchange, preceding 3 bits of the high position of the option type of IPv6 hop-by-hop options header are revised as 000, and after deleting payload data in this data message, send.
8, as the method for the described a kind of detecting maximal transmission unit of path of arbitrary claim in the claim 1 to 5, it is characterized in that described method also comprises:
Source node carries out the data message transmission according to its PMTU of determining and described destination node.
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