CN1300985C

CN1300985C - Method for processing extra-long message in two-layer virtual special-purpose network

Info

Publication number: CN1300985C
Application number: CNB031091385A
Authority: CN
Inventors: 欧阳光
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2003-04-04
Filing date: 2003-04-04
Publication date: 2007-02-14
Anticipated expiration: 2023-04-04
Also published as: CN1536832A

Abstract

The present invention discloses a method for solving the maximum transmission unit byte number of a link in a two-layer virtual private network, which comprises that an ICMP protocol is added to a PE device, and the ICMP protocol can issue an error report for the network. When the length of a message sent by a user exceeds 1522 bytes, the ICMP protocol can automatically generate an error report of an unreachable destination, and sends the maximum byte number of the message which can be sent to a host computer of the user in a feedback mode, so that the user can resend a message with a proper length according to the feedback information. By using the method, the size of messages sent by the computer of the user can be limited, that messages the length of which exceeds 1522 bytes appear is prevented from headstream, and that the messages can not be discarded can be effectively ensured.

Description

In two-layer virtual private network, handle the overlength method of message

Invention field

The present invention relates generally to network transmission technology, particularly a kind of method that solves link maximum transmission unit byte number restricted problem in the two-layer virtual private network.

Background technology

In L2VPN (two-layer virtual private network), when user's message passes through the tunnel, it must be encapsulated in new link layer frame head and the tunnel bearing protocol layer, for example, must install two-layer MPLS tag head additional based on the tunnel of MPLS (multiprotocol label switching) agreement.If the link of the link of user side and tunnel side all is based upon on the Ethernet, ethernet user's message is after installing the tunnel protocol head additional like this, maximum frame length will be considerably beyond maximum frame length 1522 bytes of Ethernet protocol, but, handles two-layer protocol because can not carrying out burst to message, so under situation without any measure, the generally all serviced merchant's edge device of this overlength message (is meant the tunnel edge device herein, be designated hereinafter simply as PE equipment) or service provider's equipment (be meant the tunnel intermediate equipment herein, be designated hereinafter simply as P equipment) abandon.Below in conjunction with accompanying drawing this problem is elaborated.

Fig. 1 is a L2VPN typical case networking schematic diagram.As shown in Figure 1, local vlan (VLAN) 8 links to each other with the vlan 12 of far-end by the L2VPN tunnel, and the message that mails to vlan 12 like this from vlan 8 all needs to install tunnel bearing protocol head additional through PE1, just can send in the tunnel then and go.Because in this process, PE1 can not be what agreement of encapsulation inside perception user's the two layer message on earth generally, handles so L2VPN can not carry out burst.L2VPN agreement regulation: surpass MTU (byte number of the link maximum transmission unit) value in tunnel if user's message length adds the length of tunnel encapsulation head, PE equipment cannot be handled by burst, but simply it is abandoned.

But this processing exists very big defective, and in order more clearly to say something, we suppose that the tunnel is based upon on the mpls protocol.Fig. 2 is based on the L2VPN tunnel encapsulation message schematic diagram of mpls protocol.As shown in Figure 2, the original user message can increase the individual byte of 22 or 26 (having under the situation of Vlan tag) after installing the tunnel protocol head additional generally speaking, like this, the message length maximum that enters the MPLS tunnel can arrive the 1522+26=1548 byte, it has substantially exceeded the MTU value 1522 that Ethernet allows, because not allowing to carry out burst, the L2VPN agreement handles, so stipulate that according to Ethernet protocol in the past these overlength messages must be thrown away.

Above-mentioned defective is the significant problem that all L2VPN agreements all face.At this problem, some solutions have been proposed in the prior art.Wherein a solution is: no matter the qualification of Ethernet protocol, MTU value with equipment outlets all on the tunnel changes into more than 1548 bytes by force, present most of Ethernet interface chip all supports to send and receive the Ethernet message that surpasses 1522 bytes, so a lot of equipment are all supported this set, CISCO is that this message has also been got a name specially, is Biggiant message.But, the problem of this solution is: must allow all P equipment and PE equipment all support to receive and send the Ethernet message of this class overlength on the way, otherwise whichever intermediate node is not supported these agreements, all can unconditionally frame be thrown away or carry out mistakenly burst and handle.Under the complex network situation,, and may belong to different equipment vendors and provide because the P node in the middle of the tunnel may be a lot.Therefore, can not guarantee fully that the involved P equipment in L2VPN tunnel all supports this set.Also have a solution, that is, utilize jumbo frame (super large frame) tunneling that Ethernet this paper is encapsulated.This agreement is a kind of agreement of unofficial standard, and it can be supported in the longest message to 9022 bytes of transmission on the Ethernet, and it was the agreement of developing for G bit Ethernet specially originally, solved the MTU problem of oneself but L2VPN can use this agreement.But, this solution also exists and above-mentioned first kind of problem that solution is similar, promptly, must allow all P equipment and PE equipment all support jumbo frame tunneling on the way, otherwise, whichever intermediate node is not supported these agreements, all can unconditionally frame be thrown away or carry out mistakenly burst and handle.Under the complex network situation, the P node in the middle of the tunnel may be a lot, and may belong to different equipment vendors and provide.Therefore, can not guarantee fully that the involved P equipment in L2VPN tunnel, PE equipment and link all support this agreement.

In addition, as to a reference of the present invention, in relevant prior art a kind of processing overlength method of message is arranged, this method adopts ICMP (Internet Control Message Protocol) that the overlength message is controlled.Fig. 3 shows the schematic diagram of this overlength message processing method.As shown in Figure 3, when operation system of computer transmits file by router on network, the message that sends all can use forbids the burst function, promptly, DF in the IP head of message (forbidding the burst flag bit) sign is set, because the DF flag bit is an important symbol position in the known IP agreement, so no longer explanation.If router receives this type of message, and find that again this message length is bigger than interface mtu, because this message has clearly been specified inaccurate burst, so IP agreement regulation, this message must be dropped, and router will be responded to type=3 of source host, the icmp packet of code=4 type, and the MTU value of in this message, carrying interface, after main frame is received this message like this, MTU value that will active adjustment oneself is a value entrained in the icmp packet, and all messages of sending of this main frame all can be worth less than this later on.But this method of the prior art has only provided in the three-layer network APPLICATION IN TRANSMISSION, and is not given in such as the application in the double layer network transmission technology of L2VPN.

Summary of the invention

In order to solve the above-mentioned defective that exists in the prior art, the purpose of this invention is to provide a kind of method that can prevent the message length overlength the two-layer virtual private network from root.

To achieve these goals, the invention provides a kind of overlength method of message of handling in two-layer virtual private network, this method may further comprise the steps: 1) message control protocol of binding on PE equipment; 2) when the message that is sent to described PE equipment from transmitting terminal be that the message of the burst that is under an embargo and its length are when surpassing a predetermined length, the described message control protocol of described PE equipment utilization produces a feedback information automatically and it is returned to transmitting terminal, comprises the permission length of next message in this feedback information at least; 3) transmitting terminal is according to the permission length adjustment message length of the next message in the described feedback information New Development literary composition of delivering newspaper of laying equal stress on.

By utilizing method of the present invention on PE equipment, to bundle a message control protocol, and utilize this agreement that the length of message is controlled, just can limit the length of the message that subscriber computer sends, thereby on the source, prevent the message that surpasses 1522 bytes.Like this, no matter whether P equipment supports above-mentioned two kinds of agreements, can guarantee that message can not be dropped.

Description of drawings

Fig. 1 is a L2VPN typical case networking schematic diagram;

Fig. 2 is based on the L2VPN tunnel encapsulation message schematic diagram of mpls protocol;

Fig. 3 is the processing schematic diagram of the overlength message of DF set in the prior art;

Fig. 4 is according to handling overlength method of message schematic diagram in the described two-layer virtual private network of the embodiment of the invention;

Fig. 5 is the structural representation of the icmp packet in the embodiment of the invention.

Embodiment

Below with reference to Fig. 4 and Fig. 5 embodiments of the invention are elaborated.

In order to reduce router Fragmentation consuming time and to improve network efficiency, present mainstream operation system basically all can be with the DF set of message when network communication, and prepare to adjust by situation the MTU value of oneself at any time.The intent of the present invention is utilized these characteristics exactly, adds an ICMP (Internet Control Message Protocol) and come the MTU value of active adjustment main frame by utilizing this agreement to respond icmp packet on PE equipment, thereby reach the problem that solves L2VPN MTU value.To be elaborated to the specific embodiment of the present invention below.

At first, need on PE equipment, bundle an ICMP agreement.The ICMP agreement is existing three layer protocols, is not to be all in the L2VPN agreement, and its most basic function is to be network issue error reporting, for example feed back to automatically inaccessible icmp packet of purpose of user (Type=3, code=4).At present, nearly all router or three-tier switch are all supported this agreement.As for the detailed process of binding ICMP agreement, because it is known in the art, so repeat no more.

Then, as shown in Figure 4, when the original message that sends at PC entered the tunnel by PE equipment, according to the L2VPN agreement, PE equipment was necessary for it and installs the tunnel protocol head additional.After having installed the tunnel protocol head additional, PE equipment will compare the length that installs the message behind the head additional and the MTU value (maximum length 1522 bytes of Ethernet just) in tunnel, and judge the whether set of DF of message.If this message is the IP message of a DF set, and the MTU value that its length has surpassed the tunnel after installing the tunnel protocol head additional (promptly, 1522 bytes), then PE equipment will abandon this message and respond an icmp packet to PC, and the MTU value that carries out interface in this icmp packet is to feed back to PC.For example, be under the situation about being based upon on the mpls protocol in the tunnel, the MTU value in entrained tunnel can be 1500-26=1474 in the icmp packet.Note, in above-mentioned example, because ICMP agreement regulation must be responded the maximum length of three layers of payload,, could correctly indicate the MTU value in tunnel like this so need remove the length (26 byte) that two layers of frame head (18 byte)+two layers frame CRC check and (4 byte) are removed the tunnel protocol head more earlier.In addition, because the DF of the message in the main flow network service at present is set, so the step of above-mentioned judgement DF set also can be omitted.

Fig. 5 shows the structure of an icmp packet.The MTU value of message (being 1474 in this example) when as shown in Figure 5, in the ICMP of icmp packet frame frame head, having pointed out next time to send.After the icmp packet that receives the above-mentioned MTU of having value, the MTU value that user's PC only needs to reduce own corresponding network interface automatically according to the numerical value that is fed back in the icmp packet (1474) gets final product.Because the main frame of present any support ICP/IP protocol is all supported the ICMP agreement certainly, and the operating process of this agreement also is known, so no longer be described.Like this, even all later on user's messages can paranormal Ethernet MTU value after installing the tunnel protocol head additional.

The present invention utilizes the error reporting feedback function of ICMP agreement, make subscriber's main station initiatively reduce the MTU value of oneself, the defective that arrive to solve on the basis that need not update the equipment that MTU value among the L2VPN does not match and can not burst can guarantee effectively that message can not be dropped.This is very significant replenishing to the L2VPN agreement.

It should be noted though above explanation of the present invention is carried out with reference to its specific embodiment, it does not also mean that it is limitation of the present invention.Those of ordinary skill in the art should be understood that and can make various modifications and conversion to it on the basis of inventive concept.In a word, do not deviate from the various remodeling of spirit of the present invention all within the protection range of the appended claim of the present invention.

Claims

1. in two-layer virtual private network, handle the overlength method of message for one kind, may further comprise the steps:

1) on tunnel edge device PE, adds a message control protocol;

2) when the message that is sent to described PE equipment from transmitting terminal be that the message of the burst that is under an embargo and its length are when surpassing a predetermined length, the described message control protocol of described PE equipment utilization produces a feedback information automatically and it is returned to transmitting terminal, comprises the permission length of next message in this feedback information at least;

3) transmitting terminal is according to the permission length adjustment message length of the next message in the described feedback information New Development literary composition of delivering newspaper of laying equal stress on.

2. method according to claim 1 is characterized in that, described message control protocol is Internet Control Message Protocol ICMP.

3. method according to claim 1 is characterized in that, described predetermined length is the maximum frame length of Ethernet.

4. method according to claim 1 is characterized in that, described step 2) in also comprise and judge that whether described message length surpasses the step of described predetermined length.

5. method according to claim 1 is characterized in that, described step 2) in also comprise the step whether burst flag bit DF is set of forbidding in the IP head of judging described message.

6. method according to claim 1 is characterized in that, described step 2) in the permission length of next message be legal Ethernet message length, maximum is less than described predetermined length.

7. according to any described method in the claim 1 to 6, it is characterized in that, comprise further in the described step 3) that transmitting terminal is adjusted into message length the step of the permission length of the described message that is included in the described feedback information.