CN108111416B

CN108111416B - Method for directly identifying MPLS internal encapsulation message

Info

Publication number: CN108111416B
Application number: CN201711351954.7A
Authority: CN
Inventors: 方沛昱
Original assignee: Centec Networks Suzhou Co Ltd
Current assignee: Suzhou Centec Communications Co Ltd
Priority date: 2017-12-15
Filing date: 2017-12-15
Publication date: 2020-10-23
Anticipated expiration: 2037-12-15
Also published as: CN108111416A

Abstract

The invention discloses a method for directly identifying an MPLS internal encapsulation message, which is characterized by comprising the following steps: using the highest bit in the MPLS label field to indicate whether the current MPLS label is followed by an ACH header; and if the back of the MPLS label is an ACH (access control channel) header, identifying the message type carried by the inner layer through a ChannelType field in the ACH header. By adopting the technical scheme disclosed by the invention, for the network equipment which does not process the label at the bottom of the MPLS stack, the type of the internal bearer message can be accurately identified, and the internal layer message can be analyzed and the related deployment can be carried out without causing the occurrence of misguess.

Description

Method for directly identifying MPLS internal encapsulation message

Technical Field

The invention relates to a network communication method, in particular to a method for directly identifying an MPLS internal encapsulation message, belonging to the technical field of computer networks.

Background

MPLS (Multi-Protocol Label Switching) is a Protocol widely applied in a network due to short Label and strong expandability. But it has an important problem in itself that none of the fields in the MPLS label is used to indicate the type of its bearer packet. Meanwhile, in the application of MPLS, there may be a variety of situations after the bottom of stack label. For example, the bottom label of the stack may be followed by a control word, may be followed directly by an IP packet, may be an ethernet packet, or may have an Entropy label. As the demand for network applications increases, the problem also comes. For example, when a node needs to perform load balancing on traffic, a factor for load balancing needs to be calculated based on a field of a packet carried in MPLS, and at the same time, the node does not perform any processing on an MPLS label. But due to the inherent problems of MPLS, the node cannot correctly identify the type of the internal packet.

In view of the above problems, the prior art solutions include:

one, according to the top 4 bits behind the label at the bottom of the stack being 4/6/others, to distinguish the inner layers are ipv4, ipv6, ethernet encapsulation.

And secondly, processing the MPLS labels one by one, and accurately knowing the message encapsulation type carried by the label after the label at the bottom of the stack is processed.

However, both solutions still have certain disadvantages:

first, with the first scheme, if there is a control word behind the bottom label of the stack, a misprediction may occur. And for ethernet MAC addresses the highest 4 bits may also appear 4 or 6, resulting in a misguess.

Second, for the second scheme, it needs to process first and then identify, which is relatively complex. Meanwhile, for the passing message, assuming that only the node for exchanging the outermost MPLS label is needed, the label at the bottom of the stack is not processed, and thus the internal message cannot be identified.

As in the foregoing prior art, only after the bottom label is resolved, guessing is performed on the message carried thereafter. However, the guessing rule has a hole and cannot be accurately identified. Therefore, in actual use, it is necessary to plan in advance and make various restrictions to correctly identify the packet carried by the inner layer. For example, the control word is uniformly carried or not carried after the label at the bottom of the stack, the highest 4 bits of the inner MAC address cannot be 4 or 6, and so on, but the flexibility of the MPLS itself is reduced by the series of restrictions.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to indicate whether an ACH head is carried after a label at the bottom of a stack or not by adding a bit indicating bit in an MPLS label, and further accurately indicate the type of an inner layer message by the ACH head.

In order to achieve the purpose, the technical scheme adopted by the invention comprises the following steps:

using the highest bit in the MPLS label field to indicate whether the current MPLS label is followed by an ACH header; and if the MPLS label is followed by an ACH (access control Channel) header, identifying the message Type borne by the inner layer through a Channel Type field in the ACH header.

Preferably, the highest bit in the MPLS label field is 1, indicating that an ACH header is located behind the current label; and the highest bit in the MPLS label field is 0, which indicates that the back of the current label is an MPLS header.

Preferably, the MPLS label exists anywhere in the label stack.

Preferably, when the MPLS label exists at the bottom of the label stack, the Type of the message carried later is identified by the indication of the Channel Type field in the later ACH header.

Preferably, when the Channel Type field value of the ACH header is 0x0806, the Type of the packet carried by the inner layer is indicated to be IPv 4.

Compared with the prior art, the invention has the advantages that: for network equipment which does not process labels at the bottom of the MPLS stack, the type of an internal bearer message can be accurately identified, an inner layer message is analyzed, related deployment is carried out, misguess is not caused, and the method has good compatibility for the existing MPLS network.

Drawings

FIG. 1 is a diagram illustrating a field format of an MPLS label in the prior art;

FIG. 2 is a diagram illustrating the format of ACH field in the prior art;

fig. 3 is a diagram illustrating a new MPLS label field as defined by an exemplary embodiment of the present invention.

Detailed Description

In view of the deficiencies in the prior art, the inventors of the present invention have made extensive studies and extensive practices to provide technical solutions of the present invention. The technical solution, its implementation and principles, etc. will be further explained as follows.

The conventional definition of the MPLS field is as shown in fig. 1, and the MPLS packet header is composed of 32 bits and is divided into four parts:

label tag value, accounting for 20 bits, can represent a 1M tag range;

exp experiment bits, accounting for 3 bits, usually priority;

and 3.S, a stack bottom flag bit occupies 1bit, and when the value is 1, the flag bit indicates whether the current label is positioned at the stack bottom.

And 4, TTL lifetime occupying 8 bits and used for encoding the lifetime value. If the outgoing TTL value of the labeled packet is 0, the lifetime of the packet in the network is considered to have expired.

The ACH (Associated Channel) field is a field defined by RFC 5586 that is located after the bottom of stack label, and its field definition is shown in fig. 2. The ACH field may be used to indicate a message Type of the back bearer, and is indicated by a Channel Type. For example, if the rear message Type is IPv4, the value of the Channel Type field is 0x 0806.

The specific process of the new MPLS header defined in the embodiment of the present invention includes: the highest bit of the Label field in MPLS is reserved for indicating whether an ACH field is next to the current Label, the format definition of which is shown in fig. 3, the definitions of the Exp field, the S field, and the TTL field are the same as the definitions of the conventional MPLS field, and the highest bit of the Label field is used as an ACH header indicator bit a, so that the Label value field occupies 19 bits, and the a field occupies 1 bit. If the value of A is 1, an ACH head is next behind the MPLS label; if the value of A is "0", it indicates that the MPLS header still exists behind.

Such a new MPLS header may exist anywhere in the label stack, and when existing at the bottom of the label stack, the Type of the message carried behind may be accurately indicated by the Channel Type in the immediately following ACH header.

As another embodiment of the present invention, when the new MPLS header exists at the bottom of the non-Label stack and indicates that the current Label is followed by the ACH header, it can also indicate whether there is an Entropy Label entry Label behind it by the Channel Type in the immediately following ACH header, and since the length of the entry Label field is fixed, it can accurately indicate that the entry Label back is still the MPLS header.

In the technical scheme of the invention, the Label field of MPLS is changed into 19 bits, and the Label range of 512K can be represented. Meanwhile, since MPLS can support an interface-based label space, the 512K label range has little influence on practical applications. By adopting the technical scheme of the invention, the type and the field of the internal bearer message can be accurately identified by analyzing the message header at any node, and corresponding action is carried out based on the analyzed field.

The technical scheme based on the invention does not change the length of the MPLS message head and the positions of other fields, thereby being completely compatible with the prior MPLS network. When the interface label space does not exceed 512K label range, the original MPLS equipment and the MPLS equipment based on the present invention can exist simultaneously. The MPLS equipment based on the invention can accurately identify the message types existing in the MPLS, and the original MPLS equipment still guesses according to the original mode, so that a certain probability of false identification exists. Therefore, the replacement of the MPLS equipment provided by the invention at the network node does not influence the overall deployment of the whole network.

It should be understood that the above-mentioned embodiments are merely illustrative of the technical concepts and features of the present invention, which are intended to enable those skilled in the art to understand the contents of the present invention and implement the present invention, and therefore, the protection scope of the present invention is not limited thereby. All equivalent changes and modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for directly identifying an MPLS internal encapsulation message is characterized in that the method comprises the following steps: using the highest bit in the MPLS label field to indicate whether the current MPLS label is followed by an ACH header;

if the MPLS label is followed by an ACH header: when the MPLS label exists at the bottom of the label stack, identifying the Type of the message borne behind by the indication of a Channel Type field in the ACH head behind; when the MPLS Label exists at the bottom of a non-Label stack, whether an Entropy Label Entrophy Label exists behind the ACH Label is indicated through a Channel Type field in a back ACH header, and if the Entropy Label Entrophy Label exists, the MPLS Label still exists behind the Entrophy Label, and the fact that the MPLS Label exists behind the Entrophy Label is indicated;

if the highest bit in the MPLS label field indicates that the current MPLS label is followed by a non-ACH header, it indicates that the back is still the MPLS header.

2. The method for directly identifying MPLS interior encapsulation packets according to claim 1, wherein: the highest bit in the MPLS label field is 1, and an ACH (access control channel) header is indicated behind the current label; and the highest bit in the MPLS label field is 0, which indicates that the back of the current label is an MPLS header.

3. The method for directly identifying MPLS interior encapsulation packets according to claim 1, wherein: the MPLS label exists anywhere in the label stack.

4. The method for directly identifying MPLS interior encapsulation packets according to any one of claims 1 to 3: the method is characterized in that when the value of the Channel Type field of the ACH header is 0x0806, the message Type carried by the inner layer is indicated to be IPv 4.