WO2016050177A1

WO2016050177A1 - Pmtu determination method, network device and system

Info

Publication number: WO2016050177A1
Application number: PCT/CN2015/090786
Authority: WO
Inventors: 陈亘; 郑立君; 杨登国; 谭伟
Original assignee: 华为技术有限公司
Priority date: 2014-09-30
Filing date: 2015-09-25
Publication date: 2016-04-07
Also published as: CN105530193A; CN105530193B

Abstract

Disclosed in an embodiment of the present invention are a PMTU value determination method, network device and system used on a path from an ingress node to an egress node, the method comprising: an ingress node transmits to a receiving node on the path a first expansion bidirectional forwarding detection (BFD) control packet, the first expansion BFD control packet comprising an MTU flag bit; the ingress node receives a second expansion BFD control packet returned by the receiving node, the second expansion BFD control packet carrying an interface MTU value of the receiving node on the path; and the ingress node selects a minimum MTU value from the interface MTU value of the receiving node on the path returned by the receiving node and the interface MTU value of the path on the ingress node to serve as the PMTU value. The method facilitates in accurately determining the PMTU value on the path, thus reducing the number of times fragmentation occurs, and reducing a defragmentation failure problem caused by a secondary fragmentation.

Description

确定隧道最大传输单元的方法、网络设备和***Method, network device and system for determining a maximum transmission unit of a tunnel

本申请要求于2014年9月30日提交中国专利局、申请号为CN201410525848.6、发明名称为“确定隧道最大传输单元的方法、网络设备和***”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。This application claims the priority of the Chinese patent application filed on September 30, 2014, the Chinese Patent Office, the application number is CN201410525848.6, and the invention is entitled "Method, Network Equipment and System for Determining the Maximum Transmission Unit of the Tunnel". This is incorporated herein by reference.

技术领域Technical field

本发明涉及通信技术领域，具体涉及一种确定隧道最大传输单元的方法、网络设备和***。The present invention relates to the field of communications technologies, and in particular, to a method, a network device, and a system for determining a maximum transmission unit of a tunnel.

背景技术Background technique

最大传输单元(MTU)是指一种通信协议的某一层上面所能通过的最大数据包大小(以字节为单位)。最大传输单元这个参数通常与通信接口有关(网络接口卡、串口等)。The Maximum Transmission Unit (MTU) is the maximum packet size (in bytes) that can pass over a layer of a communication protocol. Maximum transmission unit This parameter is usually related to the communication interface (network interface card, serial port, etc.).

在MTU基础上定义隧道最大传输单元(PMTU)，是指从源地址到目的地址所经过的一条因特网传输隧道上，所有网络协议IP跳的最大传输单元(MTU)的最小值。换句话说，就是无需进一步分片就能穿过这条“隧道”的最大传输单元的最大值。The tunnel maximum transmission unit (PMTU) is defined on the basis of the MTU, which is the minimum value of the maximum transmission unit (MTU) of all network protocol IP hops on an Internet transmission tunnel from the source address to the destination address. In other words, the maximum value of the largest transmission unit that can pass through this "tunnel" without further fragmentation.

因特网协议允许IP分片，这样就可以将数据报包分成足够小的片段以通过那些最大传输单元小于所述数据报原始大小的链路了。具体来讲，如果原始数据报文超过发送接口MTU，就对报文进行分片，如果IP分片在隧道上经过更小的接口MTU时，还会进行二次分片。分片到达目的端后，将(报文ID+源IP+目的IP+协议类型)作为同一个报文的重组依据，根据报文的分片Flag和Fragment offset定位当前分片在整个IP报文中的位置。)这一分片过程发生在IP层(开放式***互联OSI模型的第三层，即网络层)，它使用的是将分组发送到链路上的网络接口的最大传输单元的值。原始分组的分片都被加上了标记，这样目的主机的IP层就能将分组重组成原始的数据报了。The Internet Protocol allows for IP fragmentation so that the datagram packet can be divided into sufficiently small segments to pass those links whose maximum transmission unit is smaller than the original size of the datagram. Specifically, if the original data packet exceeds the MTU of the sending interface, the packet is fragmented. If the IP fragment passes through the smaller interface MTU on the tunnel, the second fragmentation is performed. After the fragment arrives at the destination, the packet ID + source IP + destination IP + protocol type is used as the reorganization of the same packet. The fragment of the packet is fragmented and the Fragment offset is used to locate the current fragment in the entire IP packet. . This fragmentation process takes place at the IP layer (the third layer of the Open Systems Interconnection OSI model, the network layer), which uses the value of the maximum transmission unit of the network interface that sends the packet to the link. The fragments of the original packet are tagged so that the destination host's IP layer can reassemble the packet into the original datagram.

在通信网络中，当数据报文穿越隧道传输时，在隧道入口有可能因为数据报文尺寸大于隧道入口设备的接口MTU而导致在隧道入口位置进行分片，在隧道出口进行分片重组。当隧道中间节点的MTU，小于隧道起点的MTU时，需要对所述数据报文进行二次分片，而且如果对数据报文先分片再封装，还会带来重组风险，即如果在隧道中间节点因MTU小于隧道起点的MTU而对分片报文进行二次分片的话，二次分片后的第二分片报文与一次分片后的第一分片报文所处层级不同，由此导致隧道终点对分片重组失败。In a communication network, when a data packet traverses a tunnel, the tunnel entry may be fragmented at the tunnel entry location because the data packet size is larger than the interface MTU of the tunnel entry device. The tunnel exit is reorganized in pieces. When the MTU of the intermediate node of the tunnel is smaller than the MTU of the start of the tunnel, the data packet needs to be fragmented twice, and if the data packet is first fragmented and then encapsulated, the risk of reorganization is also caused, that is, if the tunnel is in the tunnel. If the intermediate node performs the second fragmentation of the fragmented packet because the MTU is smaller than the MTU of the tunnel starting point, the second fragmented packet after the second fragmentation is different from the first fragmented packet after the fragmentation. Thus, the tunnel end point fails to reassemble the fragment.

发明内容Summary of the invention

本发明实施例提供的确定隧道最大传输单元的方法、网络设备和***，解决了数据报文在隧道上传送时，需要进行二次分片，以及二次分片带来的数据报文重组失败的问题。The method, the network device, and the system for determining the maximum transmission unit of the tunnel provided by the embodiment of the present invention solve the problem that the data packet needs to be re-segmented when the data packet is transmitted on the tunnel, and the data packet reassembly caused by the second fragmentation fails. The problem.

为了解决上述问题，本发明实施例第一方面提供一种确定隧道最大传输单元MTU值的方法，所述方法应用在由入口节点到出口节点的隧道上，包括：所述入口节点向所述隧道上的接收节点发送第一扩展双向转发检测BFD控制报文，所述第一扩展BFD控制报文包括MTU标志位，所述MTU标志位用于指示所述接收节点向所述入口节点返回所述接收节点在所述隧道上的接口的MTU值，所述接收节点为所述隧道上除了所述入口节点以外、经过的所有节点；所述入口节点接收所述接收节点返回的第二扩展BFD控制报文，所述第二扩展BFD控制报文中携带所述接收节点在所述隧道上的接口MTU值；所述入口节点从所述接收节点返回的所述接收节点在所述隧道上的接口MTU值和所述隧道在所述入口节点上的接口MTU值中，选择最小的MTU值，作为所述隧道MTU值。In order to solve the above problem, a first aspect of the embodiments of the present invention provides a method for determining a MTU value of a maximum transmission unit of a tunnel, where the method is applied to a tunnel from an ingress node to an egress node, including: the ingress node to the tunnel The receiving node sends a first extended bidirectional forwarding detection BFD control message, where the first extended BFD control message includes an MTU flag bit, and the MTU flag bit is used to instruct the receiving node to return the Receiving an MTU value of an interface of the node on the tunnel, the receiving node is all nodes on the tunnel except the ingress node; and the ingress node receives a second extended BFD control returned by the receiving node a packet, the second extended BFD control packet carries an interface MTU value of the receiving node on the tunnel; and the interface of the receiving node that is returned by the ingress node from the receiving node on the tunnel The MTU value and the interface MTU value of the tunnel on the ingress node select a minimum MTU value as the tunnel MTU value.

在第一方面的第一种可能的实现方式中，所述MTU标志位用所述第一扩展BFD控制报文的诊断码Diag字段中的一位标识，或者所述Diag字段的预留值标识。In a first possible implementation manner of the first aspect, the MTU flag is identified by a bit in a Diag field of the diagnostic code of the first extended BFD control packet, or a reserved value identifier of the Diag field. .

结合第一方面或者第一方面的第一种可能的实现方式，在第一方面的第二种可能的实现方式中，还包括：所述第二扩展BFD控制报文包括MTU类型长度值TLV，用于携带所述接收节点在所述隧道上的接口MTU值。With reference to the first aspect or the first possible implementation manner of the first aspect, in a second possible implementation manner of the first aspect, the method further includes: the second extended BFD control packet includes an MTU type length value TLV, An interface MTU value for carrying the receiving node on the tunnel.

结合第一方面的第二种可能的实现方式，在第一方面的第三种可能的实现方式中，还包括：所述MTU TLV具体包括：类型Type、长度Length和值Value，所述Type指示所述Value的类型为MTU，所述Length指示所述MTU TLV的长度，所述Value为所述接收节点在所述隧道上的接口MTU值；所述MTU TLV位于所述第一扩展BFD控制报文的尾部。In conjunction with the second possible implementation of the first aspect, in a third possible implementation manner of the first aspect, the method further includes: the MTU TLV specifically includes: a type Type, a length Length, and a value Value, The Type indicates that the type of the Value is an MTU, the Length indicates the length of the MTU TLV, and the Value is an interface MTU value of the receiving node on the tunnel; the MTU TLV is located at the first Extend the tail of the BFD control packet.

结合第一方面或者第一方面的第一种至第三种可能的实现方式，在第一方面的第四种可能的实现方式中，还包括：所述入口节点向接收节点发送第一扩展BFD控制报文，所述入口节点通过设置承载所述第一扩展BFD控制报文的所述隧道报文中的生存时间TTL值，来完成将所述第一扩展BFD控制报文发送到所述隧道上的指定的接收节点上。With reference to the first aspect or the first to third possible implementation manners of the first aspect, in a fourth possible implementation manner of the foregoing aspect, the method further includes: the ingress node sends the first extended BFD to the receiving node Controlling, by the ingress node, the first extended BFD control packet is sent to the tunnel by setting a lifetime TTL value in the tunnel packet that carries the first extended BFD control packet On the specified receiving node.

结合第一方面或者第一方面的第一种至第四种任一可能的实现方式，在第一方面的第五种可能的实现方式中，还包括：如果所述接收节点为所述出口节点，则所述接收节点上的接口MTU值是所述隧道在所述出口节点在所述隧道上的入接口的MTU值；和/或，如果所述接收节点为所述隧道上所述入口节点到所述出口节点之间的中间节点，则所述接收节点上的接口MTU值为所述隧道穿过所述接收节点的入接口MTU值和出接口MTU值中的最小值。With reference to the first aspect, or any one of the first to fourth possible implementation manners of the first aspect, in a fifth possible implementation manner of the first aspect, the method further includes: if the receiving node is the egress node And the MTU value of the interface on the receiving node is an MTU value of the inbound interface of the tunnel at the egress node on the tunnel; and/or, if the receiving node is the ingress node on the tunnel To an intermediate node between the egress nodes, an interface MTU value on the receiving node is a minimum value of an inbound interface MTU value and an outbound interface MTU value of the tunnel passing through the receiving node.

为了解决上述问题，本发明实施例第二方面提供一种发送最大传输单元MTU的方法，所述方法应用在由入口节点到出口节点的隧道上，所述方法包括：接收节点接收所述入口节点发来的第一扩展双向转发检测BFD控制报文，所述第一扩展BFD控制报文包括MTU标志位，所述MTU标志位用于指示所述接收节点向所述入口节点返回所述接收节点在所述隧道上的接口MTU值；所述接收节点获取所述接收节点在所述隧道上的接口MTU值；所述接收节点向入口节点返回第二扩展BFD控制报文，所述第二扩展BFD控制报文中携带所述接收节点在所述隧道上的接口MTU值。In order to solve the above problem, a second aspect of the embodiments of the present invention provides a method for transmitting a maximum transmission unit MTU, where the method is applied to a tunnel from an ingress node to an egress node, the method comprising: receiving, by the receiving node, the ingress node And sending, by the first extended bidirectional forwarding, the BFD control packet, where the first extended BFD control packet includes an MTU flag, where the MTU flag is used to indicate that the receiving node returns the receiving node to the ingress node An interface MTU value on the tunnel; the receiving node acquires an interface MTU value of the receiving node on the tunnel; the receiving node returns a second extended BFD control packet to the ingress node, the second extension The BFD control packet carries the interface MTU value of the receiving node on the tunnel.

在第二方面的第一种可能的实现方式中，包括：所述MTU标志位用所述第一扩展BFD控制报文的诊断码Diag字段中的一位标识，或者所述Diag字段的预留值标识。In a first possible implementation manner of the second aspect, the method includes: the MTU flag bit is identified by one bit in a Diagnosing Code Diag field of the first extended BFD control message, or a reservation of the Diag field Value identifier.

结合第二方面或者第二方面的第一种可能的实现方式，在第二方面的第二种可能的实现方式中，所述第二扩展BFD控制报文具体包括：MTU类型长度值TLV，用于携带所述接收节点在所述隧道上的接口MTU值。With reference to the second aspect, or the first possible implementation manner of the second aspect, in the second possible implementation manner of the second aspect, the second extended BFD control packet specifically includes: an MTU type length value TLV, And carrying an interface MTU value of the receiving node on the tunnel.

结合第二方面第二种可能的实现方式，在第二方面的第三种可能的实现方式中，所述MTU TLV具体包括：类型Type、长度Length和值Value，所述Type指示所述Value的类型为MTU，所述Length指示所述MTU TLV的长度，所述Value为所述接收节点在所述隧道上的接口MTU值；所述MTU TLV位于所述第一扩展BFD控制报文的尾部。In combination with the second possible implementation of the second aspect, the third possible implementation in the second aspect The MTU TLV includes: a Type Type, a Length Length, and a Value Value, the Type indicates that the Type of the Value is an MTU, the Length indicates a length of the MTU TLV, and the Value is the receiving node. An interface MTU value on the tunnel; the MTU TLV is located at a tail of the first extended BFD control message.

结合第二方面或者第二方面的第一种至第三种任一可能的实现方式，在第二方面的第四种可能的实现方式中，还包括：如果所述接收节点为所述出口节点，则所述接收节点上的接口MTU值是所述隧道在所述出口节点在所述隧道上的入接口的MTU值；和/或，如果所述接收节点为所述隧道上所述入口节点到所述出口节点之间的中间节点，则所述接收节点上的接口MTU值为所述隧道穿过所述接收节点的入接口MTU值和出接口MTU值中的最小值。With reference to the second aspect, or any one of the first to third possible implementation manners of the second aspect, in a fourth possible implementation manner of the second aspect, the method further includes: if the receiving node is the egress node And the MTU value of the interface on the receiving node is an MTU value of the inbound interface of the tunnel at the egress node on the tunnel; and/or, if the receiving node is the ingress node on the tunnel To an intermediate node between the egress nodes, an interface MTU value on the receiving node is a minimum value of an inbound interface MTU value and an outbound interface MTU value of the tunnel passing through the receiving node.

结合第二方面或者第二方面的第一种至第四种任一可能的实现方式，在第二方面的第五种可能的实现方式中，在所述接收节点接收入口节点发来的第一扩展双向转发检测BFD控制报文之后，还包括：所述接收节点解析承载所述第一扩展BFD控制报文的所述隧道报文中的生存时间TTL值，如果解析出TTL值等于1，则向所述入口节点发送所述接收节点在所述隧道上的接口MTU值。With reference to the second aspect, or any one of the first to fourth possible implementation manners of the second aspect, in the fifth possible implementation manner of the second aspect, the receiving node receives the first After the extended bidirectional forwarding detects the BFD control packet, the method further includes: the receiving node parsing the TTL value of the lifetime time in the tunnel packet carrying the first extended BFD control packet, and if the TTL value is equal to 1, Transmitting, by the ingress node, an interface MTU value of the receiving node on the tunnel.

为了解决上述问题，本发明实施例第三方面提供一种网络设备，用于确定隧道最大传输单元MTU值，所述网络设备应用在由入口节点到出口节点的隧道上，包括：发送单元，用于向所述隧道上的接收节点发送第一扩展双向转发检测BFD控制报文，所述第一扩展BFD控制报文包括MTU标志位，所述MTU标志位用于指示所述接收节点向所述入口节点返回所述接收节点在所述隧道上的接口的MTU值，所述接收节点为所述隧道上除了所述入口节点以外、经过的所有节点；接收单元，用于接收所述接收节点返回的第二扩展BFD控制报文，所述第二扩展BFD控制报文中携带所述接收节点在所述隧道上的接口MTU值；确定单元，用于从所述接收节点返回的所述接收节点在所述隧道上的接口MTU值和所述隧道在所述入口节点上的接口MTU值中，选择最小的MTU值，作为所述隧道MTU值。In order to solve the above problem, a third aspect of the embodiments of the present invention provides a network device, configured to determine a maximum transmission unit MTU value of a tunnel, where the network device is applied to a tunnel from an ingress node to an egress node, including: a sending unit, Transmitting, by the receiving node on the tunnel, a first extended bidirectional forwarding detection BFD control packet, where the first extended BFD control packet includes an MTU flag bit, where the MTU flag bit is used to indicate that the receiving node is to the The ingress node returns an MTU value of the interface of the receiving node on the tunnel, the receiving node is all nodes on the tunnel except the ingress node, and the receiving unit is configured to receive the receiving node to return a second extended BFD control packet, where the second extended BFD control packet carries an interface MTU value of the receiving node on the tunnel; and a determining unit, configured to receive the receiving node from the receiving node The interface MTU value on the tunnel and the interface MTU value of the tunnel on the ingress node select a minimum MTU value as the tunnel MTU value.

在第三方面的第一种可能的实现方式中，还包括：TTL设置单元，用于设置承载所述第一扩展BFD控制报文的所述隧道报文中的生存时间TTL值，来完成将所述第一扩展BFD控制报文发送到所述隧道上的指定的接收节点上。In a first possible implementation manner of the third aspect, the method further includes: a TTL setting unit, configured to set a time-to-live TTL value in the tunnel packet that carries the first extended BFD control packet, And completing the sending of the first extended BFD control message to a designated receiving node on the tunnel.

为了解决上述问题，本发明实施例第四方面提供一种网络设备，用于发送隧道最大传输单元MTU值，所述网络设备应用在由入口节点到出口节点的隧道上，包括：接收单元，用于接收所述入口节点发来的第一扩展双向转发检测BFD控制报文，所述第一扩展BFD控制报文包括MTU标志位，所述MTU标志位用于指示所述接收节点向所述入口节点返回所述接收节点在所述隧道上的接口MTU值；获取单元，用于获取所述接收节点在所述隧道上的接口MTU值；发送单元，用于向入口节点返回第二扩展BFD控制报文，所述第二扩展BFD控制报文中携带所述接收节点在所述隧道上的接口MTU值。In order to solve the above problem, a fourth aspect of the embodiments of the present invention provides a network device, configured to send a maximum transmission unit MTU value of a tunnel, where the network device is applied to a tunnel from an ingress node to an egress node, including: a receiving unit, And receiving, by the ingress node, a first extended bidirectional forwarding detection BFD control packet, where the first extended BFD control packet includes an MTU flag bit, where the MTU flag bit is used to indicate the receiving node to the portal Returning, by the node, the interface MTU value of the receiving node on the tunnel; the acquiring unit, configured to acquire the interface MTU value of the receiving node on the tunnel; and the sending unit, configured to return the second extended BFD control to the ingress node And the second extended BFD control packet carries the interface MTU value of the receiving node on the tunnel.

为了解决上述问题，本发明实施例第五方面提供一种用于确定隧道最大传输单元MTU值的***，包括：上述第三方面的网络设备和第四方面的网络设备。In order to solve the above problem, a fifth aspect of the embodiments of the present invention provides a system for determining a maximum transmission unit MTU value of a tunnel, comprising: the network device of the foregoing third aspect, and the network device of the fourth aspect.

本发明实施例通过扩展BFD控制报文，增加所述MTU标志位和所述MTU TLV，以及设置TTL的方法，精确地确定隧道MTU，有助于减少分片次数和二次分片带来的重组失败问题。In the embodiment of the present invention, by extending the BFD control packet, adding the MTU flag bit and the MTU TLV, and setting the TTL method, the tunnel MTU is accurately determined, which helps reduce the number of times of fragmentation and the second fragmentation. Reorganization failure problem.

附图说明DRAWINGS

为了更清楚地说明本申请实施例或现有技术中的技术方案，下面将对实施例或现有技术描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本申请中记载的一些实施例，对于本领域普通技术人员来讲，还可以根据这些附图获得其它的附图。In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings to be used in the embodiments or the prior art description will be briefly described below. Obviously, the drawings in the following description are only These are some of the embodiments described in this application, and other figures can be obtained from those of ordinary skill in the art in view of these drawings.

图1是本发明实施例一种确定隧道MTU方法的流程示意图；1 is a schematic flowchart of a method for determining a tunnel MTU according to an embodiment of the present invention;

图2-1是本发明实施例中扩展BFD控制报文Diag字段的示意图；2-1 is a schematic diagram of an extended BFD control packet Diag field in the embodiment of the present invention;

图2-2是本发明实施例中扩展BFD控制报文MTU TLV的示意图；2-2 is a schematic diagram of an extended BFD control message MTU TLV according to an embodiment of the present invention;

图3是本发明实施例一种发送报文方法的流程示意图；3 is a schematic flowchart of a method for sending a message according to an embodiment of the present invention;

图4是本发明实施例一种网络设备的结构示意图；4 is a schematic structural diagram of a network device according to an embodiment of the present invention;

图5是本发明实施例另一种网络设备的结构示意图；FIG. 5 is a schematic structural diagram of another network device according to an embodiment of the present invention; FIG.

图6是本发明实施例一种确定隧道MTU***的示意图； 6 is a schematic diagram of a system for determining a tunnel MTU according to an embodiment of the present invention;

图7是本发明实施例一种网络设备的结构示意图；7 is a schematic structural diagram of a network device according to an embodiment of the present invention;

图8是本发明实施例另一种网络设备的结构示意图。FIG. 8 is a schematic structural diagram of another network device according to an embodiment of the present invention.

具体实施方式detailed description

为了使本技术领域的人员更好地理解本发明方案，下面结合附图和实施方式对本发明实施例作进一步的详细说明。显然，所描述的实施例是本发明一部分实施例，而不是全部的实施例。基于本发明中的实施例，本领域普通技术人员在没有做出创造性劳动前提下所获得的所有其它实施例，都属于本发明保护的范围。The embodiments of the present invention are further described in detail below with reference to the drawings and embodiments. It is apparent that the described embodiments are a part of the embodiments of the invention, and not all of the embodiments. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the present invention without creative efforts are within the scope of the present invention.

本申请文件中所提及的入口节点、节点、中间节点和出口节点中的任意一个可以是路由器、交换机或具有类似功能网络设备。Any of the ingress nodes, nodes, intermediate nodes, and egress nodes mentioned in this application may be routers, switches, or network devices having similar functions.

在介绍本发明实施例技术方案之前，先对本发明实施例的具体应用场景进行解释说明。Before the technical solutions of the embodiments of the present invention are introduced, the specific application scenarios of the embodiments of the present invention are explained.

在通信网络中，当数据报文穿越隧道传输时，因为数据报文的尺寸大于所述隧道入口设备的接口MTU而导致在所述隧道入口位置对收到的大于接口MTU的报文进行分片，如果先对收到的大于所述接口MTU的数据报文(如IP报文)进行基于IP报文的第一次分片，然后再将所述分片封装上隧道报文头(如GRE隧道的GRE隧道头)形成GRE报文向隧道出口方向发送；如果在所述隧道上的一个中间设备的接口MTU小于隧道入口设备的接口MTU，还需要对所述GRE报文继续进行基于GRE隧道报文的第二次分片，所以在隧道出口进行解除GRE隧道封装和对所述GRE报文重组时，由于对所述GRE报文进行的第二次分片和对所述数据报文进行的第一次分片所处的层级不同，也就是对所述数据报文进行的第一次分片是基于IP报文头，对所述GRE报文进行的第二次分片基于GRE隧道报文，就会导致隧道出口进行分片重组失败的问题。In the communication network, when the data packet is transmitted through the tunnel, the size of the data packet is larger than the interface MTU of the tunnel ingress device, and the received packet larger than the interface MTU is fragmented at the tunnel entry location. If the data packet (such as an IP packet) that is received by the interface is first fragmented based on the IP packet, the packet is encapsulated on the tunnel header (such as GRE). The GRE tunnel of the tunnel is configured to send the GRE packet to the tunnel egress. If the MTU of the interface of the intermediate device is smaller than the MTU of the tunnel entry device, the GRE tunnel needs to continue to be based on the GRE tunnel. The second fragmentation of the packet, so that the GRE tunnel encapsulation and the reassembly of the GRE packet are performed at the tunnel exit, because the second fragmentation of the GRE packet is performed and the data packet is performed. The first fragmentation is in a different level, that is, the first fragmentation of the data packet is based on an IP packet header, and the second fragmentation of the GRE packet is based on a GRE tunnel. The message will cause the tunnel exit to proceed. The problem of fragmentation reorganization failed.

值得说明的是，所述隧道可以是三层隧道。例如，所述隧道可以是通用路由封装(Generic Routing Encapsulation，GRE)隧道或者因特网协议安全性(Internet Protocol Security，IPSec)隧道。所述隧道也可以是二层隧道。例如，所述隧道可以是多协议标签交换(Multi-Protocol Label Switching，MPLS) 隧道或基于流量工程扩展的资源预留协议(Resource Reservation Protocol-Traffic Engineering，RSVP-TE)隧道或者点到点隧道协议(Point to Point Tunneling Protocol，PPTP)隧道或者第二层隧道协议(Layer Two Tunneling Protocol，L2TP)隧道。It should be noted that the tunnel may be a three-layer tunnel. For example, the tunnel may be a Generic Routing Encapsulation (GRE) tunnel or an Internet Protocol Security (IPSec) tunnel. The tunnel may also be a two-layer tunnel. For example, the tunnel may be Multi-Protocol Label Switching (MPLS). Tunnel or Resource Reservation Protocol-Traffic Engineering (RSVP-TE) tunnel or Point to Point Tunneling Protocol (PPTP) tunnel or Layer 2 Tunneling (Layer Two Tunneling) Protocol, L2TP) tunnel.

本发明实施例中所提及的入口节点、中间节点和出口节点可以是路由器、交换机或具有类似功能网络设备。The ingress node, the intermediate node, and the egress node mentioned in the embodiments of the present invention may be routers, switches, or network devices having similar functions.

实施例一、 Embodiment 1

参见图1，示出了本发明实施例确定隧道MTU方法的流程示意图，该方法应用在由入口节点到出口节点的隧道上。该方法包括：Referring to FIG. 1, a schematic flowchart of a method for determining a tunnel MTU according to an embodiment of the present invention is shown, where the method is applied to a tunnel from an ingress node to an egress node. The method includes:

101、所述入口节点向所述隧道上的接收节点发送第一扩展双向转发检测BFD(Bidirectional Forwarding Detection)控制报文，所述第一扩展BFD控制报文包括MTU标志位，所述MTU标志位用于指示所述接收节点向所述入口节点返回所述接收节点在所述隧道上的接口的MTU值，所述接收节点为所述隧道上除了所述入口节点以外、经过的所有节点。The ingress node sends a first extended bidirectional forwarding detection BFD (Bidirectional Forwarding Detection) control packet to the receiving node on the tunnel, where the first extended BFD control packet includes an MTU flag bit, and the MTU flag bit And indicating that the receiving node returns, to the ingress node, an MTU value of an interface of the receiving node on the tunnel, where the receiving node is all nodes on the tunnel except the ingress node.

具体地，如图2-1所示，所述MTU标志位可以用扩展BFD控制报文中的诊断码Diag字段来标识。具体地，用扩展BFD控制报文中的诊断码Diag字段来标识所述MTU标志位，可以有两种方式：Specifically, as shown in FIG. 2-1, the MTU flag bit may be identified by using a Diagnostic Code Diag field in the extended BFD control message. Specifically, the MTU flag bit is identified by using the Diagnostic Code Diag field in the extended BFD control packet. There are two ways:

方式一：用所述Diag字段的预留值标识所述MTU标志位。Manner 1: The MTU flag bit is identified by using a reserved value of the Diag field.

所述BFD控制报文格式的所述诊断码Diag字段定义为本地***针对BFD会话状态中最近一次变化的原因，IETF标准RFC5880定义的所述诊断码取值包括：The diagnostic code Diag field of the BFD control packet format is defined as the reason for the latest change of the local system for the BFD session state. The diagnostic code values defined by the IETF standard RFC5880 include:

0——无诊断码；0 - no diagnostic code;

1——控制检测时间超时；1——Control detection timeout;

2——Echo功能失败；2 - Echo function failed;

3——邻居信令表明会话down；3 - neighbor signaling indicates that the session is down;

4——转发平面复位；4 - forwarding plane reset;

5——路径down；5 - path down;

6——串联路径down；6 - serial path down;

7——管理down； 7 - management down;

8——反向串联路径down；8 - reverse serial path down;

9-31——预留编码。9-31 - Reserved code.

从所述诊断码预留值(9-31)中选择一个预留值(如9)作为MTU标识位。A reserved value (such as 9) is selected from the diagnostic code reserved value (9-31) as the MTU flag.

方式二：用所述Diag字段中的一位标识所述MTU标志位，RFC5880已定义的编码用4个比特就足够表示诊断码，可以用BFD控制报文的诊断码域中的1个比特位作为MTU标志位，如图2-1中所述Diag字段占据第3～7比特位，例如，可以将第3位或者第7位用作MTU标志位。Manner 2: The MTU flag bit is identified by one bit in the Diag field, and the code defined by RFC 5880 is sufficient to represent the diagnostic code by using 4 bits, and BFD can be used to control 1 bit in the diagnostic code field of the message. As the MTU flag bit, the Diag field occupies the 3rd to 7th bits as shown in FIG. 2-1. For example, the 3rd bit or the 7th bit can be used as the MTU flag bit.

进一步，可选地，所述入口节点向所述接收节点发送第一扩展BFD控制报文的具体方式可以是：所述入口节点通过设置承载所述第一扩展BFD控制报文的所述隧道报文中的生存时间TTL值，来完成将所述第一扩展BFD控制报文发送到所述隧道上的指定的接收节点上。Further, optionally, the manner in which the ingress node sends the first extended BFD control packet to the receiving node may be: the ingress node sets the tunnel report that carries the first extended BFD control packet The time-to-live TTL value in the text is used to complete sending the first extended BFD control packet to a designated receiving node on the tunnel.

例如，在从节点A依次经过节点B和节点C到达节点D的一条隧道上，节点A为入口节点，节点B和节点C为中间节点，节点D为出口节点。当节点A向节点B发送所述第一扩展BFD控制报文时，将所述隧道报文中的生存时间TTL值设置为1；当节点A向节点C发送所述第一扩展BFD控制报文时，将所述隧道报文中的生存时间TTL值设置为2；当节点A向节点D发送所述第一扩展BFD控制报文时，将所述隧道报文中的生存时间TTL值设置为3；可选地，当节点A向节点D发送所述第一扩展BFD控制报文时，也可以不设置TTL值(TTL值默认为255)，仅仅通过根据隧道的目的地址进行查找转发，也可以使所述第一扩展BFD控制报文到达节点D，节点D的控制平面可以对所述第一扩展BFD控制报文进行解析处理。For example, on a tunnel from node A to node D through node B and node C, node A is an ingress node, node B and node C are intermediate nodes, and node D is an egress node. When the node A sends the first extended BFD control packet to the node B, the TTL value of the lifetime time in the tunnel packet is set to 1; when the node A sends the first extended BFD control packet to the node C. The time-to-live TTL value in the tunnel packet is set to 2; when the node A sends the first extended BFD control packet to the node D, the lifetime TTL value in the tunnel packet is set to Optionally, when the node A sends the first extended BFD control packet to the node D, the TTL value may not be set (the TTL value is 255 by default), and only the forwarding and forwarding according to the destination address of the tunnel are performed. The first extended BFD control packet may be sent to the node D, and the control plane of the node D may parse the first extended BFD control packet.

进一步，具体地，举例说明在所述隧道报文中设置TTL值的方法，例如，如果所述隧道为GRE隧道，则在GRE报文头外层的传输头(Delivery Header)中设置TTL值，所述传输头是IP报文头，设置TTL就是设置IP报文头中的TTL字段。如果所述隧道为MPLS隧道，则设置TTL就是设置MPLS报文头中的TTL字段。Further, specifically, a method for setting a TTL value in the tunnel packet is exemplified. For example, if the tunnel is a GRE tunnel, a TTL value is set in a delivery header (Delivery Header) of the outer layer of the GRE packet header. The transport header is an IP packet header. Setting the TTL is to set the TTL field in the IP packet header. If the tunnel is an MPLS tunnel, setting the TTL is to set the TTL field in the MPLS packet header.

102、所述入口节点接收所述接收节点返回的第二扩展BFD控制报文，所述第二扩展BFD控制报文中携带所述接收节点在所述隧道上的接口MTU值。 102. The ingress node receives a second extended BFD control packet returned by the receiving node, where the second extended BFD control packet carries an interface MTU value of the receiving node on the tunnel.

具体地，所述第二扩展BFD控制报文具体包括：MTU类型长度值TLV，用于携带所述接收节点在所述隧道上的接口MTU值。Specifically, the second extended BFD control packet specifically includes: an MTU type length value TLV, configured to carry an interface MTU value of the receiving node on the tunnel.

具体地，如图2-2，可以通过扩展BFD控制报文，新增所述MTU TLV来作为第二扩展BFD控制报文。所述MTU TLV具体包括：类型Type、长度Length和值Value，所述Type指示所述Value的类型为MTU，所述Length指示所述MTU TLV的长度，所述Value为所述接收节点在所述隧道上的接口MTU值；此外，可选地，对于Length的定义，也可以用来指示所述Value的长度。Specifically, as shown in Figure 2-2, the MTU TLV can be added as the second extended BFD control packet by extending the BFD control packet. The MTU TLV specifically includes: a type Type, a length Length, and a value Value, the Type indicates that the type of the Value is an MTU, the Length indicates a length of the MTU TLV, and the Value is that the receiving node is in the The interface MTU value on the tunnel; in addition, optionally, the definition of Length can also be used to indicate the length of the Value.

值得说明的是，图2-2中Type、Length和Value字段所占的比特位数仅仅是一个示意，并不局限与此。It is worth noting that the number of bits occupied by the Type, Length and Value fields in Figure 2-2 is only an indication and is not limited to this.

可选地，所述MTU TLV位于所述扩展的BFD控制报文的尾部。Optionally, the MTU TLV is located at the end of the extended BFD control message.

可选地，所述第二扩展BFD控制报文中携带所述接收节点在所述隧道上的接口MTU值，可以为：Optionally, the second extended BFD control packet carries the MTU value of the interface of the receiving node on the tunnel, and may be:

如果所述接收节点为所述出口节点，则所述接收节点上的接口MTU值是所述隧道在所述出口节点在所述隧道上的入接口的MTU值；和/或If the receiving node is the egress node, the interface MTU value on the receiving node is an MTU value of the inbound interface of the tunnel at the egress node on the tunnel; and/or

如果所述接收节点为所述隧道上所述入口节点到所述出口节点之间的中间节点，则所述接收节点上的接口MTU值为所述隧道穿过所述接收节点的入接口MTU值和出接口MTU值中的最小值。If the receiving node is an intermediate node between the ingress node and the egress node on the tunnel, the interface MTU value on the receiving node is an inbound interface MTU value of the tunnel passing through the receiving node. And the minimum value of the outbound interface MTU value.

103、所述入口节点从所述接收节点返回的所述接收节点在所述隧道上的接口MTU值和所述隧道在所述入口节点上的接口MTU值中，选择最小的MTU值，作为所述隧道MTU值。103. The ingress node returns an MTU value of the interface on the tunnel and an interface MTU value of the tunnel on the ingress node of the receiving node that is returned by the receiving node, and selects a minimum MTU value. The tunnel MTU value.

可选地，如果所述隧道只有所述入口节点和所述出口节点而没有中间节点，则所述入口节点收到所述出口节点的接口MTU值，获取所述隧道在自身的出接口MTU值，从上述所有接口MTU值中，选取一个最小值作为隧道MTU值。Optionally, if the tunnel has only the ingress node and the egress node and no intermediate node, the ingress node receives an interface MTU value of the egress node, and obtains an MTU value of the outbound interface of the tunnel. From the MTU values of all the above interfaces, select a minimum value as the tunnel MTU value.

可选地，如果所述隧道除了所述入口节点和所述出口节点，还有中间节点，则所述入口节点收到所有中间节点的接口MTU值和出口节点的接口MTU值，获取所述隧道经过的所述入口节点的出接口MTU值，从所有中间节点的接口MTU值、出口节点的接口MTU值、以及所述入口节点在所述隧道上的出接口的MTU值中，选取一个最小值作为隧道MTU值。Optionally, if the tunnel has an intermediate node in addition to the ingress node and the egress node, the ingress node receives an interface MTU value of all intermediate nodes and an interface MTU value of the egress node, and obtains the tunnel. The MTU value of the outbound interface of the ingress node, the MTU value of the interface from all intermediate nodes, the MTU value of the interface of the egress node, and the outgoing node of the ingress node on the tunnel Among the MTU values of the port, a minimum value is selected as the tunnel MTU value.

值得说明的是，本发明实施例中的第一扩展BFD报文中的“第一”和第二扩展BFD报文中的“第二”仅仅用于表明区分两个报文，这两个扩展BFD报文的格式相同，都是基于现有的BFD报文，扩展了Diag字段的使用和新增了MTU TLV。It should be noted that the “second” in the “first” and the second extended BFD packet in the first extended BFD packet in the embodiment of the present invention is only used to indicate that two packets are distinguished, and the two extensions are used. The BFD packets have the same format and are based on existing BFD packets. The use of the Diag field and the addition of the MTU TLV are extended.

值得说明的是，本实施例中只示意了单向隧道(例如从节点A到节点D方向)的隧道MTU值确定方式，还可以通过扩展的BFD控制报文，进行反向隧道的隧道MTU值的确定(例如，从节点D到节点A方向)，也就是，通过扩展的BFD控制报文，可以同时或不同时完成双向隧道的隧道MTU值的确定。It should be noted that, in this embodiment, only the tunnel MTU value determination mode of the unidirectional tunnel (for example, from the node A to the node D direction) is illustrated, and the tunnel MTU value of the reverse tunnel can also be performed by using the extended BFD control packet. The determination (for example, from node D to node A), that is, through the extended BFD control message, can determine the tunnel MTU value of the bidirectional tunnel simultaneously or at different times.

本发明实施例一提供的确定隧道MTU方法，通过所述入口节点向所述隧道上的接收节点发送第一扩展BFD控制报文，接收所述接收节点返回的第二扩展BFD控制报文，从所述接收节点返回的所述接收节点在所述隧道上的接口MTU值和所述隧道在所述入口节点上的接口MTU值中，选择最小的MTU值，作为所述隧道MTU值，从而精确地确定隧道MTU，有助于减少分片次数和避免二次分片带来的重组失败问题。The method for determining a tunnel MTU according to the first embodiment of the present invention, the first extended BFD control packet is sent to the receiving node on the tunnel by the ingress node, and the second extended BFD control packet returned by the receiving node is received. Determining, by the receiving node, the interface MTU value on the tunnel and the interface MTU value of the tunnel on the ingress node, selecting a minimum MTU value as the tunnel MTU value, thereby accurately Determining the tunnel MTU helps to reduce the number of shards and avoid reorganization failures caused by secondary sharding.

实施例二、 Embodiment 2

参见图3，示出了本发明实施例发送MTU方法的流程示意图，应用在由入口节点到出口节点所形成的隧道上。具体方法包括：Referring to FIG. 3, a schematic flowchart of a method for transmitting an MTU according to an embodiment of the present invention is shown, which is applied to a tunnel formed by an ingress node to an egress node. Specific methods include:

301、接收节点接收所述入口节点发来的第一扩展双向转发检测BFD控制报文，所述第一扩展BFD控制报文包括MTU标志位，所述MTU标志位用于指示所述接收节点向所述入口节点返回所述接收节点在所述隧道上的接口MTU值；301. The receiving node receives a first extended bidirectional forwarding detection BFD control packet sent by the ingress node, where the first extended BFD control packet includes an MTU flag bit, where the MTU flag bit is used to indicate that the receiving node is Returning, by the ingress node, an interface MTU value of the receiving node on the tunnel;

本实施例中的所述MTU标志位，请参考实施例一中相应的描述，在此不再赘述。For the MTU flag in this embodiment, refer to the corresponding description in the first embodiment, and details are not described herein again.

可选地，所述接收节点解析承载所述第一扩展BFD控制报文的所述隧道报文中的生存时间TTL值，如果所述TTL值等于1，则向所述入口节点发送所述接收节点在所述隧道上的接口MTU值。具体地，如果所述TTL值等于1 时，则把所述第一扩展BFD控制报文上送所述接收节点的控制平面处理。Optionally, the receiving node parses a time-to-live TTL value in the tunnel packet that carries the first extended BFD control packet, and if the TTL value is equal to 1, sends the receiving to the ingress node. The interface MTU value of the node on the tunnel. Specifically, if the TTL value is equal to 1 The first extended BFD control packet is sent to the control plane of the receiving node for processing.

302、所述接收节点获取所述接收节点在所述隧道上的接口MTU值；302. The receiving node acquires an interface MTU value of the receiving node on the tunnel.

303、所述接收节点向入口节点返回第二扩展BFD控制报文，所述第二扩展BFD控制报文中携带所述接收节点在所述隧道上的接口MTU值。303. The receiving node returns a second extended BFD control packet to the ingress node, where the second extended BFD control packet carries an interface MTU value of the receiving node on the tunnel.

本实施例中的所述MTU TLV，以及对第一扩展BFD报文中的“第一”和第二扩展BFD报文中的“第二”解释，请参考实施例一中相应的描述，在此不再赘述。For the MTU TLV in the embodiment, and the second representation in the first and second extended BFD packets in the first extended BFD packet, refer to the corresponding description in the first embodiment. This will not be repeated here.

本发明实施例二提供的发送MTU方法，通过接收节点接收所述入口节点发来的第一扩展双向转发检测BFD控制报文，获取所述接收节点在所述隧道上的接口MTU值，将携带所述接口MTU值的第二扩展BFD控制报文返回到所述入口节点，从而将所述接收节点的所述接口MTU值发送给所述入口节点。本发明实施例有助于精确地确定隧道MTU，有助于减少分片次数和避免二次分片带来的重组失败问题。The method for transmitting an MTU according to the second embodiment of the present invention, the receiving node receives the first extended bidirectional forwarding detection BFD control packet sent by the ingress node, and obtains the MTU value of the interface of the receiving node on the tunnel, which will carry The second extended BFD control message of the interface MTU value is returned to the ingress node, so that the interface MTU value of the receiving node is sent to the ingress node. The embodiments of the present invention help to accurately determine the tunnel MTU, help to reduce the number of slices and avoid the problem of reassembly failure caused by secondary fragmentation.

实施例三、 Embodiment 3

参见图4，本发明实施例提供一种网络设备400，该网络设备400用于确定隧道最大传输单元MTU值，该网络设备400应用在由入口节点到出口节点的隧道上。该网络设备400包括：Referring to FIG. 4, an embodiment of the present invention provides a network device 400, which is used to determine a tunnel maximum transmission unit MTU value, and the network device 400 is applied to a tunnel from an ingress node to an egress node. The network device 400 includes:

发送单元401，用于向所述隧道上的接收节点发送第一扩展双向转发检测BFD控制报文，所述第一扩展BFD控制报文包括MTU标志位，所述MTU标志位用于指示所述接收节点向所述入口节点返回所述接收节点在所述隧道上的接口的MTU值，所述接收节点为所述隧道上除了所述入口节点以外、经过的所有节点；The sending unit 401 is configured to send, by the receiving node on the tunnel, a first extended bidirectional forwarding detection BFD control packet, where the first extended BFD control packet includes an MTU flag, and the MTU flag The locator is used to instruct the receiving node to return an MTU value of the interface of the receiving node on the tunnel to the ingress node, where the receiving node is all nodes on the tunnel except the ingress node;

接收单元402，用于接收所述接收节点返回的第二扩展BFD控制报文，所述第二扩展BFD控制报文中携带所述接收节点在所述隧道上的接口MTU值；The receiving unit 402 is configured to receive a second extended BFD control packet returned by the receiving node, where the second extended BFD control packet carries an interface MTU value of the receiving node on the tunnel;

确定单元403，用于从所述接收节点返回的所述接收节点在所述隧道上的接口MTU值和所述隧道在所述入口节点上的接口MTU值中，选择最小的MTU值，作为所述隧道MTU值。其中，所述隧道在所述入口节点上的接口MTU值，可以是所述隧道经过的所述入口节点的出接口的接口MTU值。a determining unit 403, configured to select, from the receiving node, the interface MTU value on the tunnel and the interface MTU value of the tunnel on the ingress node, select a minimum MTU value, as the The tunnel MTU value. The interface MTU value of the tunnel on the ingress node may be the interface MTU value of the outbound interface of the ingress node through which the tunnel passes.

可选地，所述网络设备400可以位于所述入口节点上。Alternatively, the network device 400 can be located on the ingress node.

可选地，所述网络设备400可以单独设置，在这种情况下，所述网络设备400还包括获取单元，该获取单元用于获取所述入口节点在所述隧道上的出接口的接口MTU值，所述确定单元403从所述接收节点返回的所述接收节点在所述隧道上的接口MTU值和所述隧道在所述入口节点上的接口MTU值中，选择最小的MTU值，作为所述隧道MTU值。Optionally, the network device 400 may be separately configured. In this case, the network device 400 further includes an acquiring unit, where the acquiring unit is configured to acquire an interface MTU of the outbound interface of the ingress node on the tunnel. a value, the determining unit 403 selects, from the receiving node, the interface MTU value on the tunnel and the interface MTU value of the tunnel on the ingress node, and selects a minimum MTU value as The tunnel MTU value.

可选地，所述网络设备400还包括：Optionally, the network device 400 further includes:

TTL设置单元404，用于设置承载所述第一扩展BFD控制报文的所述隧道报文中的生存时间TTL值，来完成将所述第一扩展BFD控制报文发送到所述隧道上的指定的接收节点上。The TTL setting unit 404 is configured to set a time-to-live TTL value in the tunnel packet that carries the first extended BFD control packet, to complete sending the first extended BFD control packet to the tunnel. On the specified receiving node.

值得说明的是，本发明实施例三提供的所述网络设备400的各功能单元，是基于实施例一提供的方法的具体实现，术语的定义和解决的问题与实施例一保持一致，此处不再赘述。It should be noted that the functional units of the network device 400 provided by the third embodiment of the present invention are based on the specific implementation of the method provided in the first embodiment. The definition of the term and the solution to the problem are consistent with the first embodiment. No longer.

本发明实施例三提供的网络设备400，通过发送单元401向所述隧道上的接收节点发送第一扩展双向转发检测BFD控制报文；通过接收单元402接收所述接收节点返回的第二扩展BFD控制报文；通过确定单元403从所述接收节点返回的所述接收节点在所述隧道上的接口MTU值和所述隧道在所述入口节点上的接口MTU值中，选择最小的MTU值，作为所述隧道MTU值。从而精确地确定隧道MTU，有助于减少分片次数和避免二次分片带来的重组失败问题。The network device 400 of the third embodiment of the present invention sends a first extended bidirectional forwarding detection BFD control message to the receiving node on the tunnel by the sending unit 401, and receives the second extended BFD returned by the receiving node by the receiving unit 402. Controlling the message; selecting, by the determining unit 403, the interface MTU value of the receiving node from the receiving node on the tunnel and the interface MTU value of the tunnel on the ingress node, selecting a minimum MTU value, As the tunnel MTU value. Thus accurately determining the tunnel MTU, helping to reduce the number of slices and avoid reorganization losses caused by secondary fragmentation The problem of defeat.

实施例四、 Embodiment 4

参见图5，本发明实施例提供一种网络设备500，用于发送隧道上的节点的最大传输单元MTU值，该网络设备500应用在由入口节点到出口节点的隧道上。该网络设备500包括：Referring to FIG. 5, an embodiment of the present invention provides a network device 500 for transmitting a maximum transmission unit MTU value of a node on a tunnel, where the network device 500 is applied to a tunnel from an ingress node to an egress node. The network device 500 includes:

接收单元501，用于接收所述入口节点发来的第一扩展双向转发检测BFD控制报文，所述第一扩展BFD控制报文包括MTU标志位，所述MTU标志位用于指示接收节点向所述入口节点返回所述接收节点在所述隧道上的接口MTU值；The receiving unit 501 is configured to receive a first extended bidirectional forwarding detection BFD control packet sent by the ingress node, where the first extended BFD control packet includes an MTU flag bit, where the MTU flag bit is used to indicate that the receiving node is Returning, by the ingress node, an interface MTU value of the receiving node on the tunnel;

获取单元502，用于获取所述接收节点在所述隧道上的接口MTU值；The obtaining unit 502 is configured to obtain an interface MTU value of the receiving node on the tunnel;

发送单元503，用于向入口节点返回第二扩展BFD控制报文，所述第二扩展BFD控制报文中携带所述接收节点在所述隧道上的接口MTU值。The sending unit 503 is configured to return a second extended BFD control packet to the ingress node, where the second extended BFD control packet carries an interface MTU value of the receiving node on the tunnel.

可选地，所述网络设备500可以位于所述接收设备上或单独设置。Optionally, the network device 500 may be located on the receiving device or separately.

本发明实施例四提供的网络设备500，通过所述接收单元501接收所述入口节点发来的所述第一扩展双向转发检测BFD控制报文，通过所述获取单元502获取所述接收节点在所述隧道上的接口MTU值，通过所述发送单元503向入口节点返回第二扩展BFD控制报文，从而将所述接收节点的接口MTU值发送给所述入口节点。本发明实施例有助于精确地确定隧道MTU，有助于减少分片次数和二次分片带来的重组失败问题。The network device 500 of the fourth embodiment of the present invention receives the first extended bidirectional forwarding detection BFD control packet sent by the ingress node by using the receiving unit 501, and acquires the receiving node by using the acquiring unit 502. The MTU value of the interface on the tunnel is returned by the sending unit 503 to the ingress node to send a second extended BFD control packet, so that the interface MTU value of the receiving node is sent to the ingress node. The embodiments of the present invention help to accurately determine the tunnel MTU, and help to reduce the number of fragmentation and reassembly failure problems caused by secondary fragmentation.

实施例五、 Embodiment 5

参见图6，本发明的一个实施例提供一种确定隧道最大传输单元MTU值的***600，应用在由入口节点到出口节点的隧道上，***600包括：第一网络设备601和第二网络设备602；Referring to FIG. 6, an embodiment of the present invention provides a system 600 for determining a maximum transmission unit MTU value of a tunnel, which is applied to a tunnel from an ingress node to an egress node, where the system 600 includes: a first network device 601 and a second network device. 602;

所述第一网络设备601，包括：The first network device 601 includes:

实施例三中所述的网络设备400；The network device 400 described in the third embodiment;

所述第二网络设备602，包括：The second network device 602 includes:

实施例四中所述的网络设备500。 The network device 500 described in the fourth embodiment.

值得说明的是，本发明实施例五提供的所述第一网络设备和所述第二网络设备的各功能单元，是基于实施例一至二提供的方法的具体实现和实施例三至四网络设备的组合，术语的定义和解决的问题与实施例一至四保持一致，此处不再赘述。It is to be noted that the functional units of the first network device and the second network device provided by the fifth embodiment of the present invention are based on the specific implementation of the methods provided in Embodiments 1 to 2 and the third to fourth network devices. The combination of the terms, the definition of the terms, and the problems solved are consistent with the first to fourth embodiments, and are not described herein again.

本发明实施例五提供的***，通过实施例三描述的网络设备和实施例四描述的网络设备的组合，通过扩展BFD控制报文，将隧道上各网络设备的接口MTU值收集起来，选取取值最小的接口MTU值为隧道MTU，从而精确地确定隧道MTU，有助于减少分片次数和二次分片带来的重组失败问题。The system provided in Embodiment 5 of the present invention, through the combination of the network device described in Embodiment 3 and the network device described in Embodiment 4, expands the BFD control packet, collects the MTU value of each network device on the tunnel, and selects the network interface. The MTU value of the interface with the smallest value is the tunnel MTU, so that the tunnel MTU can be accurately determined, which helps to reduce the number of fragmentation and the reorganization failure caused by the second fragmentation.

实施例六、 Embodiment 6

请参考图7，本发明的一个实施例提供一种网络设备700，该网络设备700可以是微处理计算机。比如：该网络设备700可以是通用计算机、客户定制机、手机终端或平板机等便携设备中的一种。该网络设备700包括：处理器704、存储器706、通信接口702和总线708。处理器704、存储器706和通信接口702通过总线708连接并完成相互间的通信。Referring to FIG. 7, an embodiment of the present invention provides a network device 700, which may be a microprocessor computer. For example, the network device 700 can be one of a portable device such as a general purpose computer, a custom machine, a mobile phone terminal, or a tablet. The network device 700 includes a processor 704, a memory 706, a communication interface 702, and a bus 708. The processor 704, the memory 706, and the communication interface 702 are connected by bus 708 and complete communication with each other.

所述总线708可以是工业标准体系结构(Industry Standard Architecture，简称为ISA)总线或外部设备互连(Peripheral Component，简称为PCI)总线或扩展工业标准体系结构(Extended Industry Standard Architecture，简称为EISA)总线等。所述总线可以包括地址总线、数据总线、控制总线中的一种或多种。为便于表示，图7中仅用一条粗线表示，但并不表示仅有一根总线或一种类型的总线，The bus 708 may be an Industry Standard Architecture (ISA) bus or a Peripheral Component (PCI) bus or an Extended Industry Standard Architecture (EISA). Bus, etc. The bus may include one or more of an address bus, a data bus, and a control bus. For convenience of representation, only one thick line is shown in FIG. 7, but it does not mean that there is only one bus or one type of bus.

存储器706用于存储可执行程序代码，该程序代码包括计算机操作指令。该程序代码用于完成实施例三的步骤101～103。存储器706可以包含高速RAM(Ramdom Access Memory)存储器。可选地，存储器706还可以包括非易失性存储器(non-volatile memory)。例如存储器706可以包括磁盘存储器。 Memory 706 is for storing executable program code, the program code including computer operating instructions. The program code is used to complete steps 101-103 of the third embodiment. The memory 706 can include a high speed RAM (Ramdom Access Memory) memory. Alternatively, the memory 706 may also include a non-volatile memory. For example, memory 706 can include disk storage.

处理器704可以是中央处理器(Central Processing Unit，简称为CPU)，或者处理器704可以是特定集成电路(Application Specific Integrated Circuit，简称为ASIC)，或者处理器704可以是被配置成实施本发明实施例的一个或多个集成电路。 The processor 704 may be a central processing unit (CPU), or the processor 704 may be an Application Specific Integrated Circuit (ASIC), or the processor 704 may be configured to implement the present invention. One or more integrated circuits of an embodiment.

通信接口702，用于执行实施例三中向所述隧道上的接收节点发送第一扩展双向转发检测BFD控制报文和接收所述接收节点返回的第二扩展BFD控制报文的操作。The communication interface 702 is configured to perform the operations of sending the first extended bidirectional forwarding detection BFD control message to the receiving node on the tunnel and receiving the second extended BFD control message returned by the receiving node in the third embodiment.

处理器704，用于读取存储器706中存储的指令，从而执行实施例三中从所述接收节点返回的所述接收节点在所述隧道上的接口MTU值和所述隧道在所述入口节点上的接口MTU值中，选择最小的MTU值，作为所述隧道MTU值的操作。The processor 704 is configured to read an instruction stored in the memory 706, so as to perform an interface MTU value of the receiving node on the tunnel returned from the receiving node in Embodiment 3, and the tunnel is at the ingress node. Among the interface MTU values, the smallest MTU value is selected as the operation of the tunnel MTU value.

其中，所述隧道在所述入口节点上的接口MTU值，可以是所述隧道经过的所述入口节点的出接口的接口MTU值。The interface MTU value of the tunnel on the ingress node may be the interface MTU value of the outbound interface of the ingress node through which the tunnel passes.

可选地，所述网络设备可以位于所述入口节点上。Optionally, the network device may be located on the ingress node.

可选地，所述网络设备可以单独设置，在这种情况下，所述网络设备还用于获取所述入口节点在所述隧道上的出接口的接口MTU值，从所述接收节点返回的所述接收节点在所述隧道上的接口MTU值和所述隧道在所述入口节点上的接口MTU值中，选择最小的MTU值，作为所述隧道MTU值。Optionally, the network device may be separately configured. In this case, the network device is further configured to obtain an interface MTU value of the outbound interface of the ingress node on the tunnel, and return from the receiving node. The receiving node selects a minimum MTU value as the tunnel MTU value among the interface MTU value on the tunnel and the interface MTU value of the tunnel on the ingress node.

本发明实施例六提供的网络设备，通过向所述隧道上的接收节点发送第一扩展双向转发检测BFD控制报文，接收所述接收节点返回的第二扩展BFD控制报文，从所述接收节点返回的所述接收节点在所述隧道上的接口MTU值和所述隧道在所述入口节点上的接口MTU值中，选择最小的MTU值，作为所述隧道MTU值。从而精确地确定隧道MTU，有助于减少分片次数和避免二次分片带来的重组失败问题。The network device provided in the sixth embodiment of the present invention sends a first extended bidirectional forwarding detection BFD control packet to the receiving node on the tunnel, and receives a second extended BFD control packet returned by the receiving node, and receives the second extended BFD control packet from the receiving node. And determining, by the receiving node, the interface MTU value on the tunnel and the interface MTU value of the tunnel on the ingress node, selecting a minimum MTU value as the tunnel MTU value. Thus, the tunnel MTU is accurately determined, which helps to reduce the number of shards and avoid the problem of reassembly failure caused by the second shard.

实施例七、Example VII.

请参考图8，本发明的一个实施例提供一种网络设备800，该网络设备800可以是微处理计算机。比如：该网络设备700可以是通用计算机、客户定制机、手机终端或平板机等便携设备中的一种。该网络设备800包括：处理器804、存储器806、通信接口802和总线808。处理器804、存储器806和通信接口802通过总线808连接并完成相互间的通信。Referring to FIG. 8, an embodiment of the present invention provides a network device 800, which may be a microprocessor computer. For example, the network device 700 can be one of a portable device such as a general purpose computer, a custom machine, a mobile phone terminal, or a tablet. The network device 800 includes a processor 804, a memory 806, a communication interface 802, and a bus 808. Processor 804, memory 806, and communication interface 802 are connected by bus 808 and complete communication with one another.

所述总线808可以是工业标准体系结构(Industry Standard Architecture，简称为ISA)总线或外部设备互连(Peripheral Component，简称为PCI)总线或扩展工业标准体系结构(Extended Industry Standard Architecture，简称为EISA)总线等。所述总线可以分为地址总线、数据总线、控制总线中的一种或多种。为便于表示，图8中仅用一条粗线表示，但并不表示仅有一根总线或一种类型的总线，The bus 808 may be an Industry Standard Architecture (ISA) bus or a Peripheral Component (PCI) bus. Or extend the Industrial Standard Architecture (EISA) bus. The bus can be divided into one or more of an address bus, a data bus, and a control bus. For ease of representation, only one thick line is shown in Figure 8, but it does not mean that there is only one bus or one type of bus.

存储器806用于存储可执行程序代码，该程序代码包括计算机操作指令。该程序代码用于完成实施例三的步骤301～303。存储器806可以包含高速RAM(Ramdom Access Memory)存储器。可选地，存储器806还可以还包括非易失性存储器(non-volatile memory)。例如存储器806可以包括磁盘存储器。 Memory 806 is for storing executable program code, the program code including computer operating instructions. The program code is used to complete steps 301-303 of the third embodiment. The memory 806 can include a high speed RAM (Ramdom Access Memory) memory. Optionally, the memory 806 may further include a non-volatile memory. For example, memory 806 can include disk storage.

处理器804可以是一个中央处理器(Central Processing Unit，简称为CPU)，或者是处理器804可以特定集成电路(Application Specific Integrated Circuit，简称为ASIC)，或者处理器804可以是被配置成实施本发明实施例的一个或多个集成电路。The processor 804 may be a central processing unit (CPU), or the processor 804 may be an application specific integrated circuit (ASIC), or the processor 804 may be configured to implement the present invention. One or more integrated circuits of an embodiment of the invention.

通信接口802，用于执行实施例四中的接收所述入口节点发来的第一扩展双向转发检测BFD控制报文和向入口节点返回第二扩展BFD控制报文的操作。The communication interface 802 is configured to perform the operations of receiving the first extended bidirectional forwarding detection BFD control message sent by the ingress node and returning the second extended BFD control message to the ingress node in the fourth embodiment.

处理器804，用于读取存储器806中存储的指令，从而执行实施例四中获取所述接收节点在所述隧道上的接口MTU值的操作。The processor 804 is configured to read the instruction stored in the memory 806, so as to perform the operation of obtaining the interface MTU value of the receiving node on the tunnel in Embodiment 4.

可选地，所述网络设备可以位于所述接收设备上或单独设置。Alternatively, the network device may be located on the receiving device or separately.

本发明实施例七提供的网络设备，通过接收入口节点发来的所述第一扩展双向转发检测BFD控制报文，获取所述接收节点在所述隧道上的接口MTU值，向入口节点返回第二扩展BFD控制报文，从而将所述接收节点的接口MTU值发送给所述入口节点。本发明实施例有助于精确地确定隧道MTU，有助于减少分片次数和二次分片带来的重组失败问题。The network device provided in Embodiment 7 of the present invention obtains the MTU value of the interface of the receiving node on the tunnel by receiving the first extended bidirectional forwarding detection BFD control packet sent by the ingress node, and returns the MTU value of the interface of the receiving node to the ingress node. 2. The BFD control packet is extended, so that the interface MTU value of the receiving node is sent to the ingress node. The embodiments of the present invention help to accurately determine the tunnel MTU, and help to reduce the number of fragmentation and reassembly failure problems caused by secondary fragmentation.

本发明方案可以在由计算机执行的计算机可执行指令的一般上下文中描述，例如程序单元。一般地，程序单元包括执行特定任务或实现特定抽象数据类型的例程、程序、对象、组件、数据结构等等。也可以在分布式计算环境中实践本发明方案，在这些分布式计算环境中，由通过通信网络而被连接的远程处理设备来执行任务。在分布式计算环境中，程序单元可以位于包括存储设备在内的本地和远程计算机存储介质中。The inventive arrangements may be described in the general context of computer-executable instructions executed by a computer, such as a program element. Generally, program units include routines, programs, objects, components, data structures, and the like that perform particular tasks or implement particular abstract data types. The inventive arrangements can also be practiced in distributed computing environments where tasks are performed by remote processing devices that are connected through a communication network. In a distributed computing environment, program elements can be located in a storage device In local and remote computer storage media.

本说明书中的各个实施例均采用递进的方式描述，各个实施例之间相同相似的部分互相参见即可，每个实施例重点说明的都是与其它实施例的不同之处。尤其，对于装置实施例而言，由于其基本相似于方法实施例，所以描述得比较简单，相关之处参见方法实施例的部分说明即可。以上所描述的装置实施例仅仅是示意性的，其中所述作为分离部件说明的单元可以是或者也可以不是物理上分开的，作为单元显示的部件可以是或者也可以不是物理单元，即可以位于一个地方，或者也可以分布到多个网络单元上。可以根据实际的需要选择其中的部分或者全部模块来实现本实施例方案的目的。本领域普通技术人员在不付出创造性劳动的情况下，即可以理解并实施。The various embodiments in the specification are described in a progressive manner, and the same or similar parts between the various embodiments may be referred to each other, and each embodiment focuses on the differences from the other embodiments. In particular, for the device embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the description of the method embodiment. The device embodiments described above are merely illustrative, wherein the units described as separate components may or may not be physically separate, and the components displayed as units may or may not be physical units, ie may be located A place, or it can be distributed to multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the embodiment. Those of ordinary skill in the art can understand and implement without any creative effort.

以上对本发明实施例进行了详细介绍，本文中应用了具体实施方式对本发明进行了阐述，以上实施例的说明只是用于帮助理解本发明的方法及设备；同时，对于本领域的一般技术人员，依据本发明的思想，在具体实施方式及应用范围上均会有改变之处，综上所述，本说明书内容不应理解为对本发明的限制。 The embodiments of the present invention have been described in detail above, and the present invention has been described with reference to the specific embodiments. The description of the above embodiments is only for facilitating understanding of the method and device of the present invention. Meanwhile, for those skilled in the art, The present invention is not limited by the scope of the present invention.

Claims

一种确定隧道最大传输单元MTU值的方法，其特征在于，所述方法应用在由入口节点到出口节点的隧道上，所述方法包括：A method for determining a maximum transmission unit MTU value of a tunnel, wherein the method is applied to a tunnel from an ingress node to an egress node, the method comprising:

所述入口节点向所述隧道上的接收节点发送第一扩展双向转发检测BFD控制报文，所述第一扩展BFD控制报文包括MTU标志位，所述MTU标志位用于指示所述接收节点向所述入口节点返回所述接收节点在所述隧道上的接口的MTU值，所述接收节点为所述隧道上除了所述入口节点以外、经过的所有节点；The ingress node sends a first extended bidirectional forwarding detection BFD control packet to the receiving node on the tunnel, where the first extended BFD control packet includes an MTU flag bit, and the MTU flag bit is used to indicate the receiving node. Returning, to the ingress node, an MTU value of an interface of the receiving node on the tunnel, where the receiving node is all nodes on the tunnel except the ingress node;

所述入口节点接收所述接收节点返回的第二扩展BFD控制报文，所述第二扩展BFD控制报文中携带所述接收节点在所述隧道上的接口MTU值；The ingress node receives a second extended BFD control packet returned by the receiving node, where the second extended BFD control packet carries an interface MTU value of the receiving node on the tunnel;

所述入口节点从所述接收节点返回的所述接收节点在所述隧道上的接口MTU值和所述隧道在所述入口节点上的接口MTU值中，选择最小的MTU值，作为所述隧道MTU值。Selecting, by the ingress node, an interface MTU value of the receiving node from the receiving node and an interface MTU value of the tunnel on the ingress node, selecting a minimum MTU value as the tunnel MTU value.
根据权利要求1所述的方法，其特征在于，所述MTU标志位用所述第一扩展BFD控制报文的诊断码Diag字段中的一位标识，或者所述Diag字段的预留值标识。The method according to claim 1, wherein the MTU flag is identified by a bit in a Diag field of the Diagnostic Code of the first extended BFD control message, or a reserved value of the Diag field.
根据权利要求1或2所述的方法，其特征在于，所述第二扩展BFD控制报文包括：The method according to claim 1 or 2, wherein the second extended BFD control message comprises:

MTU类型长度值TLV，用于携带所述接收节点在所述隧道上的接口MTU值。The MTU type length value TLV is used to carry the interface MTU value of the receiving node on the tunnel.
根据权利要求3所述的方法，其特征在于，所述MTU TLV具体包括：类型Type、长度Length和值Value，所述Type指示所述Value的类型为MTU，所述Length指示所述MTU TLV的长度，所述Value为所述接收节点在所述隧道上的接口MTU值；The method according to claim 3, wherein the MTU TLV specifically includes: a type Type, a length Length, and a value Value, the Type indicates that the type of the Value is an MTU, and the Length indicates the MTU TLV. Length, the value is an interface MTU value of the receiving node on the tunnel;

所述MTU TLV位于所述第一扩展BFD控制报文的尾部。The MTU TLV is located at the end of the first extended BFD control message.
根据权利要求1至4任一所述的方法，所述入口节点向接收节点发送第一扩展BFD控制报文，其特征在于，还包括：The method according to any one of claims 1 to 4, wherein the ingress node sends a first extended BFD control message to the receiving node, further comprising:

所述入口节点通过设置承载所述第一扩展BFD控制报文的所述隧道报文中的生存时间TTL值，来完成将所述第一扩展BFD控制报文发送到所述隧道上的指定的接收节点上。The ingress node sends the first extended BFD control packet to the tunnel by setting a lifetime TTL value in the tunnel packet that carries the first extended BFD control packet. On the specified receiving node.
根据权利要求1至5任一所述的方法，其特征在于，A method according to any one of claims 1 to 5, characterized in that

如果所述接收节点为所述出口节点，则所述接收节点上的接口MTU值是所述隧道在所述出口节点在所述隧道上的入接口的MTU值；和/或If the receiving node is the egress node, the interface MTU value on the receiving node is an MTU value of the inbound interface of the tunnel at the egress node on the tunnel; and/or

如果所述接收节点为所述隧道上所述入口节点到所述出口节点之间的中间节点，则所述接收节点上的接口MTU值为所述隧道穿过所述接收节点的入接口MTU值和出接口MTU值中的最小值。If the receiving node is an intermediate node between the ingress node and the egress node on the tunnel, the interface MTU value on the receiving node is an inbound interface MTU value of the tunnel passing through the receiving node. And the minimum value of the outbound interface MTU value.
一种发送最大传输单元MTU的方法，其特征在于，所述方法应用在由入口节点到出口节点的隧道上，所述方法包括：A method for transmitting a maximum transmission unit MTU, wherein the method is applied to a tunnel from an ingress node to an egress node, the method comprising:

接收节点接收所述入口节点发来的第一扩展双向转发检测BFD控制报文，所述第一扩展BFD控制报文包括MTU标志位，所述MTU标志位用于指示所述接收节点向所述入口节点返回所述接收节点在所述隧道上的接口MTU值；Receiving, by the receiving node, a first extended bidirectional forwarding detection BFD control message sent by the ingress node, where the first extended BFD control message includes an MTU flag bit, where the MTU flag bit is used to indicate that the receiving node is to the The ingress node returns an interface MTU value of the receiving node on the tunnel;

所述接收节点获取所述接收节点在所述隧道上的接口MTU值；Receiving, by the receiving node, an interface MTU value of the receiving node on the tunnel;

所述接收节点向入口节点返回第二扩展BFD控制报文，所述第二扩展BFD控制报文中携带所述接收节点在所述隧道上的接口MTU值。The receiving node returns a second extended BFD control packet to the ingress node, where the second extended BFD control packet carries the interface MTU value of the receiving node on the tunnel.
根据权利要求7所述的方法，其特征在于，所述MTU标志位用所述第一扩展BFD控制报文的诊断码Diag字段中的一位标识，或者所述Diag字段的预留值标识。The method according to claim 7, wherein the MTU flag is identified by a bit in the Diag field of the Diagnostic Code of the first extended BFD control message or by a reserved value of the Diag field.
根据权利要求7或8所述的方法，其特征在于，所述第二扩展BFD控制报文具体包括：The method according to claim 7 or 8, wherein the second extended BFD control message specifically includes:

MTU类型长度值TLV，用于携带所述接收节点在所述隧道上的接口MTU值。The MTU type length value TLV is used to carry the interface MTU value of the receiving node on the tunnel.
根据权利要求9所述的方法，其特征在于，所述MTU TLV具体包括：类型Type、长度Length和值Value，所述Type指示所述Value的类型为MTU，所述Length指示所述MTU TLV的长度，所述Value为所述接收节点在所述隧道上的接口MTU值；The method according to claim 9, wherein the MTU TLV specifically includes: a type Type, a length Length, and a value Value, the Type indicates that the type of the Value is an MTU, and the Length indicates the MTU TLV. Length, the value is an interface MTU value of the receiving node on the tunnel;

所述MTU TLV位于所述第一扩展BFD控制报文的尾部。The MTU TLV is located at the end of the first extended BFD control message.
根据权利要求7～10任一项所述的方法，其特征在于， A method according to any one of claims 7 to 10, characterized in that

如果所述接收节点为所述出口节点，则所述接收节点上的接口MTU值是所述隧道在所述出口节点在所述隧道上的入接口的MTU值；和/或If the receiving node is the egress node, the interface MTU value on the receiving node is an MTU value of the inbound interface of the tunnel at the egress node on the tunnel; and/or

如果所述接收节点为所述隧道上所述入口节点到所述出口节点之间的中间节点，则所述接收节点上的接口MTU值为所述隧道穿过所述接收节点的入接口MTU值和出接口MTU值中的最小值。If the receiving node is an intermediate node between the ingress node and the egress node on the tunnel, the interface MTU value on the receiving node is an inbound interface MTU value of the tunnel passing through the receiving node. And the minimum value of the outbound interface MTU value.
根据权利要求7至11任一所述的方法，其特征在于，在所述接收节点接收入口节点发来的第一扩展BFD控制报文之后，还包括：The method according to any one of claims 7 to 11, wherein after the receiving node receives the first extended BFD control message sent by the ingress node, the method further includes:

所述接收节点解析承载所述第一扩展BFD控制报文的所述隧道报文中的生存时间TTL值，如果解析出TTL值等于1，则向所述入口节点发送所述接收节点在所述隧道上的接口MTU值。The receiving node parses the TTL value of the lifetime time in the tunnel packet carrying the first extended BFD control packet, and if the TTL value is equal to 1, the receiving node sends the receiving node to the ingress node. Interface MTU value on the tunnel.
一种网络设备，用于确定隧道最大传输单元MTU值，其特征在于，所述网络设备应用在由入口节点到出口节点的隧道上，该网络设备包括：A network device, configured to determine a maximum transmission unit MTU value of a tunnel, where the network device is applied to a tunnel from an ingress node to an egress node, where the network device includes:

发送单元，用于向所述隧道上的接收节点发送第一扩展双向转发检测BFD控制报文，所述第一扩展BFD控制报文包括MTU标志位，所述MTU标志位用于指示所述接收节点向所述入口节点返回所述接收节点在所述隧道上的接口的MTU值，所述接收节点为所述隧道上除了所述入口节点以外、经过的所有节点；a sending unit, configured to send, to the receiving node on the tunnel, a first extended bidirectional forwarding detection BFD control packet, where the first extended BFD control packet includes an MTU flag bit, where the MTU flag bit is used to indicate the receiving Returning, by the node, the MTU value of the interface of the receiving node on the tunnel to the ingress node, where the receiving node is all nodes on the tunnel except the ingress node;

接收单元，用于接收所述接收节点返回的第二扩展BFD控制报文，所述第二扩展BFD控制报文中携带所述接收节点在所述隧道上的接口MTU值；a receiving unit, configured to receive a second extended BFD control packet returned by the receiving node, where the second extended BFD control packet carries an interface MTU value of the receiving node on the tunnel;

确定单元，用于从所述接收节点返回的所述接收节点在所述隧道上的接口MTU值和所述隧道在所述入口节点上的接口MTU值中，选择最小的MTU值，作为所述隧道MTU值。a determining unit, configured to select, from the receiving node, an interface MTU value on the tunnel and an interface MTU value of the tunnel on the ingress node, select a minimum MTU value, as the Tunnel MTU value.
根据权利要求13所述的装置，其特征在于，还包括：The device according to claim 13, further comprising:

TTL设置单元，用于设置承载所述第一扩展BFD控制报文的所述隧道报文中的生存时间TTL值，来完成将所述第一扩展BFD控制报文发送到所述隧道上的指定的接收节点上。a TTL setting unit, configured to set a time-to-live TTL value in the tunnel packet that carries the first extended BFD control packet, to complete the designation of sending the first extended BFD control packet to the tunnel On the receiving node.
一种网络设备，用于发送隧道最大传输单元MTU值，其特征在于，所述网络设备应用在由入口节点到出口节点的隧道上，所述网络设备包括：A network device, configured to send a tunnel maximum transmission unit (MTU) value, wherein the network device is applied to a tunnel from an ingress node to an egress node, where the network device includes:

接收单元，用于接收所述入口节点发来的第一扩展双向转发检测BFD控制报文，所述第一扩展BFD控制报文包括MTU标志位，所述MTU标志位用于指示所述接收节点向所述入口节点返回所述接收节点在所述隧道上的接口MTU值；a receiving unit, configured to receive a first extended bidirectional forwarding detection BFD control sent by the ingress node a message, the first extended BFD control message includes an MTU flag bit, where the MTU flag bit is used to indicate that the receiving node returns an interface MTU value of the receiving node on the tunnel to the ingress node;

获取单元，用于获取所述接收节点在所述隧道上的接口MTU值；An acquiring unit, configured to acquire an interface MTU value of the receiving node on the tunnel;

发送单元，用于向入口节点返回第二扩展BFD控制报文，所述第二扩展BFD控制报文中携带所述接收节点在所述隧道上的接口MTU值。And a sending unit, configured to return a second extended BFD control packet to the ingress node, where the second extended BFD control packet carries an interface MTU value of the receiving node on the tunnel.
一种用于确定隧道最大传输单元MTU值的***，其特征在于，包括：第一网络设备和第二网络设备，所述第一网络设备为权利要求13或14所述的网络设备；所述第二网络设备为权利要求15所述的网络设备。 A system for determining a maximum transmission unit MTU value of a tunnel, comprising: a first network device and a second network device, wherein the first network device is the network device according to claim 13 or 14; The second network device is the network device of claim 15.