--- MPLS ATM network engineering technology Advanced articles

Detailed static LSP

Static LSP features:
do not use a label distribution protocol (LDP), do not need to exchange control packets, resource consumption is relatively small;
established by static LSP can not be dynamically adjusted according to changes in the network topology, you require administrator intervention.
Static LSP for simple and stable network topology.

Combat simulation experiment

R2:

static-lsp ingress R2_R5 destination 5.5.5.5 32 nexthop 23.1.1.3 out-label 100

R3：

static-lsp transit R2_R5 incoming-interface GigabitEthernet0/0/1 in-label 100 nexthop 34.1.1.4 out-label 200

R4：

static-lsp transit R2_R5 incoming-interface GigabitEthernet0/0/1 in-label 200 nexthop 45.1.1.5 out-label 300

R5:

static-lsp egress R2_R5 incoming-interface GigabitEthernet0/0/1 in-label 300

Check the following




tests are as follows:

The dynamic LSP Detailed

Dynamic LSP by LDP protocol for FEC classification, distribution and labeling of LSP establishment and maintenance operations.
Dynamic LSP features:
Network configuration is simple, easy to manage and maintain;
support dynamic routing based upon the establishment of LSP, the network topology changes, can reflect network conditions.

Combat simulation experiment

执行命令mpls ldp

Enable global LDP function

执行命令interface interface-type interface-number
执行命令mpls ldp

The MPLS LDP on the interface. By default, MPLS LDP capability connectors are not in an enabled state.
View the LDP neighbor relationship

LDP neighbor discovery protocol

When two devices enabled with MPLS and MPLS LDP, LSR transmits periodically (5S) Hello messages own table name exists, the message is encapsulated in UDP packets, the source and destination port 646, the message destination IP address as the multicast IP address 224.0.0.2
(224.0.0.2 router or all three switches are listening)
the LDP a Hello message carrying the Transport address field, that the configuration of the field device LSR ID, using Hello transport ID inside the three-way handshake to establish a
larger one transport address as the active side, initiates a TCP connection. RTB as the active TCP connection, RTA as a passive waiting for the other side initiates the connection.

LDP neighbor relationship

After the TCP connection is established, initialization message sent by the active side RTB, negotiated the establishment of relevant parameters LDP sessions.

LDP会话的相关参数包括LDP协议版本、标签分发方式、Keepalive保持定时器的值、最大PDU长度和标签空间等。

被动方RTA收到初始化消息后，如果RTA接受相关参数，则发送初始化消息，同时发送Keepalive消息给主动方RTB。

如果被动方RTA不能接受相关参数，则发送Notification消息终止LDP会话的建立。

主动方RTB收到初始化消息后，接受相关参数，则发送Keepalive消息给被动方RTA。

如果主动方RTB不能接受相关参数，则发送Notification消息给被动方RTA终止LDP会话的建立。

当双方都收到对端的Keepalive消息后，LDP会话建立成功。LDP会话建立成功后，进行FEC的创建与标签的分发。

实验如下：

标签发布/控制/保持方式详解

标签的发布方式

DU（Downstream Unsolicited，下游自主方式）DoD（Downstream on Demand，下游按需方式）
华为设备默认采用DU的方式发布标签。

可以直接向邻居分配标签。在网络拓扑发生变化时，采用DU方式可以快速反应为新的拓扑分发标签，收敛时间相对于DoD方式较短。

配置DoD的标签发布方式

[LSRA] interface gigabitethernet 1/0/0 
[LSRA-GigabitEthernet1/0/0] mpls ldp advertisement dod 
[LSRA-GigabitEthernet1/0/0] quit

蓝色方框里面抓不到request报文

红色方框里面可以抓到request报文

标签的分配控制方式

Work of the Independent (independent label distribution control mode): the local LSR can autonomously allocate a label is bound to an IP packet, and notifies the upstream LSR, the downstream label without waiting.
The Ordered (in ordered mode): LSR only when the IP packet has a label with this next hop, the LSR or egress node is the IP packet, the LSR can send the IP packet to the tag upstream .
Currently, the device supports only Ordered.
Ordered uses way, the LSR only when the tag has the IP packet having the next hop, in order to distribute labels to the upstream, downstream of this is to avoid unassigned IP packet label convergence time or longer, the upstream label allocated, It begins to forward data loss caused.

Question: R5 At this point it is possible to produce labels 6.6.6.6?

Hold mode label

Liberal (liberal mode): message received from a neighbor LSR label binding regardless of whether the neighbor LSR is its next hop. Conservative (conservative label retention mode): message received from a neighbor LSR label mapping only when the neighbor next-hop LSR is when their retention.
Liberal label retention mode, LSR can use the previous non-next hop labels sent quickly rebuild LSP, but requires more memory and label space.
Using conservative label retention mode, LSR leaving only the label from the next hop, saving memory and label space but the LSP reconstruction will be slower



to adjust the cost of R3 G0 / 0/0 interface greatly 10