VLL in SVC Mode

Introduction

The static virtual circuit (SVC) mode is a simplified version of Martini. Unlike the Martini mode, which uses LDP to exchange VC labels, the SVC mode uses VC labels that are manually configured on PE devices.

An SVC VLL uses static VC labels and does not need VC label mapping. Therefore, LDP is not required for transmitting VC labels.

Topology

The SVC mode sets up a public tunnel (outer label) in the same way as the Martini mode. The inner label is manually configured during VC setup, and PE devices do not need to exchange VC labels using any signaling protocol. The SVC mode does not support local connections. The network topology and packet exchange process in SVC mode are the same as those in Martini mode.

Figure 1 shows packet exchange between a VPN's two sites through SVC VLL.

Figure 1 Packet exchange in SVC mode

As shown in this example, PE1's label setting for sent packets is 4000 and the label for received packets is 3500. On PE2, the label for sent packets is 3500 and the label for received packets is 4000. When a packet travels from Site1 to Site2 of VPN1, PE1 adds the inner VC label 4000 to the packet. After PE2 receives the packet with the inner VC label 4000, it sends the packet to the CE device through the AC mapping the inner VC label.