Introduction To Vpn Tunnels - Huawei quidway s7700 Configuration Manual

Quidway S7700 Smart Routing Switch
Configuration Guide - VPN

1.1 Introduction to VPN Tunnels

This part briefly introduces VPN tunnels, including such commonly-used VPN tunnels as LSPs,
TE tunnels, and GRE tunnels, and the configuration and management of these VPN tunnels.
In Virtual Private Networks (VPNs), based on the tunnel technology, dedicated transmission
channels, namely, tunnels, can be set up in backbone networks. Packets can then be transparently
transmitted through the tunnels.
Common VPN Tunnels
Common VPN tunnels are described as follows:
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Tunnel Configuration Management
The setup and management of tunnels vary with the tunnel type. For example, GRE tunnels and
MPLS TE tunnels, both of which are Constraint-based Routed LSP (CR-LSP) tunnels, are
managed by using tunnel interfaces, whereas MPLS LSP tunnels are managed without using
tunnel interfaces.
This chapter describes the configurations of tunnel interfaces and general tunnel management.
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An application selects tunnels according to the tunnel policy. If no tunnel policy is configured,
the default tunnel policy is selected. By default, no load balancing can be performed among
tunnels, and only one LSP tunnel can be selected.
Issue 01 (2011-07-15)
LSP
When LSPs are adopted as tunnels on the public network of Multi-Protocol Label Switching
(MPLS) VPN, IP packet headers are analyzed only on Provider Edges (PEs), rather than
on each device along which VPN packets are transmitted. In this manner, the time to process
VPN packets shortens and the delay of packet transmission decreases. In addition, MPLS
labels are supported by all link layer protocols. A Label Switched Path (LSP) is similar to
an Asynchronous Transfer Mode (ATM) Virtual Circuit (VC)or a Frame Relay (FR) VC
in function and security.
MPLS TE
Generally, carriers are required to provide VPN users with Quality of Service (QoS)
guarantee for various end-to-end services, such as the voice service, video service, key data
service, and Internet access service. To meet users' requirements, carriers offer the MPLS
Traffic Engineering (MPLS TE) tunnels, which can optimize network resources and offer
users with QoS guaranteed services.
GRE
In an MPLS Layer 3 VPN (MPLS L3VPN), a CE and a PEmust have a direct connection.
If they are not directly connected, a GRE tunnel is generally set up between the CE and the
PE to ensure the CE can access MPLS VPN.
Tunnel management: informs the current application about the tunnel status and checks the
tunnel and tunnel policy based on the destination IP address reported by the application.
Tunnel policy: selects a tunnel based on the destination IP address.
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