1.2 VPN Tunnel Features Supported by the S7700
The S7700 supports such VPN tunnel features as the select-sequence tunnel policy and tunnel
binding policy.
An application (such as VPN) selects tunnels according to the tunnel policy. If no tunnel policy
is configured, the tunnel management module selects the tunnel according to the default tunnel
policy.
The tunnel policy can be in either of two modes:
l Select-sequence
l Tunnel binding
These two modes are mutually exclusive.
Select-sequence Mode
With the tunnel policy of the select-sequence mode, you can specify the sequence to select the
tunnel types, and the number of tunnels participating in load balancing.
In the tunnel policy, tunnels are selected in sequence. If a tunnel listed earlier is Up and not
bound, it is selected irrespective of whether another service has selected it. The subsequent tunnel
is not selected in most cases, except that load balancing is carried out, or the preceding tunnels
are in the Down state.
For example, in a tunnel policy, both LSPs and CR-LSPs to the same destination can be selected,
and LSPs are prior to CR-LSPs. If LSPs do not exist, a VPN chooses CR-LSPs. After an LSP
is set up, the VPN selects the LSP and does not use CR-LSPs anymore.
If there are multiple eligible tunnels of the same type, one or more tunnels are chosen randomly
in the tunnel policy.
In select-sequence mode, if both CR-LSPs and LSPs can be selected, CR-LSPs are prior to LSPs,
and the number of tunnels in load balancing is 3, the policies to select tunnels are shown as
below:
l The CR-LSP in the Up state is preferred. If the number of CR-LSPs that are Up is smaller
than 3 (CR-LSPs are not sufficient or CR-LSPs are sufficient whereas their status is Down),
LSPs in the Up state are also selected.
l Suppose three tunnels have been selected, one of which is a LSP. If a CR-LSP tunnel is
added or a CR-LSP in the Down state goes Up, the CR-LSP is selected and the LSP quits
the load balancing.
l If the number of tunnels in load balancing at the moment is smaller than the configured
number, the newly added CR-LSP or LSP in the Up state participates in load balancing.
l The number of tunnels in load balancing is decided by the number of the eligible tunnels.
For example, if only one CR-LSP and one LSP in the Up state, load balancing is performed
between them. The tunnels of other types are not selected even if they are Up.
l The load balancing for tunnels differs from the load balancing for routes. For example,
when three CR-LSPs are used for load balancing, they may be on the same path. While
three routes are used for load balancing, different three paths are used actually.
Quidway S7700 Smart Routing Switch
Configuration Guide - VPN 1 VPN Tunnel Management Configuration
Issue 01 (2011-07-15) Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
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