What is the difference between Detour and Bypass MPLS TE FRR protection modes.
Detour mode: One-to-one backup mode. In this mode, a backup LSP is established to protect a single primary LSP and the backup LSP is called a detour LSP. Thus, maintaining state information for backup paths protecting individual LSPs is a significant resource burden for the PLR. Moreover, periodic refresh messages sent by the PLR, in order to maintain each backup path, may become a network bottleneck.
Bypass mode: Facility backup mode. In this mode, a backup LSP is established to protection more than one primary LSP and the backup LSP is called a bypass LSP. Thus, fewer states need to be maintained and refreshed which results in a scalable solution.
In practice, the bypass mode is widely used.
Currently, Huawei and Cisco supports only the bypass mode.
Juniper support both detour and bypass.