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DES-7200 Configuration Guide Chapter 3 MPLS Reliability Configuration
3-15
The router without GR detection capability. It cannot detect that the neighboring router is
experiencing GR and cannot help the neighboring router to complete GR. This is generally
because the no GR feature is provided by the system software or the GR feature is disabled.
GR routers by role
During the process of router restart, routers can be classified into GR-Restarter router and
GR-Helper router according to router's role.
z GR-Restarter router
GR-Restarter router must be a GR-Capable router, and the restart process is triggered by the
administrator or fault.
z GR-Helper router
Neighbor of GR-Restarter, at least a GR-Aware router.
Working principle
The control plane and forwarding plane of a traditional device are handled by the same
processor, which maintains both the routing table and forwarding table. To enhance the
forwarding performance and reliability performance of the device, multiprocessor architecture is
employed on medium- and high-end devices. The processor handling control modules such as
routing protocol is located on the main management board, while the processor responsible for
data forwarding is located on the line card. The control plane and forwarding plane are separated
in this way. When the control plane restarts, the data forwarding on the line card won't be
affected. This technology provides a precondition for achieving GR. The GR-Capable router as
mentioned herein has separated control plane and forwarding plane.
Assuming that the network topology of VPN is shown below. The network has the following
characteristics:
z CE device represents the customer network running IGP or eBGP protocol.
z Provider network is formed between PEs and P device, running IGP protocol.
z PE1, P and PE2 establish a public-network tunnel and LSP path through LDP protocol.
z PE1 and PE2 establish a private-network tunnel through iBGP protocol.
z IGP protocol, BGP protocol and LDP protocol are GR-capable.
z PE devices are GR-Capable routers, while P device is a GR-Aware router.