Packet Type
Packet Subtype Description
Primary edge
interface
election packet
-
After an interface has SEP enabled, it considers itself
the primary edge interface if it is qualified for primary
edge interface selection. The interface then
periodically sends primary edge interface election
packets without waiting for the success of neighbor
negotiations. A primary edge interface election packet
contains the interface role (primary edge interface,
secondary edge interface, or common interface), bridge
MAC address of the interface, interface ID, and
integrity of the topology database.
Preemption
packet
Preemption
request packet
A preemption packet is used to block a specified
interface.
Preemption packets are sent by the elected primary
edge interface or brother interface of a no-neighbor
primary edge interface.
Preemption ACK
packet
8.2.3 SEP Implementation Mechanisms
Neighbor Negotiation Mechanism
After an interface is added to a SEP segment, neighbor negotiations start. The interface and its
neighbor exchange Hello packets to establish a neighbor relationship. After neighbor
negotiations succeed, the two interfaces continue to exchange Hello packets to detect their
neighbor status.
Neighbor negotiations prevent unidirectional links because neighbor negotiations are
bidirectional. Interfaces at both ends of a link, must send Hello packets to each other, as a means
of status confirmation. If an interface does not receive a Hello packet from an interface at the
other end of a link within a specified period, the interface considers the other to be Down.
Neighbor negotiations provide information required to obtain the SEP segment topology.
Interfaces establish neighbor relationships through neighbor negotiations, forming a complete
SEP segment. Therefore, the SEP segment topology can be obtained.
Synchronization of SEP LSA Databases and Topology Display
l
Synchronization of SEP link state advertisement (LSA) databases
After neighbor negotiations are complete, devices in a SEP segment enter the LSA database
synchronization phase and periodically send LSAs. After a device receives LSAs from
other devices, the device updates its LSA database. This ensures that the LSA databases of
all devices in the SEP segment are consistent.
If a device does not receive LSAs from its peer device or other devices in the SEP segment
within three LSA transmission intervals, the device will age the database that saves the
LSAs of the other devices in the SEP segment.
When a faulty device in a SEP segment recovers, the device needs to obtain topology
information from the other devices in the SEP segment and sends LSA request packets to
Huawei AR530&AR550 Series Industrial Switch Routers
Configuration Guide - Ethernet Switching
8 SEP Configuration
Issue 01 (2014-11-30)
Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
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