8.1 Introduction to SEP
This section describes the definition and purpose of SEP.
Definition
The Smart Ethernet Protection (SEP) protocol is a ring network protocol specially used for the
Ethernet link layer. A SEP segment consists of interconnected Layer 2 switching devices
configured with the same SEP segment ID and control VLAN ID. A SEP segment is the basic
unit for SEP.
Purpose
Generally, redundant links are used on an Ethernet switching network to provide link backup
and enhance network reliability. The use of redundant links, however, may produce loops,
causing broadcast storms and rendering the MAC address table unstable. As a result,
communication quality deteriorates, and services may even be interrupted. To solve the loop
problem, Huawei datacom devices support the following ring network protocols:
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STP/RSTP/MSTP
STP, RSTP, and MSTP are standard protocols for breaking loops on Ethernet networks.
They are mature and widely used. Huawei devices running STP, RSTP, or MSTP can
communicate with non-Huawei devices. Networks running these protocols converge
slowly (in seconds), failing to meet transmission requirements of some real-time services.
The convergence time is affected by the network topology.
Huawei developed SEP to overcome the disadvantages of the preceding ring network protocols.
SEP has the following advantages:
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Applies to diverse complex networks and supports all topologies and network topology
query. For example, a network running SEP can connect to a network running STP, RSTP,
or MSTP.
Network topology display helps locate blocked interfaces quickly. When a fault occurs,
SEP can quickly locate the fault, improving network maintainability.
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Allows selectively interface blocking, which effectively implements traffic load balancing.
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Prevents traffic from being switched back after link recovery, which improves network
stability.
8.2 Principles
This section describes the implementation of SEP.
8.2.1 Principles of SEP
SEP is a ring network protocol dedicated to the Ethernet link layer. A SEP segment is the basic
unit for SEP. Only two interfaces on a switching device can be added to the same SEP segment.
To prevent loops in a SEP segment, a ring protection mechanism is used to selectively block
interfaces to eliminate Ethernet redundant links. When a link on a ring network fails, the device
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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