Ethernet Protection

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Ethernet Service Protection (14 votes, average: 4.50 out of 5) Papers - Ethernet Academy Articles Monday, 17 January 2011 00:00

Ethernet Service Protection Over External Interfaces
Written by Zehavit Alon

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1 Preface 1.1 Abstract Over thelast few years, packet switching technologies, such as Ethernet and MPLS, have been widely adopted by the industry as the technologies of choice to replace existing networks based on circuit-switching technologies, such as SONET/SDH and ATM. Circuit-switched network technologies provide mechanisms that guarantee sub-50ms service protection for their subscribers. A similar protection level should beprovided by the different packet technologies when the identical set of capabilities formerly granted to the subscriber is required, in order for packet technologies to seamlessly replace circuit technologies. The various packet technologies define different ways of protecting a service within the network. However, all the currently defined local protection methods are intra-network only and thereis no standard method for protecting services against node failures over external interfaces, i.e. for protecting connectivity between attached networks.

Figure 1 illustrates a theoretical packet based network where one of the services that span several service providers is emphasized. The goal of this paper is to introduce a mechanism aiming at providing a robust solution for the missingprotection capabilities. This paper describes the following: (i) Overview of the current state, (ii) required functionality that does not exist as yet and (iii) a proposed mechanism for protection between domains, the Inter Network Service Protection (INSP)
1.2 Abbreviations

EI - External Interfaces ENNI - External Network to Network Interface INSP - Inter Network Service Protection IZ –Interconnection Zone LAG – Link Aggregation SG - Service Gateway UNI - User to Network Interface
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VLAN – Virtual LAN 1.3 Definitions This section describes the definitions used throughout this paper (Some definitions are accompanied by a figure toclarify the definition). Border Node – A node that resides at the edge of the network and connects it to another network. MEF external interfaces connect border nodes of adjacent networks.

Figure 2: Border Nodes

Subscriber- The organization purchasing and/or using Ethernet Services Domain -A collection of network elements within a common realm of address space which are operated as separateadministrative network and are managed by a single Operator ENNI, ENNI-Nx– ENNI is a reference point representing the boundary between two operator networks that are managed as separate administrative domains. ENNI-Nx is a separate, administered, functional component supporting the ENNI between a network X and a second network. External Interfaces (EI) – Interfaces between domains (ENNIs) andinterfaces between a domain and a subscriber premise (UNIs) , External Link – A link connecting the border nodes of attached domains. Can be physical or logical i.e. can be a LAG

Figure 3: External Links Interconnection Zone (IZ) – A realm that includes the border nodes of two connected domains and all the links connecting these border nodes (internal and external) that participate in the serviceprotection mechanism

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Figure 4: Interconnection Zone

Internal Link – A link that connects two border nodes within the same service portal. Can be physical or logical i.e. can be a LAG

Figure 5: Internal Links Inter Network Service...