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Carrier Ethernet: SOAM Toolkit for Verification of Service Level Specifications

Posted by Dane Weaver on Jan 16, 2017 11:49:58 AM

IMG_5494.jpgEthernet emerged in the 1980s and 1990s as the de facto layer 2 protocol for LAN networks but distance restrictions, technology limitation, and customer traffic primarily composed of voice services limited Ethernet expansion as a WAN network service.  However, 21st century has shifted primary WAN traffic from voice services to packet-based data services which has led to new implementations and standardizations of technologies and protocols by organizations - International Telecommunications Union-Telecommunication Standards Bureau (ITU-T), Institute of Electrical and Electronics Engineers (IEEE), and Internet Engineering Task Force (IETF) - to support the increasing demand of packet-based data services including VoIP, video services, wireless backhaul, and data center interconnect.  This has led to the 21st century emergence of Ethernet as a viable carrier service based on the protocol’s capabilities of supporting packet-based data services and the reduction of limitations when integrating Ethernet on a WAN. To further reduce the complexity of Ethernet integrated services on the WAN, Metro Ethernet Forum (MEF) was formed as a global industry alliance with a mission to accelerate the worldwide adoption of Carrier-class Ethernet networks and services.  The MEF distinguishes Carrier Ethernet (CE) services from traditional LAN-based Ethernet services based on five attributes:

  1. Standardized Services
  2. Scalability
  3. Reliability
  4. Quality of Service
  5. Service Management

Of the five attributes, reliability and quality of service are critical attributes for a carrier and customer on verifying performance monitoring on meeting the Service Level Specifications (SLS) agreed upon by all parties in the Service Level Agreement (SLA) for CE.  To assist in meeting the SLS for reliability and quality of service, which legacy TDM-based services have been known for, MEF has added a rich Service Operation, Administration, and Maintenance (SOAM) toolkit to the Ethernet protocol for service activation, fault management, and performance monitoring. 

Verification of CE performance during service activation allows the carrier and customer to confirm the CE is meeting the SLS or allow for identifications of fault if the CE is unable to perform to the SLS. MEF’s technical specifications MEF 48 provides SOAM guidelines for service activation of CE commonly known as a “birth certificate.” With the use of IETF RFC 2544 or ITU-T Y.1564 standards, a test generator and reflector run test patterns which are injected onto the CE service to verify throughput, frame loss, frame delay, and frame delay variation during service activation.  The birth certificate is generated with the results of the IETF RFC 2544 or ITU-T Y.1564 for validation that CE services are performing to the standards of the SLS defined in the SLA on carrier’s network and customers end devices. 

Fault management allows carrier and customer to identify a fault that will affect services of the CE in real-time or near real-time.  MEF 30.1 technical document provides guidance on using SOAM toolkit for fault management with the use of defined maintenance domains and Maintenance Entity Group (MEG) to sectionalize problems of CE service defined by ITU-T Y.1731.  Defined maintenance domains allow consecutive MEGs to operate within the CE to provide visibility to the carriers and customer networks without MEGs interfering with other MEGs on the CE.  A CE defined in a MEG uses Continuity Check Messages to verify availability of the CE between defined points (end-points or intermediate points).  When CCMs are unable to reach the defined point then the device will trigger an event message to alert the carrier or customer of fault between the defined points. 

MEF 35.1 technical document provides guidance on using performance monitoring.  Performance monitoring allows a carrier or customer to monitor the performance of the CE and verify the CE performance is within the defined SLS.  The performance metrics include frame loss ratio, frame delay, and frame delay variation that are important in supporting services such as voice and video services.  The performance data is sent from the device to Element Management System/Network Management System for allowing data to be retrieved real-time or historically. The performance metric data will allow for verifications that CE is meeting the SLS defined in the SLA.

Packet-based data services have been consistently trending upwards which has led Ethernet services, that were nearly non-existent on WAN networks in the 1980s and 1990s, to emerge as a leader WAN networks services in the 21st century.  However, reliability and quality of services are important attributes for replacing legacy TDM-based services.  MEF formed as a global industry alliance has provided guidance on how to address these attributes for CE by adding rich SOAM toolkits to CE for service activation, fault management, and performance monitoring. 


Topics: Telecom Industry

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