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Technology Brief

Technology Brief. Ethernet OAM. OAM: Operations, Administration, Maintenance. Feb 2010, ESPD. Agenda. General Challenges for Service Providers Drivers for Ethernet OAM OAM Standards OAM Domain Architecture Link OAM (IEEE 802.3ah) Service OAM (IEEE 802.1ag) ITU-T Y.1731

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Technology Brief

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  1. Technology Brief Ethernet OAM OAM: Operations, Administration, Maintenance Feb 2010, ESPD

  2. Agenda • General Challenges for Service Providers • Drivers for Ethernet OAM • OAM Standards • OAM Domain Architecture • Link OAM (IEEE 802.3ah) • Service OAM (IEEE 802.1ag) • ITU-T Y.1731 • OAM Configuration Guide • Summary

  3. General Challenges for Service Providers • Must be able to provide services quickly and efficiently. • Must be able to provide reliability and up-time (99.999%) that fulfills Service-Level Agreement (SLA). • Must be able to enhance customer satisfaction and retention. • Must be able to run the operation efficiently and still be able to reduce overall costs. • Must be able to maintain overall competitiveness and also generate revenue.

  4. General Challenges for Service Providers • What makes an Ethernet Service Provider attractive? Source: Heavy reading 2008

  5. Agenda • General Challenges for Service Providers • Drivers for Ethernet OAM • OAM Standards • OAM Domain Architecture • Link OAM (IEEE 802.3ah) • Service OAM (IEEE 802.1ag) • ITU-T Y.1731 • OAM Configuration Guide • Summary

  6. Drivers for Ethernet OAM 1. REDUCE COST!! Example: A truck roll is required each time a network event happens. The cost varies widely, but is in the USD $200~400 range per event. Ethernet OAM can drastically reduce the operational expenditure while providing equivalent or better maintenance tools than legacy devices.

  7. Drivers for Ethernet OAM (cont.) 2. Service providers want visibility across other providers’ networks, but not into other providers’ networks. 3. Service providers need standards-based, End-to-End OAM for: • Automated configuration; fast service turn up • End-to-end service control • Hop-by-hop fault management • Preventative maintenance and troubleshooting • Customer notification of service degradation • Performance Monitoring (PM) and Service-Level Agreement (SLA) verification with CoS and QoS • Network resilience and fast recovery

  8. Drivers for Ethernet OAM (cont.) • Uphold Service-Level Agreement (SLA) • - Agreement between Service Provider and customer • - Definesreliable and predictable communications networks, with metrics and operational methods similar to what they experience today • Critical for Carrier Ethernet • SLA already exists in Frame Relay, Private Line and ATM • Customers want SLAs and Proof of Compliance • Management and Reporting are key elements • Defines Responsibility • Need to sort out which carrier is at fault

  9. Agenda • General Challenges for Service Providers • Drivers for Ethernet OAM • OAM Standards • OAM Domain Architecture • Link OAM (IEEE 802.3ah) • Service OAM (IEEE 802.1ag) • ITU-T Y.1731 • OAM Configuration Guide • Summary

  10. OAM Standards Modern Carrier Ethernet “Global Interconnect” Pre-Carrier Ethernet IP IP Ethernet Ethernet SONET Physical Physical Best Effort Performance SLAs Point to Point E-LAN, E-Line, E-Tree Limited resiliency 50ms recovery Metro-only Global Interconnect Transport only OAM End-to-end Service OAM Asynchronous Sync-E, IEEE 1588

  11. OAM Standards MEF • MEF 7 – EMS-NMS Info Model • MEF 13 – UNI-Type 1 • MEF 15 – NE Management Req • MEF 17 – OAM Req & Framework • MEF 16/20 – Ethernet Local Mgmt Interface/UNI-Type 2 • Service OAM – Performance Monitoring • NID Specifications Standards Body Ethernet OAM IEEE • 802.3ah – Ethernet in the First Mile • 802.1ag – Connectivity Fault Management • 802.1aj – Two Port MAC Relay ITU • Y.1730 – Ethernet OAM Req • Y.1731 – OAM Mechanisms • G.8031 – Ethernet Protection • Y.17ethqos – QoS • Y.ethperf – Performance IETF • RFC-2544 – Benchmarking Method for Ntwk Interconnect Dev • RFC-2819 – Remote Monitoring (RMON Etherstats) TMF • TMF814 – EMS to NMS Model (Corba) • TMF854 – EMS to NMS (Web services - MTOSI)

  12. OAM Standards - User to Network Interface (UNI) • Defines an Ethernet service demarcation point between customer (subscriber) and service provider • Defines service personality – service attributes, traffic classification, bandwidth profiles, tagging, etc. • 3 types defined: Type 1, Type 2, Type 3 CE Carrier Ethernet Network customer responsibility CE: Customer Equipment UNI: User Network Interface Service provider responsibility UNI

  13. OAM Standards – UNI Types • UNI type 1 (MEF 13) • Manually configured UNI • Defines service personality - Traffic classification, bandwidth profile(s), etc • UNI Type 1.1 and 1.2 are defined • Type 1.1 : Non-multiplexed UNI for Services like EPL* • Type 1.2 : Multiplexed UNI for Services like EVPL* • Certification test suite in MEF 19 • UNI type 2 (MEF 20) • Backward compatibility with UNI Type 1 • Adds additional management capabilities including Ethernet Local Management Interface (E-LMI) from MEF-16 • Provides fault indication and automated configuration/provisioning of UNI-C • Certification test suite in MEF 21 & 24 (and others) • UNI type 3 (future) • Negotiated configuration/provisioning between UNI-C and UNI-N

  14. OAM Standards – UNI Types (cont.) • Functional Elements of the UNI • MEF-11 defines a split in the demarcation function between customer and service provider: • UNI-C: Executes the processes of the customer side • UNI-N: Executes the processes of the network side UNI-C CE Carrier Ethernet Network UNI-N customer responsibility Service provider responsibility UNI CE: Customer Equipment UNI: User Network Interface

  15. OAM Standards - Network to Network Interface (NNI) UNI UNI E-NNI UNI UNI Carrier B network Ethernet Virtual Connection Carrier A network Reference Point • External Network to Network Interface (E-NNI) • A reference point where 2 Service Providers meet in support of specified MEF Services • Supports • Multiple Carrier Ethernet networks and services, management, QoS , etc. • Supports simple interconnect and tunneling • Impact on the Industry • Creates ubiquitous service level network for large and mid-size businesses • Generates new worldwide business opportunities for service providers at lower cost • Brings new product and revenue opportunities for vendors

  16. OAM Standards Customer Site Service Provider 1 Service Provider 2 Customer Site E-NNI UNI UNI CE CE MEF NID* MEF NID* Service Layer OAM (UNI to UNI) ITU Y.1731 Service OAM Connectivity Fault Mgmt OAM IEEE 802.1ag Access Link OAM Access Link OAM Link OAM IEEE 802.3ah

  17. OAM Standards OAM Layer Components • Each layer supports OAM capabilities independently • OAMs interoperate • Component responsibilities are complementary * ** *: E2E = End-to-End **: P2P = Point-to-Point

  18. OAM Standards – Link OAM • IEEE 802.3ah - Ethernet in the first mile (EFM) • First OAM standard completed (2004) • Supports: • Remote Loopback • Remote failure indication (dying gasp, link fault and critical event) • Link monitoring • Loopback Control • Discovery • Focused on point-to-point Ethernet link OAM • Does not propagate beyond a single link or hop • Maintenance OAM, not service • Ethernet OAM shares bandwidth with data payload • Utilizes a “slow” protocol limited to 10 packets per second • OAMPDUs identified by MAC address and Ethernet Length/Type/subtype field • Uses a protocol sub layer between physical and Data link layers

  19. OAM Standards – Service OAM • Includes 802.1agandY.1731 • Uses synthetic traffic to measure end to end performance of service • Supports multiple layers of OAM and maintenance regions

  20. OAM Standards – Service OAM • IEEE 802.1ag – Connectivity Fault Management (CFM) • CFM standard is the foundation for Services OAM • Basic connectivity checking and troubleshooting across any domain, and across multiple domains at the same time • Partitions network into hierarchical OAM regions fault management • Supports up to 8 hierarchical levels of monitoring • Mechanisms include • Continuity Check (CC) • Loopback • Linktrace • Also provides the ability to monitor at specific service levels (including customer, service provider, operator, section) and support for maintenance domains.

  21. OAM Standards – Service OAM • ITU Y.1731: • Builds on 802.1ag and adds: • Performance Monitoring • Delay Measurement (DM) • Delay Variation Measurement (DVM) • Loss Measurement (LM) • AIS & RDI • Alarm Indication Signal (AIS) • Remote Defect Indication (RDI) • Test pattern & Test mode • But no test methodology or standards test suite

  22. Agenda • General Challenges for Service Providers • Drivers for Ethernet OAM • OAM Standards • OAM Domain Architecture • Link OAM (IEEE 802.3ah) • Service OAM (IEEE 802.1ag) • ITU-T Y.1731 • OAM Configuration Guide • Summary

  23. OAM Domain Architecture • A flat network is difficult to manage and define accountabilities • Green, Blue and Orange represent different levels of domains • Hierarchical Maintenance Domains will bind OAM Flows & OAM responsibilities

  24. OAM Domain Architecture • Maintenance Association (MA) – Boundaries of an Administrator’s scope of monitoring part of the network • Maintenance Domain (MD) – A level of monitoring within the hierarchy • Maintenance End Points (MEP) – End Points of the MA or MD • Maintenance Intermediate Points (MIP) – Intermediate Points within MA or MD

  25. Agenda • General Challenges for Service Providers • Drivers for Ethernet OAM • OAM Standards • OAM Domain Architecture • Link OAM (IEEE 802.3ah) • Service OAM (IEEE 802.1ag) • ITU-T Y.1731 • OAM Configuration Guide • Summary

  26. Link OAM (IEEE 802.3ah) • Provides mechanisms useful for ‘monitoring link operation’, such as: • Discovery & Link Monitoring • Remote Failure Indication • Remote Loopback Control • Improve Fault Isolation • Sometimes referred to as Ethernet OAM or more commonly EFM (Ethernet First Mile) • Defines an optional OAM sub-layer: • Intended for point-to-point IEEE 802.3 links • Uses “Slow Protocol” frames called OAMPDUs which are never forwarded by MAC clients • Standardized: IEEE 802.3ah, clause 57 (now in 802.3-2005)

  27. Link OAM (IEEE 802.3ah) • OAM Sub-layer: • OAM Client • Configures OAM sublayer through Control • Processes received PDUs • Transmits PDUs • Control • Provides interface with OAM client entity • Parser • Inspects received frames, sends PDUs to control • Sends Non-PDUs to upper layer or Multiplexer • Multiplexer • Multiplexes PDUs and non-PDUs

  28. Link OAM (IEEE 802.3ah) • Link OAM Does NOT provide capability for: • Station Management • Protection Switching* • Provisioning** • No set functions • Bandwidth Allocation • Speed / Duplex Negotiation • End-to-end OAM Communication • 802.3ah scope restricted to single links

  29. Link OAM (IEEE 802.3ah) - OAMPDU • OAMPDU: • Link OAM communicates using OAMPDUs • OAMPDUs are not forwarded by bridges: restricted to single link • Two ends of a single link are referred to as Data Terminal Equipments (DTE) in 802.3 • Communication beyond a single link is left to higher layers

  30. Link OAM (IEEE 802.3ah) - OAMPDU • OAMPDU: Size / Rate • Must be standard frame length • 64-1518 bytes • Maximum PDU size determined during Discovery process • Subtype = 0x03 [OAM] • Must be untagged • Maximum of 10 OAMPDUs per second • Slow Protocol frames

  31. Link OAM (IEEE 802.3ah) - DULD • OAM Discovery • Allows local DTE to detect OAM on remote DTE • Once OAM support is detected, both ends of the link exchange state and configuration information • PDU Size, Loopback support, etc… • If both DTEs are satisfied with settings, OAM is enabled on link • D-Link Unidirectional Link Detection (DULD) • D-Link standard implementation for detecting unidirectional link • Utilizes 802.3ah Discovery handshake process • Uses the Organizational Specific TLV field in OAMPDU • Similar in function and purpose to Cisco’s UDLD

  32. Link OAM (IEEE 802.3ah) - Flags • OAMPDU format – Flags

  33. Link OAM (IEEE 802.3ah) - Flags • OAMPDU format – Flag Bits • (15~7) Reserved • Reserved bits shall be set to zero when sending an OAMPDU and ignored on reception • (6) Remote Stable • (5) Remote Evaluating • Used to indicate status of the remote DTE • (4) Local Stable • (3) Local Evaluating • Used to indicate status of the local DTE Discovery process • (2) Critical Event • An unspecified critical event has occurred • (1) Dying Gasp • Signal remote device that an unrecoverable local fault has occurred • (0) Link Fault • Signal remote device that receive path is broken Critical Event Flags

  34. Link OAM (IEEE 802.3ah) - Code • OAMPDU format – Code (1 Byte) • Information (0x00) • Used to send OAM state information to the remote DTE • Event Notification (0x01) • Alerts remote DTE of link events • Variable Request & Response (0x02 & 0x03) • Requests & Returns one or more specific MIB variables • Loopback Control (0x04) • Enables/disables OAM remote loopback • Controls the remote DTE’s OAM remote loopback state • Organization Specific (0xFE) • Reserved for Organization Specific Extensions • Distinguished by OUI

  35. Link OAM (IEEE 802.3ah) – Loopback • 802.3ah OAM – Loopback Remote Loopback mechanism: • Loopback Control OAMPDU is used to control the remote DTE • Use 0x01 Enable to start Loopback, 0x02 Disable to exit Loopback • Traffic sent from local DTE is looped back by remote DTE except for Pause and OAMPDU

  36. Link OAM (IEEE 802.3ah) – Loopback • 802.3ah OAM – Remote Loopback Provides: • Fault localization and link performance testing • Statistics from both the local and remote DTE can be queried and compared at any time • Additional information about the health of the link • Can be used to determine which frames are being dropped due to link errors

  37. Link OAM (IEEE 802.3ah) – Loopback • 802.3ah OAM – Starting Remote Loopback

  38. Link OAM (IEEE 802.3ah) – Loopback • 802.3ah OAM – Exiting Remote Loopback

  39. Agenda • General Challenges for Service Providers • Drivers for Ethernet OAM • OAM Standards • OAM Domain Architecture • Link OAM (IEEE 802.3ah) • Service OAM (IEEE 802.1ag) • ITU-T Y.1731 • OAM Configuration Guide • Summary

  40. Service OAM (IEEE 802.1ag) • What is IEEE 802.1ag? • Provides for FAULT management of EVC-based service offerings. • 802.1ag allows troubleshooting an end-to-end Ethernet Virtual Circuit (EVC) across multiple providers / vendors. • What is “CFM”? • CFM stands for “Connectivity Fault Management” • Family of protocols that provides capabilities to detect, verify, isolate and report end-to-end Ethernet connectivity faults • CFM and 802.1ag are used interchangeably • Standardized by IEEE (P802.1ag) in late 2007 • IEEE std. 802.1ag-2007 • 802.1ag is currently at revision 8.1 (CFM 8.1)

  41. Service OAM (IEEE 802.1ag) • Refresh on the hierarchical OAM Architecture • Each MD level contains different MEP • MEP in a MD may be MIP in a higher-level MD • 802.1ag supports up to 8 hierarchical levels

  42. Service OAM (IEEE 802.1ag) • Comprised of 3 protocols that provide Fault Mgmt in Ethernet networks: • Continuity Check Message–Provides fault detection and notification. • Uni-directional "heartbeat" messages issued periodically by MEPs inward in an MD • Allow MEPs to detect loss of service connectivity and can be integrated to provide fault notification. • Allow MEP to discover other MEP within a domain, and allow MIP to discover MEPs • Linktrace Message/Reply –Provides fault isolation. • Transmitted by a MEP on demand to track the path (hop-by-hop) to a destination Maintenance Point (MP) • Allow the transmitting node to discover vital connectivity data (hops) in the path. This is quite similar to Trace Route functionality in IP. • Loopback Message/Reply–Provides fault verification. • Transmitted by a MEP on demand to verify connectivity to a particular MP. • Indicates whether the destination is reachable or not • Does not allow hop-by-hop discovery of the path (unlike Linktrace) • Similar to Ping functionality in IP

  43. Service OAM (IEEE 802.1ag) - CCM • Connectivity Check Messages (CCMs) are periodic multicast messagesused for detecting loss of continuity within an MA • Each MEP transmits CCMs to all other MEPs in the MA at a configurable interval • 3.33ms: default transmission period for protection switching • 100ms: default transmission period for performance monitoring • 1s: default transmission period for fault management • Upon loss of 3 consecutive CCMs, a loss of continuity defect is declared UNI UNI EoX EoX Carrier IPNetwork MEP (Probe) MEP (Reflector) Provider Edge Provider Edge CCM data

  44. MIP MEP MIP MEP MIP MIP Service OAM (IEEE 802.1ag) – Link Trace • Link Trace determines the path from a MEP to a MAC address UNI IP/MPLS Core Network UNI Metro Aggregation Network Metro Aggregation Network Access Network Access Network Link trace Reply Link Trace is similar to IP’s Traceroute

  45. MIP MEP MIP MEP MIP MIP Service OAM (IEEE 802.1ag) – Loopback • What is Loopback good for? • MEP can send a Loopback to any MEP or MIP in the service • Loopback follows the unicast path, not the multicast path • Sending loopbacks to successive MIPs can determine the location of the fault UNI IP/MPLS Core Network UNI Metro Aggregation Network Metro Aggregation Network Access Network Access Network Loopback is similar to IP’s Ping

  46. Service OAM (IEEE 802.1ag) • 802.1ag CFM Protocol CCMs and LTMs are carried in multicast frames with a Dest. MAC chosen according to the MD level

  47. Agenda • General Challenges for Service Providers • Drivers for Ethernet OAM • OAM Standards • OAM Domain Architecture • Link OAM (IEEE 802.3ah) • Service OAM (IEEE 802.1ag) • ITU-T Y.1731 • OAM Configuration Guide • Summary

  48. ITU-T Y.1731 • What is ITU-T Y.1731? • A set of mechanisms for user-plane OAM functionality to provide fault and performance monitoring for point-to-point Ethernet networks. • Technically aligned with IEEE 802.1ag • Introduces performance measurements for SLA monitoring • Frame Delay Measurement (DM) • Frame Delay Variation Measurement (DVM) • Frame Loss Measurement (LM) • Expands on fault notification, isolation & diagnostics • Ethernet Alarm Indication Signal function: ETH-AIS • Ethernet Locked Signal: ETH-LCK • Ethernet Test Signal function: ETH-TEST

  49. ITU-T Y.1731 – ETH-AIS • Alarm Indication Signal • ETH-AIS is used to suppress alarms following detection of defect conditions. • When a MEP detects a connectivity fault (mostly through CCM), it will multicast AIS in the direction away from the detected failure at the immediate client MA level • MIP will propagate to the MEP in their own MA level AIS CCM

  50. ITU-T Y.1731 – ETH-AIS • What is AIS good for? • Receiving MEPs may: • Catalogue AIS and wait to see whether their own CCs report a failure • If Spanning Tree repairs error, none needs to be generated • Delay the propagation of AIS • Gives Spanning Tree time to correct the problem • Propagate the failure reported by AIS • Assuming there is no Spanning Tree to correct the problem

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