1. OAM Overview draft-ietf-opsawg-oam-overview-02
Tal Mizrahi Marvell
Nurit Sprecher Nokia Siemens Networks
Elisa Bellagamba Ericsson
Yaacov Weingarten Nokia Siemens Networks

2. Status of the draft A merge of two overlapping drafts:
draft-ietf-opsawg-oam-overview-00.txt
Provides overview of existing IETF OAM tools.
Compares them with OAM mechanisms defined by the IEEE and ITU-T.
draft-sprecher-mpls-tp-oam-primer-00.txt
Provides basic information on the existing OAM tools in IETF for MPLS.
Analyzes the tools relative to the set of requirements for OAM for MPLS-TP.
Highlights features that need to be extended in order to deliver the higher-quality OAM as required for transport applications.
The document focuses on data-plane OAM.
Note: This was presented at the OAM workshop in Fairfax

3. Purpose of the document
Presents an overview of the OAM mechanisms that have been defined and are currently being defined by the IETF
Compares the IETF mechanisms to other OAM mechanisms that have been defined by the IEEE and ITU-T.

4. OAM Tools in Scope IETF Mechanisms ITU-T and IEEE ICMP LSP Ping
BFD (for IP, MPLS LSP and PW)
VCCV
IP Performance Metrics (IPPM)
ITU-T Y.1711 (MPLS OAM)
ITU-T Y.1731 (Ethernet OAM)
IEEE802.1ag (Ethernet OAM)
IEEE802.3ah (Ethernet in the first mile)
The different OAM standards use different terminology.
draft-ietf-opsawg-oam-overview-02.txt compares between the terminology used by each of the standards and provides definitions for terms such as Maintenance Entity, failure/fault/defect, continuity check and connectivity.

5. Internet Control Message Protocol (ICMP)
Provides connectivity verification function for IP. Supports both IPv4 and IPv6.
The originator transmits an echo request packet, and the receiver replies with an echo reply.
Both LSP Ping and VCCV are to some extent based on ICMP Ping.

6. MPLS LSP Ping MPLS LSP Ping Based on ICMP Ping.
Provides simple connectivity verification function between two LSRs and hop-by-hop trace-route fault localization or route determination.
Supports P2P LSPs. Ongoing work to support P2MP.
Uses an extensive algorithm to verify the LSP’s control-plane against the data-plane (which can be easily bypassed).
Identification is based on full FEC information.
Can be easily extended to support additional functionality (using TLVs). ???
Support both asynchronous and on-demand modes.

7. Bidirectional Forwarding Detection (BFD)
A unified OAM mechanism that provides bidirectional continuity check.
Can be supported by different protocols and in various medium types. So far define in IP, MPLS, PWE3 and ongoing work on MPLS-TP.
BFD control packets that are exchanged within a BFD session.
BFD sessions operate in one of two modes: Asynchronous mode (proactive) and demand (on-demand).
BFD control packets are sent independently in each direction of the link.
The session is identified by each endpoint with by local Discriminators which are exchanged at the time of session establishment.
The transmission rate is negotiated between the two end-points.
During normal operation of the session, i.e. no failures are detected; the BFD session is in the Up state. If no BFD Control packets are received during a fixed period of time, the session is declared to be Down.
The echo function is used for connectivity verification. A BFD echo packet is sent to a peer system, and is looped back to the originator. The echo function can be used proactively, or on-demand.

8. Virtual Circuit Connection Verification (VCCV)
Provides fault detection and diagnostics for PWs (Independently of the underlying tunneling technology)
Provides control channels associated with the PW being monitored. Thus, OAM packets are sent in-band with data traffic (using CC Type 1: In-band VCCV).
Consists of two components:
Signaled component to communicate VCCV capabilities
Switching component to cause the PW payload to be treated as a control packet.
Does not depend upon the presence of a control plane.
Currently, VCCV supports the following OAM mechanisms: ICMP Ping, LSP Ping, and BFD.
ICMP and LSP Ping are IP encapsulated.
BFD for VCCV supports both IP/UDP encapsulated or PW-ACH encapsulated (with no IP/UDP header).
Supports AC status signaling
The PW label provides the context.

9. IP Performance Monitoring
The IETF IPPM WG defines common criteria and metrics for performance measurement in IP networks, as well as a protocol for measuring delay and packet loss.
Two protocols are used, a control plane protocol, and a test plane protocol.
The control protocols are used to initiate, start and stops test sessions and they run over TCP.
The test protocols creates test packets (according to the schedule) and record statistics of packet arrival. They run over UDP.
IPPM test results are not returned for each test packet sent. They are collected at the receiver and returned upon request. This makes it less suitable for real-time monitoring.
Supports optional authentication and encryption .

10. ITU-T Y.1711 (MPLS OAM)
OAM packets are sent in-band with data traffic. OAM alert label (label 14) is supported for exception handling.
Supports the following functions:
Connectivity verification to detect loss of continuity or misconnectivity.
Fast Failure Detection applicable for protection switching.
Forward and backward defect indications which are used by an LSR to notify affected client layers of the defect (in forward and backward direction ), allowing them to suppress consequent alarms.

11. ITU-T Y.1731(Ethernet OAM)
Supports a SET of OAM tools for fault management and performance monitoring.
Applicable to Ethernet networks and services.
ITU-T and IEEE802.1 worked in close collaboration on OAM. IEEE802.1ag [provides fault management functions].
There are a few differences between the standards in the terminology.
Designed for Ethernet
A connectionless technology , with specific behavior, such as flooding, learning, etc.
Relies on the Ethernet MAC addresses in the packet headers (which together provide unique identification of the element being monitored).
The OAM packets do not provide an indication on the layer being monitored. The information is included in the OAM payload (e.g. operator, SP, customer layers, etc.) and require DPI.
The mechanisms are not compatible with MPLS fault detection mechanisms and require special interworking functions.
Provides procedures and messages to perform packet loss measurement and on-demand (one/two-way) frame delay and delay variation measurements. Can be used as a reference to the design of OMA PM tools.

12. IEEE802.3ah – Ethernet in the first mile
Provides connectivity fault management for the first mile.
Remote failure indication allowing a node to notify a peer about a defect in the receive path.
Remote loopback used in a diagnostic to verify the link connectivity, and to measure the packet loss rate.
Link Monitoring
Can be used to monitor a single link.

13. MPLS-TP
Ongoing work to define a set of fault management and performance monitoring tools (operating in the data-plane) which are appropriate for transport networks and support the network and services at different nested levels.
The MPLS-TP MEAD team held intensive discussions on the OAM design in the meeting IETF75 (July 2009).
The outcome of the discussions and the recommendations were presented to the MPLS WG in IETF75 at Stockholm and approved.
The recommendations are recorded in “draft-ietf-mpls-tp-oam-analysis”.
The OAM analysis document acts as a reference to the considerations and the agreed decisions . It also refers to the relevant documents for each of the OAM tools.

14. Summary of OAM Functions
Continuity Check
Connectivity Verification
Path Discovery
Defect Indication
Performance Monitoring
Other Functions
ICMP Ping
Echo
BFD
BFD Control
BFD Echo
IETF MPLS OAM (LSP Ping)
Ping mode
Traceroute mode
PW VCCV
VCCV
IPPM
-Delay Measurement
-Packet loss measurement
ITU-T MPLS OAM
-CV
-FFD
MPLS-TP OAM
WIP
ITU-T Ethernet OAM (Y.1731)
ETH-CC
ETH-LB
ETH-LT
-ETH-RDI
-ETH-AIS
-ETH-LM
-ETH-DM
-ETH-LCK -ETH-APS -ETH-TST
IEEE CFM CC
Loopback
Linktrace
IEEE link level OAM
Remote Loopback
-Remote failure indication
-Link monitoring

15. Thanks!

16. Summary of OAM Standards
Description
RFC / Standard
ICMP Ping
Internet Control Message Protocol
RFC 792, RFC 4443
BFD
Bidirectional Forwarding Detection
RFC 5880, RFC 5881, RFC 5882, RFC 5583, RFC 5884, RFC 5885
IETF MPLS OAM (LSP Ping)
Operations and Management (OAM) for Multi-Protocol Label Switched (MPLS) Networks
RFC 4377, RFC 4378, RFC 4379, RFC 4687
PW VCCV
Pseudowire Virtual Circuit Connectivity Verification (VCCV).
RFC 5085
IPPM
IP Performance Metrics
RFC 2330
ITU-T MPLS OAM
Operation & Maintenance mechanism for MPLS networks
ITU-T Y.1711
Assignment of the 'OAM Alert Label‘ for MPLS OAM functions
RFC 3429
MPLS-TP OAM
Requirements for OAM in MPLS
RFC 5860
MPLS Generic Associated Channel
RFC 5586
ITU-T Ethernet OAM
OAM Functions and Mechanisms for Ethernet-based Networks
ITU-T Y.1731
IEEE CFM
Connectivity Fault Management
IEEE 802.1ag
IEEE link level OAM
Ethernet on the First Mile (EFM)
IEEE 802.3ah