OAM: Application-driven Evolution

1. OAM: Application-driven Evolution Presented by: Yaakov (J) Stein Chief Scientist Unique Access Solutions

2. Why do we pay for services ? Generally good (and frequently much better than toll quality) voice service is available free of charge (Skype, Fring, Nimbuzz, …) So why does anyone pay for voice services ? Similarly, one can get free • (WiFi) Internet access • email boxes • file storage and sharing • web hosting • software services So why pay ?

3. Paying for QoS The simple answer is that one doesn’t pay for the service one pays for Quality of Service guarantees In our voice model But what does QoS mean and why are we willing to pay for it ? To explain, we need to review some history price toll quality with mobility QoS BE

4. Father of the telephone Everyone knows that the father of the telephone was Alexander Graham Bell (along with his assistant Mr. Watson) But Bell did not invent the telephonenetwork Bell and Watson sold pairs of phones to customers The father of the telephone network was Theodore Vail

5. Theodore Vail - Theodore Who? Son of Alfred Vail (Morse’s coworker) Ex-General Superintendent of US Railway Mail Service First general manager of Bell Telephone Father of the PSTN Why is he so important? Organized PSTN Established principle of reinvestment in R&D Established Bell Telephones IPR division Executed merger with Western Union to form AT&T Solved the main technological problems • use of copper wire • use of twisted pairs Organized telephony as a service (like the postal service!) Vailism is the philosophy that public services should be run as closed centralized monopolies for the public good

6. What’s the difference ? + In the Bell-Watson model the customer pays once, but is responsible for • installation • wires • wiring • operations • power • fault repair • performance (distortion and noise) • infrastructure maintenance while the Bell company is responsible only for providing functioning telephones In the Vail model the customer pays a monthly fee but the provider assumes responsibility for everything including fault repair and performance maintenance the telephone company owns the telephone sets and even the wires in the walls !

7. Service Level Agreements In order to justify recurring payments the provider agrees to a minimum level of service in an SLA SLAs should capture Quality of user Experience (QoE) but this is often hard to quantify So SLAs usually actually detail measurable network parameters that influence QoE, such as : • availability (e.g., the famous five nines) • time to repair (e.g., the famous 50 ms) • information rate (throughput) • information latency (delay) • allowable defect densities (noise/distortion) Availability (basic connectivity) always influences QoE It is hard to predict the effect of the other parameters on QoE even when there is only one application (e.g., voice) When multiple applications are in use - it may be impossible

8. Some Applications System traffic routing protocols, DNS, DHCP, time delivery, system update, OAM, tunneling and VPN setup Business processes database access, backup and data-center, B2B, ERP Communications - interactive voice, video conferencing, telepresence, instant messaging, remote desktop, application sharing Communications – non-interactive email, broadcast programming, music video : progressive download, live streaming, interactive Information gathering http(s), Web 2.0, file transfer Recreational gaming, p2p file transfer Malicious DoS, malware injection, illicit information retrieval

9. What do applications need ? Some applications only require availability Some also require minimum available throughput Some require delay less then some end-end (or RT) delay Some require packet loss ratio (PLR) less than some percentage and these parameters are not necessarily independent For example, TCP throughput drops with PLR 1000 B packets 50 ms RTT

10. Some rules of thumb Mission Critical (and life critical) applications require • high availability If there are any MC applications then system traffic requires high availability too MC applications do not necessarily require strict throughput but always indirectly require • a certain minimal average throughput • bounded delay If the MC application uses TCP then it requires • low PLR Real-time applications require • sufficient throughput but not necessarily low PLR (audio and video codecs have PLC) Interactive applications require • low RT delay It may be more scalable for a SP to measure 1-way delays

11. Monitoring an SLA The Service Provider’s justification for payment is the maintenance of an SLA To ensure SLA compliance, the SP must : • monitor the SLA parameters • take action if parameter is dropping below compliance levels But how does the SP verify/ensure that the SLA is being met ? Monitoring is carried out using Operations, Administration, Maintenance (OAM) The customer too may use OAM to see that the SP is compliant ! Technical note: OAM is a user-plane function but may influence control and management plane operations for example • OAM may trigger protection switching, but doesn’t switch • OAM may detect provisioned links, but doesn’t provision them

12. Operations, Administration, Maintenance Traditionally, one distinguishes between 2 OAM functionalities : • Fault Monitoring • OAM runs continuously/periodically at required rate • detection and reporting of anomalies, defects, and failures • used to trigger mechanisms in the • control plane (e.g. protection switching) and • management plane (alarms) • required for maintenance of basic connectivity (availability) • Performance Monitoring • OAM run : • before enabling a service • on-demand or • per schedule • measurement of performance criteria (delay, PDV, etc.) • required for maintenance of all other QoE attributes

13. Early OAM Analog channels and 64 kbps digital channels did not have mechanisms to check signal validity and quality Thus • major faults could go undetected for long periods of time • hard to characterize and localize faults when reported • minor defects might be unnoticed indefinitely As PDH networks evolved, more and more OAM was added on : • monitoring for valid signal • loopbacks • defect reporting • alarm indication/inhibition The OAM overhead started to explode in size ! When SONET/SDH was designed bounded overhead was reserved for OAM functions

14. OAM for Packet Switched Networks OAM is more complex for Packet Switched Networks in addition to the previous defects : • loss of signal • bit errors we have new defect types • packets may be lost • packets may be delayed • packets may delivered to the wrong destination The first PSN-like network to acquire OAM was ATM (I.610) Although technically ATM is cell-based, not packet-based

15. What about Ethernet ? Carrier Ethernet has replaced ATM as the default layer-2 Ethernet is by far the most widespread network interface Ethernet has some advantages as compared to ATM • it has network-wide unique addresses • it has a source address in every packet but some aspects make Ethernet OAM more difficult • ConnectionLess (CL) • multipoint to multipoint • overlapping layering – need OAM for operator, SPs, customer • some specific problematic ETH behaviors (flooding, multicast, …)

16. What’s the problem with CL ? OAM makes a lot of sense in Connection Oriented environments • connections last a relatively long amount of time • there is some SLA at the connection level For CL networks, the network path is neither known nor pinned So it doesn’t really make sense to talk about FM what does continuity mean if when a link goes down the network automatically reroutes around the failure ? The Ethernet CL problem is solved by overlaying CO functionality : • flows or • EVCs

17. Ethernet OAM For many years there was no OAM for Ethernet (LANs don’t need OAM) now there are two incompatible ones! • Link layer OAM – 802.3 clause 57 (EFM OAM, 802.3ah) single link only slow protocol, limited functionality some management functions • Service OAM – Y.1731, 802.1ag (CFM) any network configuration multilevel OAM functionality In some cases one may need to run both while in others only service OAM makes sense Link layer OAM is only for a single link, which is necessarily CO Service OAM is most frequently used for infrastructure networks, which are also CO

18. MEPs and MIPs

19. What about MPLS ? The other L2 used today is MPLS OAM mechanisms that work well for Ethernet can not be used as-is for MPLS This is because : • MPLS does not use absolute addresses • MPLS packets do not carry source addresses • when using LDP MPLS is not pure CO • LSPs are unidirectional entities The IETF has defined LSP ping that provides basic OAM • continuity • trace route The ITU defined Y.1711, but it has not seen widespread use The MPLS community is now working on MPLS-TP which is basically MPLS + strong OAM (FM + PM) and functionalities dependent on OAM, such as protection switching

20. What about IP ? It makes sense to monitor IP (IPv4/IPv6) performance as well • IP is the most popular end-to-end protocol • IP connectivity can be purchased (although perhaps not widely with SLAs) But from the OAM point of view, IP is the hardest of all • the IP protocol suite does not define anything beneath L3 • IP is always pure ConnectionLess In certain cases it may make more sense to jump directly to application flows

21. IP OAM For IP, one usually talks about OAM between end-points The IETF defines an all-purpose OAM+control protocol : • ICMP Internet Control Message Protocol a protocol for FM : • BFD Bidirectional Forwarding Detection and two sophisticated protocols for PM : • OWAMP One Way Active Measurement Protocol • TWAMP Two Way Active Measurement Protocol OWAMP and TWAMP are the only OAM protocols with full security features !

22. Summary It is advantageous to run networks as provided services Service Provider income depends on SLA compliance SLA compliance requires OAM – FM and PM OAM protocols now exist for all relevant technologies : • TDM – SDH • Ethernet • MPLS • IP Ethernet is leading in OAM functionality, but MPLS-TP is rapidly catching up IP can not have FM tools as robust as Ethernet/MPLS but already has more sophisticated PM ones