SLAs and Policies Part I

Transcription

1 SLAs and Policies Part I Dinesh Verma Bert Wijnen IBM T J Watson Research Center PO Box 704 Yorktown Heights, NY What are SLAs Agenda SLA Overview SLA Support in SLA Management SLA and IETF Policies What are SLAs Service Level Agreements Contract between service provider and customers. Specifies (among other things) performance Availability responsiveness Applicable to different types of services I/T department SLA to other departments. provider offers SLAs to other departments. Hosting provider offers SLAs for hosted web sites.

2 SLA Examples UUnet Average monthly latency inside US < 85 ms TransAtlantic link (NY-London) < 120 ms 100% uptime (credits for lost connectivity) IGS supporting Santa Teresa Software Lab 99% uptime for server access. Application response less than 0.5 s from clients within US. Part II. How to Support SLAs? Types of SLAs SLA Support Levels SLAs on Performance Performance Objectives Responsiveness: network latency Availability: Connectivity Suitable for ISPs/network operators. Do not offer end-to-end view. SLAs on Applications Performance Objectives Responsiveness: application response time. Application availability (not network ) Suitable for Enterprise CIOs Suitable for Application Service Providers. Offer end-to-end view Levels of SLA support Insurance Mode Measure performance/availability Give credits on SLA violation. Provisioning Mode Insurance but all customers are not equal. Put classification/rate control/qos devices. Adaptation Mode Provisioning Mode plus Take action on possible SLA violation. allocate or take resources for customers.

3 SLA Framework SLA Support Management Tool Monitor Adjuster Agent Agent SLA Specification Virtual Pipes based latency between pair of edge-devices bandwidth usage between pair of edge-devices. Single edge-device based bandwidth in from campus at edge-device Repository SLA support using QoS Different Customers have different SLA requirements. Map customers into different service classes. Allocate different rates to classes Exploit DiffServ for service classes. Different reservations with IntServ (?) Monitor performance levels validate compliance. Campus SLA Support Edge Device responsible for Encapsulation, Monitoring, Policing and Classification of packets Server provides configuration and operational policies SLA Monitor provides aggregate view of network behavior Controls are transparent to applications, hosts, most system administrators,... Campus and IP intranet belong to different organizations - one with SLA defined between them. Server Edge Device SLA Monitor IP Intranet Edge Device Edge Device Campus Campus

4 SLA Support Server SLA Architecture Repository tells edge-device what to do. rate control packets. mark packets on DiffServ network. collect information SLA Monitoring Single edge-device SLA RMON/SMON/MIB-II data Pairwise edge-device uses probes to monitor delay/loss. Monitor AGENT RSVP-ENABLED APPLICATIONS RSVP AGENT QOS Mechanisms (kernel) LEGACY & NEW APPLICATIONS POLICY AGENT SLA Monitor POLICY DATABASE SYSTEM/NETWORK ADMINISTRATOR Server SLA Support Server SLA Specification latency between server and clients TCP round-trip for connections. Application transaction time. Classify different Connections different rate limits for outbound traffic different inbound connection limits. different DiffServ marking etc. Server SLA Support Agent tells kernel TCP/IP stack to rate control, mark packets. controls on aggregates or connections. Monitoring Monitor Agent collects TCP latency, retransmissions etc on aggregate basis. SLA Monitor collect monitoring agent information generate ghost transaction for app. response time.

5 SLA Specification SLA Management How to define/manage SLAs? Two Levels of Specifications SLA Level network wide view easy to administer Human-friendly abstractions Low level precise crisp specifications device-specific view enforceable/usable. SLAs Management Process Management Tool Administrator defines SLAs for network/server. Management Tool translates SLAs into device-specific rate-control/diffserv parameters in the network. SLA Definition Access Router Server Feasibility Analysis Validator GUI SLA Specification Consistency Checker Coverage Checker Logic device-specific parameters are distributed to individual devices. Agents on devices translate parameters into exact device configuration and enforce compliance. Firewall Core Router Topology Topology Discovery Translator Low Level specification Distributor Behaviour Distribution Configuration files/directory Entries/CLI scripts

6 Logic Function Standardization Requirements Logic Functions Translation: From SLAs to low level behaviours Validation: All attributes/classes are well-formed Consistency: All SLA objectives consistent together. Feasibility: Can SLA goals be satisfied. Coverage: Are all scenarios covered Additional Features: Third party consistency signatures. Async. notification to agents on devices. Requirements SLA management tools/mechanisms are vendor-specific. No one tool can manage different devices. A standard way to define behaviour would be beneficial. Standardization s How to access policy repository. How to store policy information. Low level specification most appropriate point. IETF Architecture SLAs and IETF Policies Management Tool Decision COPS/SNMP RAP-WG Enforcement The relationship LDAP/Others Repository Decision Enforcement WG machine-boundary

7 SLA and IETF SLAs are high level specification input into a management tool. IETF policies are low level specifications output by management tool. IETF policies provide a standard way to tell devices how to configure themselves.