is your service available? or common network metrics nevil brownlee, caida nanog 19, albuquerque,...

Is your Service Available?or

Common Network Metrics

Nevil Brownlee, CAIDA

NANOG 19, Albuquerque, June 2000

NANOG 19, June 2000 Nevil Brownlee2 / 15

Overview

• CAIDA Metrics Working Group- Co-chairs from the networking industry

• Sue Moon (SprintLabs)

• Brett Watson (MFN/Abovenet)

• Measurement FAQ

• Service Definitions

• Common Metrics

• Availability


Metrics WG Goals

• Education- Publish ‘Measurement FAQ’- Publish ‘Metrics and Measurement Survey’

• Service Metrics- Define metrics for new / emerging services- Recommend a ‘Service Measurement Toolkit,’

encourage implementors- Publish revised ‘Measurement Requirements

for Hardware/Software Vendors’• User / customer participation needed !


FAQ Contents (1)

• Target audience- Corporate users, smaller providers,

hosting service users

• Generally Accepted Terms - Networking, types of service, faults and

failures

• Measurement Topics - Active vs passive, one point vs many,

sampling, statistics


FAQ Contents (2)

• The Most Common metrics - Latency, packet loss, throughput,

link utilisation, availability

• Common Measurement Tools - ping, traceroute, SNMP, flow measurement

application monitoring, visualization

• Comparing Service Offerings - Provider ‘net status’ pages - Internet ‘weather maps’ - Rating services


Defining Network Service

• Service definitions (SLAs) on the Web- Many providers publish these, e.g.

AT&T, PSInet, UUNET and MCI WorldCom- They describe service offered to customers

• We’re only interested in describing the service, not in contractual aspects

• Metrics used in the service descriptions are often poorly defined


Service Example: UUNET (1)

- Network Quality • Average monthly latency of no more than

85ms roundtrip within UUNET's network in North America and of no more than 120ms between New York and UUNET's international gateway hub in London

• Comments- Restricted to provider’s own network- Latency not defined- Nothing said about packet loss %


Service Example: UUNET (2)

- Service Quality • 100 percent availability that covers the UUNET

backbone and the UUNET-ordered customer access circuit.

• Scheduled maintenance .. will take place .. Tuesdays and Thursdays with at least 48 hours advance notice

• Comments- 1 minute per week = 0.01%- Does ‘available’ time include maintenance?- ‘100% availability’ - but what is availability?


ISP Network Report Pages

• Many providers publish these- Sean Donelan email thread lists 13, e.g.

Abovenet, AT&T, C&W, UUNET, ELI, Jet Net ..

• Amount of detail varies- Outage information, NOC contacts- Latency, packet loss matrices (or averages)

• Such ‘overall’ reports don’t say much about performance as seen from your network- You need some measurements at your site


Common Metrics

• Throughput, link utilisation- Commonly measured with SNMP, RRDtool

• Latency, packet loss- Latency is round-trip, transit + server delay- Commonly measured with ping

• Availability- WG definition based on IETF IP Performance

Measurement (IPPM) connectivity metrics

- Need to specify what’s available, how to measure it, and what values are acceptable


Levels of Availability

Service availability: being able to send packets for a specified service - say WWW request packets - to a particular Internet host, and to receive answering packets

Host availability: being able to send packets, say ping packets, to a particular Internet host, and to receive answering packets

Network availability: being able to send packets from your network to the Internet, and to receive answering packets


Measuring Availability

Web service availability test: download specified pages from target web server using web browser, measure latency, packet loss and throughput

Host availability test: ping the target host, having made sure that it will respond to ICMP packets

Network availability test: traceroute to the target host, so as to determine whether there is connectivity to the target network


Defining Availability

• Requires negotiation between provider and customer- What services are important?- What performance level is acceptable?

• Be realistic!- Providers only control their own networks- Some packet loss is inevitable

• Measurements are important- Both sides should work together on this- Make some ‘baseline’ measurements


Conclusion

• The CAIDA Metrics WG has begun by producing its ‘Measurement FAQ’, which provides background material on many measurement topics

• The FAQ attempts a new definition of Service Availability - the Metrics WG needs feedback on this !

• The WG seeks input for its other goals, especially for defining new metrics


More Information (CAIDA)

• Metrics WG (FAQ, mailing list)www.caida.org/outreach/metricswg

• FAQ ContributorsCindy Bickerstaff, Carter Bullard, Les Cottrell, Sean Donelan, Dave O’Leary, Brett Watson, ..

• CAIDA tools taxonomywww.caida.org/tools


More Information (Net Status)

• Provider web pages are listed in FAQ[ISP_SERV] service definitions[ISP_REPT] network performance reports

• NOC pages (search ‘xxx network status’)www.pictureview.com/support/PVTS2.htmlwww.psinet.com/netstatus/www.sprintlink.net/netstat.html

• Network performance pagesstats.sjc.above.net/traffic/ipnetwork.bgtmo.ip.att.nettraffic.cwusa.com/index.html

is your service available? or common network metrics nevil brownlee, caida nanog 19, albuquerque,...

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