Is your Service Available

1
Is your Service Available? orCommon Network
Metrics Nevil Brownlee, CAIDANANOG 19,
Albuquerque, June 2000
2
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

3
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 !

4
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

5
FAQ Contents (2)

• The Most Common metrics
• Latency, packet loss, throughput, link
  utilisation, availability
• Common Measurement Tools
• ping, traceroute, SNMP, flow measurementapplicati
  on monitoring, visualization
• Comparing Service Offerings
• Provider net status pages
• Internet weather maps
• Rating services

6
Defining Network Service

• Service definitions (SLAs) on the Web
• Many providers publish these, e.g. ATT, PSInet,
  UUNET and MCI WorldCom
• They describe service offered to customers
• Were only interested in describing the service,
  not in contractual aspects
• Metrics used in the service descriptions are
  often poorly defined

7
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 providers own network
• Latency not defined
• Nothing said about packet loss

8
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?

9
ISP Network Report Pages

• Many providers publish these
• Sean Donelan email thread lists 13, e.g.
• Abovenet, ATT, CW, UUNET, ELI, Jet Net ..
• Amount of detail varies
• Outage information, NOC contacts
• Latency, packet loss matrices (or averages)
• Such overall reports dont say much about
  performance as seen from your network
• You need some measurements at your site

10
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 whats available, how to measure
  it, and what values are acceptable

11
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

12
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

13
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

14
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

15
More Information (CAIDA)

• Metrics WG (FAQ, mailing list)
• www.caida.org/outreach/metricswg
• FAQ Contributors
• Cindy Bickerstaff, Carter Bullard, Les Cottrell,
  Sean Donelan, Dave OLeary, Brett Watson, ..
• CAIDA tools taxonomy
• www.caida.org/tools

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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.html
• www.psinet.com/netstatus/
• www.sprintlink.net/netstat.html
• Network performance pages
• stats.sjc.above.net/traffic/
• ipnetwork.bgtmo.ip.att.net
• traffic.cwusa.com/index.html