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One-Way Ping

One-Way Ping. - Introduction to OWAMP. Dr. Quincy Wu, Associate Professor ( solomon@ipv6.club.tw ) Graduate Institute of Communication Engineering National Chi Nan University. Growth of Internet. Number of computers attached to the Internet

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One-Way Ping

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  1. One-Way Ping - Introduction to OWAMP Dr. Quincy Wu, Associate Professor (solomon@ipv6.club.tw) Graduate Institute of Communication Engineering National Chi Nan University

  2. Growth of Internet • Number of computers attached to the Internet • In 1998, the average rate of new computers being added to the Internet reached more than one per second • And has accelerated Computer Networks and Internets, Douglas E. Comer, Pearson Prentice hall, 2004.

  3. Growth of Internet (cont.) • Plotted on a log scale • The growth appears approximately linear • Exponential growth • The Internet has been doubling in size every nine to twelve months Computer Networks and Internets, Douglas E. Comer, Pearson Prentice hall, 2004.

  4. Hosts & Routers LAN: Local Area Network

  5. Probing The Internet • Q: How do we know the number of computers attached to the Internet? • In the early days when the Internet consisted of a dozen sites, this size could be determined manually. • Now we use programs that test to see whether a computer is currently online. • ping www.80216.com.ncnu.edu.tw • www.80216.com.ncnu.edu.tw is alive • ping 163.22.24.102 • 163.22.24.102 is alive • Certainly, this probing is not very precise, for two reasons.

  6. Interpreting A Ping Response C:\>ping www.cse.yzu.edu.tw Pinging cswww.cse.yzu.edu.tw [140.138.144.172] with 32 bytes of data: Reply from 140.138.144.172: bytes=32 time=14ms TTL=115 Reply from 140.138.144.172: bytes=32 time=11ms TTL=115 Reply from 140.138.144.172: bytes=32 time=10ms TTL=115 Reply from 140.138.144.172: bytes=32 time=11ms TTL=115 Ping statistics for 140.138.144.172: Packets: Sent = 4, Received = 4, Lost = 0 (0% loss), Approximate round trip times in milli-seconds: Minimum = 10ms, Maximum = 14ms, Average = 11ms C:\>ping www.csie.nctu.edu.tw Pinging www.csie.nctu.edu.tw [140.113.209.41] with 32 bytes of data: Reply from 140.113.209.41: bytes=32 time=6ms TTL=56 Reply from 140.113.209.41: bytes=32 time=6ms TTL=56 Reply from 140.113.209.41: bytes=32 time=6ms TTL=56 Reply from 140.113.209.41: bytes=32 time=6ms TTL=56 Ping statistics for 140.113.209.41: Packets: Sent = 4, Received = 4, Lost = 0 (0% loss), Approximate round trip times in milli-seconds: Minimum = 6ms, Maximum = 6ms, Average = 6ms

  7. Probing Packets

  8. Round-Trip Time Client Server 0.000 ms request reply 9.952 ms 1006.122 ms request reply 1017.039 ms

  9. Why Didn’t We Measure One-Way Delay? • Asynchronous system clocks would make the measurement result confusing. 19:20:19 Receiver 19:20:21 Sender 19:20:20 Delay = -1 sec !

  10. ICMP Packet Format • RFC 792 – Internet Control Message Protocol

  11. Why Do We Favor One-Way Delay? • The path from a source to a destination may be different than the path from the destination back to the source ("asymmetric paths"). • Even when the two paths are symmetric, the behavior of applications can be quite different: • File transfer • Web browsing • IPTV

  12. Why Can We Measure 1-Way Delay Now? • Available Time Source: • Cesium oscillator: Definition of time (subject to relativistic effects) • Rubidium oscillator: found in cell towers, very stable • GPS receiver: accuracy circa 10 ns • CDMA receiver: accuracy circa 10 μs • The stratum of any NTP-synchronized device is the stratum of the device it is synchronized to, plus 1. • GPS receiver: stratum 0 • Computer connected to it by a serial line: stratum 1 • Client that gets the time from that computer: stratum 2 • Stratum 1 Time Servers: • http://ntp.isc.org/bin/view/Servers/StratumOneTimeServers

  13. Synchronization 19:20:22 Measuring One-Way Delay 19:20:19 19:20:21 Receiver 19:20:21 Sender Delay = 1 sec

  14. OWAMP Design Goals • One-Way Active Measurement Protocol • RFC 4656, September 2006. • Wide deployment of “open” servers would allow measurement of one-way delay to become as commonplace as measurement of RTT using ICMP tools such as ping.

  15. OWAMP Logical Model Session Sender OWAMP-Test Session Receiver Server OWAMP-Control OWAMP-Control Control-Client Fetch-Client

  16. Commonly Implemented Model Session-Sender Control-Client Fetch-Client Session-Receiver Server OWAMP-Test OWAMP-Control

  17. OWAMP-Test • Transport Protocol: • UDP • Sender/Receiver IP and port numbers: • Negotiated by OWAMP-Control message • OWAMP-Test does not run on a fixed port • To prevent some devices may assign higher priorities to these measurement packets

  18. OWAMP-Test Packet Format • Sequence: start with 0; incremented by 1 • Timestamp: RFC1305 format • Padding is random, but users have an option to configure it to consist of all zeros. • Minimum data length: 14 octets

  19. OWAMP Errors • Preliminary Findings: • Min error estimates look to be in the 55-60 usec range. • Serialization Delay: ~5usec x 2 • Get Timestamp: ~15usec x 2 • Additional error is: • Time from userland “send” to 1st byte hits the wire • Time from kernel has packet to userland “recv” returns • Potentially recv process data processing before calling “recv”

  20. Internet2 OWAMP deployment • 2 overlapping full meshes (IPv4 & IPv6) • 11 measurement nodes = 220 ongoing tests • UDP singletons • singleton: a single observation of one-way delay • Rate: 10 packets/second • Packet size: 32-byte payload • Results are continuously streamed back to “Measurement Portal” for long-term archive and data dissemination (Near real-time)

  21. Weather Map http://weathermap.grnoc.iu.edu/abilene.png

  22. owping $ owping -c 5 nms4-nycm.abilene.ucaid.edu --- owping statistics from [2001:e10:6840:20:20f:eaff:fe56:ea22]:52711 to [nms4-nycm.abilene.ucaid.edu]:64337 --- SID: fef1505dc8e1a459016511e87b0e310c 5 sent, 0 lost (0.000%), 0 duplicates one-way delay min/median/max = 138/138/147 ms, one-way jitter = 8.6 ms (P95-P50) Hops = 10 (consistently) no reordering --- owping statistics from [nms4-nycm.abilene.ucaid.edu]:64338 to [2001:e10:6840:20:20f:eaff:fe56:ea22]:52896 --- SID: fe56ea22c8e1a4591f6c8b43d56f48c2 5 sent, 0 lost (0.000%), 0 duplicates one-way delay min/median/max = 112/112/113 ms, one-way jitter = 0.8 ms (P95-P50) Hops = 7 (consistently) no reordering

  23. Captured OWAMP Packets

  24. R&D Issues • Design a system to scale (eliminate centralizations) • How to discover OWAMP servers • DNS SRV, • DHCP option, • Multicast address • How to insert On-Demand tests into regularly-scheduled test set • Balance centralization and distributed database requirement • Dynamically allocated AES key • Currently, the shared secret between sender and receiver is statically assigned

  25. Security Considerations • Protecting Your OWAMP Testing Traffic • To make it impossible for an attacker to tamper with test results. • To make it hard for a party in the middle of the network to make results look "better" than they should be. • Preventing Third-Party Denial of Service • Covert Information Channels • Requirement to Include AES in Implementations • Resource Use Limitations • Disk, Memory, Bandwidth • Use of Cryptographic Primitives in OWAMP • TLS • Stream-based. Not suitable for OWAMP-Test. • DTLS • Duplication and reordering information are missing • IPSec • Few deployments • SSH 2-4% • HTTPS: 0.2-0.6% • IPsec: 0.05%

  26. HW 3 • Install OWAMP client/server on your own hosts. Try to test the one-way delay. • Your host may possess a public IP address. If this is not the case for IPv4, at least you know how to get a public IPv6 address. • Show me your measurement, and the OWAMP packets which you captured.

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