Presentation is loading. Please wait.

Presentation is loading. Please wait.

One-Way Ping - Introduction to OWAMP

Similar presentations


Presentation on theme: "One-Way Ping - Introduction to OWAMP"— Presentation transcript:

1 One-Way Ping - Introduction to OWAMP
Dr. Quincy Wu, Associate Professor 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 is alive ping is alive Certainly, this probing is not very precise, for two reasons.

6 Interpreting A Ping Response
C:\>ping Pinging cswww.cse.yzu.edu.tw [ ] with 32 bytes of data: Reply from : bytes=32 time=14ms TTL=115 Reply from : bytes=32 time=11ms TTL=115 Reply from : bytes=32 time=10ms TTL=115 Ping statistics for : Packets: Sent = 4, Received = 4, Lost = 0 (0% loss), Approximate round trip times in milli-seconds: Minimum = 10ms, Maximum = 14ms, Average = 11ms C:\>ping Pinging [ ] with 32 bytes of data: Reply from : bytes=32 time=6ms TTL=56 Ping statistics for : 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 9.952 ms 1006.122 ms
request reply 9.952 ms ms request reply ms

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

13 Measuring One-Way Delay
Synchronization Sender 19:20:21 Receiver 19:20:19 19:20:21 19:20:22 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 Session Receiver Server
OWAMP-Test Session Receiver Server OWAMP-Control OWAMP-Control Control-Client Fetch-Client

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

17 OWAMP-Test Transport Protocol: Sender/Receiver IP and port numbers:
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 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) * These are the values we are currently we are planning on using, but this is not set in stone.

21 Weather Map

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]: SID: fef1505dc8e1a e87b0e310c 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]: SID: fe56ea22c8e1a4591f6c8b43d56f48c2 one-way delay min/median/max = 112/112/113 ms, one-way jitter = 0.8 ms (P95-P50) Hops = 7 (consistently)

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: % 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.


Download ppt "One-Way Ping - Introduction to OWAMP"

Similar presentations


Ads by Google