Skype Relay Calls Measurements and Experiments

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Skype Relay CallsMeasurements and Experiments

• Wookyun Kho
• Salman Abdul Baset
• Henning Schulzrinne

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Contents

• Background
• Experimental Setup
• Results and Discussion
• Factors impacting Skype relay calls
• Characterizations of Skype relay nodes
• Conclusion and Future Work

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Background
Skype Network
TCP connection
TCP connection
Media

• Host cache (HC)
• A
• B
• C
• D
• E

Media
Media
SC Skype ClientSN Super Node
SN D
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Experimental Setup
Internet
Unrestricted
SC 1
SC 2
Internet
NATed
NAT
NAT
SC 1
SC 2
Internet
Direct-blocked
SC 1
SC 2
Block SC 2
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Results and Discussion

• Factors Impacting Skype Relay Calls
• Internet connectivity, host cache.
• Characterizations of Skype Relay Nodes
• Relay distribution (geographical, ISP, AS)
• Round trip time (RTT)
• Call distribution over relay nodes
• Uptime of relay nodes

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Factors Impacting Skype Relay Calls
100
98.4
73.6
7.3
98.4
73.6
16.4
Possible Failure Reasons of Skype Relay Calls
a) The stale information about the IP address and
port number of the callee and its SN in the cache
of other Skype nodes. b) The inability of Skype
to find a relay at the time of call establishment.
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Relay Distribution (1/3)
Geographical distribution
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Relay Distribution (2/3)
Domain name suffix vs. RNs
Domain name suffix vs. RCs
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Relay Distribution (3/3)
Top Ten ASes
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Round Trip Time (RTT)
Total Average 52.2ms Median
43.6ms Partial Median NAT 95.6ms
Direct-blocked 13.3ms
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Call Distribution Over Relays (1/2)
Through RNs in US - NAT 81.2 -
Direct-blocked 92.4
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Uptime of Relays
Uptime Maximum 42.5 days Median 3.5
hrs Downtime Maximum 63.5 days Median 2
hrs Median lifetime cycle 3.5 2 5.5
hrs Median uptime probability 63.6
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Conclusions and Future Work

• The success rate of Skype relay calls depends on
• The network conditions
• The presence of a host cache
• Caching of callee reachable address by super
  nodes
• Skypes relay selection mechanism can further be
  improved.
• The median one-way network latency for relay
  calls in a NAT setup is 95.7ms.

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QA