View
53
Download
0
Category
Tags:
Preview:
DESCRIPTION
An Experimental Study of the Skype Peer-to-Peer VoIP System. Saikat Guha, Cornell University Neil DasWani, Google Ravi Jain, Google IPTPS ’ 06 Presenter: Te-Yuan. What do they want to know?. What makes Skype so successful? Compare with File-sharing P2P network By Observing Skype ’ s - PowerPoint PPT Presentation
Citation preview
An Experimental Study of the Skype Peer-to-Peer VoIP System
Saikat Guha, Cornell UniversityNeil DasWani, GoogleRavi Jain, GoogleIPTPS’06
Presenter: Te-Yuan
What do they want to know?
What makes Skype so successful? Compare with
File-sharing P2P network By Observing Skype’s
User behavior Node Session Time
Overlay Network Traffic SuperNode overlay network Overall utilization & resource consumption
Skype Three Services
two-way audio streams & conference call up to 4 users
Instant Message file-transfer
Structure Alike KaZaA
– SuperNode-based Ordinary Node (ON) Super Node (SN)
Outline - Experiments
Expt. 1: Basic operation Expt. 2: Promotion to supernode Expt. 3: Supernode network activity Expt. 4: Supernode and client population Expt. 5: Supernode presence
Expt. 1: Basic operation To Answer: How do two Skype clients co
nnect to each other? Normally,
ON send control traffic through SN-p2p Including
Availability information Instant messages Request for VoIP & File-transfer
What if ON is behind NAT/Firewall?
Expt. 1: Basic operation – Cont. NAT Traversal in Skype:
Level 0: Initiator NAT’ed Level 1: Recipient NAT'ed Level 2: Both NAT'ed (well-behaved NATs) Level 3: Both NAT'ed
Expt. 1: Basic operation – Cont. Level 0: Initiator NAT’ed
Expt. 1: Basic operation – Cont. Level 1: Recipient NAT’ed
Expt. 1: Basic operation – Cont. Level 2: Both NAT'ed (well-behaved NAT
s)
Expt. 1: Basic operation – Cont. Level 3: Both NAT'ed
Expt. 1: Basic operation – Cont.
Level 0
Level 1
Level 2
Level 3
Outline - Experiments
Expt. 1: Basic operation Expt. 2: Promotion to supernode Expt. 3: Supernode network activity Expt. 4: Supernode and client population Expt. 5: Supernode presence
Expt. 2: Promotion to supernode To Answer: What kind of node will be pro
mote to SN? Setup several Skype clients
One behind a saturated network uplink One behind a NAT One with a 10 Mbps connection & public IP
Key to be SN plenty of spare bandwidth publicly reachable
Outline - Experiments
Expt. 1: Basic operation Expt. 2: Promotion to supernode Expt. 3: Supernode network activity Expt. 4: Supernode and client population Expt. 5: Supernode presence
Expt. 3: Supernode network activity Goal: To observe the network traffic of a
Skype supernode Duration: 135 days (Sep. 1, 2005 to Jan. 1
4, 2006) Data captured: 13GB with ethereal
Expt. 4: Supernode and client population Goal: Collect SN & client IP/port Duration:2005/7/25 – 2005/10/12 Result:
Crawl 150K SN Collect 250K SN info
Expt. 4: Supernode and client population
A list of SN
Connect to a SN
Save the list
Connect to a SN from the list
A list of SN
Expt. 4: Supernode and client population Collect client info
Collect the number reported by skype client
Expt. 5: Supernode presence Goal: how many SN online at a give time Flow
Randomly Select 6000 SN - from the list collected by expt.
4 Send “application-layer Ping” Repeat every 30 mins for a month
Expt. 5: Supernode presence - Cont
Num. of SuperNode is more Stable
diurnal behavior of SNWeekend
Expt. 5: Supernode presence - Cont Geographic Distribution of Active SuperNodes
45--60%
peak at 11am UTC
(Europe mid-day)
20-25%
15-25%
Expt. 5: Supernode presence - Cont SuperNode Session Time
Median is 5.5h
Expt. 5: Supernode presence - Cont Fraction of supernodes joining or departing
Node arrival concentrated toward morning
Node departureconcentrated toward evening
Skype usage is correlated with working hours
Different from P2P file-sharing
Expt. 5: Supernode presence - Cont Node Arrival dependent
on Time Not Poisson or Uniform
process Poisson process with
varying hourly rate
Node arrival concentrated toward morning
Node departureconcentrated toward evening
VoIP in Skype: Preliminary Observation SuperNode Traffic
90.4%SN no need to relay VoIP traffic
VoIP in Skype: Preliminary Observation VoIP Relayed Session Arrival Behavior
Inter arrival time of Relayed VoIP/File sessions may be Poisson
VoIP in Skype: Preliminary Observation VoIP Session Length Behavior Skype:
Median: 2m50s
Average: 12m53s
Longest: 3h 26s
Traditional:
Average: 3m
Fraudulent:
Average: 9m
VoIP in Skype: Preliminary Observation File-transfer sizes
File size:
Median: 346kB
Conclusion First measurement study of Skype VoIP system Skype differs significantly from file-sharing P2P User Behavior
Diurnal & Work-week Calls are significantly longer File transferred are significantly smaller
SuperNode of Skype Consume little bandwidth Relatively stable
Recommended