1. Evaluation of Objectivity/AMS on the Wide Area Network
SATO Hiroyuki
KEK Computing Research Center

2. Introduction Measured the performances of Objectivity/AMS :
AMS write/read access (5.1 vs 5.2)
AMS over LAN and WAN
Resource utilization of the AMS server is monitored for 5.1 and 5.2 on LAN
CPU utilization
TCP/IP packet was monitored for AMS transaction over LAN and WAN.
Transfer rate

3. Testbed Configuration
Monitored
CPU/Packet/…

4. AMS/Write-Read Performance Test on LAN and WAN
Objectivity page size is 8192 bytes
Test object (40 bytes) : 175~176 objects / page
#’objects for the write/read :
1,000,000 objects for LAN : 570 pages
100,000 objects for WAN : 57 pages

5. CPU Utilization for Write/Read for V5.1 and V5.2 on LAN20 40 60
(sec) 80
100 30 10
CPU Utilization (%)
Time
V5.1
V5.2
AVE:12%
AVE:18%
AVE:4%
AVE:8%

6. Measurements on the WAN
Characteristics of the network between KEK and CERN
RTT (Round Trip Time) is about 300 msec
The bandwidth is 2Mbps 10 20 30
500
400
300
(msec)
Day in 2000
Round Trip Time between KEK and CERN

7. Data Transfer for Write on LAN and WAN20 40 60 80
(sec)
Time
1000
200
400
600
800
1200
Transfer Rate (kB/s)
Server (AMS)
at KEK
Client
at KEK/CERN
52 bytes
Control
Transfer
Phase
(CTP)
8236 bytes
8280 bytes
36 bytes
Data
Transfer
Phase
(DTP)
8280 bytes
Bulk
Transfer

8. Data Transfer for Read on LAN and WAN25 50 75
100
(sec)
Time
500
200
300
400
Transfer Rate (kB/s)
150
Server (AMS)
at KEK
Client
at KEK/CERN
Control
Data
Transfer
Phase
(CDTP)
52 bytes
RTT
8236 bytes 1 2
Time since #’4M is sent (sec)
4000
4100
4200
x 103
Seq. Number
Write
Read

9. Comparison with AMS Write and ftp
Write performance
over WAN is faster
than ftp ! 20 40 60 80
100
120
140
Transfer Rate (kB/s)
AMS
ftp 20 40 60 80
Time
(sec)

10. Window Size in TCP/IP Monitored with tcpdump
AMS : bytes
ftp : bytes
Window size affects the transfer rate
It can be changed with “setsockopt” function (standard max : bytes / optional 232 bytes)
Bulk data transfer rate for various received window size is measured

11. Bulk Data Transfer Rate for Various Window Size (KEK - CERN)
64240 bytes
(Test Program)
33580 bytes
(Objectivity)
24820 bytes
(ftp)
Window size 6 12 18 24
(hour)
Time 50
100
150
200
250
Data Transfer Rate (kB/s)
02/Feb/2000

12. Effective Bandwidth for RTT = 280 ms (KEK - CERN)
10 -2
10 -1 1
10 1
10 2
ftp
AMS
Efficiency (%)
2Mbps
Efficiency =
Window Size
RTT
Bandwidth
20Mbps
Needs the window scale option
200Mbps
10 3
10 7
10 6
10 5
10 4
Window Size
(bytes)

13. Comparison with network of surface and satellite
CERN 1 2 3 4 5 6 7 8 9
KEK
100
150
200 1 2 3
Page Number
Transaction Time / Page (sec)
surface (RTT=300ms)
satellite (RTT=655ms)
Read 1 2 3 4 5 6 7 8
TCP Timeout
LOST! 10 11
ack2 10 11
ack8 12 13
ack4 12 13 14 15 16
ack6 14 15 16
ack8 9
ack16
8236 = 536* ==> 16 segmets
MSS for satellite
The congestion window is
initialized after this transaction.

14. Summary Write/Read operation of Objectivity 5.2 works on the WAN
AMS server 5.2 is multi-threaded
Consumes more CPU cycles than 5.1
Does not matter when network is a bottleneck
Write performance over WAN is faster than ftp
more speedup is expected with a larger window size
(Optimal window size may vary with the available buffer size of the network router)
Read performance is poor due to the hand-shaking
Oscillation of congestion window is observed in satellite network — further study needed