1. IEEE 802.21 MEDIA INDEPENDENT HANDOVER DCN: 21-08-0206-01-0000
Title: An Implementation Report on MIH Fragmentation
Date Submitted: July 15, 2008
Presented at:
Authors or Source(s):
  Donald Baker (Telcordia) and Yoshihiro Ohba (Toshiba)
Abstract: This document contains an implementation report for MIH fragmentation functionality

2. IEEE 802.21 presentation release statements
This document has been prepared to assist the IEEE Working Group. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein.
The contributor grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEE’s name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEE’s sole discretion to permit others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor also acknowledges and accepts that this contribution may be made public by IEEE
The contributor is familiar with IEEE patent policy, as outlined in Section 6.3 of the IEEE-SA Standards Board Operations Manual < and in Understanding Patent Issues During IEEE Standards Development

3. Environment
Two MIHFs on the same Windows XP PC run the MIH protocol using network socket
CPU: Intel Pentium 4, Dual core 3.4 GHz
Memory: 1.5G
MIH Fragmentation : enabled
MIH Acknowledgment: enabled
Piggybacking ACK in response: disabled
MIH Transport Protocol: UDP

4. Conditions aFragmentationThreshold
= fragment size (except for the last fragment)
= 1500 octets
Message retransmission timer timeout value: 3000 ms, though not relevant
Reassembly timeout timer value: 1000ms
Number of fragments in a message: 1, 2, …, 20
To get larger fragments, an MIH_Get_Information request message was constructed with larger query strings
Each data points represent 100 samples. No samples had dropped packets
All times are milliseconds.
All samples were collected in one execution of the program
Sender and receiver are in the same address space which makes message transmit time negligible and may make "all packets sent" artificially low

5. Measured Data
Data is based on "linearizing" the overall send process and taking time samples at key points in the process:
1) When the stack client (at the sender) has a message and begins the send Message call
2) Just before the first send packet is put on the socket
3) Just before the last packet is put on the socket.
4) Just after the last packet is received.
5) Just before the receiver sends the ack
6) Just after the sender receives the ack
7) When the stack client has the send message call return
Series2
Series3
(1)
Series1
(2)
(3)
(4)
Series4
(5)
Series5
(6)
Series6
(7)
Sender
Message
Processing
Sender
All Packets
Sent
Last Packet
Transit
Time
Receiver
Assembly
Time
ACK
Transit
Time
Sender ACK
Processing
Time

6. Result (table view) 21-08-0206-01-0000 Frags Original size
Sender Message Processing (ms)
Sender All Packets Sent (ms)
Last Packet Transit Time (ms)
Receiver Assembly (ms)
Ack Transmit Time (ms)
Sender Ack Processing (ms)
Total Send Time (ms) 1 52
0.22
0.00
0.17
0.77
0.13
0.87
2.17 2
2256
0.28
0.23
0.10
1.33
1.15
3.31 3
3356
0.35
0.39
1.39
3.32 4
4456
0.52
0.58
0.12
1.70
0.27
0.62
3.80 5
6656
0.80
2.03
0.29
4.46 6
7756
1.03
0.83
0.11
3.03
0.30
0.93
6.23 7
8856
0.98
0.94
0.09
0.33
0.43
4.94 8
11056
1.14
1.25
0.14
2.47
0.46
5.78 9
12156
1.31
2.32
0.34
0.45
5.76 10
13256
1.44
2.60
0.41
6.29 11
15456
1.56
1.61
2.52
6.56 12
16556
1.64
1.72
2.94
0.32
0.57
7.29 13
17656
1.87
1.80
3.36
0.37
7.82 14
19856
2.07
2.46
0.08
3.48
0.36
8.79 15
20956
2.28
2.04
3.60
0.49
8.84 16
22056
2.13
2.16
4.56
9.65 17
24256
2.21
0.07
4.09
0.38
9.11 18
25356
2.54
2.41
4.39
10.12 19
26456
3.02
2.92
4.68
11.41 20
28656
2.90
3.43
0.20
4.52
11.88

7. Result (graph view)

8. Analysis
The sender message processing time goes up linearly, as expected due to the time it takes to fragment ever larger messages
The sender all packets sent also goes up linearly at about the same rate.
The packet transmit time and ack transmit time are constant, as expected.
The receiver message processing time is the dominant cost and in this implementation, the cost is largely due to Java thread hand-offs
The sender ack processing cost is relatively high due to thread handoffs in the implementation.