IP Fragmentation |
Ejercicio/ejemplo
Dada la red de la figura
Describir el estado de:
- el bit MF (More Fragments)
- el campo Fragment Offset
- el campo Total Length (describiendo su composición parcial)
para los datagramas y sus correspondientes fragmentos en los siguientes casos:
a) H1 envía un echo request a H2 cuyo payload ICMP es de 600 bytes (ej.[WIN] ping -l 600)
b) H1 envía un echo request a H2 cuyo payload ICMP es de 1000 bytes
c) H1 envía un echo request a H2 cuyo payload ICMP es de 1472 bytes
d) H2 envía un echo request a H1 cuyo payload ICMP es de 1472 bytes
Resolución:
a) al Host H2 le llegan 2 fragmentos que conforman el echo request c/payload de 600 bytes
| Red |
MF |
Foffset |
Total Length |
Hip |
Pip=Hicmp+Picmp |
| A |
0 |
0 |
628 |
20 |
608=8+600 |
| B |
0 |
0 |
628 |
20 |
608=8+600 |
| D |
1 |
0 |
396 |
20 |
376=8+368 |
| 0 |
376 |
252 |
20 |
232=0+232 |
| E |
1 |
0 |
396 |
20 |
376=8+368 |
| 0 |
376 |
252 |
20 |
232=0+232 |
b) al Host H2 le llegan 3 fragmentos que conforman el echo request c/payload de 1000 bytes
| Red |
MF |
Foffset |
Total Length |
Hip |
Pip=Hicmp+Picmp |
| A |
0 |
0 |
1028 |
20 |
1008=8+1000 |
| B |
1 |
0 |
700 |
20 |
680=8+672 |
| 0 |
680 |
348 |
20 |
328=0+328 |
| D |
1 |
0 |
396 |
20 |
376=8+368 |
| 1 |
376 |
324 |
20 |
304=0+304 |
| 0 |
680 |
348 |
20 |
328=0+328 |
| E |
1 |
0 |
396 |
20 |
376=8+368 |
| 1 |
376 |
324 |
20 |
304=0+304 |
| 0 |
680 |
348 |
20 |
328=0+328 |
c) al Host H2 le llegan 5 fragmentos que conforman el echo request c/payload de 1472 bytes
| Red |
MF |
Foffset |
Total Length |
Hip |
Pip=Hicmp+Picmp |
| A |
0 |
0 |
1500 |
20 |
1480=8+1472 |
| B |
1 |
0 |
700 |
20 |
680=8+672 |
| 1 |
680 |
700 |
20 |
680=0+680 |
| 0 |
1360 |
140 |
20 |
120=0+120 |
| D |
1 |
0 |
396 |
20 |
376=8+368 |
| 1 |
376 |
324 |
20 |
304=0+304 |
| 1 |
680 |
396 |
20 |
376=0+376 |
| 1 |
1056 |
324 |
20 |
304=0+304 |
| 0 |
1360 |
140 |
20 |
120=0+120 |
| E |
1 |
0 |
396 |
20 |
376=8+368 |
| 1 |
376 |
324 |
20 |
304=0+304 |
| 1 |
680 |
396 |
20 |
376=0+376 |
| 1 |
1056 |
324 |
20 |
304=0+304 |
| 0 |
1360 |
140 |
20 |
120=0+120 |
|
Applet |
| Provide an MTU (maximum transfer unit) and an incoming datagram size, and
the applet will generate all the fragments for you. |
|
This applet was coded by Albert Huang in 1997 as part of course work at the University of Pennsylvania. |
