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albakiara
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 Esercizio tabella NAT (esame 31 gennaio)

Salve a tutti,
qualcuno potrebbe spiegarmi come si svolge questo quesito:

Alle stazioni di una lan sono stati assegnati gli indirizzi ip da 10.24.0.0 a 10.24.0.8. Il router che fornisce accesso a Internet svolge funzioni di NAT. Riportare la struttura della tabella NAT nel caso in cui le stazioni 10.24.0.2 e 10.24.0.7 hanno ciascuna una connessione TCP aperta verso il server 194.64.20.0.

Grazie a chiunque mi possa aiutare!
11-02-2011 12:49
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gab217
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Sono interessato ankio, e poi volevo sapere per RTO e RTT come si risolveva
11-02-2011 13:47
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mostrielo
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Immaginando che il router NAT abbia indirizzo 198.168.2.2, che 2750 e 2771 siano i numeri di porta dei processi utente che vogliono andare in Internet e che 4001 e 4009 siano gli indici che il router NAT usa per indirizzare la tabella allora la tabella NAT sarà:

IP privato porta IP pubblico porta IP pubblico porta
---------------------------------------------------------
10.24.0.2 2750 198.168.2.2 4001 194.64.20.0 80
10.24.0.7 2771 198.168.2.2 4009 194.64.20.0 80

Ciò è quanto ho capito dalla Figura 6.7 di Halsall

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12-02-2011 15:30
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mostrielo
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RTT e RTO

(i) calcola subito il D di partenza ((RTO - RTT)/4) e poi applica le seguenti formule (Halsall 7.3.2):

RTT' = 0.9 x RTT + 0.1 x M
D' = 0.9 x D + 0.1 x |RTT' - M|
RTO = RTT' + 4 x D

(ii) se scade un t.o. RTT rimane invariato e RTO viene raddoppiato

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12-02-2011 16:38
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albakiara
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quindi in conclusione nell'esercizio cosa si deve scrivere in modo da rispondere corretamente?
14-02-2011 09:41
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gab217
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Originally posted by mostrielo
RTT e RTO

(i) calcola subito il D di partenza ((RTO - RTT)/4) e poi applica le seguenti formule (Halsall 7.3.2):

RTT' = 0.9 x RTT + 0.1 x M
D' = 0.9 x D + 0.1 x |RTT' - M|
RTO = RTT' + 4 x D

(ii) se scade un t.o. RTT rimane invariato e RTO viene raddoppiato


Ti ringrazio.
15-02-2011 11:57
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mostrielo
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Per la precisione nella formula di RTO, il D è l'ultimo calcolato:

RTT' = 0.9 x RTT + 0.1 x M
D' = 0.9 x D + 0.1 x |RTT' - M|
RTO = RTT' + 4 x D'

Ciao

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15-02-2011 13:05
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