grazie, è stata la risposta + rapida che abbia mai avuto da un forum...
in attesa di mettermi ad attimizzare mi permetto di darti i risultati dei test...cmqil mio SO è W2kpro sp4; modem d-link dsl200 usb; PPPoverATM contratto Linea adsl sempre di libero 320/128 (linea affari)...


**************************************23-feb-2004 17.43.05 MISURE TERMINATE Prove :10 Velocita' Media :256.31888553580603Kbit/sec
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C:\WINNT\system32>ping www.ngi.it

Esecuzione di Ping www.ngi.it [194.185.88.15] con 32 byte di dati:

Risposta da 194.185.88.15: byte=32 durata=80ms TTL=120
Risposta da 194.185.88.15: byte=32 durata=80ms TTL=120
Risposta da 194.185.88.15: byte=32 durata=80ms TTL=120
Risposta da 194.185.88.15: byte=32 durata=111ms TTL=120

Statistiche Ping per 194.185.88.15:
Pacchetti: Trasmessi = 4, Ricevuti = 4, Persi = 0 (0% persi),
Tempo approssimativo percorsi andata/ritorno in millisecondi:
Minimo = 80ms, Massimo = 111ms, Medio = 87ms

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SpeedGuide.net TCP/IP Analyzer


TCP properties for IP = 151.38.51.227 ()
Browser/OS = Mozilla/4.0 (compatible; MSIE 5.01; Windows NT 5.0; PCM_06a; SlimBrowser [flashpeak.com])
Notes: Read the Analyzer FAQ if the above is not your IP address.

TCP options string = 020405ac01010402
MTU = 1492
MTU is optimized for PPoE DSL broadband. If not, consider raising MTU to 1500 for optimal throughput.
MSS = 1452
MSS is optimized for PPPoE DSL broadband. If not, consider raising MTU to 1500 for maximum throughput.

Default Receive Window (RWIN) = 8760
RWIN Scaling (RFC1323) = 0 bits
Unscaled Receive Window = 8760

For optimum performance, consider changing RWIN to a multiple of MSS.
Other values for RWIN that might work well with your current MTU/MSS:
511104 (MSS x 44 * scale factor of 8)
255552 (MSS x 44 * scale factor of 4)
127776 (MSS x 44 * scale factor of 2)
63888 (MSS x 44)
bandwidth * delay product:

Your RcvWindow limits you to: 350.4 kbps (43.8 KBytes/s) @ 200ms
Your RcvWindow limits you to: 140.16 kbps (17.52 KBytes/s) @ 500ms
Consider increasing your RWIN value to optimize TCP/IP for broadband.
MTU Discovery (RFC1191) = ON
Time to live left = 54 hops

TTL value is ok.
Timestamps (RFC1323) = OFF
Selective Acknowledgements (RFC2018) = ON
IP type of service field (RFC1349) = 00000000