top | item 41394130 (no title) drones | 1 year ago > Achieves 94.9 Mbit/sec when Pico is overclocked to 300 MHz, as measured by iperfIs this an effective rate, or just the reflection of a hardware limit? discuss order hn newest gonzo|1 year ago A 1500 byte (octet) MTU frame is 1538 bytes “on the wire”.7 byte preamble1 byte SFD6 byte dst MAC6 byte src MAC2 byte ethertype or length46-1500 bytes of payload (ignoring “Jumbo” frames and 802.1q tags)4 byte CRC12 byte IFG (which is silence, but still counts for time on the wire)Add it up and you have 1538 bytes “on the wire”.TCP overhead for IPv4 is 20 bytes for IP(v4) (no options) and 20 bytes for TCP (again, no options).So 1460 bytes of data for 1538 bytes on the wire. 1460/1538 = 0.949284So for 100M Ethernet, 94.9284Mbps is “perfect”.
gonzo|1 year ago A 1500 byte (octet) MTU frame is 1538 bytes “on the wire”.7 byte preamble1 byte SFD6 byte dst MAC6 byte src MAC2 byte ethertype or length46-1500 bytes of payload (ignoring “Jumbo” frames and 802.1q tags)4 byte CRC12 byte IFG (which is silence, but still counts for time on the wire)Add it up and you have 1538 bytes “on the wire”.TCP overhead for IPv4 is 20 bytes for IP(v4) (no options) and 20 bytes for TCP (again, no options).So 1460 bytes of data for 1538 bytes on the wire. 1460/1538 = 0.949284So for 100M Ethernet, 94.9284Mbps is “perfect”.
gonzo|1 year ago
7 byte preamble
1 byte SFD
6 byte dst MAC
6 byte src MAC
2 byte ethertype or length
46-1500 bytes of payload (ignoring “Jumbo” frames and 802.1q tags)
4 byte CRC
12 byte IFG (which is silence, but still counts for time on the wire)
Add it up and you have 1538 bytes “on the wire”.
TCP overhead for IPv4 is 20 bytes for IP(v4) (no options) and 20 bytes for TCP (again, no options).
So 1460 bytes of data for 1538 bytes on the wire. 1460/1538 = 0.949284
So for 100M Ethernet, 94.9284Mbps is “perfect”.