If we:
1) Count bytes/bits at the network adapter level (raw # of bits through the NIC) and,
2) Count bytes in all HTTP/S request/responses.
Assuming only HTTP/S traffic is on the box, and assuming a statistically relevant amount of "typical" web traffic:
I want to know about how much more traffic will be counted at the NIC level than at the HTTP/S level (counting http headers and all) because of the extra network overhead.
You have zero knowledge about the layers below HTTP. You can't even assume the HTTP request will be delivered over TCP/IP. Even if it is, you have zero knowledge about the overhead added by the network layer. Or what the reliability of the route will be and what overhead will be due to dropped/resent packets.
Update: Based on your comment, here are some back-of-the-napkin estimates:
The maximum segment size (which does not include the TCP or IP headers) is typically negotiated between the layers to the size of the MTU minus the headers size. For Ethernet MTU is usually configured at 1500 bytes. The TCP header is 160 bits, or 20 bytes. The fixed part of the IPv4 header is 160 bits, or 20 bytes as well. The fixed part of the IPv6 header is 320 bits, or 40 bytes. Thus:
- for HTTP over TCP/IPv4
overhead = TCP + IP = 40 bytes
payload = 1500 - 40 = 1460 bytes
overhead % = 2% (40 * 100 / 1460)
- for HTTP over TCP/IPv6
overhead = TCP + IP = 60 bytes
payload = 1500 - 60 = 1440 bytes
overhead % = 4% (60 * 100 / 1440)
Here are the assumptions:
- Amazon counts the NIC payload without the Ethernet headers, not the whole NIC packet
- your HTTP responses are fully utilizing the TCP/IP packet - your typical page size + HTTP headers results in one or more full TCP/IP packets and one with more than 50% used payload
- you set explicit expiration date on cached content to minimize 302 response
- you avoid redirects or your URLs are long enough to fill the payload
With 100Mbit/s Ethernet, a large file transfers at 94.1Mbit/s.
That's 6% overhead. If you also count the TCP ACKs flowing in the opposite direction, it's closer to 9%. For gigabit Ethernet the overhead (in percent) remains the same. Assumptions: TCP/IPv4 and file size >100kB. (At this size we can neglect the initial HTTP and TCP setup.)
When comparing download rates, beware the factor 8 from bits to bytes. I guess nobody will charge you for Ethernet preamble or interframe gap, but "payload" shouldn't be taken literally.
Calculation: payload / overall
payload = 1500 - 20 - 32 (Ethernet_MTU - IPv4 - TCP)
overall = 8 + 14 + 1500 + 4 + 12 (Preamble + Ethernet_header + Ethernet_MTU + CRC + Interframe_gap)
Because Ethernet is always full-duplex these days, the occasional TCP ACK flowing the other way does not change the transfer rate. If you add one ACK for every two data frames to the overhead (that's what I observed in Wireshark), you get 8.5% total overhead. And while the MTU size is usually 1500 bytes, it can be smaller in some networks, or much larger if every piece of equipment in the path is configured for it.
What extra network overhead? the TLS overhead on top of the HTTP amounts to the key exchange. It's mostly processing overhead that you notice.
http://en.wikipedia.org/wiki/HTTP_Secure#Difference_from_HTTP
Down the line (after the server) wan accelerator or proxies will treat your traffic differen't as it isn't cacheable or compressible.
来源：https://stackoverflow.com/questions/3613989/what-of-traffic-is-network-overhead-on-top-of-http-s-requests