3 ms·
TCP header does have a checksum that is supposed to check both the header and the payload. So either the bit corruption is such that is not detected by the che
by noncoml 6y ago
TCP header does have a checksum that is supposed to check both the header and the payload.
So either the bit corruption is such that is not detected by the checksum
Or ATT is doing something nefarious and touches layer 4 and corrupts the data while doing so
- willis936 6y agoI don’t have numbers off hand, but from a feeling I have from memory, I would think it is extremely unlikely that TCP checksums are consistently failing to trigger retransmission. Someone must be altering packets along the way.
- _-___________-_ 6y agoIt is triggering retransmission. It just retransmits until it gets lucky with the (pretty weak) TCP checksum.
- cranekam 6y agoTCP checksums are notoriously weak: https://www.evanjones.ca/tcp-checksums.html https://www.evanjones.ca/tcp-checksums.html With enough packets passing the dodgy RAM a noticeable number will manage to get mangled in such a way that the checksum is still correct.
- ericbarrett 6y agoChecksums are also often recomputed on transit if the packet is intercepted, e.g. to limit TTL, unflag odd/unused TCP features, that kind of ISP-ish preening. So if it was a software error or even a hardware problem in the right (wrong) spot it’s possible to get this kind of corruption without retransmits.
- noncoml 6y agoI think you are confusing the IP header with TCP header. Routers don’t touch the TCP header at all
- Avery3R 6y agoif your router does NAT it touches the tcp header
- noncoml 6y agoYou are right, although NAT could be classified as a firewall feature, that runs on routers. But in any case it's irrelevant in this context as ATT shouldn't be doing any NAT
- ericbarrett 6y agoNo. URG, “Christmas tree” packets, etc. all can be mangled by the ISP. Or more commonly dropped
- deleted 6y ago[deleted]
- bytesandbots 6y agoIn that case, won't there be significant packet loss causing throughput to be very slow? I don't know if this is possible without something messing with TCP headers.