[e2e] Is a non-TCP solution dead?

[Ayyasamy, Senthilkumar (UMKC-Student)]

> - For a few minutes during the early days of the PILC working
> group, we were excited to think that we might be able to treat
> ECN as an unambiguous indicator of congestion, so when we were
> using ECN (even "fully-deployed" ECN), we could interpret loss
> in the absence of ECN Congestion Encountered as an indication of
> transmission error, and not congestion.
> 
> Of course, we couldn't do this, because at a sufficiently high
> congestion level, we lose packets marked with CE, so we would be
> retransmitting at exactly the wrong time.
> 
> One of the reasons we were "dragging our feet" on error
> notification in PILC was because we couldn't come up with a
> reliable way to tell a sender about transmission errors that
> allowed the sender to know that there was no possibility of
> simultaneous loss due to congestion, so no possibility of making
> congestion worse for a sustained period of time.


Error notification seems to be possible with ECN ...

http://nms.lcs.mit.edu/projects/mecn/


But, I don't know how the proposal can be used in practice or the 
related engineering issues... But, IETF (more closely IESG) will 
have problems with re-using of existing fields in a protocol
header.