nanog mailing list archives
Re: MTU of the Internet?
From: Phil Howard <phil () charon milepost com>
Date: Mon, 9 Feb 1998 09:02:35 -0600 (CST)
Patrick McManus writes:
At the risk of introducing meaningful background literature: ftp://ds.internic.net/rfc/rfc2068.txt I direct folks to 14.36.1 "Byte Ranges" which when interleaved with pipelined requests comes very close to achieving client-driven multiplexing that I'd suggest from a UI pov will behave much better than the multiple connections method (eliminating the cost of tcp congestion control but at the cost of some application protocol overhead).
More than application overhead, I suspect the biggest problem with this otherwise good idea is that it won't be implemented corrently by the browsers or the servers. For example on the server end, it would see multiple requests for the same object, at different byte ranges. If that object is being created on the fly by a program process (e.g. CGI) the browser won't have a clue of the size. What is the correct behaviour of the server if the request is made for bytes 0-2047 of an object which invokes a CGI program to create that object? Obviously it can send the first 2048 bytes, but then what? Should it leave the process pipe blocked until the next request comes in? One httpd listener might well have to have dozens of these stalled processes. Should they all remain there until the persistent connection is broken? Of course with multiple connections, you have all these processes, anyway. But at least you know when the process should go away (when the connection is dropped). If the persistent connection gets dropped before all the object get loaded, then loading _must_ start from the beginning, since objects may now become inconsistent (a different GIF image can be created by a new instance of the program that generates it). Of course, all of this can be done. But can you trust the developers of every browser and every server to get it right? What I am saying is that if this is to be pursued, it needs to be pursued with a lot of details addressed that even the RFC doesn't seem to touch on. Consider CGI. Should the server start a new instance of CGI for each range request, passing that request via the CGI environment? Or should the server keep each CGI persistent as long as each range request is sequential to the previous one? What if there are two different requests for the same path, which in the ordinary case can indeed generate distinctly different objects (not cacheable). How would the server know which of them to continue when the next range request comes in (previously the distinction is managed by the connection). While I can see that persistent connections with range requests can solve many things, I believe the implementations will botch it up in most cases to the extreme that it won't get used. A subchannelized method of doing request/response transactions over a single persistent connection would handle more (if not all) of these cases better (IMHO). -- Phil Howard | suck7it9 () spammer9 com end4it79 () spammer9 com stop5269 () anywhere net phil | no6spam9 () anywhere net stop7643 () dumb8ads net crash384 () no54ads0 org at | stop5it2 () dumbads1 com no2spam8 () no56ads2 org end2it50 () no7place net milepost | stop7it7 () no98ads8 edu stop3538 () anywhere com w5x5y6z3 () no9place net dot | end5ads1 () dumbads1 com no1way00 () spammer0 net eat20me8 () noplace9 edu com | end5ads6 () spammer2 net ads0suck () noplace9 org die8spam () dumbads1 net
Current thread:
- Re: MTU of the Internet?, (continued)
- Message not available
- Re: MTU of the Internet? Jay R. Ashworth (Feb 09)
- Re: MTU of the Internet? Marc Slemko (Feb 07)
- Re: MTU of the Internet? Paul A Vixie (Feb 07)
- Re: MTU of the Internet? Phil Howard (Feb 08)
- HTML layout (was Re: MTU of the Internet?) Stephen Sprunk (Feb 08)
- Re: HTML layout (was Re: MTU of the Internet?) Patrick W. Gilmore (Feb 12)
- Message not available
- Re: MTU of the Internet? Jay R. Ashworth (Feb 08)
- Re: MTU of the Internet? Marc Slemko (Feb 08)
- Re: MTU of the Internet? Phil Howard (Feb 08)
- Re: MTU of the Internet? Patrick McManus (Feb 09)
- Re: MTU of the Internet? Phil Howard (Feb 09)
- Re: MTU of the Internet? Marc Slemko (Feb 09)
- Re: MTU of the Internet? Patrick McManus (Feb 09)
- HTTP proxy servers (was Re: MTU of the Internet?) Matt Ranney (Feb 12)
- Message not available
- Re: MTU of the Internet? Jay R. Ashworth (Feb 08)
- Re: MTU of the Internet? Mike Hedlund (Feb 08)
- Re: MTU of the Internet? Phil Howard (Feb 08)
- Re: MTU of the Internet? Mike Hedlund (Feb 09)
- Message not available
- Re: MTU of the Internet? Jay R. Ashworth (Feb 08)
- Re: MTU of the Internet? Dean Gaudet (Feb 08)