On 28-jan-04, at 22:00, Randall R. Stewart (home) wrote:Let me go through these one by one...
In other words, when there is a serious solution to multihoming -- ie, being able to preserve a connection when using more than one IP Address -- it will likely work for IPv4.
Yes.. SCTP solves the problem for V4 and V6 (missed that bit last time).
That remains to be seen. The list of issues that SCTP has or at least seems to have is long. To name a few:
- increased overhead compared to TCP
Ok lets see. SCTP takes on average 4 more bytes per data packet then TCP. However, if the TCP implementation enables timestamps then that is not true and TCP takes more overhead by about 4 bytes...
Unless you are discussing another type of overhead...
- requires significant changes from applications
Ok let see.. for Mozilla we converted two lines of code
sd = socket(AF_INET6, SOCK_STREAM, IPPROTO_TCP); became --------------> sd = socket(AF_INET, SOCK_STREAM, IPPROTO_SCTP);
and
setsockopt(sd, IPPROTO_TCP, TCP_NODELAY, &on_off, sizeof(on_off));
became ---------------> setsockopt(sd, IPPROTO_SCTP, SCTP_NODELAY, &on_off, sizeof(on_off));
Now to take advantage of the stream feature you would need to do more.. but for pure multi-homing one or two lines of change does not seem that big of deal to me ...
- no backward compatibility of any kind
I am not sure what you mean by backward compatable? You definetly can't have TCP and SCTP talk.. they are after all different protocols... But if an application needs the redundancy move to it.. its there today with about 2 lines of coding change...
- source address selection problem isn't addressed fully, if at all
I don't think I understand this issue either.. We have fully addressed source address selection in the KAME implementation. It is not a difficult problem.. it does require some code.. but any good implementation must address this issue... And since the site scope went away in IPv6 (at least for now) its easier to do then it was).
I can't be sure right now, but I also suspect SCTP could very well be vulnerable to some of the threats identified lately in the multi6 wg.
I would have to look at your threats... if you add the dynamic address feature.. sure
thats why the document has not progressed.. but that will change when the
Purpose Built Keys instantation in SCTP happens.. hopefully soon.. just another
draft to write :-D
I think you may want to have a little closer look at SCTP.. you might want to get the KAME BSD implementation and play with it for a bit.. I think you would be amazed at how simple it is to convert an application and you end up with multi-homing for free with those 2 lines of code :->
R
-- Randall R. Stewart 815-477-2127 (office) 815-342-5222 (cell phone)