Re: Using DNS for SSM

[Osnat Mokryn <osnaty@cs.huji.ac.il>]

On Wed, 14 Feb 2001, Stephen Sprunk wrote:

> Thus spake "Jeff Schoch" <jschoch@sprint.net>
> > I've just submitted a draft which I think the SSM working group should
> > be interested in.It can be found at:
> > http://www.ietf.org/internet-drafts/draft-schoch-dns-ssm-00.txt
> >
> > It's a relatively short, five page read.Please feel free to send any
> > comments to Sunny and me.Thanks for you time and attention.
> 
> I don't see the rationale for making the source the primary key and the
> channels the secondary keys.I think apps will more likely know the
> channel (DNS name) and want a listing of servers.

I agree. 
Furthermore, I think that the domain name should not be changed. Instead
of using a new channel naming convention such as MCAST, or any other
string, I suggest to use the same domain name and change only the protocol
specifier, from HTTP to HTTPM. Thus, people who are used to the site 
http://www.example.com don't have to go to a new 'mcast.example.com' but
rather to a : httpm://www.example.com/url_name where url_name is the
multicast channel name. A specific software in the user's side recognizes
the 'httpm' specifier, and sends the entire URL to the DNS for
resolution, with the 'url_name' concatenated at the end :
<com><example><www><url_name>
Since the resolution process looks for the biggest prefix it can match, it
does not affect current DNS structure. All is needed is to have special
entries for each channel, as in your scheme, which consists of the full
domain name + url_name.

This also solves the problem of having more than one source per domain
name, without changing the domain name.
The mapping in this case is: domain name is the group, the URL is
the specific source (which conforms with reality, in my opinion).

I previously suggested this as part of an overall solution to use
multicast to distribute very hot web pages, as can be seen in DIMACS
technical report 2000-47.

-Ossi Mokryn.





> 
> Have you considered using some variation of SRV records so that you can
> specify port numbers per server?Depending on how you do it, this would
> eliminate the need for a magic ".mcast." in thehostname.
> 
> > Jeff Schoch jschoch@sprint.net
> > Operations Engineering 703-689-7716
> 
> S
> 
>    |          |         Stephen Sprunk, K5SSS, CCIE #3723
>   :|:        :|:        Network Design Consultant, GSOLE
>  :|||:      :|||:       New office: RCDN2 in Richardson, TX
> .:|||||||:..:|||||||:.  Email: ssprunk@cisco.com
> 
> 
> 

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 Osnat (ossi) Mokryn         :: tel: +972-2-6585770
 Computer Science Institute :: http://www.cs.huji.ac.il/~osnaty
 Hebrew University          :: osnaty@cs.huji.ac.il
 Jerusalem, Israel          :: fax: +972-2-6585439
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