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Re: Is WAP mobile Internet??

2000-07-06 19:10:03


Masataka Ohta wrote:

Joe;

would pacbell filtering all multicast at all CPE equipemt fall into your
bucket, where do you draw the line?

At IP, as Bob Braden said.

SMTP is _over_ IP.

Wrong. RFC821 says:

   SMTP is independent of the particular transmission subsystem and
   requires only a reliable ordered data stream channel.  Appendices A,
   B, C, and D describe the use of SMTP with various transport services.
   A Glossary provides the definitions of terms as used in this
   document.

Appendix A is SMTP over TCP (over IP). (I was implying that it was on
TOP of IP, not that it was exclusively on top of IP).

SMTP in the Internet is, by definition, over IP. STD1 defined only one
required reliable ordered data stream protocol - TCP.

Multicast _redefines_ IP (or portions of the address space thereof); it
could be argued that a service provider sells 'Internet' without selling
multicast IP.

See STD1 for a list of "required" protocols.

Multicasting is RFC1112, one of the 'required' protocols.

On page 1 of that RFC:   

        Level 0: no support for IP multicasting

   There is, at this time, no requirement that all IP implementations
   support IP multicasting.  Level 0 hosts will, in general, be
   unaffected by multicast activity.  The only exception arises on some
   types of local network, where the presence of level 1 or 2 hosts may
   cause misdelivery of multicast IP datagrams to level 0 hosts.  Such
   datagrams can easily be identified by the presence of a class D IP
   address in their destination address field; they should be quietly
   discarded by hosts that do not support IP multicasting. 

Interestingly, the RFC indicates 'should be quietly dropped' where not
supported. There is no requirement that they not be dropped, or that the
dropping be quiet.

Joe



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