Steve's boss didn't have the budget.
Here is how we can sort all the numbers out:
Multicast (class D) begins with 1110 for the IP. That is 4 bits out of 32, leaving 28 bits left.
This is old news.
According to the story above, Postel only had the budget for 1 OUI which is 48 bits and a person who purchases one is assigned the the first 24 bits, and the vendor can do whatever they want with the last 24 bits. Postel purchased this one (first 6 characters = the first 24 bits):
And he could do anything he wants with the last 24 bits.
The range would have been:
01-00-5E-00-00-00 through 01-00-5E-FF-FF-FF
Because an IPv4 class D (multicast address) begins (in binary) as 1110, there are 28 bits left in the IPv4 address. If Jon had purchased 16 consecutive OUIs, for example:
all the way through
(for a total of 16 OUIs)
Then the last 28 bits of the OUI would all be available for the use by the vendor (in this case for use by Multicast). With the first 4 bits of an IPv4 address locked in at 1110, the last 28 bits of the multicast IPv4 group address address could exactly fit into the last 28 bits of the OUI ranges purchased (see above) to be used as the Layer 2 address, and there would be a one to one mapping.
Now for Steve Deering. Jon only purchased/registered 1 OUI. So the one to one mapping was out of the question. To add insult to injury, Jon gave 1/2 of the one OUI purchased for Steve to use for his "multicast project". Jon told Steve he could use the range of:
01-00-5E-00-00-00 through 01-00-5E-7F-FF-FF
color coded binary:
01-00-5E-0000 0000-00-00 through 01-00-5E-0111 1111-FF-FF
Which is where we get the 23 bits worth that Steve had to make everything fit in. The single leading zero bit in red (above) is not available for Steve to change.
The half that Steve didn't get to use was
01-00-5E-80-00-00 through 01-00-5E-FF-FF-FF
In short, this results in several IPv4 multicast groups that end up mapping to the same L2 address, so planning is required within an organization to select IPv4 groups that are far enough away from each other as to not end up with the same L2 address used.
Here is a video on the conversion.
Back to the origin, amazing, thx for sharing the story !
If i understand well (i've bad english), the moral of the story is J. tightwad in 90's (i'm kidding of course)
Perhaps a rumor but i heard that the (IPv6 to Ethernet) multicast address was allocated by J. when i goes to the doctor and the doctor ask him to say " 33 33 "