Also, about the ACL on Tokenring interface, should it
be non-canonical? I could not remember from where I
read about that all the ACL should be in canonical,
ples clarify this for me.
Thanks
Kent
--- Neil Desai <[EMAIL PROTECTED]> wrote:
> I have looked through the archives and a post from
> Howard Berkowitz is what
> lead me to the RFC. All of the posts that I have
> seen only refer to the
> swapping of bits within the byte. None of the
> explanations that I have seen
> go any further. I have also scoured the Internet
> and CCO.
> Neil
>
> ""Neil Desai"" <[EMAIL PROTECTED]> wrote in
> message
> 8n9llp$83c$[EMAIL PROTECTED]">news:8n9llp$83c$[EMAIL PROTECTED]...
> > I am having a problem understanding the issues
> between canonical and
> > non-canonical addressing. I understand that the
> bits are flipped within
> the
> > byte. On page 32-33 of Interconnections Second
> Edition she gives the
> example
> > of the address a2-41-42-59-31-51.
> > Canonical:
> > 10100010 01000001 01000010 01011001 00110001
> 01010001
> > Non-Canonical:
> > 01000101 10000010 01000010 10011010 10001100
> 10001010
> >
> > If you look at this you can clearly see that the
> address in canonical
> format
> > is not a group address (last bit of first byte is
> zero) but in
> non-canonical
> > format it is a group address. At this point I can
> see a big problem
> because
> > she also states:
> >
> > ".the group bit in addresses was defined not as
> "the most significant
> bit"
> > or the "least significant bit" but rather as "the
> first bit on the wire."
> > Thus, an address that was a group address on 802.3
> would not necessarily
> > look like a group address when transmitted on
> 802.5 because a different
> bit
> > would be transmitted first."
> >
> > Here is the confusion: In canonical format the
> least significant bit is
> > transmitted first and in non-canonical format the
> most significant bit is
> > transmitted first. So on the wire the 1's and 0's
> would be in the same
> > order. Here is an excerpt from RFC 2469:
> >
> > The figure below illustrates the difference
> between
> > canonical and non-canonical form using the
> canonical form address
> > 12-34-56-78-9A-BC as an example:
> >
> > In memory, 12 34 56 78
> 9A BC
> > canonical: 00010010 00110100 01010110
> 01111000 10011010 10111100
> >
> > 1st bit appearing on LAN (group
> address indicator)
> > |
> > On LAN: 01001000 00101100 01101010
> 00011110 01011001 00111101
> >
> > In memory,
> > MSB format: 01001000 00101100 01101010
> 00011110 01011001 00111101
> > 48 2C 6A 1E
> 59 3D
> >
> >
> > This shows that no matter how the information is
> stored in memory it looks
> > the same on the wire. So if it looks the same on
> the wire wouldn't an
> > adapter pickup the packet and flip the bits in the
> byte if it needed to.
> > Since it on the wire it looks like the bits are in
> non-canonical format a
> > canonical format media would automatically take
> the first byte and flip
> the
> > bits and so on, or so I would think.
> >
> > If anyone can figure out where I am going wrong
> please let me know. If it
> > would be best to talk, email me directly with a
> daytime phone number and
> I
> > will call you. Thanks.
> > Neil
> >
> >
> >
> > ___________________________________
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>
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