Neil,
I'm not sure what your question is. The bits on the wire are transmitted
the same 01000000. Token-ring reads them one way (non-canonical) 01000000,
and Ethernet reads them another way (canonical)00000010. It is how the
network interface cards (NIC)/device drivers read the 0s and 1s that is
different.
I would be happy to help(since I have struggled with this myself) if you can
clarify your question
Regards,
Drew R. Maness, CCNP, CCDA, CCSI, MCSE
-----Original Message-----
From: Neil Desai [mailto:[EMAIL PROTECTED]]
Sent: Tuesday, August 15, 2000 12:47 PM
To: [EMAIL PROTECTED]
Subject: Re: canonical and non-canonical addresses
Does any body know the answer to this one? Now I am getting a bit
frustrated. I have posted to this group only a couple of times and I never
get an answer. All I get is people asking me to look at the archives. I did
as much homework as possible before asking the group.
""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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