Ethernet on recent FPGAs

<snip>

> 1) Buy a batch of unique addresses (which isn't cheap and involves
> administrative hassle).  If you're designing a LAN for an airliner I'm
> going to fly on, I'd like you to use this method.

Mike,

While I agree that the MAC ID space is so large that the chance of a
collision for a random address is very low, I do not agree with that
statement.  Buying a range of unique addresses is cheap and easy, and
no administrative hassle is involved.

The IEEE administers MAC IDs, and you can buy a range of them for a
one time fee online.  I bought the OUI package online with a credit
card and have no regrets. Take a look at:

http://standards.ieee.org/regauth/oui/index.shtml
http://standards.ieee.org/regauth/oui/pilot-ind.html
http://standards.ieee.org/regauth/oui/forms/

You can buy a 4K block of MAC IDs for $500 USD, or a 2^24 block of IDs
for $1650.  That is lost in the noise for producing a commercial
product.

This is a far better deal than I get from the PCI SIG where I have to
pay every year to retain my vendor ID. For the MAC IDs, I pay once and
it is mine for ever.

While I am a small business owner and complain about every penny
spent, I think that the IEEE gives me a fair deal.

Regards,

John McCaskill
www.FasterTechnology.com
Xilinx Alliance Partner
Impulse C Platform Partner

>While I agree that the MAC ID space is so large that the chance of a
>collision for a random address is very low, I do not agree with that
>statement.  Buying a range of unique addresses is cheap and easy, and
>no administrative hassle is involved.

I accept your point about the cost.  By "administrative hassle", I
mean that of maintaining records within one's own company.  If this
were negligible for MAC addresses then you could say the same about
DHCP, but you'd make a lot of network admins very unhappy if you took
away DHCP.

Mike

On Jan 5, 8:50 pm, MikeShepherd...@btinternet.com wrote:
> >While I agree that the MAC ID space is so large that the chance of a
> >collision for a random address is very low, I do not agree with that
> >statement.  Buying a range of unique addresses is cheap and easy, and
> >no administrative hassle is involved.
>
> I accept your point about the cost.  By "administrative hassle", I
> mean that of maintaining records within one's own company.  If this
> were negligible for MAC addresses then you could say the same about
> DHCP, but you'd make a lot of network admins very unhappy if you took
> away DHCP.
>
> Mike


Well you can make it easy by making it some one else's problem. Make
the MAC ID be a starting address plus the serial number. Some where in
the company will be an accountant that cares greatly about the serial
number and will deal with that issue for you. That is what I do.

Don't let reality get in the way of enjoying the engineering.

Regards,

John McCaskill
www.FasterTechnology.com
Xilinx Alliance Partner
Impulse C Platform Partner

>...you can make it easy by making it some one else's problem. Make
>the MAC ID be a starting address plus the serial number. Some where in
>the company will be an accountant that cares greatly about the serial
>number and will deal with that issue for you. That is what I do.

Giving the job to someone else doesn't make it disappear.  In this
company, I do it all.  There's no "accountant" to be assigned the
dirty jobs.  Whatever it is, it has to be efficient.  Offloading work
to others is just a "big company" trick.

In 2008 we automate.  Sure, you don't need DHCP or other automated ID
allocation systems.  Just fill in form B31 and send it to the
accountant.  He'll reply as soon as he returns from vacation.  You
could manage without e-mail, too.  Just tell that accountant he's also
a messenger boy.

Mike

On Jan 6, 4:34 am, MikeShepherd...@btinternet.com wrote:
> >...you can make it easy by making it some one else's problem. Make
> >the MAC ID be a starting address plus the serial number. Some where in
> >the company will be an accountant that cares greatly about the serial
> >number and will deal with that issue for you. That is what I do.
>
> Giving the job to someone else doesn't make it disappear.  In this
> company, I do it all.  There's no "accountant" to be assigned the
> dirty jobs.  Whatever it is, it has to be efficient.  Offloading work
> to others is just a "big company" trick.
>
> In 2008 we automate.  Sure, you don't need DHCP or other automated ID
> allocation systems.  Just fill in form B31 and send it to the
> accountant.  He'll reply as soon as he returns from vacation.  You
> could manage without e-mail, too.  Just tell that accountant he's also
> a messenger boy.
>
> Mike


Well I may have been a bit flippant with the accountant remark, ours
does not actually put the serial numbers on the boards either, but she
does care that we do it.

My point is that if you are manufacturing commercial hardware for sale
you probably already have serial numbers on the products you are
building. Just piggy back MAC ID assignment off of those.

We never put a MAC ID in our products.  The software just uses the
serial number and our IEEE OUI to generate them.

Enjoy the rest of your weekend,

John McCaskill

On Jan 6, 2:54 am, John McCaskill <jhmccask...@gmail.com> wrote:
> <snip>
>
> > 1) Buy a batch of unique addresses (which isn't cheap and involves
> > administrative hassle).  If you're designing a LAN for an airliner I'm
> > going to fly on, I'd like you to use this method.
>
> Mike,
>
> While I agree that the MAC ID space is so large that the chance of a
> collision for a random address is very low, I do not agree with that
> statement.  Buying a range of unique addresses is cheap and easy, and
> no administrative hassle is involved.
>
> The IEEE administers MAC IDs, and you can buy a range of them for a
> one time fee online.  I bought the OUI package online with a credit
> card and have no regrets. Take a look at:
>
> http://standards.ieee.org/regauth/oui/index.shtmlhttp://standards.ieee.org/regauth/oui/pilot-ind.htmlhttp://standards.ieee.org/regauth/oui/forms/
>
> You can buy a 4K block of MAC IDs for $500 USD, or a 2^24 block of IDs
> for $1650.  That is lost in the noise for producing a commercial
> product.
>
> This is a far better deal than I get from the PCI SIG where I have to
> pay every year to retain my vendor ID. For the MAC IDs, I pay once and
> it is mine for ever.
>
> While I am a small business owner and complain about every penny
> spent, I think that the IEEE gives me a fair deal.

Another option is to let the customer set the ID through some
configuration option. That way collisions can be avoided post
manufacture. And the administrator can't claim that you used an ID
"without permission".

John McCaskill wrote:

> While I agree that the MAC ID space is so large that the chance of a
> collision for a random address is very low, I do not agree with that
> statement.  Buying a range of unique addresses is cheap and easy, and
> no administrative hassle is involved.

There is a story that in the beginnings of ethernet using random 48 bit
MAC addresses was considered, but rejected because of the (small)
probability of two accidentally choosing the same address.

As I understand it, in the current system there have been devices
produced that accidentally had the same address.  As the current system
involves humans, such as programming ROMs and installing them in cards,
there is a relatively high probability of accidents.

Choosing a random 46 bit number with the local administration bit
on and the multicast bit off might not be so bad.

-- glen

glen herrmannsfeldt <gah@ugcs.caltech.edu> wrote:

>John McCaskill wrote:
>
>> While I agree that the MAC ID space is so large that the chance of a
>> collision for a random address is very low, I do not agree with that
>> statement.  Buying a range of unique addresses is cheap and easy, and
>> no administrative hassle is involved.
>
>There is a story that in the beginnings of ethernet using random 48 bit
>MAC addresses was considered, but rejected because of the (small)
>probability of two accidentally choosing the same address.
>
>As I understand it, in the current system there have been devices
>produced that accidentally had the same address.  As the current system
>involves humans, such as programming ROMs and installing them in cards,
>there is a relatively high probability of accidents.
>
>Choosing a random 46 bit number with the local administration bit
>on and the multicast bit off might not be so bad.

Yes and no. Like others already pointed out, devices need a serial
number anyway. Not just for administration but also to keep track of
devices. So having a fixed number (MAC address) assigned to unit xyz
generally saves a lot of trouble.

Besides, if you are going to generate random MAC addresses you may get
intermittant errors because fixed MAC addresses are expected. Those
kind of errors are the last you want on a network.

-- 
Reply to nico@nctdevpuntnl (punt=.)
Bedrijven en winkels vindt U op www.adresboekje.nl

In article <B_KdnWf0IICN1hzanZ2dnUVZ_t6onZ2d@comcast.com>,
	glen herrmannsfeldt <gah@ugcs.caltech.edu> writes:
> 
> There is a story that in the beginnings of ethernet using random 48 bit
> MAC addresses was considered, but rejected because of the (small)
> probability of two accidentally choosing the same address.
> 
> As I understand it, in the current system there have been devices
> produced that accidentally had the same address.  As the current system
> involves humans, such as programming ROMs and installing them in cards,
> there is a relatively high probability of accidents.

In the early days, address allocations were notified to
applicants in the order the bits are transmitted in an
ethernet frame on the wire, and a significant number of
the early vendors produced loads of kit using completely
the wrong OUI as a consequence (with the bits in every
octet of the OUI in reverse order).

-- 
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

In article <B_KdnWf0IICN1hzanZ2dnUVZ_t6onZ2d@comcast.com>,
 glen herrmannsfeldt <gah@ugcs.caltech.edu> wrote:

> John McCaskill wrote:
> 
> > While I agree that the MAC ID space is so large that the chance of a
> > collision for a random address is very low, I do not agree with that
> > statement.  Buying a range of unique addresses is cheap and easy, and
> > no administrative hassle is involved.
> 
> There is a story that in the beginnings of ethernet using random 48 bit
> MAC addresses was considered, but rejected because of the (small)
> probability of two accidentally choosing the same address.
> 
> As I understand it, in the current system there have been devices
> produced that accidentally had the same address.  As the current system
> involves humans, such as programming ROMs and installing them in cards,
> there is a relatively high probability of accidents.
> 
> Choosing a random 46 bit number with the local administration bit
> on and the multicast bit off might not be so bad.
> 

We *did* consider using randomly-chosen addresses, but in a 64-bit 
address space; the probability of a clash in a 48-bit space was 
considered too high. I wrote a paper on the subject back in 1979-80, 
which is probably lost to history.

Although properly-implemented random addresses would have worked, we 
chose the administered-vendor-space 48-bit scheme of today as being more 
"politically palatable"; I am sure we would have been hammered even 
worse about letting randomness control network addressing than we were 
about letting randomness control the backoff algorithm.


--
Rich Seifert              Networks and Communications Consulting
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