William H. Magill on 26 Jun 2005 19:41:45 -0000


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Re: [PLUG] OT: high speed internet connection


On 25 Jun, 2005, at 15:10, Jeff Abrahamson intoned:
On Fri, Jun 24, 2005 at 09:26:00PM -0400, William H. Magill wrote:

However, note that while DCAnet offers "fixed" IP addresses, they no
longer offer Static IP addresses.  All new Fixed IP addresses are
permanently assigned to a MAC address, and served up via DHCP. The
only issue this raises is that of configuration. You really can't
configure everything yourself anymore, you have to use the DHCP
access so that your lease actually renews when it expires. (They use
a 7 day lease as I recall.) Since I've been a customer since the
beginning, I have a mix of both real static and fixed IP addresses...
as I've replaced hardware with a new MAC address, I've had to switch
over to the DHCP scheme. No big deal. It just works differently, but
the IP address doesn't change.

What's the advantage to DCA of doing this, other than the fact that there's extra tech support when people upgrade machines and forget to reregister their new MAC address?

It's a scale and management issue.

DCA has always required that your MAC address be registered with their routers if you want your data to pass.

When DCA started DHCP was actually still a primitive set of software tools. Maintaining MAC mapped DHCP assigned addresses was just as labor intensive as manually maintaining DNS tables. Over time, DHCP tools were improved and developed which both "scaled" (allowed for maintenance of much larger networks) and were "easy to use." Similarly, what in the Telecom business is called "Operational Support Software" (OSS) was developed which had "buckets" to track things like MAC addresses and IP addresses, allowing meaningful databases to be developed which could be queried on a per client basis by someone without a PHD in SQL.

Today, it is simply "easier" to maintain one system -- DHCP -- for assigning and tracking already assigned IP addresses. That DHCP database is then fodder for the DNS environment rather than having to maintain both DHCP and DNS databases independently.

The other reason for MAC address assignment is what I alluded to in the first sentence -- it is both a protection against "spoofing" and a verification that you are who you claim to be. Because the routers are cognizant of what MAC addresses are permitted to present data on any given port, they can prevent "unauthorized" activity on that port. This is also tied into the issue of billing -- by preventing unregistered MAC addresses, it prevents services from being used which are not being paid for. They don't care if you let a router spoof your registered MAC address and then allow that router to NAT a bunch of other machines -- that router is registered and being paid for... so if there is ever a problem, they have someone to come after.

T.T.F.N.
William H. Magill
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