nanog mailing list archives
Re: Point to Point Ethernet
From: William Herrin <herrin-nanog () dirtside com>
Date: Wed, 8 Jul 2009 10:30:00 -0400
On Wed, Jul 8, 2009 at 6:01 AM, Andre Oppermann<nanog-list () nrg4u com> wrote:
Do you think this is useful?
Andre, Some thoughts on this: 1. What's the point of increasing the max MTU from 9000 to 9012? If we want a higher MTU, why not just ask for one in the next standard? 2. Why do we need to save 12 bytes per packet by eliminating the MAC address? Why not just get the next larger ethernet size? 3. Could we be better served by using RFC1918 addresses that we define as link-local and asking the router vendors to support a "link local" config option that causes it to use the address from loopback0 for any communications it initiates over that interface instead of using the interface IP address? In other words, if your loop0 is 199.33.224.1 and your g0/0 is 10.3.2.1/30 the link-local option would cause the router to send any host-unreachable messages out g0/0 from 199.33.225.1 instead of 10.3.2.1. Likewise, pings and snmp traps would originate from 199.33.224.1. Only packets to 10.3.2.2 would originate from 10.3.2.1. Such a software-only change would be less expensive to implement than custom ethernet hardware and it would be applicable on all interface types, not just ethernet. And of course we already have tools to prevent such link-local addresses from entering the routing protocol. At a software level, we could also declare a specific remote address as the point-to-point destination so that we could use the interface name as shorthand elsewhere in the config if that proves desirable. 4. L3->L2 lookup is a pretty negligible cost. It's cached for a good long while. And you already have tools to hardcode it if so desired. With Ciscos at least, you can even hardcode addresses to ffff.ffff.ffff though this causes some unexpected behavior. Regards, Bill -- William D. Herrin ................ herrin () dirtside com bill () herrin us 3005 Crane Dr. ...................... Web: <http://bill.herrin.us/> Falls Church, VA 22042-3004
Current thread:
- Point to Point Ethernet Andre Oppermann (Jul 08)
- RE: Point to Point Ethernet Ivan Pepelnjak (Jul 08)
- RE: Point to Point Ethernet David Barak (Jul 08)
- RE: Point to Point Ethernet Scott Berkman (Jul 08)
- RE: Point to Point Ethernet Frank Bulk (Jul 08)
- RE: Point to Point Ethernet David Barak (Jul 08)
- Re: Point to Point Ethernet William Herrin (Jul 08)
- Re: Point to Point Ethernet Mikael Abrahamsson (Jul 08)
- Re: Point to Point Ethernet Marshall Eubanks (Jul 08)
- Re: Point to Point Ethernet William Herrin (Jul 08)
- Re: Point to Point Ethernet sthaug (Jul 08)
- Re: Point to Point Ethernet William Herrin (Jul 08)
- Re: Point to Point Ethernet Mikael Abrahamsson (Jul 08)
- Re: Point to Point Ethernet Mikael Abrahamsson (Jul 08)
- RE: Point to Point Ethernet Ivan Pepelnjak (Jul 08)
- Re: Point to Point Ethernet sthaug (Jul 08)
- Re: Point to Point Ethernet William Allen Simpson (Jul 08)
- Re: Point to Point Ethernet sthaug (Jul 08)