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Re: routable interfaces

To: kuznet@xxxxxxxxxxxxx
Subject: Re: routable interfaces
From: Ben Greear <greearb@xxxxxxxxxxxxxxx>
Date: Mon, 15 Jan 2001 19:39:49 -0700
Cc: jamal <hadi@xxxxxxxxxx>, netdev@xxxxxxxxxxx
Organization: Candela Technologies
References: <200101151928.WAA12705@xxxxxxxxxxxxx>
Sender: owner-netdev@xxxxxxxxxxx
kuznet@xxxxxxxxxxxxx wrote:
> Hello!
> > A vlan device could be a simple IP-alias.
> Sorry, Jamal you messed all the things completely.
> ifaddr is not a virtual device. "Alias" was virtual device, but
> this was bogus ill-defined device which created nothing but problems for 
> routing,
> that's why we have no "aliases", but use plain ifaddrs.
> VLAN is true "virtual" device, using nice well-defined encapsulation,
> and from viewpoint of routing/addressing such device is not distinguishable
> of "physical" one. The question: "physical" or "virtual" is just meaningless
> from the viewpoint of routing and from any other viewpoint but packet
> scheduling and policing.

I agree with that.

> What's about VLANs, they can be handled as separate virtual devices
> provided you have _couple_ of them. It the number is higher, they must
> be clustered as single nbma interface via framing (i.e neighbour) level
> or via tags in routing tables.

Why must they be clustered (and what is an nbma interface?)  Is it just because
of manability of the system, or are there performance reasons too?  If there
are performance reasons, please elaborate.

 The same thing is with MPLs.

> That's why I strongly dislike the idea to create zillions of net_devices
> and consider that approach to VLANs as stupid one. And this is reason
> why hashing device list (being great in principle) is not considered
> to be some really required feature.
> Alexey

Ben Greear (greearb@xxxxxxxxxxxxxxx)
Author of ScryMUD: 4444        (Released under GPL)     

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