[Xorp-hackers] Large Number of Interfaces

[Yonghong Ren]

Atanu and Pavlin,

Thank you very much for replying to my questions on fea/ interface
compilation questions.

I would like to set the compilation issues aside for a moment and
discuss a different aspect, namely the best way to support large number
of interfaces.

A system may have say 40 physical interfaces, with X number of logical
interfaces (virtual router interface for example).

The current design choice appears to be leveraging the native OS
Ethernet interface mechanism. In other words, every interface would
appears as a native OS interface.

What are the pros and cons (if there is any :)) of this approach? Some
questions I have are:

1) Is this scalable? That is, would say 100 interfaces cause problems to
the OS?
2) The interfaces may be added and removed dynamically. Would this be
OK?
3) What assumptions and requirements does XORP stack requires each
interface? For example, the routing protocols would be assuming socket
library access through the interfaces and therefore the interface has to
provide socket access. So, that would be a big advantage to make each
interface a network interface at the OS level so to leverage the TCP/IP
stack and socket mechanism.

4) I wonder how this is typically done in a large commercial router.

Thanks and look forward to some enlightening responses.

Yonghong Ren