Routing Protocol and Table building Confusion

[Ubaid ur Rahman]

Hello again!

My problem outline: I am still confused in creating a routing protocol for FAT Tree. I read some question regarding the addressing scheme, which I agree with you ( T. ) a 100% has issues. I have restructured the addressing scheme with a little adjustment. I have depicted Pod 0 in the file attached, and I am trying to build the tables shown in that file, and my question are also typed. How should I approach this problem.

P.S How would I decide the current interface is local loop?

[Tommaso Pecorella]

Hi,

I'll reply here and not in the PDF, hope you don't mind.

First and foremost, there's an error in the Routing tables you have shown. it's impossible to have:

- 0.0.0.2/8 to port 3

- 0.0.0.6/8 to port 4

because the two networks are the same (0.x.x.x). moreover, it's not wise to use a "0" as the first byte. It's reserved if I remember right.

And now the questions.

A1: In RipNg the loop checks if the interface is not the loopback *and* if there is a non-link-local address. In IPv4 there's no equivalent concept for link-local, at most you'll have the non-routable address space. We never enforced the use of global Vs non-routable addresses in ns-3, but we don't guarantee that this will not change in the future (i.e., we could add a function to drop packets in routers if they have a non-routable address).

Anyway, 127.0.0.1 is "global" (not really, but we don't really care) and loopback. Tbh I don't even know if there's a function to check if an address is global in IPv4.

A2: yes, you need to create your own packet format. Feel free to borrow an existing one if it fits your needs.

A3: Don't feel dumb for not thinking to it.... CombineMask (!mask) - i.e., use the reverse bit network mask (255.255.255.0 becomes 0.0.0.255).

Cheers,

T.

[Ubaid ur Rahman]

Hello,

Thanks a lot! It is clear now... And you are right 0.0.0.x/8 is not valid, I was following that paper's convention. The algorithm is supposed to check the suffix of destination address, for which such entries were given as an example. But now that I know how can I extract and check the suffix -- amazing I didn't thought of this, we don't see the simple solutions which are the right ones!! (Ah! too many things in mind :D)