Re: [PANRG] draft-rass-panrg-mpath-usecase

[Yingzhen Qu <[e-mail]>]

Hi  Ruediger,

Thanks for your interests in our draft and comments at the mic during Stefan's presentation.

I didn't get a chance to answer your question during the presentation because of the shortness of time. If I understand right, you were suggesting to add different source and destination address to achieve multiple path, it is useful in some circumstances but I see some limitations. Let's take a single domain/AS as an example:

*        Adding more source and destination address, if IGP is used to calculate routing, then you still end up on the same route because of SPF.

*        This will require change on hosts because you can't use one TCP or MPTCP session.

Acrossing domains is more complicated, but the 2nd point still applies.

Thanks,
Yingzhen

From: [e-mail] [mailto:[e-mail]]
Sent: Thursday, March 28, 2019 7:23 AM
To: [e-mail]
Cc: Yingzhen Qu <[e-mail]>; Lin Han <[e-mail]>; [e-mail]; [e-mail]
Subject: draft-rass-panrg-mpath-usecase

Hi Stefan,

the idea to route packets containing encrypted information via different paths sound reasonable to me. This may be challenging for higher layers, but well, one may be able to design them to cope with packets received from different paths, I think.

I've recommended to investigate available options rather that path detection this morning. Some of these are:
-        An end system can be multihomed
-        There's multi-path transport, like MPTCP
-        If the IP-addresses can be varied, the packets will likely follow different Equal Cost Multi-Path's (ECMP, search the Internet). Varying source address will do.

Multipath could mean:
-        Same fiber, different router interfaces/headers (imagine the LTE path and fixed access sharing the same fiber at some part of a layer 0 path) .
-        Different parallel ports of a router, but same router to router hop
-        Different router hops (combined with different ports).

What likely is difficult is to vary the AS path. That might work, if you are multihomed with different networks. For a single domain, you may have to use a proxy or a tunnel to reach a different section of that domain (but I assume that there are multiple peerings to reach the destination AS - that might not be the case).

I'm not an onion routing expert. That may help too.

You could try different paths with the methods described above and measure delays to figure out different router paths (different ports between the same routers a hard to detect). No matter what you do, and even with path aware networking, you'll not be able to figure out or avoid using the same fiber by different networks.

Please note, I'm not on the panrg list and readers there may receive this message delayed. While I like your idea, my time doesn't suffice for an ongoing support.

Regards,

Ruediger