[Taps] Some comments on draft-ietf-taps-impl-12

Fernando Gont <fgont@si6networks.com> Fri, 05 August 2022 11:02 UTC

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Subject: [Taps] Some comments on draft-ietf-taps-impl-12
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Some comments/feedback on the aforementioned I-D:

* Section Local Endpoint candidates

You should probably consider PCP/UPnP here. see e.g. 

* Section 4.3.3. Failover

I haven't recently checked what's the status of current 
TCP implementations. But at least at some point in time there are some 
that would failover more quickly based on notifications from the network 
(e.g., ICMP errors). see: https://datatracker.ietf.org/doc/html/rfc5461

Section 4.7:

> 4.7. Implementing listeners When an implementation is asked to 
> Listen, it registers with the system to wait for incoming traffic to 
> the Local Endpoint. If no Local Endpoint is specified, the 
> implementation should use an ephemeral port.

Note: there are implications of using a port number from the ephemeral
port range. See e.g. Section 3.1 of

TL;DR; The general idea is that one should use the same range to pick
port for outgoing connections than to pick ports for listening endpoints.

> If the Selection Properties do not require a single network
> interface or path, but allow the use of multiple paths, the Listener
> object should register for incoming traffic on all of the network
> interfaces or paths that conform to the Properties. The set of
> available paths can change over time, so the implementation should
> monitor network path changes, and change the registration of the
> Listener across all usable paths as appropriate. When using multiple
> paths, the Listener is generally expected to use the same port for
> listening on each.

I'd probably stress this a bit more e.g., quite often the port needs to 
be registered somewhere (e.g., directory service), so having different 
ports for each interface would seem problematic.

Section 4.7.2.:
> On platforms with facilities to create a "virtual connection" for
> connectionless protocols implementations should use these mechanisms
> to minimise the handling of datagrams intended for already created
> Connection objects.

I don't necessarily disagree, but you should probably elaborate here -- 
e.g., on one hand, "stateless" is good in the sense that you don't tie 
system resources unnecessarily. However, it's also more prone to 
spoofing, to the extent that an attacker might require "a lot of work" 
from a server without even proving that it can receive the return packets.


Fernando Gont
SI6 Networks
e-mail: fgont@si6networks.com
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