[Lsr] Fwd: Devil's Advocate - Segment Routing, Why?

Robert Raszuk <robert@raszuk.net> Thu, 18 June 2020 10:51 UTC

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From: Robert Raszuk <robert@raszuk.net>
Date: Thu, 18 Jun 2020 12:51:06 +0200
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To: lsr@ietf.org
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Subject: [Lsr] Fwd: Devil's Advocate - Segment Routing, Why?
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Just FYI ...

An interesting discussion on nanog/cisco-nsp lists ... started innocent
with SRv6 bashing, now went into IGP - specifically ISIS territory  :)

---------- Forwarded message ---------
From: Saku Ytti <saku@ytti.fi>
Date: Thu, Jun 18, 2020 at 12:43 PM
Subject: Re: Devil's Advocate - Segment Routing, Why?
To: Robert Raszuk <robert@raszuk.net>
Cc: Mark Tinka <mark.tinka@seacom.mu>, nanog@nanog.org <nanog@nanog.org>,
cisco-nsp NSP <cisco-nsp@puck.nether.net>

On Thu, 18 Jun 2020 at 13:28, Robert Raszuk <robert@raszuk.net> wrote:

> To your IGP point let me observe that OSPF runs over IP and ISIS does
not. That is first fundamental difference. There are customers using both
all over the world and therefore any suggestion to just use OSPFv3 is IMHO
quite unrealistic. Keep in mind that OSPF hierarchy is 2 (or 3 with super
area) while in IETF there is ongoing work to extend ISIS to 8 levels. There
is a lot of fundamental differences between those two (or three) IGPs and I
am sure many folks on the lists know them. Last there is a lot of
enterprise networks happily using IPv4 RFC1918 all over their global WAN
and DCs infrastructure and have no reason to deploy IPv6 there any time
soon.  If you are serious about converging to a single IGP I would rather
consider look towards OpenR type of IGP architecture with message bus
underneath.

On Thu, 18 Jun 2020 at 13:43, Saku Ytti <saku@ytti.fi> wrote:

I view the 802.3 and CLNS as liability, not an asset. People who
actually route CLNS are a dying breed,  think just DCN of a legacy
optical.

Many platforms have no facilities to protect ISIS, any connected
attacker can kill the box. Nokia handles generated packets
classification by assigning DSCP value to  application then DSCP to
forwarding-class, which precludes from configuring ISIS qos. Very few
people understand how ISIS works before ISIS PDU is handed to them,
world from 802.3 to that is largely huge pile of hacks, instead of
complete CLNS stack implementation. There is no standard way to send
large frames over 802.3, so there is non-standard way to encap ISIS
for those links. Also due to lack of LSP roll-over, ISIS is subject to
a horrible attack vector which is very difficult to troubleshoot and
solve.

-- 
  ++ytti

[Lsr] Fwd: Devil's Advocate - Segment Routing, Wh… Robert Raszuk