nanog mailing list archives
Re: why am i in this handbasket? (was Devil's Advocate - Segment Routing, Why?)
From: Masataka Ohta <mohta () necom830 hpcl titech ac jp>
Date: Sun, 21 Jun 2020 21:36:38 +0900
Mark Tinka wrote:
If information to create labels at or near sources to all the possible destinations is distributed in advance, may be.But this is what happens today.
That is a tragedy.
Whether you do it manually or use a label distribution protocol, FEC's are pre-computed ahead of time. What am I missing?
If all the link-wise (or, worse, host-wise) information of possible destinations is distributed in advance to all the possible sources, it is not hierarchical but flat (host) routing, which scales poorly. Right?
But it is effectively flat routing, or, in extreme cases, flat host routing.I still don't get it.
Why, do you think, flat routing does not but hierarchical routing does scale? It is because detailed information to reach destinations below certain level is advertised not globally but only for small part of the network around the destinations. That is, with hierarchical routing, detailed information around destinations is actively hidden from sources. So, with hierarchical routing, routing protocols can carry only rough information around destinations, from which, source side can not construct detailed (often purposelessly nested) labels required for MPLS. > So why create labels on-demand if > a box to handle the traffic is already in place and actively working, > day-in, day-out? According to your theory to ignore routing traffic, we can be happy with global *host* routing table with 4G entries for IPv4 and a lot lot lot more than that for IPv6. CIDR should be unnecessary complication to the Internet With nested labels, you don't need so much labels at certain nesting level, which was the point of Yakov, which does not mean you don't need so much information to create entire nested labels at or near the sources. The problem is that we can't afford traffic (and associated processing by all the related routers or things like those) and storage (at or near source) for routing (or MPLS, SR* or whatever) with such detailed routing at the destinations. Masataka Ohta
Current thread:
- Re: Devil's Advocate - Segment Routing, Why?, (continued)
- Re: Devil's Advocate - Segment Routing, Why? Mark Tinka (Jun 19)
- Re: Devil's Advocate - Segment Routing, Why? Robert Raszuk (Jun 19)
- Re: Devil's Advocate - Segment Routing, Why? Randy Bush (Jun 19)
- Re: Devil's Advocate - Segment Routing, Why? Dorian Kim (Jun 19)
- why am i in this handbasket? (was Devil's Advocate - Segment Routing, Why?) Randy Bush (Jun 19)
- Re: why am i in this handbasket? (was Devil's Advocate - Segment Routing, Why?) Masataka Ohta (Jun 20)
- Re: why am i in this handbasket? (was Devil's Advocate - Segment Routing, Why?) Robert Raszuk (Jun 20)
- Re: why am i in this handbasket? (was Devil's Advocate - Segment Routing, Why?) Mark Tinka (Jun 21)
- Re: why am i in this handbasket? (was Devil's Advocate - Segment Routing, Why?) Masataka Ohta (Jun 21)
- Re: why am i in this handbasket? (was Devil's Advocate - Segment Routing, Why?) Mark Tinka (Jun 21)
- Re: why am i in this handbasket? (was Devil's Advocate - Segment Routing, Why?) Masataka Ohta (Jun 21)
- Re: why am i in this handbasket? (was Devil's Advocate - Segment Routing, Why?) Robert Raszuk (Jun 21)
- Re: why am i in this handbasket? (was Devil's Advocate - Segment Routing, Why?) Masataka Ohta (Jun 22)
- Re: why am i in this handbasket? (was Devil's Advocate - Segment Routing, Why?) Mark Tinka (Jun 22)
- Re: why am i in this handbasket? (was Devil's Advocate - Segment Routing, Why?) Masataka Ohta (Jun 23)
- Re: why am i in this handbasket? (was Devil's Advocate - Segment Routing, Why?) Owen DeLong (Jun 23)
- Re: why am i in this handbasket? (was Devil's Advocate - Segment Routing, Why?) Masataka Ohta (Jun 24)
- Re: why am i in this handbasket? (was Devil's Advocate - Segment Routing, Why?) Nick Hilliard (Jun 22)
- RE: why am i in this handbasket? (was Devil's Advocate - Segment Routing, Why?) adamv0025 (Jun 22)
- Re: why am i in this handbasket? (was Devil's Advocate - Segment Routing, Why?) Mark Tinka (Jun 22)
- Re: why am i in this handbasket? (was Devil's Advocate - Segment Routing, Why?) Masataka Ohta (Jun 23)