Date: Fri, 28 May 1999 16:33:05 +0900 From: Yasuhiro Ohara <yasu@sfc.wide.ad.jp> To: andreas@klemm.gtn.com, andreas.klemm.ak@bayer-ag.de, freebsd-net@freebsd.org, zebra@zebra.org, kunihiro@zebra.org Subject: Re: [zebra 553] OSPF eequal-cost paths, which algorithm, how exactly load balancing ? Message-ID: <19990528163305R.yasu@sfc.wide.ad.jp> In-Reply-To: Your message of "Fri, 28 May 1999 08:40:02 %2B0200" <19990528084002.A41138@titan.klemm.gtn.com> References: <19990528084002.A41138@titan.klemm.gtn.com>
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I think... From: Andreas Klemm <andreas@klemm.gtn.com> Subject: [zebra 553] OSPF eequal-cost paths, which algorithm, how exactly load balancing ? Date: Fri, 28 May 1999 08:40:02 +0200 andreas> Hi ! andreas> andreas> I'm looking for the algorithm how OSPF does a routing decision and andreas> what kind of load balancing is been done, between the two 4 MBit andreas> leased lines, when OSPF has equal-cost paths like this. andreas> Cisco IOS 11.2 or 11.3. andreas> andreas> Rstart andreas> |e0 andreas> |10MBit andreas> | andreas> -----------+---------------- andreas> |10MBit |10MBit andreas> |e0 |e0 andreas> | | andreas> R1 R3 andreas> || || andreas> s0||s1 s0||s1 load balancing between 2 serial andreas> ||2x2=4MBit ||2x2=4MBit (4 MBit, process switching to get andreas> || || load balancing between 2 serial andreas> || || andreas> R2 R4 andreas> | | andreas> |10MBit |10MBit andreas> |e0 |e0 andreas> -----------+----------------- andreas> | andreas> |10 MBit andreas> |e0 andreas> Rdest andreas> andreas> All I read in the OSPF V2 RFC is, that OSPF creates one routing andreas> entry for the interface Rstart e0, that has to destinations andreas> R1 and R3 and that it does a load sharing between the two ways, andreas> but how ? OSPF V2 RFC only says "it can". Don't touch anything about how to share loads, because that is not routing protocol matter. How to share loads depends on how to lookup nexthop from routing table.So this is a issue of implementing routing table lookup function. andreas> How is the routing decision being done. What impact does load andreas> have on a routing decision and how often it is re-calculated ??? Again, this is a seperate matter, so the re-calculation will not be happen. andreas> When is perhaps only one route used between R1-R2 or R3-R4 ? andreas> andreas> The question is, in an redundant environment, how well does OSPF andreas> scale when it comes to the point of question, are and how well andreas> are the links shared. Do users get 2 x 4 = 8 MBit throughput or andreas> only 1 x 4 MBit ??? "How well" depends on algorithm to decide which way really to use. OSPF just makes multiple ways that can be used. yasu To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message
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