{"guid":"import-3936e1a286f3d9ffb2","title":"Comparison of WAN IGP protocols","subtitle":"RSTP+flooding/learning for Ethernet, OSPFv2 for IPv4, and IS-IS for CLNP","slug":"mrmcd101b_-_Comparison_of_WAN_IGP_protocols","link":"https://mrmcd101b.metarheinmain.de/fahrplan/events/1400.en.html","description":"Most companies with large WANs use either RSTP+flooding/learning or OSPFv2·\r\nfor two purposes: to route around network link failures, and to\r\nautomatically find the correct path to a destination address on a\r\nlarge network with many hops.  Including RSTP in the comparison is a\r\nrealistic acknowledgement of the way L2 switching is abused these·\r\ndays.  Including OSI in the comparison should reveal some habitually\r\nirritating aspects of switched IP networks that are mere accidents of\r\nhistory, and others that are more fundamental.\r\n\r\nI'll provide background about how Ethernet switching works, what is an\r\nIGP, and what the now mostly-abandoned supposed-future OSI world feels\r\nlike.\r\n\r\nIGP's are not just for fault-resilience.  They also function as a network\r\nmanagement protocol: like SNMP, it's impractical to deal with a very\r\nlarge network without using an IGP.\r\n\r\nThe talk will not discuss EGP's, exterior gateway protocols like BGP.\r\nAll these IGP's are used within one administrative domain.  They are\r\nnever used between one ISP and another, nor between a customer and his\r\nISP.\r\n\r\nI say ``loosely about'' because I'll be introducing three protocols,\r\nonly one of which is an IGP in common use on today's Internet:\r\n\r\n * RSTP + flooding/learning.  L2 switches use a combination of RSTP\r\n   and the flooding/learning system to route Ethernet frames.  They\r\n   can route traffic around a failed link, and they can direct traffic\r\n   toward a wireless user that's roaming among access points.\r\n\r\n * OSPF.  This is the standard routing protocol for IPv4.  There are\r\n   other important/popular ones like 'Integrated IS-IS' and 'EIGRP',\r\n   but OSPF is the best example and probably the most popular.  ISP's\r\n   and big companies use this protocol to route around the failure of\r\n   WAN links within their own networks, and to manage their large\r\n   networks.\r\n\r\n * IS-IS.  This is _the_ routing protocol for the ISO/OSI CLNP\r\n   (ConnectionLess Network Protocol).  OSI networking was designed\r\n   many years ago through expensive necktie conferences in mountain·\r\n   resort towns, and proposed as the replacement for\r\n   IP on the future Internet.  It included CLNP which was analagous to\r\n   IP.  No one fell for it.  At least, no one uses it at the edge,\r\n   although it's still used ubiquitously, I'm not sure how exactly, on\r\n   most Sonet/SDH rings.  More importantly, almost everything\r\n   complicated and difficult at the core of the modern Internet right\r\n   now is a simplified/adapted version of some earlier OSI Master\r\n   Vision which you can find referenced in the bibliography of the\r\n   relevant IETF RFC.  The difficult algorithmic and conceptual pieces·\r\n   in BGP, OSPF, LDAP, and many other things, are borrowed from OSI·\r\n   standards.\r\n\r\nI want to teach people about these three protocols for two reasons.··\r\nFirst, what's similar and what's different about\r\nthe three types of routing?  How, and with what limitations, do small\r\nand large networks route around failures?  Second, which limitations\r\nare abstract, essential problems of network routing, and which are\r\nquirks of a particular implementation that has become overwhelmingly\r\ndominant, like IP or L2 switching.\r\n\r\nI think most people don't really understand how L2 switches\r\nwork---they just think ``they're like hubs, only better.''  Switches\r\nunfortunately fall a bit short of that ideal lego-networking model.··\r\nNow that such a bastard hack has attained such prominence in large·\r\nnetworks, I think we should have a second look at switches with the·\r\naim of borrowing ideas from them, like how most of the modern Internet's·\r\nnew ideas are borrowed from OSI.\r\n\r\nAlso, we've become accustomed to IPv4 networks where there is a strict·\r\nrule: if you move to a different part of the L3 network, you have to·\r\nchange your end system's IP address to match the new subnet.  OSI CLNP·\r\ndoes not work that way.  I think this will surprise and interest many·\r\npeople, as it did me.\r\n\r\nI think the talk will broaden people's minds by introducing three\r\nstandards central to our Internet heritage of which most people have\r\nvaguely heard, but have no idea how they work or even exactly what\r\nthey are.  Optimistically it'll help them think about new\r\npossibilities for how to design large networks and protocols, and will\r\nhelp them do it in a more historically grounded way than the usual\r\ncreativity-heavy bikeshed moment of ``I've just invented this great·\r\nidea for a new kind of peer-to-peer filesharing network!  see, it's·\r\nshaped like a tetrahedron, and when one node `drops out', then·\r\nthere's the `discovery phase,' to replace it, and...''","original_language":"eng","persons":["Miles Nordin"],"tags":["mrmcd"],"view_count":0,"promoted":false,"date":"2007-01-01T01:00:00.000+01:00","release_date":"2009-09-28T02:00:00.000+02:00","updated_at":"2021-01-02T20:34:52.810+01:00","length":6233,"duration":6233,"thumb_url":"https://static.media.ccc.de/media/conferences/mrmcd/mrmcd101b/mrmcd101b - Comparison of WAN IGP protocols.jpg","poster_url":"https://static.media.ccc.de/media/conferences/mrmcd/mrmcd101b","timeline_url":"https://static.media.ccc.de/media/conferences/mrmcd/mrmcd101b","thumbnails_url":"https://static.media.ccc.de/media/conferences/mrmcd/mrmcd101b","frontend_link":"https://media.ccc.de/v/mrmcd101b_-_Comparison_of_WAN_IGP_protocols","url":"https://api.media.ccc.de/public/events/import-3936e1a286f3d9ffb2","conference_title":"MRMCD 101b","conference_url":"https://api.media.ccc.de/public/conferences/mrmcd101b","related":[],"recordings":[{"size":147,"length":6233,"mime_type":"video/mp4","language":"eng","filename":"mrmcd101b - Comparison of WAN IGP protocols.mp4","state":"new","folder":"","high_quality":true,"width":320,"height":240,"updated_at":"2021-01-02T20:01:07.593+01:00","recording_url":"https://cdn.media.ccc.de/events/mrmcd/mrmcd101b/mrmcd101b - Comparison of WAN IGP protocols.mp4","url":"https://api.media.ccc.de/public/recordings/50159","event_url":"https://api.media.ccc.de/public/events/import-3936e1a286f3d9ffb2","conference_url":"https://api.media.ccc.de/public/conferences/mrmcd101b"}]}