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Ethernet History Deepdive – Why Do We Have Different Frame Types?

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Re: Ethernet History Deepdive – Why Do We Have Different Frame Types?

#81

Post by p_l »

Hikikomori wrote: post #66
p_l wrote: post #52

Earlier quoted context omitted.

Scalability was one part. Later the fact that you didn't need separate routing setup for v6 also was part of it. But for a telco, the fact that you didn't have to setup IP connectivity in order for routers to see each other, was also a crucial ability.

OSPF has supported unnumbered links for a long time, don't need IP on the link with point to point and multicast.

Unnumbered just means you have no IP address exclusive to the link. IS-IS works without establishing IP connectivity at all, not just about tricks to handle leaky internals.

This also meant autoconfiguration or supporting non-ip protocols (like routed ethernet) is simpler, though I will admit that OSPFv3 adding default use of link local V6 for router interfaces made the gap smaller.

Re: Ethernet History Deepdive – Why Do We Have Different Frame Types?

#82

Post by myrandomcomment »

leoc wrote: post #9
dale_glass wrote: post #4

I wish we could have another and bump the packet size. We're at the point where we can have millions of packets per second going through a network interface, and it starts to get very silly. It's at the point where even a 10G connection requires some thought to actually perform properly. I've managed to get bottlenecked on high end hardware requiring a whole detour into SR-IOV just to get back to decent speeds.

(Intentional) jumbo frames at layer 2 and expanded MTUs at layer 3 are certainly available (as you may know). In fact it seems (I am, it should be obvious, not an expert) that using jumbo frames is more or less the common practice by now. There does in fact seem to have been some standards drama about this, too: I can't find it now, but IIRC in the '00s someone's proposal to extend the header protocols to allow the h…

The use of jumbo frames is NOT normal and is only used in very specific setups. In general something like a storage system that is isolated to its own layer2 network. At some point your jumbo network has to hit the reset of the network and packet fragmentation is done in software via the CPU which is very expensive and not linerate. The normal outcome is you break your network.

Re: Ethernet History Deepdive – Why Do We Have Different Frame Types?

#83

Post by ninkendo »

p_l wrote: post #79
ninkendo wrote: post #58

Earlier quoted context omitted.

I mean sure, you’d definitely use a scoped address to talk to the next hop, but it still doesn’t solve how the router/switch knows which port to send the packet to for its next destination. Say I have a global unicast address on my desktop, 2 hops from my router, and I want to allow traffic to it. My router gets a packet sent to it over its link-local address, with a destination header of my desktop’s IP. Say it has…

STP does not cover filling in MAC forwarding tables, it only tells the switches which ports to shut down so that no loops would be created. RSTP and later evolutions just made it faster as well as capable of creating multiple spanning trees, but the core logic is still based on the "oh fuck" realisation of a corporation that sold nonrouteable ethernet protocol and thus had to figure how to deal with larger L2 domains…

Interesting.

I guess since IPv6 solves the address allocation problem natively (with SLAAC), it’s not allocation you need to worry about so much as “what IP’s does this router see vs that router, recursively”, which it sounds like IS-IS can provide.

This would mean each router box in my network would grab its own random (SLAAC) address within the /64 advertised by my “main” router (found via multicast all-routers), and would then each (through IS-IS or something similar) announce and forward individual /128 routes for each host plugged into them. The network would converge such that each individual box would have a complete routing table of what next-hop to use for each IP address in the tree.

I can see this being a preferable setup if it allows you to completely eliminate layer 2 from the equation… alas this never happened so it’s all a thought exercise.

Re: Ethernet History Deepdive – Why Do We Have Different Frame Types?

#84

Post by zik »

yusyusyus wrote: post #64
zik wrote: post #63

Earlier quoted context omitted.

TCP/IP was developed in the 1970s and adopted as the protocol standard for ARPANET (the predecessor to the Internet) in 1983.

and commercialization wasnt done until the like 1994. OSI as a successor was still proposed when the first BGP4 rfc came out. before commercialization happened, IP was mostly the realm of government and education.

I feel like your experience was quite different to mine. I used TCP/IP in the late 80s at university and doing commercial contract work. I remember OSI existing but at the places I worked it was treated as less common.

Re: Ethernet History Deepdive – Why Do We Have Different Frame Types?

#85

Post by kjs3 »

thaumasiotes wrote: post #68
ninkendo wrote: post #46

Earlier quoted context omitted.

A really interesting article covering this: “The world in which IPv6 was a good design” https://apenwarr.ca/log/20170810 It talks about how when IPv6 was being designed, they wanted to do exactly that: drop most of the layer 2 stuff, abandon the idea of a bus network, make everything point-to-point, all switches would be L3 routers, etc. Search for “What if instead the world worked like this?” for the relevant part.…

> Would my router get a /64, then delegate a /68 to the next “router” (ie. The physical thing I currently call a switch) This is another weird thing about networking. As far as I've been able to learn, a "router" is a device with two ports that handles transmission of data between those ports, whereas a "switch" is a device with more than two ports that handles transmission of data between those ports. But nobody wou…

This is wrong and networking people care very much.

(Wildly oversimplifying here, there are always exception, YMMV, no warranty expressed or implied, may cause blurred vision or a rash)

A switch is a device that handles things like "I need to get a packet from my desktop PC to the printer down the hall". It has lots of ports because, usually, there are a lot of things local to you that you might want to talk to, and you want that traffic as fast as possible without the expense and overhead of 'routing'. If those things aren't on the same L3 network, a switch won't be able to get there[1].

A router is something that maintains a table that maps non-local (not the same L2 network, collision domain, VLAN, whatever) destinations to a 'next hop' based on various metrics[2]. In the general case, routers are concerned with questions like "I'm in Atlanta and I need to get this packet to Tokyo so is the best way to send it via my connection to Comcast or Level-3?".

The degenerate case for routers is a two-port box that does nothing but move packets not destined for something in your local network to your ISP or other upstream network for forwarding to a non-local destination. Since that's the use case most folks see, it's easy to misunderstand the bigger pix. Much is done via various kinds of virtual interfaces now, but I have in my career worked on routers with hundreds of physical ports.

[1] Yes, some switches have a router in them. Stop overthinking. [2] Yes, it's more complicated than that. Stop overthinking.

Re: Ethernet History Deepdive – Why Do We Have Different Frame Types?

#86

Post by kjs3 »

addaon wrote: post #43
londons_explore wrote: post #36

I wish layer 2 and layer 3 were 'refactored' to force all links to be point to point, which they effectively are in the modern world. When was the last time you saw ethernet frame collisions because you used a hub not a switch? We'd get rid of the idea of a broadcast domain. We'd get rid of Mac address and ARP. Switches and routers would become the same device. We'd just use ip addresses for routing, and the 'next ho…

> When was the last time you saw ethernet frame collisions because you used a hub not a switch? 10base-T1S is just beginning to ramp up in the automotive industry, which modifies the super-successful 100base-T1 to be cheaper by (a) allowing cheaper PHYs; (b) allowing cheaper endpoints due to the lower data rate to handle; (c) allowing lower-spec single twisted pair wiring; and ... (d) allowing multi-drop. This is int…

So it's like RS-485, but more complicated?
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