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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?

#71

Post by MisterTea »

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…

That sounds a lot like ATM where you called a machine and received a point to point pipe. Though you had to call first unlike Ethernet where you fling packets into the ether at will. ATM over SONET is used heavily in teleco but is on its way out in favor of OTN and Ethernet.

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

#72

Post by tlb »

supahfly_remix wrote: post #6
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.

> I wish we could have another and bump the packet size. The clock precision (100s of ppm) of the NIC oscillators on either side of a network connection gives a physical upper limit on the Ethernet packet size. The space between the packets lets the slower side "catch up". See https://en.wikipedia.org/wiki/Interpacket_gap for more info. We could use more precise oscillators to have longer packets but at a more expens…

I don't get how that limits the packet size. If a sender's clock is 500 ppm faster than an intermediate node's, you need 500 ppm of slack. That could be short packets with a short gap, or large packets with a large gap.

Ethernet specs the IPG as a fixed number of bits, but it could easily be proportional to the size of the previous packet.

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

#73

Post by brk »

jpm_sd wrote: post #70
addaon wrote: post #43

Earlier quoted context omitted.

> 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…

I think this is a terrible idea. Daisy chain multi drop is so last century. Switched point to point networks are so much better!

On paper, yes absolutely.

In reality, the wiring harness is one of the more expensive and complex components in a modern vehicle. The majority of the data being carried is low speed and low risk signalling: climate system controls, entertainment system, lighting control, etc. Obviously braking, steering, throttle controls and things like that are a different class.

Look at a modern luxury vehicle and how many things are in one door alone. Accent lights, window controls and motors, locks and lock controls, speakers (yeah, often plural), side mirrors and controls, side-looking cameras, etc. The wiring harness into a door needs consolidation or else it can become a giant heavy thing, the multi-drop approach makes a lot of sense here.

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

#75

Post by kbolino »

fsckboy wrote: post #59
FuriouslyAdrift wrote: post #41

Earlier quoted context omitted.

All wifi is a giant collision domain. Also, each segment of a wired network is a collision domain. What you are describing is more in line with MPLS or Infiniband. I agree with you frustration. I prefer to design networks that start routing right at the access port or even using an agent, virtual network port, or VPN endpoint at the client or application (like QUIC), but that is very expensive from a resource standpo…

> Also, each segment of a wired network is a collision domain huh? where "segment" means where you are using a hub not a switch? cuz that was a long time ago

If the links are operating at only 10Mbps or 100Mbps, it's possible for them to operate in half-duplex mode (e.g., if the cables don't have all 8 pins wired properly), even with a switch. In this mode, there's a collision domain between the host device and the switch.

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

#76

Post by aylons »

userbinator wrote: post #2

Ironically, this version of the header published in 1980 is what we still use to this day. IMHO Ethernet is one of the of great examples of backwards compatibility in the computing world. Even the wireless standards present frames to the upper layers like they're Ethernet. It's also a counterexample to the bureaucracy of standards bodies --- the standard that actually became widely used was the one that got released…

> It's also a counterexample to the bureaucracy of standards bodies --- the standard that actually became widely used was the one that got released first.

Sounds like a cautionary tale: whatever gets released first will stick. If you make a blunder, generations will have to live with it (like IPv4).

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

#77

Post by myrandomcomment »

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…

Too expensive to do in an ASIC. There is a reason the MAC table is bigger than the routing table on a chip, because it is cheaper. Think of an ASIC as a box that can be divided up in to smaller boxes that are an index. The total number of boxes is limited by the size of the ASIC. The bigger chip, the more box and greater the cost. To do MAC forwarding it takes 2 boxes. To do routing it takes 5. To do an ACL match it takes 14. This is the reason OpenFlow never really worked on switches at scale. What you are asking for is someone simpler to MPLS and that is an expensive feature die size wise. I have highly oversimplified this post, but it is mostly correct at a 1000ft level.

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

#78

Post by addaon »

londons_explore wrote: post #67
addaon wrote: post #43

Earlier quoted context omitted.

> 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…

> 10base-T1S I think that standard is a huge mistake... 10Mbits isn't enough for a modern vehicle (no cameras, radars, screens etc). Many sensors alone can push megabits, and in the modern world engineers want to send their data json formatted not with bitfields. Instead they should have used an cdma-like design with the physical being a 2 cent microcontroller for things like bulbs and micro switches. Then, for thing…

The 100base-T1 and 1000base-T1 standards already exist, and are already widely adopted. 10base-T1S is intended to replace CAN, which is sub-10 Mb/s, and often ~2 Mb/s; this is a niche where cost comes first. For non-multidrop links, intermixing 1000, 100, and 10 Mbit/s ethernet links on the same switch is trivial, so each link can be independently chosen and cost-minimized; and for sensors and high bandwidth items with safety impact, multidrop is generally not the preferred approach anyway. Basically -- 10base-T1S fits a new niche (for Ethernet), where the niches you mention are already well addressed.

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

#79

Post by p_l »

ninkendo wrote: post #58
p_l wrote: post #54

Earlier quoted context omitted.

For v6-specific world, scoped addresses and scoped multicast are explicitly for that purpose. You do not need to hierarchically subnet each following router, you just need to be able to express "next hop" for the subnets you need to route towards. You use link-local autoconfiguration, and use appropriately-scoped multicast addresses to ask "all-nodes" or "all-routers", making autoconfiguration a breeze compared to v4…

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 than designed (while keeping logic simple to not make switches too expensive).

For both IP, OSI, and routed ethernet, you run a complete routing protocol (IS-IS actually will handle both OSI, IP, and routed ethernet) where routers tend to send "hello" packets to announce themselves on the links to establish communication. This is how IP routing works since some of the oldest routing setups. On IP-bound protocols like OSPFv2/V3 or BGP you have to configure connections between the routers then tell them to peer with router at given IP, with IS-IS it has its own independent low level mechanism so you connect to a link and tell it which router ids to trust/peer with.

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

#80

Post by throw0101d »

londons_explore wrote: post #67
addaon wrote: post #43

Earlier quoted context omitted.

> 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…

> 10base-T1S I think that standard is a huge mistake... 10Mbits isn't enough for a modern vehicle (no cameras, radars, screens etc). Many sensors alone can push megabits, and in the modern world engineers want to send their data json formatted not with bitfields. Instead they should have used an cdma-like design with the physical being a 2 cent microcontroller for things like bulbs and micro switches. Then, for thing…

> I think that standard is a huge mistake...

You have to start somewhere. They're going for 25 Gbps:

> In addition to the more computer-oriented two and four-pair variants, the 10BASE-T1,[20] 100BASE-T1[21] and 1000BASE-T1[22] single-pair Ethernet (SPE) physical layers are intended for industrial and automotive applications[23] or as optional data channels in other interconnect applications.[24] The distances that single pair operates at full duplex depends on the speed: 1000m (1km) with 802.3cg-2019 10BASE-T1L; 15 m or 49 ft with 100BASE-T1 (link segment type A); up to 40 m or 130 ft using 1000BASE-T1 link segment type B with up to four in-line connectors. Both physical layers require a balanced twisted pair with an impedance of 100 Ω. The cable must be capable of transmitting 600 MHz for 1000BASE-T1 and 66 MHz for 100BASE-T1. 2.5 Gb/s, 5 Gb/s, and 10 Gb/s over a 15 m single pair is standardized in 802.3ch-2020.[25] In June 2023, 802.3cy added 25 Gb/s speeds at lengths up to 11 m.[26]

* https://en.wikipedia.org/wiki/Ethernet_over_twisted_pair#Sin...

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