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What is the advantage you get from having a sophisticated software stack on a top of rack switch? I was under the impression that you only really configured vla

by minimax 13y ago

What is the advantage you get from having a sophisticated software stack on a top of rack switch? I was under the impression that you only really configured vlans and maybe a span port every now and again. Someone care to enlighten me?

fourspace 13y ago
It isn't always the software. Having open, controlled, customizable hardware can offer a huge advantage over what you're able to purchase from Cisco/Juniper/etc. Also, a software switch allows you potentially massively scale the number of ports on a single switch.
wmf 13y ago
In that case, eliminating the complexity of existing control plane software will be a win. Some people may want to run OSPF or IS-IS, or do some kind of performance analysis, or do ARP/ND/DHCP proxying, or perhaps use switches to aggregate BMC monitoring & control, or who knows what.
- minimax 13y ago
  I get that you would want all that stuff in a router, but the article is mostly about a new type of top-of-rack switch. My understanding (based on experience that is now a few years old) is that a top-of-rack switch basically only handles layer two switching duties and a separate core router handles the layer three business.
  - wmf 13y ago
    Some people perform routing in the ToR because STP doesn't scale. And TRILL/SPB have been proposed to make Ethernet scale, but then they end up having similar complexity as routing (even using IS-IS).
csears 13y ago
In many common environments (single-tenant, fairly static configs) it probably doesn't make sense to use an SDN. However, if your environment looks more like EC2's, with lots of VMs/apps/services, lots of tenants, and lots of virtual networks, you need some way create an overlay that provides logical layer 2 switching beyond what simple VLANs can provide. For example, if I want to migrate a running VM from one host to another, it would be nice if the top of rack switches could be made aware of the change as it happens so CAM tables could be updated on the fly. Cisco and VMware do something similar today with the DVS and Nexus 1000v virtual switches, and a lot of the OpenFlow/SDN vendors are hoping to extend that type of dynamic orchestration out to physical switches as well.
- mdellabitta 13y ago
  > if I want to migrate a running VM from one host to another If only you could do this on EC2. >_<
zdw 13y ago
It's not putting the complex stack in the switch, it's putting hooks into the switch so that a complex algorithm can run on a generic server and direct the switches function. For example, lets say you're moving VM's around, or needed more bandwidth between two areas. You could reconfigure the switch all in software much faster by doing it programmatically rather than going through even a standard CLI interface. Want to design a new L2/3 routing protocol for your specific traffic needs? Now you can. Think of this as the difference between a graphing calculator and a copy of R, or SciPy. Sure, they both can do the same basic calculations, but the latter has so much more programmability and headroom.

by minimax 13y ago

fourspace 13y ago

It isn't always the software. Having open, controlled, customizable hardware can offer a huge advantage over what you're able to purchase from Cisco/Juniper/etc. Also, a software switch allows you potentially massively scale the number of ports on a single switch.

wmf 13y ago

In that case, eliminating the complexity of existing control plane software will be a win. Some people may want to run OSPF or IS-IS, or do some kind of performance analysis, or do ARP/ND/DHCP proxying, or perhaps use switches to aggregate BMC monitoring & control, or who knows what.

minimax 13y ago
I get that you would want all that stuff in a router, but the article is mostly about a new type of top-of-rack switch. My understanding (based on experience that is now a few years old) is that a top-of-rack switch basically only handles layer two switching duties and a separate core router handles the layer three business.
- wmf 13y ago
  Some people perform routing in the ToR because STP doesn't scale. And TRILL/SPB have been proposed to make Ethernet scale, but then they end up having similar complexity as routing (even using IS-IS).

csears 13y ago

In many common environments (single-tenant, fairly static configs) it probably doesn't make sense to use an SDN. However, if your environment looks more like EC2's, with lots of VMs/apps/services, lots of tenants, and lots of virtual networks, you need some way create an overlay that provides logical layer 2 switching beyond what simple VLANs can provide. For example, if I want to migrate a running VM from one host to another, it would be nice if the top of rack switches could be made aware of the change as it happens so CAM tables could be updated on the fly. Cisco and VMware do something similar today with the DVS and Nexus 1000v virtual switches, and a lot of the OpenFlow/SDN vendors are hoping to extend that type of dynamic orchestration out to physical switches as well.

mdellabitta 13y ago
> if I want to migrate a running VM from one host to another If only you could do this on EC2. >_<

zdw 13y ago

It's not putting the complex stack in the switch, it's putting hooks into the switch so that a complex algorithm can run on a generic server and direct the switches function. For example, lets say you're moving VM's around, or needed more bandwidth between two areas. You could reconfigure the switch all in software much faster by doing it programmatically rather than going through even a standard CLI interface. Want to design a new L2/3 routing protocol for your specific traffic needs? Now you can. Think of this as the difference between a graphing calculator and a copy of R, or SciPy. Sure, they both can do the same basic calculations, but the latter has so much more programmability and headroom.