White Rabbit Switch Hardware 4.0

Overview

This page summarizes the GSI requirements in context with the development of a new version of the White Rabbit Switch.

A workshop on this topic took place on 26 June 2020. The slides are available here.

We (GSI/FAIR) have purchased ~350 pcs of the WRS hardware version 3. However, we will need more switches in the future

• for extension of the facility
• as replacement of broken WRS

Hence, we will need to buy more WRS in the future.

Regarding WRS v3, we expect

• it will be difficult to build new WRS v3 in a few years due to electric components no longer available on the market
• at some moment, support will come to an end because
  • FPGA resources on WRS v3 are exhausted
  • WRS developer will focus on WRS v4

To conclude, the option of purchasing and using WRS v4 is important.

Remarks

A main reason to obtain WRS v4 is as drop-in replacement for WRS v3. The most important criterea are

• the WRS v4 must be 1U. It must physically fit in the the same place as WRS v3, but it may be longer (towards the back of the rack)
• the WRS v4 must support at least 18 ports @1GBit/s Ethernet
  • we have thousands of nodes that support WR @1GBit/s only
  • if the switch has more ports, the additional ports may support WR @ 10GBit/s
  • all ports must be capable of Ethernet switching. Our main use-case is broadcast traffic with upper bound latency

My (db) five cent: I don't care about stuff like redundant power supplies that make the switch more expensive. Just assume the following we need to replace 30 half-broken WRS we have only 100kEuros: If I had the choice between a basic switch for 3k/piece and a fancy switch for 5k/piece, it makes more sense to replace all 30 half broken switches by new basic ones. It does not help if I can only buy 20 fancy switches, but there remain 10 dying old switches jeopardizing the network.

Requirements

These are the main requirements.

• locator light on the back (usefull when you have 20 WRS in the rack and you like to replace one in operatoin, it is important to find the right mains-cable)
• most important: continued supply of WRS as drop-in replacement for WRS v3. Use case: Broken WRS3 switch in a rack. The new switch must have at least 18 ports with 1GB. Height 1U, it must physically fit into the same space as WRS3.
• full backward compatibility to 1GBit for at least 18 ports
• 20 ports or 24 ports are fine too. In case there are a few additional (to the 18) ports, they may support 10 GBit/s
• Ethernet switching between all ports with focus on low latency for broadcast traffic; of course: all 'soft' features (management via ssh, dot-config, SNMP, VLANs....) of hardware version 3 shall be supported on version 4.
• some solution that prevents dust sucked (by internal fans) into connectors on the front side
• price
  • comparable to WRS v3
  • better skip fancy stuff like super redundant hot swappable fans and power supplies?
  • but use fans with a large MTBF
• 4 IOs for clocks; PPS and 10MHz in, PPS and 10MHz out
• form factor 1U; must fit in the same space as WRS v3; but it may be a bit longer (towards the back of the rack), if this makes cooling or building easier
• front panel connectors may be located differently on the front panel (in case this helps for the cooling concept)
• no need for a display; it just makes cooling and mechanics more difficult and has a limited life-time
• full open hardware design
• of course: CE and so on...

-- DietrichBeck - 6 Aug 2020