The DCB world is not enough

TRILL needed too


TRILL

When several Ethernet switches, operating as layer 2 devices in in terms of the OSI 7-layer network reference model, are interconnected by inter-switch links ( ISLs), the IEEE 802.1D Rapid Spanning Tree (RSTP) protocol or a similar one is used to workout the best paths through the network and avoid things like endless loops. Spanning Tree allows only one link to be active between two Ethernet nodes, so this is achieved using the concept of active and inactive ports, with the former needed to construct a path through the network. Active bridging ports are put into a forwarding state, and un-needed ones into a blocked state.

A blocked link cannot be used for data transport and such ports are present but inactive, thereby literally wasting network bandwidth. This limits the overall bandwidth of a network and means reconfiguration when a port or switch fails takes time. It also limits the size of layer 2 Ethernet domains, and data centres will often have several of then delimited by layer 3 boundaries. We can't be having that; spanning tree approaches are inadequate.

What's needed is a routing protocol in layer 2, then we could get rid of spanning tree limitations, but routing is a layer 3 activity. The developing IEEE Transparent Interconnection of Lots of Links (TRILL) standard should solve this. It also enables multiple access paths at layer 2, which will increase available network bandwidth.

It uses the concept of a routing bridge (pdf) (RBridge) running an IS-IS (Intermediate System - Intermediate System) routing protocol, a link state routing protocol which operates by sending link state information through a network of routers or switches. Each router can then construct a representation of the network’s topology.

DCE plus TRILL

A DCE network, supporting DCB, built with switches supporting TRILL will mean that FCoE traffic can traverse the network, making multiple hops, without losing frames due to them being dropped as a result of congestion, or without taking too long a time, thus breaking the FC link, because the FCoE frames have a high enough priority be unaffected by the congestion. Such a network will also be able to have more than one link between switches, and these links can be simultaneously active, thus increasing effective bandwidth and availability.

A DCE network lacking TRILL can have multi-hop FCoE but it won't be routable and will be limited in scale and reconfigurability.

If the network needs more capacity then more switches and links are added. The IEEE is expected to, or hoped to, finalise DCE and TRILL next year. For now both Brocade and Cisco, the leading FCoE promoters, have announced products that will have a superset of TRILL functionality and, hopefully, support TRILL itself when it is standardised. These are Brocade One and FabricPath.

Combining Ethernet and Fibre Channel intricasies

Storage people considering FCoE will need to be really very well-educated about the intricacies of Ethernet indeed - the text above is simply the most basic overview imaginable - and how it will need to change to properly and effectively support FCoE. You will need to understand how different suppliers' products intercept the emerging standards.

It won't be practicable to have separate storage networking and Ethernet disciplines in your shop; the two have to converge; if they don't then your FCoE implementation will be done by Ethernet people that don't understand Fibre Channel or Fibre Channel people ignorant of Ethernet. You might as well draft your resignation letter now. ®


Other stories you might like

  • Prisons transcribe private phone calls with inmates using speech-to-text AI

    Plus: A drug designed by machine learning algorithms to treat liver disease reaches human clinical trials and more

    In brief Prisons around the US are installing AI speech-to-text models to automatically transcribe conversations with inmates during their phone calls.

    A series of contracts and emails from eight different states revealed how Verus, an AI application developed by LEO Technologies and based on a speech-to-text system offered by Amazon, was used to eavesdrop on prisoners’ phone calls.

    In a sales pitch, LEO’s CEO James Sexton told officials working for a jail in Cook County, Illinois, that one of its customers in Calhoun County, Alabama, uses the software to protect prisons from getting sued, according to an investigation by the Thomson Reuters Foundation.

    Continue reading
  • Battlefield 2042: Please don't be the death knell of the franchise, please don't be the death knell of the franchise

    Another terrible launch, but DICE is already working on improvements

    The RPG Greetings, traveller, and welcome back to The Register Plays Games, our monthly gaming column. Since the last edition on New World, we hit level cap and the "endgame". Around this time, item duping exploits became rife and every attempt Amazon Games made to fix it just broke something else. The post-level 60 "watermark" system for gear drops is also infuriating and tedious, but not something we were able to address in the column. So bear these things in mind if you were ever tempted. On that note, it's time to look at another newly released shit show – Battlefield 2042.

    I wanted to love Battlefield 2042, I really did. After the bum note of the first-person shooter (FPS) franchise's return to Second World War theatres with Battlefield V (2018), I stupidly assumed the next entry from EA-owned Swedish developer DICE would be a return to form. I was wrong.

    The multiplayer military FPS market is dominated by two forces: Activision's Call of Duty (COD) series and EA's Battlefield. Fans of each franchise are loyal to the point of zealotry with little crossover between player bases. Here's where I stand: COD jumped the shark with Modern Warfare 2 in 2009. It's flip-flopped from WW2 to present-day combat and back again, tried sci-fi, and even the Battle Royale trend with the free-to-play Call of Duty: Warzone (2020), which has been thoroughly ruined by hackers and developer inaction.

    Continue reading
  • American diplomats' iPhones reportedly compromised by NSO Group intrusion software

    Reuters claims nine State Department employees outside the US had their devices hacked

    The Apple iPhones of at least nine US State Department officials were compromised by an unidentified entity using NSO Group's Pegasus spyware, according to a report published Friday by Reuters.

    NSO Group in an email to The Register said it has blocked an unnamed customers' access to its system upon receiving an inquiry about the incident but has yet to confirm whether its software was involved.

    "Once the inquiry was received, and before any investigation under our compliance policy, we have decided to immediately terminate relevant customers’ access to the system, due to the severity of the allegations," an NSO spokesperson told The Register in an email. "To this point, we haven’t received any information nor the phone numbers, nor any indication that NSO’s tools were used in this case."

    Continue reading

Biting the hand that feeds IT © 1998–2021