Virtual Cluster Switching (VCS) is Brocade's brand of datacenter ethernet switching. VCS allows for the creation of a network fabric that's capable of converging storage and data traffic via standards-based datacenter bridging. It also solves the “Spanning Tree Protocol (STP) problem” by implementing a standards-based TRILL data plane paired with their own control plane in the form of Fabric Shortest Path First (FSPF). This data + control plane enable the “routing” of MAC addresses through the fabric, negates the need for STP, enables the use of all cabled links, and prevents traffic loops. VCS is only (currently) available on the VDX line of switches from Brocade.
In this post I'm going to outline five aspects of VCS that I found particularly interesting or unique. This is a companion article to an earlier one titled Five Functional Facts about FabricPath where I broke down five features of Cisco's fabric technology.
The CoDel AQM algorithm by Kathie Nichols and Van Jacobson provides us with an essential missing tool to control queues properly. This work is the culmination of their at three major attempts to solve the problems with AQM algorithms over the last 14 years.
Eric Dumazet wrote the codel queuing discipline (based on a quick prototype by Dave Täht, who spent the last year working 60 hour weeks on bufferbloat) which landed in net-next a week or two ago; yesterday, net-next was merged into the Linux mainline for inclusion in the next Linux release. Eric also implemented a fq_codel queuing discipline, combining fair queuing and CoDel (pronounced “coddle”), and it works very well. The CoDel implementation was dual licensed BSD/GPL to help the *BSD community. Eric and others have tested CoDel on 10G Ethernet interfaces; as expected, CoDel performance is good in what’s been tested to date.
Linux 3.5 will likely release in August. So it was less than a month from first access to the algorithm (which was formally published in the AQM Queue May 6) to Linux mainline; it should be about four total from availability of the algorithm to Linux release. Not bad at all :-).
Felix Fietkau Continue reading
BitTorrent is a lightning rod on two fronts: it is used to download large files, which the MPAA sees as a nightmare to their business model, and BitTorrent has been a performance nightmare to ISP’s and some users. Bram Cohen has taken infinite grief for BitTorrent over the years, when the end user performance problems are not his fault.
Nor is TCP the performance problem, as Bram Cohen recently flamed about TCP on his blog.
I blogged about this before but several key points seem to have been missed by most: BitTorrent was never the root cause of most of the network speed problems BitTorrent triggered when BitTorrent deployed. The broadband edge of the Internet was already broken when BitTorrent deployed, with vastly too much uncontrolled buffering, which we now call bufferbloat. As my demonstration video shows, even a single simple TCP file copy can cause horrifying speed loss in an overbuffered network. Speed != bandwidth, despite what the ISP’s marketing departments tell you.
Cisco's Identity Services Engine (ISE) is a powerful rule-based engine for enabling policy-based network access to users and devices. ISE allows policy enforcement around the Who?, What?, and When? of network access.
These questions can all be answered easily within ISE and are all standard policy conditions that are relatively easy to implement. In the post below I'm going to focus on the How? — How is the user or device connecting to the network? Asked another way, the question is Wired? or Wireless?