Bruce has worked in educational technology for thirty years, but his real love is history and teaching. This BLOG represents that. In addition to technology and history, Bruce is the author of several books, including Sands of Time, Towering Pines Volume One: Room 509, The Star of Christmas, Philadelphia Story, The Insider's Story, How to Play Guitar, and How to Read the Bible.
I find that talking about and explaining how to prevent loops in a network is something I do an awful lot. So I thought I'd post something up that helps explain how to prevent it, and what the Spanning Tree Protocol is. The Spanning Tree Protocol (STP) is a network protocol that ensures a loop-free topology for any bridged Ethernet local area network. Spanning Tree offers your network redundant and loop-free operation. Think of spanning tree as a tree that the bridge keeps in memory for optimized and fault-tolerant data forwarding.
What is Spanning Tree?
STP provides a means to prevent loops by blocking links in an Ethernet network. Blocked links can be brought in to service if active links fail.
The root bridge in a spanning tree is the logical center and sees all traffic on a network.
Spanning tree recalculations are performed automatically when the network changes but cause a temporary network outage.
Newer protocols, such as TRILL, prevent loops while keeping links that would be blocked by STP in service.
Eliminating loops with spanning tree If your switches are connected in a loop without STP, each switch would infinitely duplicate the first broadcast packet heard because there's nothing at Layer 2 to prevent a loop. STP prevents loops by blocking one or more of the links. If one of the links in use goes down, then it would fail over to a previously blocked link. How spanning tree chooses which link to use depends entirely on the topology that it can see. The idea behind a spanning tree topology is that bridges can discover a subset of the topology that is loop-free: that's the tree. STP also makes certain there is enough connectivity to reach every portion of the network by spanning the entire LAN. STP configuration Bridges will perform the spanning tree algorithm when they are first connected to the network or whenever there is a topology change. When a bridge hears a "configuration message," a special type of BPDU (bridge protocol data unit), it will begin its disruptive spanning tree algorithm. This starts with the election of a "root bridge" through which all data will flow. The next step is for each bridge to determine the shortest path to the root bridge so that it knows how to get to the "center." A second election happens on each LAN, and it elects the designated bridge, or the bridge that's closest to the root bridge. The designated bridge will forward packets from the LAN toward the root bridge. The final step for an individual bridge is to select a root port. This simply means "the port that I use to send data towards the root bridge." Note: Every single port on a bridge, even ones connected to endpoints, will participate in the spanning tree unless a port is configured as "ignore." A newly connected bridge will send a reconfiguration BPDU, and the other connected devices will comply. All traffic is stopped for 30-50 seconds while a spanning tree calculation takes place. Rapid STP In 2001, certain vendors started introducing rapid spanning tree, a modified version of the spanning tree algorithm that reduces outages. It's fully compatible with older devices that only know the old spanning tree algorithm and reduces the 30-50-second outage time to less than ten in most cases, so use it if you can. Note: RSTP works by adding an alternative port and a backup port. These ports are allowed to immediately enter the forwarding state rather than passively wait for the network to converge. VLANs and PVST STP can cause problems with VLANs if one of the physical links happens to be a VLAN trunk. That's because with only one spanning tree, it's possible the link with the VLAN trunk will need to be blocked. That could result in no connectivity for a particular VLAN to the rest of its LAN. To solve this, enable per-VLAN spanning trees (PVST). With PVST enabled, a bridge will run one spanning tree instance per VLAN on the bridge. If a trunk link contains VLANs 1, 2, and 3, it can then decide that VLANs 1 and 2 should not take that path, but still allow VLAN 3 to use it. Spanning tree drawbacks One of the drawbacks of STP is that even though there may be many physical or equal-cost multiple paths through your network from one node to another, all your traffic will flow along a single path that has been defined by a spanning tree. The benefit of this is that traffic loops are avoided, but there is a cost. Restricting traffic to this unique path means blocking alternative, and sometimes more direct, paths. That means that your full potential network capacity can never be realized. (It is possible to use multiple simultaneous spanning trees for separate VLANs, as mentioned above, but the traffic in any given VLAN will still not be able to use all your available network capacity.) In the past this has been acceptable, but with the increasing use of virtualization technology in many data centers, there is a need for a more efficient and reliable routing infrastructure that can handle the very high I/O demands of virtualized environments. Spanning tree alternatives: TRILL and NPB Transparent Interconnection of Lots of Links (TRILL) is a routing protocol network standard which:
Uses shortest path routing protocols instead of STP.
Works at Layer 2, so protocols such as FCoE can make use of it.
Supports multihopping environments.
Works with any network topology, and uses links that would otherwise have been blocked.
Can be used at the same time as STP.
The main benefit of TRILL is that it frees up capacity on your network which can't be used (to prevent routing loops) if you use STP, allowing your Ethernet frames to take the shortest path to their destination. This in turns mean more efficient utilization of network infrastructure and a decreased cost-to-benefit ratio. These benefits are particularly important in data centers running cloud computing infrastructure. TRILL is also more stable than STP because it provides faster recovery time in the event of hardware failure. ~~~ Bruce has worked in educational technology for over 18 years and has implemented several 1:1/BYOD programs. He also has served as a classroom teacher in Computer Science, History and English classes. Bruce is the author of five books: Sands of Time, Towering Pines Volume One:Room 509, The Star of Christmas, Philadelphia Story: A Lance Carter Detective Novel and The Insider's Story: A Lance Carter Detective Novel. Follow Bruce's Novel releases by subscribing to his FREE newsletter!
The website says, "Targeted practice questions for student success." And that is what LearningPod delivers -- not just questions but success. With a current database of around 50,000 questions in every subject imaginable, LearningPod delivers on their promises to allow students to practice any subject, as much as they need to in order to help build mastery.
LearningPod is a free resource for educators that encompasses practice test questions on everything from Common Core aligned 2nd grade subjects all the way through AP Chemistry, and even some undergraduate level course work! LearningPod has put together an innovative way to point their students in the right direction to get the practice that they need, when they need it. They do this by creating "pods" that steer the learning towards the student and their needs. But you aren't on your own with LearningPod. In addition to the thousands of questions loaded into their pod database, they also have newly created content that teachers can look to in their premium content area. LearningPod truly is a one-stop shop for your curriculum, advanced testing and college prep needs! Interested? Check it out at LearningPod -- and you can also take a look at this recent article on the Washington Times BLOG pages.
Buffalo Wild Wings 1510 Egypt Road Phoenixville, PA 610-676-0136 As a rule, I absolutely adore buffalo wings. And -- as another rule, if you have a bunch of sauces of differing types and hotness -- even better! I have seen commercials for Buffalo Wild Wings all over as I've traveled around, and always lamented that there wasn't one closer to where we live that we could try. Well, now there is! The new one in Phoenixville opened up a couple of months ago, and the wife and I were heading home from King of Prussia and decided to give it a whirl. Possibly the worst food-related decision since the Mighty Wings. To begin with, as we were pulling up to the restaurant we weren't entirely clear if it was open. It was around 5:00PM and the sign was not lit up nor were there any exterior lights on. But based on the cars in the parking lot we figured it was. As soon as we walked in the door we were smacked in the face by a cacophony of noise. Between the TVs, waitstaff and patrons, this place was very, very loud. It was busy, but we were seated quickly. It only took moments to realize that we were surrounded by ten televisions with various sporting events on and the volume of one was quite loud. We tried to have a conversation about what to order, but that was quickly squashed because we had to shout to hear each other. Our waiter, Brian, was very cordial and very good. He took our orders, answered our questions and even got me a sample of one of their featured beers. It is worth noting that they had two featured beers, one of which was Bud Light (Really?) and the other he told me was a dark beer. When he brought the sample, it was not a dark beer at all. He apologized for his mistake. No big deal. We ordered and waited for our food... and waited... and waited. Brian came over and explained to us that the kitchen runs on a rotating cycle, and sometimes that makes things take longer but everything comes out together and hot. That's fine. Eventually our food did come out. My wife got a buffalo chicken sandwich and I got the Thai Curry boneless wings. I'm too lazy to deal with bones anymore... After one or two bites, we both decided that while they smelled delicious, they lacked any sauce. We asked for extra sauce -- and Brian was happy to oblige. We say and waited and waited.. no sauce. So I started eating and found that I could barely taste the sauce and the chicken was over-breaded and hard. So I waited for sauce. About ten minutes later, Brian came by and we reminded him about the sauce.... he apologized and told us about the kitchen thing rotating or whatever and it makes things take longer. I just want a cup of sauce.
Finally, we got more sauce. After two pieces of chicken I understood why they barely put any sauce on -- it was terrible. It was salty and had very little actual curry flavoring to it. So, I had dry chicken -- and a disgusting sauce. My wife had a similar reaction to their "classic" buffalo sauce. Very salty and barely edible. After asking for a refill on our drinks (which took ten minutes) we decided to bail on this meal, which ended up costing twice what it should have. Overall, I disliked Buffalo Wild Wings enough that we will never eat there again. It was too loud, too expensive and the food was possibly the worst buffalo style restaurant I've ever been to. I don't usually write scathing reviews like this -- but I had such high hopes for this place, that even now -- almost a week later -- I'm sadly disappointed. Overall: Atmosphere: 1/5 - It's a bar that serves food, and a poor one at that. Service: 3/5 Food: 1/5 Price: 1/5 Overall: 1.5/5
Math... how much torture do young students go through trying to master things like multiplication tables? If your classroom is like the average American classroom -- quite a bit. How do we make learning math easier? Many teachers are turning to technology and trying to find the perfect app for their iPads that helps kids use and memorize these math facts in a way that is fun and easy for them. And that is a good solution, but sometimes the best solution is the simplest. Enter X-Bandz.
X-Bandz are little bands that kids can wear on their wrists that have the math facts literally written all over them. These wrist bands come in multiple colors and are very affordable, so it is easy for schools and teachers to acquire classroom sets of these. And they come in versions for multiplication, division, addition and subtraction -- so they fit into several different grade levels of learning. I think we all want to help students in their pursuit of learning, and we know how being confident in subject matter not only leads to academic success but can also boost their self-esteem. X-Bandz is a product that can help your students gain this self-confidence and continue building upon these foundational learning block every day. For more information on these fun and easy-to-use learning aids, click here.
When I was in high school, everyone wanted their driver's license. It was a key to life, liberty, freedom and the pursuit of going to the mall! I guess that dates me a little bit... but we all wanted to drive! I went to a private military school, and we did not have driver training like the local public schools did. But today, many private schools do offer some soft of driver instruction -- and of course there is tech for that. Can't hire a driving instructor? Well -- what about a driving simulator? Need to do research on driving habits or how certain road conditions can affect the way a car handles? Enter a driving simulator!
At Carnetsoft, they have created an affordable Driving Simulator that any school can get into and make available to their students. This software can help students become comfortable with driving under conditions, help treat people who have fear of driving, can help people brush up on their basic driving skills and can even help test people who tend to fall asleep at the wheel. Not only can you have people just use it, but you can use it for research as well. You can create any number of customized courses with various different road and weather conditions, and then store it in a database that keeps track of things like reaction time, success in navigating courses and many more variables. This system can be used for testing of individuals, or research projects that students at high school or university level might be doing. Sound awesome? Check it out on Carnetsoft's website -- and see how this system can benefit you and your students!
It's simple... it's easy... and most of all, it is fun. The Apps created by Little Clever speak to your preschooler in a way apps haven't been able to in the past. The company is on a mission to create apps that help your preschooler develop critical thinking skills coupled with the mechanical skills that are necessary as they grow older in a technical world. They create games that support children's learning and development through fun, interactive games that help develop hand-eye coordination, pattern recognition, numeracy and language.
Currently, they have two apps. Both are available for your Apple iOS, Android, Amazon Kindle and Windows Mobile devices -- and couldn't be easier to download and install for your little one. Both games respect your privacy by not collecting any data about you, or your little one's gaming habits and there are no advertisements at all -- plus work great in "Airplane Mode" so that they can play the games any time, anywhere. The first game they offer is completely free! The 21 Animal Puzzles for Children app features 21 different animal themed puzzles, each with 7 levels of difficulty giving you a total of 147 different puzzles! These animals can come from one of two areas: The Farm or The Riverside. The difficulty on the app can be set to adapt to your child's progression and has some really great, friendly and fun sounds and voices in it!
The second game is not free, but features 101 different animals from 9 different places (The Farm, Riverside, Woodland, In The Sea, Africa, In the Garden, Dinosaurs, Pets and Around the World). This app would literally be a never ending source of animal puzzles for your preschooler! Want to know more? Visit them at LittleClever.Com and check out the promo video below!
