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| Cisco CCNP Certification Exam Training For The ONT Exam: QoS Models |
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Thursday, September 6, 2007
If you don't have a QoS model in place, you actually do. Best-effort QoS is just that - best-effort. No priority is given to any traffic. If your network is carrying voice or video traffic, best-effort is definitely not the way to go. The Integrated Services model, more popularly known as IntServ, uses the Resource Reservation Protocol (RSVP) to reserve network resources in advance of the data actually traveling across the network. Once the end-to-end bandwidth reservation is in place, the data is transmitted. That sounds great, but there are some drawbacks. It's a waste of bandwidth to have the entire end-to-end path reserved in advance. Additionally, IntServ isn't as scalable a solution as we'd like. Everything we do on a router or switch has a cost of some kind, and in this case it's RSVP overhead. One or two paths won't cause much overhead, but as the number of reserved paths increases as a network becomes larger, the RSVP overhead can take its toll on the routers involved. Differentiated Services (DiffServ) is the latest of the three models, and many would agree that it's also the greatest. DiffServ doesn't use RSVP, but instead uses Per-Hop Behavior (PHB) to allow each router across the network to examine the packet and decide what service level it should receive. With DiffServ, one router along the path from source to destination could consider a packet to be of the highest priority, while another router could consider it "just another packet". A term you hear often with DiffServ is "marking and classification". Marking a packet is the process of assigning the packet a value reflecting the level of QoS it should receive, while classification is placing that packet into a queue in accordance with that level of QoS. When it comes to marking, there are different values we can use to decide what value to mark the frame or packet with. In my experience, here are the four that are used most often: • IP Precedence (IP Prec) • Differentiated Services Code Point (DSCP) • CoS value • Interface that received the data (ingress interface) Which one you choose depends on your particular network's needs, and of course, the OSI layer at which the marking is taking place. We’ll take a look at each of these methods in future CCNP ONT exam training tutorials! What Are The Benefits Of Mobile Dual-Core Processors? When browsing through different notebook computer models, you are guaranteed to encounter the "Intel Core 2 Duo" or the "AMD Turion 64 x2" labels. These labels indicate dual-core processing technology for mobile computing. Multi-core processing is the buzz-word of the day, but what does it mean for you? Mobile Dual-Core Processors Mobile dual-core processors refer to a processor system consisting of two independent processor cores combined in one integrated circuit (IC) or, as industry professionals say, in a single die. Basically, mobile dual-core processors place two central processing unit (CPU) cores in one processor. Dual-core processing was first applied to desktop computing and home console gaming, but it was quickly adapted for mobile computing. As expected, AMD and Intel both have numerous mobile dual-core processing options available. Dual-core processors have a different architecture than twin- or double-core processors. Dual-core processors refer to a processing system where two processors are integrated in one IC die. On the other hand, twin-core processors refer to a processing system where two independent processors – each on its own die – are directly plugged into the motherboard. Each of the processors in a dual-core processor has a built in cache (Level 1 cache) so each has its own potential for speedy and efficient recovery and processing of frequently used instructions. More than that, however, there is a Level 2 cache, in the same IC board, which the two processors share in Intel's Mobile Core 2 Duo chipsets (either 2 or 4 MB); In AMD's Turion 64 x2 chipsets, each of the two processor has a dedicated 512 kb cache per core. The L2 cache is the processor’s backup cache in case the L1 cache is not enough. The Benefits of Mobile Dual-Core Processing The foremost advantages of dual-core processors are speed and efficiency. Instruction processing and data retrieval are handled by two processors, so more processing speed can be achieved without overheating either processor. The fact that the two processors have their own easily accessible L1 cache also assures more speed. Furthermore, especially in the case of the Intel Core 2 Duo where the L2 cache is shared, full L2 cache memory can be quickly utilized by either one or both processors as the need arises. In a nutshell, a notebook computer which has a dual-core processor is assured of fast and efficient processing performance with a greatly reduced risk of overheating. Multi-tasking is much improved. Dual-core processors also consume less power than twin-core processors. One other benefit of dual-core processors in notebook computers is the possibility of lighter and smaller notebooks that can approximate desktop PC performance. Since two processors share one IC die, one can enjoy the benefits of dual-CPU processing without having to deal with extra bulk. It is important to note that users of older programs will not see any benefit from their dual-core processors if they only run one program at a time. Older programs were not designed for dual-core processing, so they are only able to take advantage of a single core. A dual-core processor still gives considerable advantages in multi-tasking, however, as each core is able to handle a different program, speeding up multi-tasking considerably when compared to a single-core computer. As time goes on, more and more software developers are developing their products with dual-core processors in mind, so users will see more and more benefit out of their dual-core processors in the near future. This article may be republished freely as long as this copyright notice and box of resource links are included at the bottom. Copyright © 2007 MALIBAL, lLc MALIBAL is the Home of the World's Fastest Laptop! Headquartered in Las Vegas, this groundbreaking company has transmuted the world of mobile computing with its nonpareil laptops and unrivaled 24-hour USA-based support. Please, check out these recommendations for the best notebook computers. Protect Your Work – Lock Your Computer Anyone who has put in many hours, or at times even weeks of effort into work, may know what its like to lose a part of that work, but the worst thing you can do is to be the cause of your own loss. When you leave your computer, lets say for a bathroom break, an emergency meeting, or even to discuss something away from your machine, it may be natural to just walk away and do what you have to do, but I know from experience that this is a habit you should engrave into your computer work ethic just the same as being polite to the CEO of your organization. Allow me to go deeper, it will make more sense by example: A while back, I took a basic CAD (Computer-Aided-Design) class where we learned how to use the software and along the way, the concepts of good CAD-work, understanding of views, and being able to draw anything we saw in any variation. One of the first things my instructor told the class was to lock our computers. "Hold down the 'windows' button, and push 'L'. This will lock your computer and protect your work." Now why would you want protection? Look at condoms and you'll see why...Okay, so you won't get AID's if you don't lock your computer, but those of us who didn't heed the advice of my instructor learned the hard way to lock it up. By good nature, lots of us used to love to walk over to each other's workstations and talk, hang out, and mess around. By the time we came back, one of several things generally happened to our computers: 1. Our directories were cleared out of any and all work we had in them (hours, or rather weeks of hours, of racking your head over something has just gone down the drain), or 2. Our current drawing file was modified (i.e. a few lines being offset, stretched and skewed) thereby throwing off all dimensions, which is especially bad when being graded on dimensions. Even worse is when somebody scales your entire project, so when you actually build a model, instead of a 1/8 scale between the model and full-size, you have a 19/128ths scale. Firsthand experience sucks. 3. All of our file names were mixed and mismatched, so when we sat down to work, we faced the unique issue of figuring out each time which of the twenty files is which. Lots of fun when you have an upcoming deadline. 4. Any other creative mischief (i.e. turning the screen by 90 degrees, making windows look retro, or even hiding parts of our drawings so they appear deleted and we appear to be redoing it when we come back) Besides an annoyance ranging from mild all the way up to a promise of an a$s-kicking after class, locking your computer is important for security. From my experience with multiple private networks, leaving your console unattended while in full access can cause many problems for you and the network. One of your peers with lesser access rights may decide to play a joke on another and it doesn't turn out funny to the one it was being played on. He reports it to his boss. If the 'joke' was in any way decided as unacceptable by the boss, guess which two guys lose their jobs? Or even better if there is a visitor from somewhere and suddenly he has access to all of the top-secret files which are sworn by all employees to only stay on facility? Let me express it in one word: espionage. A car just doesn't sell as well when every other major car-maker sells exact knock-offs of it because someone from your company left the assembly plans in easy access. Windows Button + L OR Alt+Ctrl+Delete , then 'k' For this to work, you must have a password set on your account. If your account doesn't have a password setup, here's how to set one up: (Instructions assume that the user has full admin. access rights) For Windows XP: 1) Click on the 'Start' menu 2) Click on 'Control Panel' 3) Double-Click on 'User Accounts' 4) Click on your user account name 5) Click on 'Create a Password' 6) Follow the on-screen instructions |
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