Proxy server

Schematic representation of a proxy server, where the computer in the middle acts as the proxy server between the other two.

In computer networks, a proxy server is a server (a computer system or an application program) that acts as an intermediary for requests from clients seeking resources from other servers. A client connects to the proxy server, requesting some service, such as a file, connection, web page, or other resource, available from a different server. The proxy server evaluates the request according to its filtering rules. For example, it may filter traffic by IP address or protocol. If the request is validated by the filter, the proxy provides the resource by connecting to the relevant server and requesting the service on behalf of the client. A proxy server may optionally alter the client's request or the server's response, and sometimes it may serve the request without contacting the specified server. In this case, it 'caches' responses from the remote server, and returns subsequent requests for the same content directly.

A proxy server has a large variety of potential purposes, including:

• To keep machines behind it anonymous (mainly for security).^[1]
• To speed up access to resources (using caching). Web proxies are commonly used to cache web pages from a web server.^[2]
• To apply access policy to network services or content, e.g. to block undesired sites.
• To log / audit usage, i.e. to provide company employee Internet usage reporting.
• To bypass security/ parental controls.
• To scan transmitted content for malware before delivery.
• To scan outbound content, e.g., for data leak protection.
• To circumvent regional restrictions.

A proxy server that passes requests and replies unmodified is usually called a gateway or sometimes tunneling proxy.

A proxy server can be placed in the user's local computer or at various points between the user and the destination servers on the Internet.

A reverse proxy is (usually) an Internet-facing proxy used as a front-end to control and protect access to a server on a private network, commonly also performing tasks such as load-balancing, authentication, decryption or caching.

AMD

AMD Phenom-II X2-560BE Callisto Processor Review

With the release of the Deneb based quad core processors known as the Phenom II series, AMD started to grab a nice share of the mid-range and higher market share by offering quad-core processors for quite a bit less than the competition. Back in June of 2009, Benchmark Reviews was there when AMD started a new trend with Deneb based processors that didn't quite meet the rigorous standards of testing on all four cores. Rather than tossing the processors that had two or three cores that still functioned perfectly, AMD decided to turn off the bad cores and release them as much less expensive dual and triple-core processors. The dual-core versions got a couple of extra perks as well. For one, the price was enticing at $99. For another, the processors were Black Editions, meaning they had unlocked multipliers for easier overclocking. The first black edition dual-core Phenom-II to hit the market was the X2-550BE. Just over a year later and 200MHz faster, AMD is releasing the Phenom-II X2-560BE at 3.3GHz with the same promise, to give would-be overclockers and enthusiasts the opportunity to toy around without spending a bundle. In this article, Benchmark Reviews is bringing you the details on the X2-560BE (model HDZ560WFGMBOX). The new dual-core's unlocked multiplier will be pushed to the limit and we will see how it measures up to the competition.

According to the August Steam Hardware Survey, more than half of gamers use a dual-core processor in their systems. While quad-core processing is on the rise, it still represents only about a quarter of gamers. That's may have something to do with the fact that still few programs, including games, utilize more than one or two cores effectively. The Phenom-II X2-560BE is the latest release of Phenom-II series dual-core processors made specifically for overclocking. The Black Edition versions of AMD CPUs are released with unlocked multipliers so that overclocking is as easy as a couple of quick changes to the BIOS.

The release of Black Edition CPUs from AMD and Extreme Edition CPUs from Intel marks a change in the way the CPU manufacturers have done business for the last little while. Originally, most processors came without a lock on the multiplier and PC enthusiasts were left to their own designs when it came to overclocking. Soon, both chip manufacturers became to clamp down on the freedoms provided to their customers and overclocking became something that took a lot of work. Motherboard manufacturers have often tried to provided users ways of getting around the overclock killers put on CPUs. This once meant that changing jumper settings on motherboard in order to increase bus speeds or voltage was the way to do things. Now, even without unlocked CPUs, many motherboard manufactures have begun putting new features into their BIOS that allow for easy increases in bus speed and core CPU voltage.

Phenom-II_X2-560BE_CPU_Die2.jpg

The Black Edition CPUs with unlocked multipliers make overclocking easier than ever. All a user needs to do to overclock their system now is enter the bios and change the standard multiplier on their CPU and increase it. To find the best possible stable overclock, some tweaking of the CPU voltage and bus speeds may be necessary, but for a quick and effective overclock, nothing beats the ease of a Black Edition (or Extreme Edition in the case of Intel CPUs) processor.

At Benchmark Reviews, we have already seen the incredible ability of Athlon-II and Phenom-II AMD processors to overclock. The CPUs are frequently able to reach clock speeds in excess of 20% faster than their stock speeds. With a black edition CPU like the Phenom-II X2-560BE, we expect no less and the CPU will be pushed to the limit in order to find its breaking point.

With each new release of a Phenom-II processor, AMD reasserts its control on the mid-level market segment by providing another great quality CPU at an affordable price. The release of the Phenom-II X2-560BE HDZ560WFGMBOX dual-core processor is no different. At 3.3GHz, the X2-560BE becomes the fastest Phenom-II dual-core processor on the market. Similar to previous Phenom-II dual-core entrants to the market, the Phenom-II X2-560BE will have a relatively low MSRP, this time of $105. Benchmark Reviews as been there for the release of many of the most recent Athlon-II and Phenom-II processors and we wouldn't miss the chance to bring you the test results on the latest Phenom-II Black Edition dual-core release. In this article, Benchmark Reviews compares the Phenom-II X2-560BE HDZ560WFGMBOX dual-core to a variety of other processors in a comparable price range, as well as some more expensive dual and quad-core processors.

With the August Steam Hardware Survey showing us that less than 6% of gamers are using DX11 compatible systems, we are taking this opportunity to bring you a review focused at discovering the performance increase, if any, of upgrading just one piece of equipment, your CPU. Many of the review articles I read make me feel as though the performance they offer are just too far out of reach because it will require nearly a complete system overhaul in order to see the increased levels of performance with the new equipment. Using a high-end DX10 video card in this review can help show the performance increase available for those of us who may need to upgrade just one piece at a time.

The Phenom-II X2-560BE HDZ560WFGMBOX in this review will be tested against many of the Athlon-II line of processors including the X4-640, X4-645 and two other Athlon-II processors, the X2-260 and the X3-445. This will give us a good overview of the scaling of dual, triple, and quad-core members of the Athlon-II family when compared to the Phenom-II dual-cores with an L3 cache. Results from recent tests of a couple of Intel Core i5 processors, the 655K and the 680, will be included to show performance across the platforms available. Finally, a Core i7-920 will round out our review, giving us a view of the relative high-end of quad core processing.

Let's move in and take a look at some of the features and specifications of the Phenom-II X2-560BE HDZ560WFGMBOX AM3 dual-core processor.

DHCP SERVER

A DHCP (Dynamic Host Configuration Protocol) server is a protocol used on networks that lets computers be automatically configured for network communication without manual intervention by an administrator. A DHCP server will automatically assign an IP address to a computer connected to a network from a per-defined range of IP addresses and ensures that no two computers on a network are assigned the same address. DHCP can be used for both Ipv4 and Ipv6 network addressing but are considered to be separate protocols for each model of IP address assignments.

How Does a DHCP Server Work?

When a computer that is connected to a network which uses the DHCP protocol, the computer will send a request called a DISCOVER or DHCPDISCOVER message in an attempt to find a DHCP server on the network. The network router will then send the DISCOVER packet to the best or closest DHCP server to answer the request from the computer. The server will then determine an appropriate IP address for the computer based on the administrator-set policies and address availability on the network. Once this assignment is made, it sends an “OFFER” or “DHCPOFFER” packet back to the client computer with the network address information. Once the client computer receives this response, it sends a “DHCPREQUEST” or “REQUEST” packet back to the server to let it know that the address will be used. The DHCP server will then send an “ACK” or “DHCPACK” packet back to confirm the IP address lease and time of the lease.

What Are the Benefits of DHCP?

The single, biggest benefit of DHCP is that it removes the requirement for a network administrator to manage the available IP addresses on a network. Additionally, DHCP helps eliminate the problem that arises with static IP assignment of two computers being assigned the same address which ultimately results in a loss of network service. DHCP dynamic assignment of IP addresses helps minimize these conflicts.

What Are the Methods of DHCP Address Allocation?

Depending on the network requirements, there are three ways that DHCP can assign IP addresses to a network computer:

Dynamic Allocation – This is where the administrator assigns an IP address range to the DHCP server and each client computer on the network must request an IP address from the DHCP server when the network is initialized under the “Lease” concept. When a lease expires, the DHCP server is free to reclaim an address if not renewed and used for other client computers.

Automatic Allocation – The DHCP server will permanently assign a free IP address from a range set by the admin to a requesting computer. The primary difference with dynamic allocation is that the server keeps a record of past IP assignments to computers and attempts to assign the same address to the same computer on future network connections.

Static Allocation – The DHCP server makes IP address assignments based solely on a table that pairs MAC addresses with IP assignments that are normally filled in manually by a network administrator. If a computer's MAC address is not listed in the table, it will not be assigned a network address. This is also referred to as Static DHCP.

DHCP Security

The base-line DHCP protocol does not include separate security mechanisms for computers to authenticate themselves. Due to this fact, there are several attacks that can take advantage of the lack of security in the DHCP protocol: 1 – Unauthorized computers that can gain access to network resources, 2- Unauthorized DHCP servers that give false address assignments to client computers, and network resource exhaustion by rogue network computers. There are DHCP extensions that exist which implement different authentication methods, however, these are not widely adopted in industry. As a result, many network administrators rely on controlling access to a network to help prevent DHCP exploitation.