Arranging Wireless Computers For The Greatest Signal Gain

There are some issues to consider when arranging wireless computers on a wireless home or business network.

One is the distance between wireless systems the other is potential sources of interference with the wireless radio signals

 

Proper antenna configuration is a critical factor in maximizing radio range. As a general guide, range increases in proportion to antenna height.

I know this might seem difficult to do but it’s not as difficult as it sounds just try and move the wireless router or antenna to a different location – higher is always better when arranging wireless computers

Wireless Distances Can Be Tricky

When arranging wireless computers, although there are usually ways to extend distance when using signal boosters and multiple wireless routers or access points.

Wi-Fi networking can work through most walls and other building structures, but the range is much better in open spaces.

The range of wireless adapters outdoors can be up to 1500 feet (457 meters)
Indoors at up to 300 feet (91 meters)
But Don’t Forget That These Ranges Are Under Ideal Circumstances Without Interference.

Quick Tip: When arranging wireless computers. The indoor range is the most sensitive and really depends on the structural elements of your home.

Which Will Have The Best Range

Range of a wireless system is based more on the frequency Then the band that it operates in vs. the standard that it uses.

Although makers of 802.11a equipment might disagree, the 5GHz frequency that 802.11a wireless equipment operates in results in a shorter range than 802.11b or g products when used in the typical residential environment.

802.11b and g-based equipment operates in the lower-frequency 2.4GHz frequency band, which suffers from less signal reduction when passing through the walls and ceilings of your home.

802.11b and 802.11g’s range advantages will tend to be neutralized if your wireless LAN is set up in an “open field” environment that has no obstructions between the Access Points and clients.

Interference With Home Wireless Devices

Large amounts of metals in the walls can be a problem for example heating-air conditioning-metal lath, especially older homes. Wireless networks broadcast on the same 2.4Ghz frequency as cordless phones and microwave ovens.

These devices are not supposed to interfere with each other, but occasionally they might, so try and keep your computers away from the deices (ex: micro wave ovens-cordless phones) this is especially true for base stations when arranging wireless computers.

Although normal desktops which function without mission critical services are relatively unaffected by the odd drop in connection.  That’s not the case if you’re running servers which provide remote access or applications.  For example always on systems such as firewalls and proxies like these rotating proxies should be shielded from any interference if possible.

The 802.11a equipment , and especially the dual band A and G products, is appealing in cases where there is potential conflicts, specifically, if you are heavily dependent on 2.4GHz cordless phones, and most of the cordless phones use this range.

Try This And Overcome The Wireless Obstruction

Keep your wireless devices away from the above appliances

Raise your access point and keep them out of the way of office workers which can cause interference

Move the PC away from any metal cabinets to a better location that’s not under your desk

Use a repeater that rebroadcast a signal from the access point, can eliminate dead spots

Introduction to IP Routing

Conceptually IP routing is pretty straight forward, especially when you look at it from the hosts point of view.  If the destination is directly connected such as a direct link or on the same Ethernet network then the IP datagram is simply forwarded to it’s destination.  If it’s not connected then the host simply send the datagram to it’s default router and lets this handle the next stage of the delivery.  This simple example illustrates most scenarios, for example if an IP packet was being routed through a proxy to allow access to the BBC iPlayer – like this situation.

The basis of IP routing is that it is done on a hop-by-hop basis. The Internet Protocol does not know the complete route to any destination except those directly connected to it.  Ip routing relies on sending the datagram to the next hop router – assuming  this host is closer to the destination until it reaches a router which is directly connected to the destination.

IP routing performs the following –

  • Searches the routing table to see if there is a matching network and host ID.  If there is the packet can be transferred through to the destination.
  • Search the routing table for an entry that matches the network ID.  It only needs one entry for an entire network and the packet can then be sent to the indicated next hop.
  • If all other searches fail then look for the entry marked – ’default’.  The packet then is sent to the next hop router associated with this entry.

If all these searches fail then the datagram is not  marked deliverable.  Even if it has a custom address perhaps an IP address for Netflix routing, it still will not matter.  In reality most searches will fail the initial two searches and be transferred to the default gateway which could be a router or even a proxy site which forwards to the internet.

If the packet cannot be delivered (usually down to some fault or configuration error) then an error message is generated and sent back to the original host.  The two key points to remember is that default routes can be specified for all packets even when the destination and network ID are not known.  The ability to specify specific routes to networks without having to specify the exact host makes the whole system work – routing tables thus contain a few thousand destinations instead of several million!!

It also involves the protocol to cope with complicated and disparate environments with ease.  It’s arguably one of the reasons why the internet has developed so quickly.  Even when we operate complicated client side tools like this Smart DNS Tool designed to access BBC iPlayer abroad, which rotates our IP addresses every few minute.  The protocol is able to reconnect and complete connections even when the client is changing and rotating it’s addresses.

 

HTTP (Hypertext Transfer Protocol)

For many of us a network is either our little home setup consisting of perhaps a modem and wireless access point and a few connected devices, or perhaps that huge global wide network – the internet.  Whatever the size all networks need to allow communication between the various devices connected to them.  Just like human beings need languages to communicate so do networks only in this context we call them ‘protocols’.

The internet is built primarily using TCP/IP protocols to communicate, this is used to transport information between ‘web clients’ and ‘web servers’.   It’s not enough though to enable the media rich content delivered to our web browsers and a host of secondary protocols site above the main transport protocol – the most important one which enables the world wide web is called HTTP.

This provides a method for web browsers to access content stored on web servers, which is created using HTML (Hypertext Markup Language).  HTML documents contain text, graphics and video but also hyperlinks to other locations on the world wide web.   HTTP is responsible for processing these links and enabling the client/server communication which results.

Without HTTP the world wide web simply wouldn’t exist and if you want to see it’s origins search for RFC 1945 where you’ll find HTTP defined as an application level protocol designed with the lightness and speed necessary for distributed, collaborative, hypermedia information systems.   It is a stateless, generic and object orientated protocol which can be used for a huge variety of tasks – crucially it can be used on a variety of platforms which means it doesn’t matter whether you’re platform your computer is on (linux, Windows or Mac for instance) – you can still access the web content via HTTP.

The content is largely irrelevant as well although obviously your computer may need plugins or codecs in order to handle things like specific video formats.  The fact is that the protocol doesn’t limit you in any way.  I can just as easily watch something like the BBC iPlayer on a high end Unix server as I can on a cheap desktop PC.  Indeed in many environments this has become to be a problem where traffic into corporate networks is rising rapidly because so many formats can be supported under HTTP.

It’s incredible to see something like a video being streamed across the internet, across many different forms of hardware all encapsulated in a single web page powered by HTTP.   When many people worried that tehir access to the BBC iPlayer stopped working last year, it was thought it could be some sort of compatibility problems.  In truth it was simply the BBC VPN not working that most ex-pats used to bypass the geo-blocking introduced earlier in the decade.

So what happens? When someone types a web name or address into the address field of their web browser, the browser attempts to locate the address on the network it is connected to.  This can either be a local address or more commonly it will look out on to the internet looking for the designated web server.   HTTP is the command and control protocol which enables communication between the client and the web server allowing commands to be passed between the two of them.   HTML is the formatting language of the web pages which are transferred when you access a web site.

The HTTP connection between the client and server can be secured in two specific ways – using secure HTTP (SHTTP) or Secure Sockets Layer (SSL) which both allow the information transmitted to be encrypted and thus protected.  It should be noted though that the vast majority of communication is standard HTTP and is transmitted in clear text insecurely which is why so many people use proxies and VPNs like this to protect their connections.

Choosing the Right Proxies for Instagram

In the technology world, all proxies are not created equally.  Indeed there is a huge variation of the servers and their respective IP addresses which can often be confusing.  It’s almost 30 years now since the first proxies were created in the CERN labs and in the intervening time, they have changed into all sorts of different formats.  The very first proxies were actually just simple gateways and in many environments they remain just like this.  However the global network that is the internet means that proxies now have to deal with a whole lot more protocols and communication metrics.

The use of proxies has also developed greatly too, especially as they have slowly migrated from the server room out into internet.  However not only is the actual server configuration important so is the IP address ranges that are assigned to it.  Now obviously the operating system does have some impact, after all an outdated copy of IIS installed on a version of Windows NT is going to have a serious amount of vulnerabilities built into it.   Yet for many purposes this is not as important as the actual IP addresses that are assigned to the server.

Take for example people who want to use proxies to run multiple accounts on social media platforms like Instagram.   This is a very popular social site which focuses on the upload and sharing of online photos.  Over the passed few years it has developed from a simple photo album site to one of the rivals to sites like Facebook.  As it has millions of users, then there are lots of people who now make money from running various accounts.  The issue is that Instagram only want people to run single accounts and takes many steps to block multiple or concurrent access.

To bypass these blocks there’s only one real solution – hiding your real IP address when accessing multiple accounts.  Most of the entrepreneurs use proxies in order to achieve this.  The key to achieving this is to minimize the footprint so that each account is being accessed by a completely different person.   Now just picking up a free proxy address from the internet is obviously possible however it’s an extremely bad idea for a variety of reasons.  However the main one is that often these are already being used to access Instagram and therefore you risk your account being flagged too.  This is one of the reasons that people using the site for business purposes will almost always use private proxies for Instagram whenever they can.

These private servers have two crucial components – firstly they are not used by anyone else, so you know that some spammer isn’t trying to use them for fake likes or account management.  The secondly is that the very best ones have residential IP addresses assigned to them.  This is also important as currently most proxies have commercial IP address ranges assigned as they generally reside in datacentres.  However Instagram and many other sites know that their genuine home customers will never have these sorts of IP addresses at all.

So they are often flagged as suspicious and commonly blocked from accessing the social media site.  It’s a growing practice as last year Netflix blocked all access from commercial IP address ranges which instantly stopped people using commercial VPNs to access the site.  So if you want to buy proxies for Instagram you should ensure that they have residential IP addresses and definitely are’t already blocked by the site.   Sure these Instagram proxies are  likely to cost a bit more but they will ensure that your Instagram accounts are safe and will not be risked.  Obviously these are only needed if you’re trying to run multiple accounts or some Instagram promotion software.  Otherwise just continue to use your own IP address to access the site.

 

Causes of Network Latency – TCP Proxies

On any sort of internet connection, speed is of course important.  The fastest response will be direct connections when the two computers are physically connected.  Of course the internet enables connections over thousands of miles but obviously this involves many more hops in the route.   If you start to use proxy servers or VPNs then you add an additional hop in the route which will almost always slow down your connection even more.

Overall speed is obviously one issue, but depending on what you’re doing online then there’s another that may be even more important.  Latency can actually cause a real problem with all sorts of online applications and especially for people playing games online.  If there is a long delay on the connection playing any sort of online action game can be virtually impossible online. If  you don’t believe me try playing Call of Duty using a satellite internet connection!   If you combine these with a slow VPN or even rotating residential proxies then you can seriously impact performance of your link.

TCP Hybla is an experimental TCP enhancement developed with the principal objective of combating the performance decline triggered by the prolonged RTTs typical of satellite links. It consists of a set of procedures that includes, among others:

  • an enhancement of the standard congestion control algorithm (to grant long RTT connections the exact same instantaneous segment transmission rate of a comparatively fast reference connection).
  • the compulsory adoption of the SACK policy.
  • the use of timestamps.
  • the adoption of Hoe’s channel bandwidth estimate.
  • the application and compulsory use of packet spacing methods (also known as “pacing”).
  • TCP Hybla includes only sender-side modification of TCP. As that, it is totally compatible with standard receivers.

For a full description of goals and characteristics of TCP Hybla refer to the publications section.

Performance.
TCP Hybla offers a pretty impressive efficiency improvement to long RTT satellite hookups with respect to TCP NewReno. It may be adopted either as an end-to-end protocol, or as satellite segment transport protocol in PEP (Performance Enhancing Proxy) designs based upon the TCP splitting principle. It can be also used as transport protocol in DTN architectures. See the performance section for further information.

Linux implementation.
Starting from kernel 2.6.13 Hybla has been included in the official Linux kernel. This implementation, based on the “module” Linux technology, does not include the last two Hybla components: Hoe’s channel bandwidth estimate and packet spacing. Their enhancement is mandatory to totally benefit from Hybla performance improvement. To this end, it is enough to patch the official kernel with the MultiTCP package, downloadable from the downloads section.

NS-2 implementation.
A TCP Hybla module has been developed for the widely adopted NS-2 simulation platform. This element can be downloaded from the downloads section.  At the time of writing this has yet to be tested extensively, it should work with all platforms and even with proxies designed for Instagram for instance.

TATPA testbed.
TATPA stands for Testbed for Advanced Transport Protocols and Architecture. It is a testbed developed by Hybla’s publishers to carry out comparative efficiency assessment of new TCP variants (included Hybla) and alternative architectures, such as PEPs (Performance Enhanced Proxy) and also DTN (Delay Tolerant Networks). It could be fully managed by remote through a powerful web interface. For further information see the TATPA testbed and the publications sections.

Projects.
TCP Hybla development is supported by the European Satellite Network of Excellence (SatNEx) project.

Using Proxy Servers for Privacy and Profit

Everyone online has a digital address.  It’s nothing complicated but it’s usually directly linked to your internet protocol address or IP address for short.  Although this number does vary throughout time, at the moment you connect to the internet it’s completely unique to you and you alone.  This number can be used to track your online activity to a surprising degree, it is the primary way that careless online criminals are tracked down.  There are of course huge privacy issues to having this address recorded and  technology exists to hide your location from websites you visit and your ISP.  At the heart of these are tools like VPN and proxy servers which we’ll cover briefly in this article.

Lots of us most probably have made use of a proxy server in all sorts of environments. In the case that you use the internet at the workplace or college and university, there’s a strong probability that you connect to it through a proxy server. They are actually frequently deployed to regulate access inwards and outwards to a company network from the world wide web. The idea is that as opposed to examining a wide variety of individual connections, the proxy can channel web traffic through a solitary point that makes it less complicated to monitor and check for things like viruses.

To impose making use of the proxy server, a large number of network administrators will definitely enforce their usage by a range of techniques. From the client computer the use of the proxy will be made mandatory by hard coding the settings into the browser. So for instance, Internet Explorer would certainly be set up and the settings pre-configured by using something like the Internet Explorer Application kit. The settings can also be installed by utilizing group policy settings released to the client from the Active directory.

In addition, the system administrator may even release configurations on the exterior firewall to control access throughout the network perimeter. This would be achieved by defining the IP address of the proxy and ensuring all other addresses are blocked out from leaving the network. If there are numerous proxies or they are set up in an array then multiple addresses would be configured. This would stop any individual from bypassing client side settings or setting up an additional browser and trying to gain access to the internet directly. If the address isn’t specified then the access would be blocked.

Proxies on the internet are normally used in a marginally different context although the functionality is relatively the same. They are mostly used to provide a level of privacy and hide your internet address from web servers. The idea is that rather than seeing the IP address of your client, then the web server (and your ISP) will only observe the IP address of the proxy. This would also allow you to circumvent some of the many geo-blocks which exist on the web. Essentially if you route your connection through a proxy located in the right nation then you can bypass the block. Countless people use these to view things like the BBC from Spain or anywhere outside the UK, though it can be challenging to find a UK proxy fast enough to stream video at least without paying for one. This has become a bit more complicated over the last handful of years though, as the websites have begun to detect the use of proxies and are blocking them automatically. Nowadays you normally need a VPN so as to watch video from one of the primary media sites, due to the fact that proxies won’t function any longer.

Presently there are other common uses of proxies online and that’s usually to make money. Countless individuals and companies, use proxies so as to create more electronic identities. Doing this means instead of being restricted to one connection, then you can efficiently make use of hundreds at the same time. This is most especially useful for performing online research, posting adverts, internet marketing and even utilizing e-commerce sites to buy stock to resale. A common use is to use automated software to buy things like sneakers or tickets to popular concerts, normally you’ll only be allowed to try and buy once but using proxies you can purchase many. This is why people employ computer software to speed up these methods and purchase the best rotating proxies so as to facilitate these purchases. There are many individuals making thousands from simple software programs, a few of the best rotating proxy networks and an ordinary home computer acquiring and selling limited availability items such as these.

Specialized Proxies with Residential IP Addresses

Now to 99% of the population, this principle is going to sound a little bizarre however it does illustrate the relevance of proxies today. The term sneaker proxies does not describe some incredibly, sneaky configuration of a proxy server more to the function they carry out. However before we explain what they in fact are and their function then we initially need a little background.

This subject is concerned all about the latest style, and more particularly the latest sneakers and shoes (maybe known as trainers outside the U.S.A). Now in my day, if you desired the trendiest trainers then you ‘d wait for their release and pop down to the sports shop and purchase them. Obviously life is a lot more complicated nowadays and there’s actually a selection of minimal edition tennis shoes that are quite in demand but extremely challenging to get. Exactly what takes place is the manufacturer launches a minimal amounts of these and they do so in an extremely particular way to maintain need.

  • Producer Releases Limited Edition Sneakers to Sellers
  • Middle Men typically get them.
  • These are sold online to consumers

This sounds basic however unfortunately, the demand is extremely high worldwide and the makers just release a very small number of the tennis shoes. It’s really a crazy market and it’s incredibly difficult to obtain even a single pair of these sneakers if you play the game by the book. Essentially even if you await alert then instantly go to among these sneaker sites you ‘d need to be extremely lucky to get even single pair. It’s so exceptionally hard to choose these up an entire sub industry has been developed with supporting technology to acquire them. So here’s exactly what you require and why utilizing tennis shoe proxies is an important component of this struggle.

Unfortunately if you just play the game, it’s pretty unlikely you’re going to get any of these unusual tennis shoe releases. So if you’re desperate for the latest fashion or possibly simply want to make a couple of bucks selling them on at a profit then they’re are approaches to significantly enhance your opportunities of getting lots of pairs. All of these releases are generally offered online from various sneaker professional sellers, however just wishing to click and purchase isn’t really going to work.

Exactly what do you require? How can you get a couple of or perhaps great deals on the latest sneakers? Well ideally there’s 3 components you need to basically warranty at least a couple of pairs.

A devoted server: now if you’re just after a number of pairs for your self, then this action is perhaps not necessary. If you’re in it for organisation and want to increase return it’s a sensible investment. Tennis shoe servers are merely devoted web servers preferably located to the datacentres of the business like Nike, Supreme, Footsite and Shopify who offer these sneakers. You use these to host the next phase, the Bots and automated software application described below.

Sneaker Bots— there are a great deal of these and it’s best to do your research on what’s working best at any point in time. A few of the Bots work best with specific sites, but they all work in a similar way. It’s automated software which can keep looking for defined tennis shoes without a human having to sit there for hours pushing the buy button. You can set up the software application to imitate human behaviour with infinite perseverance– obtaining these sneakers day and night when they’re released. You can run these bots on your PC or laptop with a fast connection although they’re more effective on devoted servers.
Sneaker Proxies
Now this is perhaps the most vital, and frequently mostly forgotten action if you’re heading to become a sneaker baron. Automated software application is fantastic for sitting there gradually aiming to fill shopping baskets with the latest tennis shoes however if you try it they get prohibited pretty quickly. Exactly what takes place is that the retail sites quickly spot these multiple applications since they’re all originating from the exact same IP address of either your server or your computer system. As soon as it occurs, and it will extremely rapidly, they obstruct the IP address and any request from there will be disregarded– then it’s game over for that address I’m afraid.

If you do not get the proxy stage proper then all the rest will be meaningless expenditure and effort. Exactly what makes an appropriate sneaker proxy? Well there’s certainly tons of complimentary proxies around on the internet, and totally free is certainly great. It’s pointless utilizing these and indeed very risky.   Free proxies are a combination of misconfigured servers, that is accidentally exposed which people get on and utilize. The others are hacked or taken over servers intentionally exposed so identity thieves can use them to take usernames, accounts and passwords. Considered that you will require at some point to spend for these sneakers utilizing some sort of credit or debit card using totally free proxies to send your financial information is utter insanity– do not do it.

Even if you do take place to pick a safe proxy which some dozy network administrator has actually exposed, there’s still little point. They are going to be slow which indicates however fast your computer system or sneaker server is, your applications will run at a snail’s rate. You’re not likely to be successful with a sluggish connection and often you’ll see the bot timing out. The second problem is that there is an important component to the proxy which you’ll have to succeed and essentially no free proxies will have these– a domestic IP address.
Numerous business websites now are well aware of people using proxies and VPNs to bypass geoblocks or run automated software. They discover it challenging to spot these programs however there’s a basic approach which blocks 90% of people who attempt– they ban connections from commercial IP addresses. Residential IP addresses are just allocated to home users from ISPs and so it’s very difficult to obtain great deals of them – read about them here. Virtually all proxies and VPNs available to employ are assigned with business IP addresses, these are not effective as sneaker proxies at all.

The Sneaker proxies are different, they utilize residential IP addresses which look identical to home users and will be enabled access to essentially all websites. Certainly you still have to be careful with numerous connections but the companies who supply these usually provide something called rotating backconnect configurations which switch both setups and IP addresses automatically. These are able to replicate rotating proxies but make them  more affordable than purchasing devoted property proxies which can get exceptionally pricey.

Software Testing: Static Analysis

There are several phases to a proper test analysis, the initial stage is normally the static review. This is the process of examining the static code initially to check for simple errors such as syntax problems or fundamental flaws in both design and application. It’s not normally a long exhaustive check, unless of course some obvious or major issues are identified at this stage.

Just like reviews, static analysis looks out for problems without executing the code. Nonetheless, as opposed to reviews static analysis is undertaken once the code has actually been written. Its objective is to find flaws in software source code and software models. Source code is actually any series of statements recorded some human-readable computer programming language which can then be transposed to equivalent computer executable code– this is normally produced by the developer. A software model is an image of the final approach developed using techniques such as Unified Modeling Language (UML); it is commonly generated by a software designer.  Normally this should be accessed and stored securely, with restrictions on who can alter this.  If accessed remotely it should be through a dedicated line if possible or at least using some sort of secure residential VPN (such as this).

Static analysis can find issues that are hard to find during the course of test execution by analyzing the program code e.g. instructions to the computer can be in the style of control flow graphs (how control passes between modules) and data flows (making certain data is identified and accurately used). The value of static analysis is:

Early discovery of defects just before test execution. Just like reviews, the sooner the issue is located, the cheaper and simpler it is to fix.

Early warning regarding questionable aspects of the code or development, by the calculation of metrics, such as a high-complexity measure. If code is too complicated it could be a lot more prone to error or a lot less dependent on the focus given to the code by programmers. If they recognize that the code has to be complicated then they are more probable to check and double check that this is correct; nevertheless, if it is unexpectedly complex there is a higher chance that there will certainly be a problem in it.

Identification of defects not easily found by dynamic testing, such as development standard non-compliances as well as detecting dependencies and inconsistencies in software models, such as hyperlinks or user interfaces that were actually either incorrect or unknown before static analysis was carried out.

Enhanced maintainability of code and design. By executing static analysis, defects will be removed that would certainly typically have increased the volume of maintenance needed after ‘go live’. It can also recognize complex code which if fixed will make the code more understandable as well as consequently easier to manage.

Prevention of defects. By pinpointing the defect early in the life cycle it is actually a great deal easier to identify why it was there in the first place (root cause analysis) than during test execution, therefore providing information on possible process improvement that could be made to prevent the same defect appearing again.

Source: Finding Residential Proxies, James Williams

Understanding ARP and Lower Protocols

They’re are many important protocols that you need knowledge of if you’re troubleshooting complicated networks. First of all there’s TCP, IP and UDP plus a host of application protocols such as DHCP and DNS. Any of these could be an issue if you’re having problems with a network. However often the most difficult to troubleshoot and indeed to understand are the lower level protocols such as ARP. If you don’t have some understanding of these it can be extremely confusing to understand how they interact.

The address resolution protocol often sits in the background happily resolving addresses, however if you get issues it can cause some very difficult problems. If you’re working on some sort of complicated network such as a residential proxy set up or ISP like this, there will be all sorts of hardware resolution requests taking place on both local and remote networks.

Both logical and physical addresses are used for intercommunication on a network. The use of logical addresses permits communication among a wide range of networks and not directly connected devices. The use of physical addresses assists in communication on a single network segment for devices that are directly connected to each other with a switch. In the majority of cases, these two kinds of addressing must collaborate in order for communication to happen.

Consider a scenario where you want to communicate with a device on your network. This device may be a server of some kind or simply another work- station you have to share files with. The application you are utilizing to launch the communication is already aware of the IP address of the remote host (by means of DNS, addressed elsewhere), meaning the system should have all it needs to build the layer 3 through 7 information of the packet it wishes to transmit.

The only piece of info it needs at this point is the layer 2 data link information consisting of the MAC address of the intended host. MAC addresses are required for the reason that a switch that interconnects devices on a network uses a Content Addressable Memory (CAM) table, which specifies the MAC addresses of all devices plugged into each of its ports. When the switch acquires traffic destined for a specific MAC address, it makes use of this table to know through which port to send the traffic.
If the destination MAC address is not known, the transmitting device will definitely first check for the address in its cache; if it is not there, then this must be resolved by means of supplementary communicating on the network.

The resolution procedure that TCP/IP networking (along with IPv4) uses to resolve an IP address to a MAC address is referred to as the Address Resolution Prrotocol (ARP), which is defined in RFC 826. The ARP resolution process uses only two packets: an ARP request and an ARP response.

Source: http://bbciplayerabroad.co.uk/free-trial-of-bbc-iplayer-in-australia/

Proxy Selection Using Hash Based Function

One of the difficulties in running a large scale proxy infrastructure is how to choose which proxy to use. This is not as straight forward as it sounds and there are various methods commonly used in selecting the best proxy to be used.

In hash-function-based proxy selection, a hash value is calculated from some information in the URL, and the resulting hash value is used to pick the proxy that is used. One approach could be to use the entire URL as data for the hash Function. However, as we’ve seen before, it is harmful to make the proxy selection completely random: some applications expect a given client to contact a given origin server using the same proxy chain.

For this reason, it makes more sense to use the DNS host or domain name in the URL as the basis for the hash function. This way, every URL from a certain origin server host, or domain, will always go through the same proxy server (chain). In practice, it is even safer to use the domain name instead of the full host name (that is, drop the first part of the host- name)—this avoids any cookie problems where a cookie is shared across several servers in the same domain.

It’s also useful when large amounts of data are involved and can indeed be used to switch proxies even during the same connection.  For example if someone is using a proxy to stream video – such as in this article – BBC iPlayer France, then the connection will be live for a considerable time with a significant amount of data.  In these situations, there is also limited requirement for any caching facilities particularly with live video streams.

This approach may be subject to “hot spots”—that is, sites that are very well known and have a tremendous number of requests. However, while the high load may indeed be tremendous at those sites’ servers, the hot spots are considerably scaled down in each proxy server. There are several smaller hot spots from the proxy’s point of view, and they start to balance each other out. I-lash—function-based load balancing in the client can be accomplished by using the client proxy auto-configuration feature (page 322). In proxy servers, this is done through the proxy server’s configuration file, or its API.

Cache Array Routing Protocol [CARP], is an advanced hash function based proxy selection mechanism. It allows proxies to be added and removed from the proxy array Without relocating more than a single proxy’s share of documents. More simplistic hash functions use the module of the URL hash to determine which proxy the URL belongs to. If a proxy gets added or deleted, most of the documents get relocated—that is, their storage place assigned by the hash function changes.

Where the allocations are shown for three and four proxies. Note how most of the documents in the three-proxy scenario are on a different numbered proxy in the four-proxy scenario. Simplistic hash-function-based proxy allocation using modulo of the hash function to determine which proxy to use. When adding a fourth proxy server, many of the proxy assignments change, these changed locations are marked with a diamond. Note that we have numbered the proxies starting from zero in order to be able to use the hash module directly.

John Ferris:

Further Reading Link