Best effort delivery

From Wikipedia, the free encyclopedia

Best effort delivery describes a network service in which the network does not provide any guarantees that data is delivered or that a user is given a guaranteed quality of service level or a certain priority. In a best effort network all users obtain best effort service, meaning that they obtain unspecified variable bit rate and delivery time, depending on the current traffic load. By removing features such as recovery of lost or corrupted data and preallocation of resources, the network operates more efficiently, and the network nodes are inexpensive.

The postal service delivers letters using a best effort delivery approach. The delivery of a certain letter is not scheduled in advance - no resources are preallocated in the post office. The mailman will make his "best effort" to try to deliver a message, but the delivery may be delayed if too many letters arrive to a postal office all of a sudden. The sender is not informed if a letter has been delivered successfully. However, the sender can pay extra for a delivery confirmation receipt, which requires that the carrier get a signature from the recipient to prove the successful delivery.

Conventional telephone networks are not based on best-effort communication, but on circuit switching. During the connection phase of a new call, resources are reserved in the telephone exchanges, or the user is informed that the call is blocked due to lack of free capacity. An ongoing phone call can never be interrupted due to overloading of the network, but is guaranteed constant bandwidth.

Conventional IP routers only provide best-effort service. The simplicity of routers is a key factor why IP has been much more successful than more complex protocols such as X.25 and ATM. In X.25, data was retransmitted on a node-to-node basis in case of detected errors. An ATM network can offer service categories with guaranteed bandwidth or latency. The Available Bit Rate (ABR) ATM service category gives best effort delivery, without Quality of Service guarantees.

However, the best-effort paradigm is to some extent abandoned on the Internet. Modern IP routers also provide mechanisms for differentiated or guaranteed quality of service to certain data flows, based on for example the IntServ or DiffServ protocols. This may be utilized in networks with capacity problems for the reservation of resources to delay-sensitive services and services that require constant bit rate, for example real time multimedia communication such as IP telephony and IP-TV.

Albeit Internet in its primary form is based on best-effort communication, guaranteed delivery can be provided by higher layer protocols, handled by host computers rather than the network nodes. The TCP transport protocol provides guaranteed services while UDP transport protocol provides best effort delivery. TCP verifies that all information transmitted is received fully on the other end. UDP does its best to deliver packets to the destination, but takes no steps to recover packets that are lost or misdirected. The more stable TCP protocol is often used to deliver data like web pages and email, while UDP is often used for media streaming or network gaming.

Note that TCP does not reserve any resources in advance, and does not provide any guarantees regarding quality of service, for example bit rate. In that sense, it can be considered as best-effort communication. For end-to-end transport layer reservation of resources, the resource reservation protocol (RSVP) may be used.

Although UDP is used, higher layer application protocols may provide guaranteed delivery of messages and files. Examples are protocols for shared disk access, which in the early days were based on UDP.


Book sources
Encyclopedia of Networking & Telecommunications ISBN 0-07-212005-3
Retrieved from "http://en.wikipedia.org/wiki/Best_effort_delivery"
Categories: Telecommunications

Windows Server 2008 Delivers Web-based Experiences

by Nick Pegley


plug itFor increased control of your servers, efficient management, and configured Web tasks, there's Windows PowerShell, Windows Server Manager and IIS7. eNetwork Access Protection and Read-Only Domain Controller protect and fortify the server environment, putting your business on a strong foundation.
Internet Info Services 7 simplifies management of Web services. As a modular platform with an interface based on tasks, better control, improved security, and Web service health management, the user connects to their information and to others using Info Server (IIS) 7.0 and .NET 3.0. Visualization, sharing and acting upon the information with this inclusive apps platform.

It's possible to virtualize multiple operating systems to one server to max out the value, and virtual capabilities are bundled with the operating system for more flexible licensing. Sever 2008 facilitates dynamic data centers to meet business needs. Optimized for remote access and integrated apps, Terminal Services' Gateway and RemoteApp apply secure app deployment and do not require a VPN (Virtual Private Network).

Sever 2008 does a great job creating a hard operating system with great security features including network access protection, rights management, and read-only domain control. Levels of security which were previously not possible are now available for your business network data, including defense against data failure and network intrusion.

Machines that disobey the company's security policies are isolated by Network Access Protection, which completes ongoing maintenance including checks of compliance and remediation. Sensitive information is persistently protected by Federated Rights Management Services to lower the risk and make compliance possible in a total info protection system. Read-Only Domain Controller deploys Active Directory Domain Services while disallowing copying of the entire data base for better defense against data compromise.

Windows Server 2008, the most robust and flexible OS available, comes with Server Core, Windows Deployment Services, PowerShell, and better clustering technology, providing the best reliability and flexibility for your needs. Faster setup and configuration is possible, as well as easy ongoing management with a unified management console.

PowerShell, a command-line shell with over one hundred tools, uses a script language that lets sysadmins make routine tasks fully automated across servers. The new installation option Server Core has only the required components to provide good server availability with less service updates - without using a graphical user interface.



About the Author
Nick Pegley is a marketing expert with All Covered: Technology Services Partner for Small Business, providing information technology consulting and IT services in 20 major U.S. metro areas. Outsource your procurement, installation and technical headaches.

What Is An Ip Address? Understanding Your Ip Address

by Gabriel Adams

plug itIP stands for Internet Protocol. The IP Address is a number that identifies a computer or router. In order for computers to communicate on a network or on the internet, each computer must be identified somehow, and this is done using private IP addresses (for local networks) and public IP addresses (for the internet).
An IP address, when it comes to the internet, is a number that represents your router. When you connect, this number sends commands out to another IP address to get information.

For example, when you visit a popular website (like Google), your computer doesn't actually send a request for google dot com. The real request that it sends is the IP address of Google's server.

The word-based website addresses (such as www dot whatever dot com) that we use are just there to make the internet more convenient and user-friendly to the average person. In reality, all websites are sending and receiving information using numerical addresses called IP addresses. DNS servers act as liaisons and convert word-based addresses into number-based IP addresses when you go online.

An IP address comprises four groups of numbers separated by a period (or dot or decimal point, whatever you want to call it). There are over 4.2 billion combinations of numbers that can create a unique IP address.

Two Main Types of IP Addresses

There are two main types of IP addresses you may encounter.

One is your private IP address, also known as a local IP address. This is the address that your computer and router use to communicate with each other inside your home.

Private IP addresses are not reachable from the outside world or the internet. The most common private IP address is 192.168.1.1. Most routers default to identifying themselves on your local network as either that address or 192.168.2.1.

A situation where one might need to know their private IP is when port forwarding. Certain online games and other online applications need to access ports on your local computer but a firewall prevents such port traffic.

To bypass this, there is a setting in your router called port forwarding, persistent port forwarding or tunneling wherein your router makes an exception and allows traffic on a certain specified port. The port must be forwarded from router to the local IP (private IP) of your particular computer in order for port-based applications to work.

The other main type of IP address is called a public IP. A public IP address is the one that your router uses to connect to the internet. One instance where a public IP address is important to know is when using a VPN (virtual private network) or VNC (virtual network computing) application.

VPN and VNC applications allow you to create a virtual network that functions just like your local network, with another computer somewhere on the internet (a friend or colleague's office or home, even far away, for example). VNC apps (such as RealVNC) also allow you to control another computer remotely. You can see its screen, control its keyboard and mouse functions and so on.

These applications would not be possible without the use of Public IP addresses for the main connection, and Private IP addresses for the port forwarding to your local computer.

If you do use an application where port forwarding is required, be sure that the port has been opened not only on your router's setup page (usually under security or gaming tabs) but also in your windows firewall. You'll also need to check your anti-virus, anti-spyware, and other similar programs to see if they block ports as well.

Public IP Addresses and Concerns about Privacy and Security

You'll also be interested to know that any activity you do online is traceable back to your Public IP address. This can be averted to some degree by using a proxy server to access the internet. However, no matter how private the internet feels when you are at home, it is a public place. Let your behavior online reflect this lack of true privacy!



About the Author
Want to learn more about your Ip Address? Find Ip Address and Ip Information at our website.

Why use VPN, Anonymizers, Proxy Servers ?

by Patrick Holm

Anonymizers are online services that eliminate the trail of information that you leave behind, whilst surfing, so that your online activities cannot be traced back to you. Web Anonymizers are special web sites that let you access other web sites while making it impossible for them to have any information about you. Anonymizers are a useful tool to ensure that identifying information is not transferred during online interactions in which no personal information need be revealed. Anonymizers are web-based services or downloadable programs that keep your Internet browsing anonymous. Anonymizers are Internet tools developed by the private sector to strip out personal information in order to protect user privacy.

Proxy Anonymizers In computer networks, a proxy server is a server (a computer system or an application program) which services the requests of its clients by forwarding requests to other servers. Using a proxy anonymizer is the most common method of anonymous surfing. A number of free proxy anonymizers use proxy servers from free, open, proxy lists. Many of these lists do indicate whether a proxy is anonymous or not, but sometimes they are not accurate or up-to-date. You will need to be aware that everything you do via these free proxies can be logged and used by the proxy administrators for their own interests and uses. Another problem is that malicious hackers (crackers) and spammers set up proxies in the free proxy lists and can use this source to integrate your computer or collect your personnel information to later send unsolicited emails to you. To anonymize ALL your connections, you will need to use an https proxy anonymizer -- commercial or free proxy anonymizers that use SSH or SSL encryption between the proxy server, website and your computer. Inevitably, by using commercial or free proxy anonymizers, you will have to expect a certain slowdown in your connection speeds. When using an http proxy anonymizer-- http is a standard, unsecured connection -- your IP will not be visible.

VPN connections:

A VPN anonymizer is a technology that establishes a private or secure network connection within a public network, such as the Internet. VPN or what are commonly known as VPN (Virtual Private Network) tunnels, are frequently used by corporations and government bodies, to allow remote workers to make secure internet connections to the office network. VPN is currently the most advanced form of anonymity and data security for use on the Internet. VPN users often have dynamic IP addresses and can have a different IP address with every connection that they make. The main difference between an SSL or SSH encrypted tunnel proxy and VPN (Virtual Private Network) tunnelling, is that VPN doesn't use a proxy and anonymizes and encrypts all activities. Both SSL and SSH encryption can be used with VPN as well as proxy servers.

Conclusion:

Most web-proxy services or anonymizers are not free, but many do offer partial service for free or a free trial period, which might work for you depending on what type of firewall your school or office uses. One of the most common uses for anonymizers is to unblock myspace, or unblock sites which are deemed unsuitable for viewer ship by local ISP (Internet Service Providers). After carrying out several tests on free proxy anonymizers versus paid VPN providers, I would recommend staying clear of the free proxy providers due to the dangers of using them and the generally poor data transfer speed and opt to pay for a strong VPN provider that will ensure quick and reliable performance. One of the best VPN providers to give you this is www.thenetgate.org.

Net Gate is a Secure VPN Messenger & VOIP internet service & community that enables users to access & interact with their social networks, through a totally secure VPN secured platform.




About the Author
Patrick Holm on behalf of www.thenetgate.org