The Problem You receive a Windows 7 access denied error when accessing a folder through Windows Explorer even though you have set the permissions correctly. You are an administrator and the administrators groups have full control over the folder but you can’t access it without Windows re-writing the permissions. The cause of this is because of a new feature in Windows 7 called User Access Control (UAC). It is the combination of UAC and a bug in Windows Explorer that causes the access denied error. The easiest solution is to simply disable UAC. If this is not possible (for security reasons) then read on for alternatives.
The Problem When making audio calls using SIP the phone rings but when it is answered there is only one way audio or no way audio. What Cause One Way Audio The cause of one way audio is a combination of NAT and STUN (which we’ll come onto later). Let’s talk about NAT first. NAT by default blocks ALL incoming connections from the Internet. This is well known and isn’t normally a problem; if you want a server accessible through the Internet you just port forward the relevent ports to it. The issue here is that SIP uses a large range of ports and it will choose one at random for each SIP call. We can’t just open our network up to a massive range of ports, it is bad security practice. More to the point how does it even work if you are not port forwarding any ports? All inbound traffic should be blocked by the NAT because there is no port forwarding going on. So how does it work? It works by using a technique known as UDP Hole punching.
I'm not going to list ALL the differences between TCP and UDP but just the fundamental ones. This article will list them along with the pros and cons of each. Main Characterises of TCP TCP is reliable - This means it guarantees the delivery packets uncorrupted. This is all done by controlling the session with flow control, error detection, congestion control and re-transmission of lost packets. TCP is a connection orientated protocol - This means a connection or socket must first be established before data can flow. Data travels both ways. TCP is ordered - TCP uses sequence numbers to ensure that packets are re-constructed in the correct order. TCP is slower than UDP - Because TCP does all the above there is additional overhead needed and processing time which makes TCP slower than UDP. Main Characteristics of UDP UDP is unreliable - UDP does not guarantee delivery of packets. There is no error detection, flow control or re-transmission of lost packets. It just sends them and doesn't care whether they arrive or not. UDP is a connection-less protocol - Data is just sent and no socket needs to be established first. Data can flow one way (as in a radio broadcast)
This article is to help you understand computer network basics and enable you to troubleshoot network problems by yourself. In this article we will cover the basics of the IP address, subnet mask, router, default gateway and DHCP.
This guide is for Exchange 2007 with ISA 2006. Go here for the BIS ISA Exchange 2003 solution. Ok firstly this guide assumes you know how to configure and publish secure websites through ISA. If you do not know how to do this then read up on it. Until you are confident you can set up and publish websites through ISA using web listeners there is not point continuing. This guide also assumes the ISA and Exchange servers are both in the same domain. If they are not there are additional steps you must take (explained at the end of the guide). The first thing we need to do is enable Forms Based Authentication (from now on called FBA) at the ISA box and disable FBA at the Exchange level (if enabled).
This article is for Microsoft Exchange 2003 and ISA 2004. Go here for the BIS, ISA and Exchange 2007 OWA Solution. This is caused by ISA 2004 being used to do the authentication and not the exchange box itself. I figured this out by investigating why Blackberry phones work perfectly well with an SBS 2003 server (which has ISA2004 and exchange 2003 installed on them) but not when they are installed on separate servers. It is all do to with Outlook forms and how the authentication is handled. When you use Outlook forms for authentication you are prompted with a nice Outlook splash page. At this point you type in your username and password to log in. This feature is enabled by default in a SBS 2003 installation but not with Exchange 2003 on a Windows Standard install. By default (on a win 2k3 std server) you will not get this splash page. Instead you get the grey pop up style box and have to log in this way instead. If you want to allow Outlook forms you must install and configure this component yourself on the exchange box. Now onto ISA.... Out the box ISA comes with Outlook forms
The Problem You move a hard drive from one computer to another but receive a blue screen with a stop 0x0000007b error on boot up. At this point usually your best option is to re-install the OS. Most people however, would prefer not to. This article will show you the various methods I tried including the ones that failed. If you wish to jump straight to the solution read Method 6 but note it requires a Hyper-V server. For the rest of you that STILL think there are other alternatives there aren’t! Still not convinced? Then read on and you will see why…