Learning IOS and JUNOS

You may have heard of denial-of-service attacks launched against websites, but you can also be a victim of these attacks. Denial-of-service attacks can be difficult to distinguish from common network activity, but there are some indications that an attack is in progress. What is a denial-of-service (DoS) attack? In a denial-of-service (DoS) attack, an attacker attempts to prevent legitimate users from accessing information or services. By targeting your computer and its network connection, or the computers and network of the sites you are trying to use, an attacker may be able to prevent you from accessing email, websites, online accounts (banking, etc.), or other services that rely on the affected computer. The most common and obvious type of DoS attack occurs when an attacker "floods" a network with information. When you type a URL for a particular website into your browser, you are sending a request to that site's computer server to vie...

The DISA, Direct Inward System Access, application allows someone from outside the telephone switch (PBX) to obtain an "internal" system dialtone and to place calls from it as if they were placing a call from within the switch. DISA plays a dialtone. The user enters their numeric passcode, followed by the pound sign (#). If the passcode is correct, the user is then given system dialtone on which a call may be placed.

There are two types of circuits an enterprise can use to route 911 calls to the proper PSAPs (public safety answering points) and deliver the 10-digit caller ID: ISDN PRIs or Centralized Automatic Message Accounting (CAMA) trunks. "ISDN is the wea port of choice from our perspective," says Guy Clinch, Avaya's government solutions director and a member of the National Emergency Number Association's PBX/multi-line telephone system technical subcommittee, because you can fit more phone lines in a PRI and assign each of those numbers to represent a separate ERL. In short, you can map your location and send more granular location information to the PSAP. But as many as 85% of enterprises choose instead to retrofit their IP PBXs using legacy analog CAMA trunks for entry into the public safety system, Clinch says. It's cheaper, because the CAMA trunk is equivalent to on phone number, so they get charged only once. The downside: CAMA trunks cannot deliver a custom caller ...

Cisco Monitor Director , a centralized proactive solutions-management tool for Cisco channel partners to offer multicustomer outsourced 24-hour network management services. It communicates with the Cisco Monitor Manager residing on a customer's premises to provide comprehensive, real-time monitoring, alerting and reporting to help troubleshoot and fix issues remotely. Combining these management tools helps enable Cisco channel partners become trusted advisers to their customers.

The Smart Phone Control Protocol, or SPCS, is an addition to the Simple Call Control Protocol (SCCP) that is only supported on the CP-500 phones and the SPA525 phone. 79XX phones register with their SCCP call control using a proprietary handshake that consists of a series of messages. During the registration phase a number of things happen: 1. Phone (Station) sends a Registration Request 2. Request is acknowledged by the Call Control (CME/UC500) 3. Capabilities are advertised 4. Button template, Softkeys, Line Status, Display message, Speed dials Time and date are requested by the phone and sent by CME/UC500 When the phone is a 500 series phone, two additional messages precede all this handshake, namely an SPCP Token Request and an SPCP Token Acknowledgement (if successful) or Token rejection (if unsuccessful). A Token ACK can only be sent by UC500 , while an ISR will always send a Token Reject . This prevents the phone from registering to any call control different than UC500.

2008/08/27-杜念魯 所謂的PTZ攝影機，其實與一般的監控用攝影機並沒有太多的差異，但是所謂的PTZ則是表示攝影機的鏡頭可以進行左右轉動(Pan)、上下傾斜(Tilt)與放大(Zoom)等不同的功能。 而透過PTZ攝影機，可以隨時改變攝影的角度與所涵蓋的範圍與清晰度，相較於傳統僅能單一運動的攝影機，可以獲得更好的監控效果。而且透過多台PTZ攝影機之間在空間位置上的相互關係，更有利於智慧型監控目的的達成。所以PTZ攝影機在目前監控市場中，已經成為多數使用者所偏好的產品。