Captain ATM Simulator - Instructions

 

"Captain ATM" is a tool for designing and simulating an ATM network. This section describes each of the features "Captain ATM" supplies.

 

 

GUI Description

 


 

The Toolbar

The toolbar contains all the construction/deconstruction tools. The toolbar can be undocked by dragging and placed anywhere on the screen. Pressing the 'x', to close the toolbar, will return it to its original location. Here is a brief explanation of the function of each of the tools (more detailed explanations appear in the different sections):

 

Image

Name

Description

 


 

 

Add End System

 

Creates an icon, that represents an End System, on the upper left corner of the Working Area. An End System is either a router or an actual computer.

 

 


 

 

Add Switch

 

Creates an icon, that represents an ATM switch, on the upper left corner of the Working Area.

 

 


 

 

Remove Switch/End System

 

The user can choose a single Switch or End System and by clicking it - remove it from the Working Area. The removal will also affect any PVCs and SVCs that passed through the Switch/End System. Pressing the button again will abort the deletion mode, without needing to remove a Switch or an End System.

 

 

 

Add connections

 

 

As long as the button isn't pressed again, each time the user clicks two Devices (a Device is either a Switch or an End System) a physical connection is created between them and a connecting line is drawn between them in the Working Area. However, there're some restrictions:

 

  • It is not possible to connect two End Systems since such a connection is trivially not a part of an ATM network, and will have no use for the purposes of this applet.

 

  • An End System can't be directly connected to more than one Switch. Again, this restriction reflects the actual structure of an ATM network.

 

As mentioned above, pressing the button again aborts the connecting mode.

 

 


 

 

Remove connection

 

The user can delete a single connecting line by pressing the two Devices on both ends of the line. The removal will also affect any PVCs and SVCs that passed through the connecting line. Pressing the button again will abort the deletion mode, without needing to remove a connecting line.

 

 


 

 

Order PVC

 

 

The user will be asked to choose between "Automatic" and "Manual" creation modes:

 

  • Automatic – "Captain ATM" will find a path between two selected (clicked) End Systems. If no path exists, an error message will be generated.

 

  • Manual – The user can define a path manually, by clicking each Device in the path. Trivially, the first Device clicked must be an End System and each clicked Switch must be connected by a connecting line to the previous Device. The path definition is completed once another End System is clicked.

 

After the path is defined (by whatever method) the user will be asked to confirm the PVC. Pressing "OK" will configure the network and will set-up the PVC. Pressing "Cancel" will cancel the creation of the PVC. Pressing the button again will abort the PVC creation mode, without needing to set a PVC.

 

 


 

 

Order SVC

 

 

The user will be asked to choose between "Automatic" and "Manual" creation modes:

 

  • Automatic – "Captain ATM" will find a path between two selected (clicked) End Systems. If no path exists, an error message will be generated.

 

  • Manual – The user can define a path manually, by clicking each Device in the path. Trivially, the first Device clicked must be an End System and each clicked Switch must be connected by a connecting line to the previous Device. The path definition is completed once another End System is clicked.

 

After the path is defined (by whatever method) the user will be asked to confirm the SVC. Pressing "OK" will configure the network and will set-up the SVC. Pressing "Cancel" will cancel the creation of the SVC. Pressing the button again will abort the SVC creation mode, without needing to set an SVC.

 

 


 

 

Send A Message

 

 

Clicking two End Systems will pop-up a message that asks the user to authorize the message between the two selected End Systems. Trying to send a message between two End Systems that aren't connected by a Virtual Circuit (either PVC or SVC) will issue an error message. Pressing the button again will abort the message sending mode, without needing to send the message.

 

 


 

 

Clear all

 

 

Empties the Working Area.

 

 

 

 

The Working Area


This is where all the components of the network are placed. The End Systems and the Switches can be moved around.

 

 

The System Console


This is where messages regarding the processes (e.g. – call setting) that take place in the network are logged.

 

 

The Status Line


This is where the status of the system is shown. If the system is idle and ready to perform actions "Ready" is displayed.

 

 

 

Features' Details



 

End Systems' and Switches' Internal Information


 

Placing the mouse curser over an End System or a Switch will display its name (or ID).

Double-clicking a Device will display its routing table, if available (when this Device is part of a Virtual Circuit), or an appropriate message about its current state.

 

 

End Systems' and Switches' IDs


 

Unlike in a real ATM network, "Captain ATM" doesn't use AESAs to identify the End Systems. The End Systems and the Switches are both identified by simple integers preceded by one letter – 'e' for End Systems and 's' for Switches. Hence, "e7" is a typical ID for an End System and "s10" is a typical ID for a Switch.

This is done in order to simplify devices identification by the user. For more information about AESAs - see ATM in a nutshell - ATM Addressing.

 

 

Virtual Circuits


 

Unlike in a real ATM network, we use only VCIs - Virtual Channel Identifiers for switching purposes (real networks use VPIs - Virtual Path identifiers as well). This is done due to our desire to focus on the Virtual Circuit creation process, rather than on the different types of Virtual Circuits. For more information about Virtual Circuits - see ATM in a nutshell - ATM Connections.

In real networks the VCI values ranged from 0 to 31 are reserved for different signaling operations. We don't use those reserved VCI values for VC switching purposes as well.

A real ATM cell contains 2 bytes that hold the VCI, and according to that, the VCI values we generate move from 32 to 65535. For more information about ATM cells - see ATM in a nutshell - Cell Format.

 

Permanent Virtual Circuit (PVC) – Once configured, the VC stays permanent unless disrupted by removing a Device or an End System.

 

Switched Virtual Circuit (SVC) – Once configured, the VC stays for a symbolic period of 30 seconds. The counting of this period is restarted each time a message is sent using the SVC. The reason for this timeout is our desire to emphasize the locality of an SVC (compared to PVC). In real life, an SVC stays configured for the duration of the call. Here we simulate such a call by setting the timeout described. Once an SVC is authorized, "Captain ATM" simulates a Call Setup. Since a real call setup involves, in most cases, a reply ("CALL PROCEEDING" and "CONNECT ACK") from each switch to the previous Device on the path, as well as a message to the next Device on the path ("SETUP" and "CONNECT"), the result of animating such a process will just cause a lot of mess on the Working Area that the user will find difficult to follow. "Captain ATM" animates the call-setup process as one message to each direction, while the System Console shows more accurate details. Once an SVC expires, all related entries in the involved Devices are removed.

For more information about Call Setup - see ATM in a nutshell - ATM Connections - Signaling.

 

 

Effect of Component Removal

 

Unless a VC is involved, the effect of removing a component (End System, Switch or connecting line) is trivial - it's graphically removed from the Working Area. However, in most cases a VC WILL be involved. As a rule of thumb, if an SVC is damaged - it's simply removed as though it was expired, and in the case of damaging a PVC -  "Captain ATM" will try to re-establish the connection by finding an alternate path. If this attempt fails - an error message will be issued. There're two cases in which no such attempt is made:

 

  • If an End System is removed, there's, obviously, no way that the PVCs it was part of could be re-established.
  • If a connecting line that connects an End System to a Switch is removed, it means the End System is now physically disconnected from the rest of the network and there's no way the PVCs it was part of could be re-established.