AXC (ATM Cross Connect)

ATM Cross Connect (AXC) is a networking technology used to establish connections between Asynchronous Transfer Mode (ATM) networks. It is a switching device that allows different ATM networks to communicate with each other by providing a bridge between them.

ATM is a high-speed networking technology that uses fixed-sized packets called cells. Each cell is 53 bytes long, consisting of a 5-byte header and a 48-byte payload. The header contains information about the cell's destination and the connection it belongs to, among other things. ATM networks were designed to support real-time applications such as voice and video, as well as high-bandwidth data transfers.

AXC is used to interconnect different ATM networks or segments of the same ATM network. It is a layer-2 device, which means that it operates at the data-link layer of the OSI model. The AXC's primary function is to switch cells between input and output ports based on their destination.

AXC has several key features that make it an important part of ATM networks. These features include:

1. Scalability: AXCs can handle a large number of connections simultaneously, making them suitable for large-scale ATM networks.
2. Traffic management: AXCs can perform traffic management functions, such as congestion control, to ensure that the network operates efficiently.
3. Quality of Service (QoS): AXCs can provide QoS guarantees to applications by prioritizing traffic based on its importance or characteristics.
4. Virtual circuits: AXCs can establish virtual circuits between different ATM networks, which are logical connections that enable communication between two endpoints.
5. Redundancy: AXCs can be configured in a redundant configuration, where a backup device takes over in case the primary device fails.

There are two types of AXC devices: centralized and distributed.

Centralized AXC devices are typically used in large-scale ATM networks, where they are located at a central location and connect multiple ATM switches. They are responsible for switching cells between different ATM networks, as well as performing traffic management and QoS functions.

Distributed AXC devices are used in smaller ATM networks or segments of larger networks. They are typically located closer to the endpoints and are responsible for switching cells within the same network segment.

AXC devices can be configured in several ways, depending on the network's requirements. Some common configurations include:

1. Point-to-point: In this configuration, the AXC establishes a direct connection between two endpoints.
2. Point-to-multipoint: In this configuration, the AXC connects one endpoint to multiple endpoints.
3. Multipoint-to-point: In this configuration, the AXC connects multiple endpoints to a single endpoint.
4. Multipoint-to-multipoint: In this configuration, the AXC connects multiple endpoints to multiple endpoints.

The AXC's operation can be divided into two main phases: cell switching and signaling.

Cell switching is the process of forwarding cells from input ports to output ports based on their destination. The AXC performs this operation by examining the cell's header and forwarding it to the appropriate output port.

Signaling is the process of establishing and tearing down virtual circuits between different ATM networks. This process is essential for enabling communication between two endpoints. The AXC performs signaling by exchanging messages with other devices in the network, such as ATM switches or other AXCs.

In conclusion, ATM Cross Connect (AXC) is a switching device used to interconnect different ATM networks. It provides a bridge between them and enables them to communicate with each other. AXCs are scalable, provide traffic management and QoS functions, and can establish virtual circuits between different ATM networks. There are two types of AXC devices: centralized and distributed. They can be configured in several ways, depending on the network's requirements. The AXC's operation can be divided into two main phases: cell switching and signaling. Cell switching involves forwarding cells from input ports to output ports based on their destination, while signaling involves establishing and tearing down virtual circuits between different ATM networks.

AXC devices use two types of signaling protocols: User-Network Interface (UNI) and Network-Node Interface (NNI). UNI is used between the AXC and ATM endpoints, while NNI is used between different AXCs or ATM switches.

UNI signaling messages are used to establish and tear down virtual circuits between endpoints. The AXC uses UNI signaling to exchange messages with ATM endpoints to negotiate the characteristics of the connection, such as the QoS requirements and the maximum transmission unit (MTU) size. Once the connection is established, cells can be sent between the endpoints.

NNI signaling messages are used to establish and tear down virtual circuits between different ATM networks. The AXC uses NNI signaling to exchange messages with other AXCs or ATM switches to negotiate the characteristics of the connection, such as the QoS requirements and the traffic shaping parameters. Once the connection is established, cells can be switched between the networks.

AXC devices can also perform traffic management functions, such as congestion control and traffic shaping. Congestion control is the process of preventing network congestion by slowing down the transmission rate of cells or discarding cells when the network becomes congested. Traffic shaping is the process of regulating the flow of traffic by delaying or buffering cells to ensure that they are transmitted in a more efficient manner.

AXCs can be configured in a redundant configuration to ensure network availability. In a redundant configuration, two or more AXCs are connected in parallel, with one acting as the primary device and the others acting as backup devices. If the primary device fails, one of the backup devices takes over the switching and signaling functions.

AXCs have several advantages over other networking technologies. First, they provide a high degree of scalability, making them suitable for large-scale ATM networks. Second, they provide QoS guarantees to applications, ensuring that real-time applications such as voice and video are given priority. Third, they can establish virtual circuits between different ATM networks, enabling communication between endpoints. Finally, they can perform traffic management functions, ensuring that the network operates efficiently.

In conclusion, ATM Cross Connect (AXC) is a switching device used to interconnect different ATM networks. It provides a bridge between them and enables them to communicate with each other. AXCs are scalable, provide traffic management and QoS functions, and can establish virtual circuits between different ATM networks. They operate in two phases: cell switching and signaling. Cell switching involves forwarding cells from input ports to output ports based on their destination, while signaling involves establishing and tearing down virtual circuits between different ATM networks. AXC devices use two types of signaling protocols: User-Network Interface (UNI) and Network-Node Interface (NNI). UNI is used between the AXC and ATM endpoints, while NNI is used between different AXCs or ATM switches. AXCs can also perform traffic management functions, such as congestion control and traffic shaping. Finally, AXCs can be configured in a redundant configuration to ensure network availability.