pointer (SDH) (PTR)

The term pointer (PTR) is used in a wide variety of techniques, including Synchronous Digital Hierarchy(SDH), memory technology, and IP addresses.

1. In theSDH hierarchy, a pointer indicates the position of the first channel in the STM data frame. It is the first byte in the STM data frame, i.e. the beginning of a container. Since the information is of particular importance to the receiver, the pointer is protected against bit errors by encoding.
2. In memory technology, a pointer is a link to the stored data. Depending upon storage concept one stores only the Pointer, since these contain the connection to the data records. One saves thereby the storage of metadatas.
3. In the case of IP addresses, a domain name pointer can be used to draw conclusions about the host name. This means that the IP address of a computer can be used to infer its owner. This procedure is also known as reverse DNS. If reverse DNS entries were maintained, this could be an active aid against spam. Since this would simplify authentication.