{{Unreferenced, date=December 2009 Dynamic Packet Transport (DPT) is a

Cisco Cisco Systems, Inc., commonly known as Cisco, is an American-based multinational digital communications technology conglomerate corporation headquartered in San Jose, California. Cisco develops, manufactures, and sells networking hardware, ...

transport protocol Transport (in British English), or transportation (in American English), is the intentional movement of humans, animals, and goods from one location to another. Modes of transport include air, land (rail and road), water, cable, pipeline, ...

designed for use in

optical fiber An optical fiber, or optical fibre in Commonwealth English, is a flexible, transparent fiber made by drawing glass ( silica) or plastic to a diameter slightly thicker than that of a human hair. Optical fibers are used most often as a mea ...

ring networks. In overview, it is quite similar to POS and DTM. It was one of the major influences on the

Resilient Packet Ring Resilient Packet Ring (RPR), as defined by IEEE standard 802.17, is a protocol designed for the transport of data traffic over optical fiber ring networks. The standard began development in November 2000 and has undergone several amendments since ...

/802.17 standard.

Protocol design

DPT is implemented as two counter-rotating rings. This means the network is composed of two completely separate rings of fiber that are both able to transmit data concurrently. This design provides for redundancy in case of a fiber cut or link failure, and increased throughput in common situations. DPT as opposed to POS or normal

SONET/SDH Synchronous optical networking (SONET) and synchronous digital hierarchy (SDH) are standardized protocols that transfer multiple digital bit streams synchronously over optical fiber using lasers or highly coherent light from light-emitting diod ...

is able to use both rings at the same time whereas POS only uses one ring under normal circumstances but switches to the second upon failure of the first. Cisco claims that DPT can run with double the bit-rate of POS due to this characteristic. DPT is not a PPP whereas POS is, this means that traffic between two nodes of a DPT ring does not affect intermediate nodes. With the introduction of DPT came the introduction of another Cisco developed MAC layer protocol,

Spatial Reuse Protocol {{About, spatial re-use in optical fiber rings, spatial re-use over-the-air, spatial multiplexing Spatial Reuse Protocol is a networking protocol developed by Cisco. It is a MAC-layer (a sublayer of the data-link layer (Layer 2) within the OSI Mode ...

or SRP. The use of SRP in conjunction with DPT makes it possible for DPT to communicate with the physical layer.

Types of data in DPT networks

As with most other lower layer protocols, there are methods for communicating not only application data between the nodes of a DPT network. It is necessary for the nodes to be able to communicate control data between each other in case of a fiber cut or link failure so the nodes can forward traffic on the appropriate interfaces and maintain network connectivity. Both control

packet Packet may refer to: * A small container or pouch ** Packet (container), a small single use container ** Cigarette packet ** Sugar packet * Network packet, a formatted unit of data carried by a packet-mode computer network * Packet radio, a fo ...

s, and data packets are transmitted on both rings in order to maintain connectivity and full bandwidth utilization in normal situations; but once a failure occurs, the control data will notify the applicable routers of the failure and all the routers will switch to using only their active interfaces for data and control packets.

DPT packet structure

The structure of a DPT Packet is quite similar to that of

Ethernet Ethernet () is a family of wired computer networking technologies commonly used in local area networks (LAN), metropolitan area networks (MAN) and wide area networks (WAN). It was commercially introduced in 1980 and first standardized in 1 ...

. It contains a source and destination MAC address (both 48-bits long), a protocol type identifier (used for identifying the upper layer protocol contained in the payload), and a

frame check sequence A frame check sequence (FCS) is an error-detecting code added to a frame in a communication protocol. Frames are used to send payload data from a source to a destination. Purpose All frames and the bits, bytes, and fields contained within ...

used to validate the data.

DPT topologies

Both DPT and SRP are independent of their physical layers. This means that the DPT protocol can operate above several physical mediums such as SONET/SDH,

Gigabit Ethernet In computer networking, Gigabit Ethernet (GbE or 1 GigE) is the term applied to transmitting Ethernet frames at a rate of a gigabit per second. The most popular variant, 1000BASE-T, is defined by the IEEE 802.3ab standard. It came into use ...

, and others. As aforementioned, DPT is composed of two rings for fault tolerance and increased throughput. The method for switching between these two rings in the event of a failure is called Intelligent Protection Switching, or IPS. This ensures that a fiber cut or link failure (layer 1 error) will be rectified and IP traffic will be resumed within 50 ms. DPT also contains a "plug and play" feature which dynamically fetches the MAC addresses of neighboring devices which provides for very simple configuration with little to no setup prior to functional data transfer. Data transmission Packets (information technology)