Procedure of stablishment, erasing of paths and forwarding frames for TCP transport conections and network bridge.

Summary of the technology

The Telematic Services Engineering research group of the University of Alcalá, in collaboration with IMDEA NETWORKS, has developed a mechanism for advanced TCP-Path Ethernet switches that explores a network of transparent bridges to establish a specific path for each new TCP connection established between two terminals. The main applications of this Ethernet switch technology are networks of data centers and computer networks in general, audio-video bridges and other types of transparent Ethernet bridges.
The group is looking for companies in the telecommunications sector with the aim of reaching technical collaboration agreements, commercial agreements or patent licenses.

Details of the Technology Offer

The present invention describes mechanisms that allow to search, establish, use and delete a specific path for each TCP connection established between two terminals and a network bridge that implements said mechanisms. The diversity of the created paths is parameterizable. The invention includes a procedure for establishing paths in the network associated with each new flow of the TCP transport layer when establishing a new TCP connection between two terminals, a procedure for resending frames through that paths and a procedure for deleting them at closing the TCP connections.

These procedures will be applied by TCP-Path bridges that have activated this functionality, configurable according to the requirements of the network.

Establishment of roads

When the ARP-Path path between two terminals A and C is created, a TCP SYN segment is received at the frontier bridge of the sending terminal (A), the segment is encapsulated in a special PathRequest frame with the source address the MAC address of the sending terminal A e protocol identifier (Ethertype) the specific assigned to TCP-Path and associated, in a table, for forwarding purposes, the source MAC addresses and origin TCP port, as well as the identifier of the TCP-Path connection, to the identity of the port of the bridge that first received the frame, an indicator of expiration and the moment of arrival of the frame; and it is forwarded in diffusion through all the ports except the reception port.

In each crossed network bridge the association is made in the same way and, if the port of reception of the frame coming from A is different from the one associated with the path to A already existing, an alternative path is registered associating that port with the tuple. The duplicated PathRequest frames that arrive later by other ports are discarded so that their source MAC address is not associated with the receiving port.

Finally, only a PathRequest packet containing the SYN segment will arrive at the boundary bridge, directly connected to the C terminal. The bridge will de-encapsulate the frame and forward it to terminal C, also associating an expiration identifier with the MAC and TCP origin and at the same time of the arrival of the plot. Terminal C will answer with a SYN + ACK segment confirming the establishment of the TCP connection.

The destination boundary bridge (connected to C) encapsulates the SYN + ACK segment in a PathReply packet with MAC source C address, destination MAC address A and protocol identifier (Ethertype) assigned to the TCP-Path protocol, and forwards it in unicast by the port associated with the AC tuple, previously associated with that port when the PathRequest package was received.

In turn, the bridge associates (learns) the MAC address of C, the MAC address of A, the transport port of C, and the transport port of A to the port through which it was received, identified as the tuple {C, A, pC, pA} (abbreviated, tuple CA), associating them with the previously created expiration identifier of the tuple AC, updating the arrival time, confirming and renewing the validity of the association.

The PathReply packet finally arrives in unicast to the destination border bridge, to which the destination terminal A is directly connected.


Path erasing

If the paths are not used by the frames associated with them (with tuples of transport ports and MAC addresses in the forwarding table) for a time longer than the persistence timer (cache) of the bridges, they expire automatically, erasing from the memory of the ports associated with the road. Likewise, when an established path is interrupted, if a link or bridge fails, the addresses learned in the port are immediately erased, associated in the forwarding table to the port connected to the link or bridge in fault. Similar to the establishment, TCP-Paths can be explicitly deleted by the terminals when they send a FIN segment in each direction to close the TCP connection.

Frame forwarding

When a data frame is received in a TCP-Path bridge, the TCP connection fields are consulted: source and destination of MAC addresses, origin and destination transport ports, and it is verified if there is a port associated with that connection as a destination; if it exists, the frame is forwarded by the port associated with that connection to the destination terminal and the timer associated with the destination MAC address and associated TCP-Path connection is renewed for an additional period; if it does not exist, it is checked, in a less restrictive way, if there is any bridge port associated to the destination MAC address of the frame or to the destination MAC address pair and MAC origin of the frame; If it exists, the frame is forwarded by that port; in other cases, the process of repair of roads will be initiated by sending a multicast frame.

Current development status

Laboratory prototypes

Desired business relationship

Technology selling

Patent licensing

Technology development

New technology applications


The main applications of this Ethernet switch technology are networks of data centers and computer networks in general, audio-video bridges and other types of transparent Ethernet bridges.

Intellectual property status

Related Keywords

  • Communications
  • Data Communications
  • Communications processors/network management
  • Computer related
  • routing
  • ethernet
  • shortest path bridges
  • transport bridge
  • software defined network

About Universidad de Alcalá-OTRI

The Technology Transfer Office at Alcalá University serves as a liaison between the University and its socioeconomic environment in terms of research and innovation. It encorages collaboration between research groups from universities and companies/institutions, with the objective to promote and commercialize research results and scientific capabilities.

Some of the services offered by this office are specified in the following list:

- Promotion of R & D and improvement of the relationships with companies.
- Promote the participation in R & D projects applicants to public calls (regional, national and European).
- Advising, processing and monitoring of patents and other forms of industrial protection.
- Support in the negotiation of contracts and agreements for R&D&i

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