1. A method comprising:
in response to detection of a break in a network loop in a control plane of a network, sending a special data packet;
unblocking a port if the special data packet fails to circumnavigate the network loop in a data plane of the network, wherein
the port was blocked in response to detection of the network loop in the control plane; and
preventing the port from being unblocked if the special data packet successfully circumnavigates the network loop in the data plane.
2. The method of claim 1, wherein the blocking the port is performed by an instance of a spanning tree protocol.
3. The method of claim 1, wherein the blocking the port is performed by an instance of a ring protocol.
4. The method of claim 1, wherein the sending the special data packet comprises temporarily configuring the port to send the special data packet from the port.
5. The method of claim 4, wherein the temporarily configuring the port comprises generating a forwarding table entry corresponding to the special data packet.
6. The method of claim 1, further comprising:
detecting that the special data packet has successfully circumnavigated the network loop in the data plane if a network device receives the special data packet within a timeout period, wherein
the network device sent the special data packet, and
the network device comprises the port.
7. A network node comprising:
a loop prevention module, wherein
the loop prevention module comprises a control plane loop detection module and a data plane loop detection module, and
a network comprises the network node; and
a port coupled to the loop prevention module, wherein
the loop prevention module is configured to block the port, in response to detection of a network loop in a control plane of the network by the control plane loop detection module,
the data plane loop detection module is configured to send a special data packet, in response to detection of a break in the network loop in the control plane by the control plane loop detection module,
the data plane loop detection module is configured to unblock the port if the special data packet fails to circumnavigate the network loop in a data plane of the network, and
the data plane loop detection module is configured to prevent the port from being unblocked if the special data packet successfully circumnavigates the network loop in the data plane.
8. The network node of claim 7, wherein the loop prevention module implements a spanning tree protocol.
9. The network node of claim 7, wherein the loop prevention module implements a ring protocol.
10. The network node of claim 7, wherein
the data plane loop detection module is configured to temporarily configure the blocked port to send the special data packet from the port.
11. The network node of claim 10, wherein
the data plane loop detection module is configured to temporarily configure the blocked port by generating a forwarding table entry corresponding to the special data packet.
12. The network node of claim 7, wherein
the data plane loop detection module is configured to detect that the special data packet has successfully circumnavigated the network loop in the data plane if the network node receives the special data packet within a timeout period.
13. The network node of claim 12, wherein
the data plane loop detection module is configured to allow the port to be unblocked if the special data packet fails to circumnavigate the network loop in the data plane within the timeout period.
14. A system comprising:
a network comprising a plurality of network nodes, wherein
a first network node of the plurality of network nodes comprises a loop prevention module,
the loop prevention module comprises a control plane loop detection module and a data plane loop detection module, and
the network comprises the first network node of the plurality of network nodes; and
a port coupled to the loop prevention module, wherein
the loop prevention module is configured to block the port, in response to detection of a network loop in a control plane of the network by the control plane loop detection module,
the data plane loop detection module is configured to send a special data packet, in response to detection of a break in the network loop in the control plane by the control plane loop detection module,
the data plane loop detection module is configured to unblock the port if the special data packet fails to circumnavigate the network loop in a data plane of the network, and
the data plane loop detection module is configured to prevent the port from being unblocked if the special data packet successfully circumnavigates the network loop in the data plane.
15. A system comprising:
means for blocking a port in response to detection of a network loop in a control plane of a network;
means for detecting a break in the network loop in the control plane;
means for sending a special data packet around the network loop, in response to detection of the break in the network loop in the control plane;
means for unblocking the port, if the special data packet fails to circumnavigate the network loop in a data plane of the network; and
means for preventing the port from being unblocked if the special data packet successfully circumnavigates the network loop in the data plane.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. An apparatus for foaming a slurry of sand, water and a hydraulic binding medium by adding a foaming agent with a cylindrical vessel for receiving the slurry and an agitator (7) comprises agitating units (10) distributed over the cross section of the vessel, which agitating units each consist of a rotor parallel to the vessel axis with agitator rods (14) between retainers (12,13) on the face side, which rods are distributed over the circumference, are parallel to the axis and can be driven in an alternating manner in opposite directions.
2. An apparatus according to claim 1 wherein, the rotors of the agitator (7) comprise drive shafts (11) which are operatively connected at least in groups by way of mutually combing gearwheels (16).
3. An apparatus according to claim 1, wherein the retainers (12, 13) for the agitator rods (14) can sit on the drive shafts (11) of the agitating units (10) and that the agitator rods (14) of the agitating units (10) enclose the respective drive shaft (11) in at least one concentric pitch circle.
4. An apparatus according to claim 3, wherein the agitator rods (14) of the agitating units (10) are mutually arranged in at least two concentric pitch circles in an offset manner to form a gap with respect to the respective drive shaft (11).
5. An apparatus according to claim 1, wherein the relative direction of rotation between the vessel (2) and the agitator (7) is reversible.
6. An apparatus according to claim 1, wherein the rotational speed of the agitating units (11) is controllable depending on the degree of foaming.