1. A tunnel endpoint device comprising:
a network interface connected to a local area network having a cluster of tunnel endpoint devices, the tunnel endpoint device being one of the cluster, the network interface configured to receive a Start-Control-Connection-Request (SCCRQ) message via the local area network to initiate establishment of a tunnel connection, wherein the SCCRQ includes a destination address field modified to be set to a local address of the tunnel endpoint device and a tunnel ID value assigned by a tunnel initiator to the tunnel connection being set-up;
means for forming a Start-Control-Connection-Reply (SCCRP) message having an address of the tunnel initiator, the tunnel ID value assigned to the tunnel connection by the tunnel initiator, and a tunnel ID value assigned to the tunnel connection by the tunnel endpoint device; and
means for transmitting the SCCRP message to a network address translation server via the network interface.
2. The tunnel endpoint device of claim 1, further comprising means for receiving a Start-Control-Connection-Connected (SCCN) message to establish a tunnel connection between the tunnel initiator and the tunnel endpoint device.
3. The tunnel endpoint device of claim 1, further comprising means for forming load status messages that indicate a current traffic load of the tunnel endpoint device.
4. A cluster master device comprising:
a first interface coupled to a first network having a plurality of network devices; and
a second interface for communicating with a second network,
wherein the cluster master device has a master global address that is unique on the second network, and
wherein the cluster master device is configured to receive from the second network tunnel connection request messages having the master global address in a destination address field and, for each tunnel connection request message received:
(i) select one of the plurality of network devices;
(ii) insert a local address for the selected network device into the destination address field of the received tunnel connection request message; and
(iii) transmit the received tunnel connection request message as modified over the first network interface onto the first network.
5. The cluster master device of claim 4, wherein the cluster master device selects one of the plurality of network devices based on a traffic load of each network device.
6. The cluster master device of claim 4, wherein the cluster master device receives load status messages from each network device and assigns the received tunnel connection request message to the network device that currently has the lowest traffic load as indicated by the load status messages.
7. The cluster master device of claim 4, wherein the tunnel connections are Layer 2 Tunneling Protocol (L2TP) connections.
8. The cluster master device of claim 4, wherein the first network is a local area network (LAN) and the second network is an Internet protocol (IP) network.
9. The cluster master device of claim 4, wherein the tunnel connection request messages include a source address field set to an IP address of a tunnel initiator, and a source tunnel ID field set to a tunnel ID value assigned to the tunnel connection by the tunnel initiator.
10. The cluster master device of claim 4, wherein the cluster master device keeps track of network devices that are out of service or temporarily inactive.
11. A method for terminating tunnel connections comprising:
receiving a tunnel connection request message;
receiving a load status message from each tunnel endpoint device of a plurality of tunnel endpoint devices on a network;
based on the load status messages, selecting a tunnel endpoint device to receive the tunnel connection request message; and
assigning the tunnel connection request message to the selected tunnel endpoint device.
12. The method of claim 11, wherein selecting the tunnel endpoint device to receive the tunnel connection request message comprises:
based on the load status messages, determining which tunnel endpoint device has the lowest load; and
selecting the tunnel endpoint device that has the lowest load.
13. The method of claim 11, wherein assigning the tunnel connection request message to the selected tunnel endpoint device comprises:
inserting a local address for the selected tunnel endpoint device into a destination address field of the tunnel connection request message; and
transmitting the tunnel connection request message as modified onto the network.
14. A method for terminating tunnel connections comprising:
receiving tunnel connection request messages having a master global address in a destination address field and, for each tunnel connection request message received:
selecting one of a plurality of network devices connected to a network;
inserting a local address for the selected network device into the destination address field of the received tunnel connection request message; and
transmitting the received tunnel connection request message as modified onto the network.
15. The method of claim 14, further comprising transmitting a tunnel set-up reply message over the network, wherein the tunnel set-up reply message includes a source address field having the address of the selected network device.
16. The method of claim 15, wherein transmitting the tunnel set-up reply message over the network comprises:
transmitting the tunnel set-up reply to a network address translation (NAT) server;
replacing the address of the selected network device in the source address field of the tunnel set-up reply message with a global address for the NAT server;
storing a table entry accessible to the NAT server that relates the global address to the address of the selected network device; and
transmitting the tunnel set-up reply message onto the network.
17. The method of claim 14, wherein selecting one of the plurality of network devices connected to the network comprises selecting one of the plurality of network devices based upon a traffic load on each of the network devices.
18. The method of claim 14, further comprising receiving load status messages from each of the plurality of network devices.
19. The method of claim 18, wherein selecting one of the plurality of network devices connected to the network comprises selecting one of the plurality of network devices based upon which network device currently has the lowest load as indicated by the load status messages.
20. The method of claim 14, wherein the tunnel connections are Layer 2 Tunneling Protocol (L2TP) connections.
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. A backplane comprising:
a) a first region having a first plurality of signal launches positioned in a first plurality of groups, the signal launches in each of the first plurality of groups positioned for interconnection to at least one electrical connector;
b) a second region adjacent the first region having a second plurality of signal launches positioned in a second plurality of groups, the signal launches in each of the second plurality of groups positioned for interconnection to at least one electrical connector, with each of the groups of the second plurality of signal launches disposed in at least a first column and a second column; and
c) a plurality of groups of signal traces each having a first end and a second end, wherein, for each group of signal traces, the first ends of the traces are connected to signal launches in a group in the first plurality of groups, and
i) for a first portion of the traces in the group, the second ends of the traces are connected to signal launches in a group in the first column; and
ii) for a second portion of the traces in the group, the traces are routed between groups of signal launches in the first column and the second ends of the traces are connected to signal launches in a group in the second column:
2. The backplane of claim 1 having a plurality of connector modules mounted thereto, each connector module interconnected to the signal launches in one of the plurality of groups.
3. The backplane of claim 1 wherein the backplane consists of less than 10 routing layers.
4. The backplane of claim 3 wherein the backplane has between 3 and 5 routing layers.
5. The backplane of claim 4 wherein the first column and the second column each comprises at least 800 signal launches.
6. The backplane of claim 1 wherein both the first portion of the traces in each of the plurality of groups of signal traces and the second portion of the traces in each of the plurality of groups of signal traces comprises at least 40 traces.
7. The backplane of claim 6 wherein the traces in both the first portion of the traces in each of the plurality of groups of signal traces and the second portion of the traces in each of the plurality of groups of signal traces are positioned in pairs.
8. The backplane of claim 7 wherein the on-center spacing between adjacent pairs is greater than 1.22 mm.
9. The backplane of claim 1, further comprising:
a third region having a third plurality of signal launches positioned in a third plurality of groups, the signal launches in each of the third plurality of groups positioned for interconnection to at least one electrical connector.
10. An electronic assembly comprising the backplane of claim 9, additionally comprising:
a) a first plurality of backplane connectors connected to the first plurality of signal launches;
b) a second plurality of backplane connectors connected to the second plurality of signal launches;
c) a third plurality of backplane connectors connected to the third plurality of signal launches;
d) a plurality of daughter cards having daughter card connectors engaged to the first plurality of backplane connectors;
e) a plurality of a daughter cards having daughter card connectors engaged to the second plurality of backplane connectors; and
f) a plurality daughter cards having daughter card connectors engaged to the third plurality of backplane connectors.
11. The electronic assembly of claim 10 wherein the plurality of daughter cards engaged to the second plurality of backplane connectors comprise switch cards.
12. The electronic assembly of claim 11 wherein plurality of daughter cards having daughter card connectors engaged to the first plurality of backplane connectors comprise IO cards.
13. The backplane of claim 9 further comprising:
a second plurality of groups of signal traces each having a first end and a second end, wherein, for each group in the second plurality of groups of signal traces, the first end of each trace is connected to a signal launch in a group in the third plurality of groups and
i) for a first portion of the traces in the group, the second ends of the traces are connected to signal launches in a group in the second column; and
ii) for a second portion of the traces in the group, the traces are routed between groups of signal launches in the second column and the second ends of the traces are connected to signal launches in a group in the first column.
14. A backplane comprising:
a) a first plurality of groups of backplane connector modules including at least a first central group and a second central group, each group disposed in a column, with the columns being parallel, with each connector module having a plurality of contact tails and the connector modules being positioned to leave spaces between modules in each column;
b) a second plurality of groups of backplane connector modules, each group disposed in a column, with each connector module having a plurality of contact tails and with the columns being parallel to the columns of the first plurality of groups, and the columns being disposed on a first side of the first central group and the second central group;
c) a third plurality of groups of backplane connector modules, each group disposed in a column, with the columns being parallel to the columns of the first plurality of groups, with each connector module having a plurality of contact tails and the columns being disposed on a second side of the first central group and the second central group;
d) a first plurality of groups of signal traces, each group connecting contact tails of a first module in each of the second plurality of groups to contact tails of a module in the first central group;
e) a second plurality of groups of signal traces, each group connecting contact tails of a second module in each of the second plurality of groups to contact tails of a module in the second central group, each group of signal traces in the second plurality of groups passing through a space between adjacent connector modules in the first central group;
f) a third plurality of groups of signal traces, each group connecting contact tails of a first module in each of the third plurality of groups to contact tails of a module in the second central group; and
g) a fourth plurality of groups of signal traces, each group connecting contact tails of a second module in each of the third plurality of groups to contact tails of a module in the first central group, each group of signal traces in the fourth plurality of groups passing through a space between adjacent connector modules in the second central group.
15. The backplane of claim 14 wherein the backplane connector modules in the first plurality of groups have contact tails disposed in a regular rectangular array.
16. The backplane of claim 14 wherein the backplane connector modules in each of the first, second and third plurality of groups have contact tails spaced by 2 mm or less on center.
17. The backplane of claim 16 wherein the backplane connector modules in each of the first, second and third plurality of groups comprise greater than or equal to 40 pairs.
18. The backplane of claim 16 further comprising a dielectric substrate with the first, second, third and fourth signal traces disposed on routing layers formed in the substrate.
19. The backplane of claim 18 comprising ten or fewer routing layers.
20. The backplane of claim 19 wherein the first, second, third and fourth plurality of groups of signal traces comprise pairs of signal traces, each pair having an impedance between 90\u03a9 and 110\u03a9.
21. The backplane of claim 20 wherein the substrate comprises a material having a loss tangent between 0.007 and 0.025.
22. A method of designing a backplane for an electronic system having a plurality of first type daughter cards each having a plurality of connections to at least two second type daughter cards, with each first type daughter card connected to the backplane at a point that is nearer to the connection point for one of the second type daughter cards than to the connection point for another of the second type daughter cards, the method comprising:
a) generating a schematic for the backplane;
b) generating a netlist from the schematic;
c) back annotating the schematic to direct traces carrying signals from a daughter card to a further one of the second type daughter cards to pass in groups through routing channels between connectors for attaching to a nearer one of the second type daughter cards; and
d) re-generating the netlist from the back annotated netlist.
23. The method of claim 22 wherein the netlist is generated with a CAD tool.