# US 9,882,838 B2 · Forwarding inter-switch connection (ISC) frames in a network-to-network interconnect topology

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- Number: US 9,882,838 B2
- Document ID: US9882838B2
- Status: Granted
- Kind: B2
- Application number: 15/242,633
- Filed: 2016-08-22
- Published: 2016-12-08
- Granted: 2018-01-30
- Earliest claimed: 2011-03-10
- Assignees: Extreme Networks, Inc.
- Applicants: Extreme Networks, Inc.
- Inventors: Stephen R. Haddock
- Web page: https://patentgrep.com/patent/US9882838B2

## CPC

- H04L 49/15: Interconnection of switching modules
- H04L 12/4633: {Interconnection of networks using encapsulation techniques, e.g. tunneling}
- H04L 45/58: Association of routers
- H04L 49/253: using establishment or release of connections between ports
- H04L 45/12: Shortest path evaluation
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)

## Abstract

Systems, mechanisms, apparatuses, and methods are disclosed for forwarding Inter-Switch Connection (ISC) frames in a Network-to-Network Interconnect (NNI) topology, for example, via a network switch which includes a first physical switch port to receive a physical switch link from a second network switch; logic to implement a first logical ISC and a second logical ISC′ connection to the second network switch via the physical switch link; a second physical switch port to receive an interface connection from a third network switch; and switch forwarding logic to forward frames received at the first network switch to the second network switch via the logical ISC or logical ISC′ based on whether or not the physical switch link is part of an active topology upon which the network switch operates or is not part of the active topology upon which the network switch operates. Other embodiments are disclosed.

## Claims

### Claim 1

A first network switch, comprising:
a first network switch element coupled to a physical switch link to transmit a first untagged and not encapsulated frame for a local network over a first logical connection of the physical switch link to a first network switch element of a second network switch coupled to the physical switch link, when the physical switch link is part of an active topology of the local network; and
a second network switch element coupled to the physical switch link to transmit a second untagged and not encapsulated frame for a foreign network over a second logical connection of the physical switch link to a second network switch element of the second network switch coupled to the physical switch link, when the physical switch link is not part of the active topology of the local network, wherein the first network switch element and the second network switch element are nodes within the active topology of the network for receiving frames; and
wherein the first network switch and the second network switch select a link for transmitting each received frame, wherein the selection is made dependent upon a gateway selection rule stipulating that any node receiving a frame on a link other than the first logical connection is designated as a gateway for that received frame, wherein the gateway selection rule is utilized when the physical switch link is part of the active topology upon which the first network switch operates and when the received frame is not associated with a pre-determined link selection.

### Claim 2 (depends on 1)

The first network switch of claim 1, wherein, when the physical switch link is not part of the active topology of the local network, the first network switch element is configured to determine whether the physical switch link is blocked according to a loop prevention protocol.

### Claim 3 (depends on 2)

The first network switch of claim 2, wherein the first network switch element and the second network switch element transmit their respective untagged and not encapsulated frames at different times.

### Claim 4 (depends on 2)

The first network switch of claim 2, wherein the first network switch element of the first network switch is a node in the local network and wherein the second network switch element of the first network switch is a node in the foreign network.

### Claim 5 (depends on 2)

The first network switch of claim 2, wherein the second network switch element is coupled to a third network switch via a connection consisting of one of:
a Network-to-Network Interface (NNI) connection; or
a Multi-system Link Aggregation (MLAG) connection.

### Claim 6 (depends on 5)

The first network switch of claim 5, wherein the third network switch operates in the foreign network.

### Claim 7 (depends on 6)

The first network switch of claim 6, wherein the connection coupling the second network switch element to the third network switch is a first connection, and wherein the second network switch is coupled to the foreign network via a second connection that does not include the first connection.

### Claim 8 (depends on 2)

The first network switch of claim 2, wherein the first network switch further comprises:
memory to store instructions comprising switch forwarding logic; and
a processor to execute the instructions comprising switch forwarding logic.

### Claim 9 (depends on 8)

The first network switch of claim 8, wherein the switch forwarding logic is configured to monitor whether the physical switch link is part of the active topology of the local network.

### Claim 10 (depends on 2)

The first network switch of claim 2, wherein the first network switch is further configured to identify a Virtual Local Area Network Identifier (VLAN ID) related to the first untagged and not encapsulated frame.

### Claim 11 (depends on 10)

The first network switch of claim 10, wherein the first network switch is configured to identify a network switch element based on the identified VLAN ID, wherein the second network switch element is configured to transmit the first untagged and not encapsulated frame to the identified network switch element.

### Claim 12 (depends on 11)

The first network switch of claim 11, wherein the identified network switch element is the first network switch element.

### Claim 13 (depends on 2)

The first network switch of claim 2, wherein the first network switch is configured to identify a Service Identifier related to the first untagged and not encapsulated frame.

### Claim 14 (depends on 13)

The first network switch of claim 13, wherein the second network switch element is configured to select a link for transmitting each received frame based on a given service type, the given service type being designated by a field within each frame.

### Claim 15 (depends on 2)

The first network switch of claim 2, wherein the second network switch element is configured to deterministically discard a received frame based on a data field in the received frame.

### Claim 16 (depends on 2)

The first network switch of claim 2, wherein the first network switch is configured to transmit to the foreign network.

### Claim 17 (depends on 2)

The first network switch of claim 2, wherein the physical switch link is part of the active topology upon which the first network switch operates when the physical switch link has not been blocked by a loop prevention algorithm; and
wherein the physical switch link is not part of the active topology upon which the first network switch operates when the physical switch link has been blocked by a loop prevention algorithm.

### Claim 18 (depends on 2)

The first network switch of claim 2, wherein the physical switch link is part of the active topology of the local network upon which the first network switch operates during receipt of a first set of received frames;
wherein the physical switch link is transitioned to not being part of the active topology of the local network upon which the first network switch operates responsive to a topology change for the local network; and
wherein the physical switch link is not part of the active topology of the local network upon which the first network switch operates during receipt of a second set of received frames.

### Claim 19 (depends on 18)

The first network switch of claim 18, wherein the first set of received frames and the second set of received frames are disjoint sets.

### Claim 20 (depends on 2)

The first network switch of claim 2, wherein when the physical switch link is part of the active topology of the local network comprises when the first logical connection of the physical switch link is part of the active topology of the local network.