# US 2014/0192817 A1 · Virtual link aggregation using state machine

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- Number: US 2014/0192817 A1
- Document ID: US20140192817A1
- Status: Published application
- Kind: A1
- Application number: 13/734,214
- Filed: 2013-01-04
- Published: 2014-07-10
- Earliest claimed: 2013-01-04
- Assignees: International Business Machines Corporation
- Applicants: International Business Machines Corporation
- Inventors: Tamanna Z. Sait; Venkatesan Selvaraj; Shoou Yiu; Yu H. Guo
- Web page: https://patentgrep.com/patent/US20140192817A1

## CPC

- H04L 49/30: {Peripheral units, e.g. input or output ports}
- H04L 45/245: {Link aggregation, e.g. trunking}
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)

## Abstract

Physical links between an access switch and a pair aggregation switches are aggregated into a virtual link aggregation group (vLAG). Each aggregation switch is a local switch to itself and a remote switch to the other aggregation switch. Each aggregation switch maintains a state machine including initialization, local-up, remote-up, and formed states. In the initialization state, the physical link between the access switch and each aggregation switch is down, and the vLAG is down. In the local-up state, just the physical link between the access switch and the local switch is up, and the vLAG is down. In the remote-up state, just the physical link between the access switch and the remote switch is up, and the vLAG is down. In the formed state, the physical link between the access switch and each aggregation switch is up, and the vLAG is up.

## Claims

### Claim 1

A method for virtual link aggregation among physical links between an access switch and a pair of aggregation switches including a local aggregation switch at which the method is performed and a remote aggregation switch, the method comprising:
maintaining a state machine for the local aggregation switch, the state machine comprising a plurality of states include an initialization state, a local-up state, a remote-up state, and a formed state; and
transitioning among the states of the state machine responsive to detecting the physical links between the access switch and the pair of aggregation switches,
wherein in the initialization state, the physical link between the access switch and the local aggregation switch and the physical link between the access switch and the remote aggregation switch are down, and a virtual link aggregation group (vLAG) is down,
wherein in the local-up state, the physical link between the access switch and the local aggregation switch is up, the physical link between the access switch and the remote aggregation switch is down, and the vLAG is down,
wherein in the remote-up state, the physical link between the access switch and the remote aggregation switch is up, the physical link between the access switch and the local aggregation switch is down, and the vLAG is down,
wherein in the formed state, the physical link between the access switch and the local aggregation switch and the physical link between the access switch and the remote aggregation switch are up, and the vLAG is up.

### Claim 2 (depends on 1)

The method of claim 1, further comprising:
from the initialization state, transitioning to the local-up state in response to detecting that the physical link between the access switch and the local aggregation switch is up.

### Claim 3 (depends on 2)

The method of claim 2, further comprising:
from the local-up state, transitioning to the formed state in response to detecting that the physical link between the access switch and the remote aggregation switch is up.

### Claim 4 (depends on 1)

The method of claim 1, further comprising:
from the initialization state, transitioning to the remote-up state in response to detecting that the physical link between the access switch and the remote aggregation switch is up.

### Claim 5 (depends on 4)

The method of claim 4, further comprising:
from the remote-up state, transitioning to the formed state in response to detecting that the physical link between the access switch and the local aggregation switch is up.

### Claim 6 (depends on 1)

The method of claim 1, further comprising:
from the formed state, transitioning to the local-up state in response to detecting that the physical link between the access switch and the remote aggregation switch is down.

### Claim 7 (depends on 6)

The method of claim 6, further comprising:
from the local-up state, transitioning to the initialization state in response to detecting that the physical link between the access switch and the local aggregation switch is down.

### Claim 8 (depends on 1)

The method of claim 1, further comprising:
from the formed state, transitioning to the remote-up state in response to detecting that the physical link between the access switch and the local aggregation switch is down.

### Claim 9 (depends on 8)

The method of claim 8, further comprising:
from the remote-up state, transitioning to the initialization state in response to detecting that the physical link between the access switch and the remote aggregation switch is down.

### Claim 10 (depends on 1)

The method of claim 1, further comprising:
upon transitioning to the formed state, performing one or more vLAG formation processes corresponding to and denoting that the vLAG has been formed.

### Claim 11 (depends on 1)

The method of claim 1, further comprising:
upon transitioning from the formed state, performing one or more vLAG termination processes corresponding to and denoting that the vLAG has been terminated.

### Claim 12 (depends on 1)

The method of claim 1, wherein the vLAG aggregates the physical links between the access switch and the pair of aggregation switches into a virtual link transparent to the access switch.

### Claim 13 (depends on 1)

The method of claim 1, wherein the pair of aggregation switches includes a first aggregation switch and a second aggregation switch,
wherein the method is performed at each of the first aggregation switch and the second aggregation switch,
wherein where the method is performed at the first aggregation switch, the first aggregation switch is the local aggregation switch the second aggregation switch is the remote aggregation switch,
and wherein where the method is performed at the second aggregation switch, the second aggregation switch is the local aggregation switch and the first aggregation switch is the remote aggregation switch.

### Claim 14

An aggregation switch comprising:
a hardware network port to communicate with an access switch over a physical link between the access switch and the aggregation switch, the physical link to be aggregated with a physical link between the access switch and a remote aggregation switch within a virtual link aggregation group (vLAG) corresponding to a virtual link transparent to the access switch;
a communication mechanism to communicate with the remote aggregation switch to receive a status of the physical link between the access switch and the remote aggregation switch as one of up and down; and
logic to maintain a state machine for the aggregation switch by which the aggregation switch is to assist in aggregation of the physical link between the access switch and the aggregation switch and the physical link between the aggregation access switch and the remote aggregation switch as the vLAG.

### Claim 15 (depends on 14)

The aggregation switch of claim 14, wherein the state machine comprises:
an initialization state in which the physical link between the access switch and the aggregation switch and the physical link between the access switch and the remote aggregation switch are down, and the vLAG is down;
a local-up state in which the physical link between the access switch and the aggregation switch is up, the physical link between the access switch and the remote aggregation switch is down, and the vLAG is down;
a remote-up state in which the physical link between the access switch and the remote aggregation switch is up, the physical link between the access switch and the aggregation switch is down, and the vLAG is down; and
a formed state in which the physical link between the access switch and the aggregation switch and the physical link between the access switch and the remote aggregation switch are up, and the vLAG is up.

### Claim 16

A computer program product comprising:
a computer-readable storage medium having executable computer-readable code embodied therein comprising:
first computer-readable code to transition from an initialization state of a state machine for a local aggregation switch to a local-up state in response to detecting that a physical link between an access switch and the local aggregation switch is up;
second computer-readable code to transition from the initialization state to a formed state of the state machine in response to detecting that a physical link between the access switch and a remote aggregation switch is up;
third computer-readable code to transition from the initialization state to a remote-up state of the state machine in response to detecting that the physical link between the access switch and the remote aggregation switch is up; and
fourth computer-readable code to transition from the remote-up state to the formed state in response to detecting that the physical link between the access switch and the local aggregation switch is up,
wherein a virtual link aggregation group (vLAG) aggregates the physical link between the access switch and the local aggregation switch and the physical link between the access switch and the remote aggregation switch into a virtual link transparent to the access switch.

### Claim 17 (depends on 16)

The computer program product of claim 16, wherein the executable computer-readable code further comprises:
fifth computer-readable code to transition from the formed state to the local-up state in response to detecting that the physical link between the access switch and the remote aggregation switch is down;
sixth computer-readable code to transition from the local-up state to the initialization state in response to detecting that the physical link between the access switch and the local aggregation switch is down;
seventh computer-readable code to transition from the formed state to the remote-up state in response to detecting that the physical link between the access switch and the local aggregation switch is down; and
eighth computer-readable code to transition from the remote-up state to the initialization state in response to detecting that the physical link between the access switch and the remote aggregation switch is down.

### Claim 18 (depends on 16)

The computer program product of claim 16,
wherein in the initialization state, the physical link between the access switch and the local aggregation switch and the physical link between the access switch and the remote aggregation switch are down, and the vLAG is down,
wherein in the local-up state, the physical link between the access switch and the local aggregation switch is up, the physical link between the access switch and the remote aggregation switch is down, and the vLAG is down,
wherein in the remote-up state, the physical link between the access switch and the remote aggregation switch is up, the physical link between the access switch and the local aggregation switch is down, and the vLAG is down,
wherein in the formed state, the physical link between the access switch and the local aggregation switch and the physical link between the access switch and the remote aggregation switch are up, and the vLAG is up.