System for providing fair access for VLANs to a shared transmission medium

• US 6,470,025 B1
• Filed: 02/02/1999
• Issued: 10/22/2002
• Est. Priority Date: 06/05/1998
• Status: Expired due to Term

• Current Assignee: 3COM Technologies
• Original Assignee: 3COM Technologies
• Inventors: Wilson, Peter J., Moran, Paul J.
• Primary Examiner(s): NGUYEN, STEVEN H D
• Application Number:
  US09/241,477
• Time in Patent Office: 1,358 Days
• Field of Search: 370/229-236, 370/411-418, 370/468, 370/397, 370/428, 370/429, 370/444, 370/445, 370/447, 370/448, 370/461-462, 370/395--39, 709/224, 709/225, 709/226, 709/229, 709/227, 709/228, 709/233, 709/235, 709/240
• US Class Current: 370/462
• CPC Class Codes: H04L 12/4641 Virtual LANs, VLANs, e.g. virtual private networks [VPN] LAN interconnection over a bridge based backbone H04L12/462; encapsulation techniques H04L12/4633; routing of packets H04L45/00; packet switches H04L49/00; virtual private networks for security H04L63/0272
• CPC Class Codes: H04L 43/0876 Network utilisation, e.g. volume of load or congestion level
• CPC Class Codes: H04L 43/16 Threshold monitoring
• CPC Class Codes: H04L 43/20 the monitoring system or the monitored elements being virtualised, abstracted or software-defined entities, e.g. SDN or NFV
• CPC Class Codes: H04L 47/10 Flow control; Congestion control
• CPC Class Codes: H04L 47/12 Avoiding congestion; Recovering from congestion
• CPC Class Codes: H04L 47/13 in a LAN segment, e.g. ring or bus
• CPC Class Codes: H04L 47/21 using leaky-bucket
• CPC Class Codes: H04L 47/70 Admission control; Resource allocation
• CPC Class Codes: H04L 47/745 Reaction in network

Abstract

A method of controlling access to a common physical data transmission link from a multiplicity members of a packet-based local area network, wherein the members are partitioned into a plurality of virtual local area networks (VLANs) and wherein packets are identified according to the virtual local area network from which they come, comprises (a) monitoring packet traffic from the virtual local area networks on the link and thereby obtaining measures of the traffic flow from each of the virtual local area networks; (b) determining whether the traffic flow for each respective VLAN is above or below a threshold; (c) denoting a VLAN which is above its threshold as in a restricted state and denoting a VLAN which is below its threshold as in a priority state; (d) arbitrating between requests from the VLANs to transmit data packets on the link; and (e) according priority in the arbitration to a VLAN which is in a priority state over any VLAN which is in a restricted state. A request to transmit is gated with a signal denoting the state of the respective VLAN to provide a set of priority requests. In response to the presence of any priority request the arbitration is made only in respect of the set of priority requests and in the absence of a priority request arbitration is made in respect of the VLANs which indicate a request to transmit. A ‘leaky bucket’ counter may be used for monitoring the traffic for each VLAN.

Claims

1. A method of controlling access to a common physical data transmission link from a multiplicity of members of a packet-based local area network wherein the members are partitioned into a plurality of virtual local area networks (VLANs) and wherein packets are identified according to the virtual local area network from which they come, the method comprising:

(a) monitoring packet traffic from the virtual local area networks on said common physical data transmission link and thereby obtaining measures of the traffic flow from each of the virtual local area networks;

(b) determining whether the traffic flow for each respective VLAN is above or below a threshold;

(c) denoting a VLAN which is below its threshold as in a priority state and denoting a VLAN which is above its threshold as in a restricted state;

(d) arbitrating between requests from the VLANs to transmit data packets on said common physical data transmission link; and

(e) according priority in the arbitration to a VLAN requesting to transmit which is also in a priority state over any request from a VLAN which is in a restricted state.

2. A method according to claim 1 wherein each request to transmit is gated with a signal denoting the state of the respective VLAN to provide a set of priority requests and wherein:

in response to the presence of any priority request the arbitration is made only in respect of the set of priority requests, and

in the absence of a priority request, arbitration is made in respect of the VLANs which request to transmit.

3. A method according to claim 1 wherein the traffic flow from each VLAN is monitored by means of a counter which is decremented at a fixed rate and is incremented in accordance with the traffic flow for its respective VLAN which is denoted as in the restricted state when the counter attains a threshold count.

4. A method according to claim 2 wherein the traffic flow from each VLAN is monitored by means of a counter which is decremented at a fixed rate and is incremented in accordance with the traffic flow for its respective VLAN which is denoted as in the restricted state when the counter attains a threshold count.

5. A device for monitoring and controlling a traffic flow from each of a plurality of VLANs over a common physical data link, the traffic flow comprising data packets which include identification of the VLAN from which a packet comes, said device comprising:

means for monitoring the traffic from each VLAN and producing a signal indicating a restricted state of a VLAN when the traffic exceeds a respective threshold;

means for gating each of respective said signals with a signal indicating a request from the VLAN to transmit whereby to produced a priority request for a VLAN in a priority state; and

a selector which enables selection of all the requests to transmit in the absence of a priority request and preferentially enables the selection of a priority request if any VLAN indicates a request to transmit and is in a priority state.

6. A device according to claim 5 comprising for each VLAN a counter which is decremented at a constant rate and is incremented is response to the traffic from the respective VLAN.

7. A method of controlling access to a common physical data transmission link of packet traffic from a multiplicity of members of a packet-based local area network wherein said members are partitioned into a plurality of virtual local area networks (VLANs) and wherein said packet traffic comprises packets which are identified according to the VLAN from which they come, the method comprising:

(a) monitoring said packet traffic from the virtual local area networks on said link and thereby obtaining measures of the respective packet traffic from each of the VLANs;

(b) determining whether the respective packet traffic from each VLAN is above or below a respective threshold;

(c) denoting a VLAN for which the packet traffic is below the respective threshold as in a priority state and denoting a VLAN for which the packet traffic is above the respective threshold as in a restricted state;

(d) providing a request to transmit from each VLAN which has packets to transmit on said link;

(d) arbitrating between such requests to transmit to control access to said link;

wherein priority is accorded in the arbitrating step to a VLAN which is in a priority state over any VLAN which is in restricted state.

8. A method as in claim 7 wherein said step of arbitrating comprises:

providing a priority signal for any VLAN which is in a priority state;

gating a request to transmit from a VLAN with any priority signal for the same VLAN to provide a set of priority requests denoting those VLANs which are in a priority state and have packets to transmit;

in the presence of any priority request, arbitrating between only those priority requests in the set of priority requests; and

in the absence of any priority request, arbitrating between the requests to transmit from the VLANs which have made a request to transmit and are in a restricted state.

9. A method as in claim 7 wherein said monitoring step comprises:

monitoring the respective packet traffic from each VLAN by means of a respective counter which is decremented at a fixed rate and is incremented in accordance with the respective packet traffic from the VLAN;

denoting the VLAN as in the priority state when a respective count is below a threshold count, and

denoting the VLAN as in the restricted state when the count is above the threshold count.

10. A device for monitoring and controlling packet traffic from a plurality of VLANs over a common physical data link, said packet traffic comprising data packets which include identification of the VLAN from which a data packet comes, said device comprising:

means for monitoring the respective traffic from each VLAN to determine whether the VLAN is in a priority state, when the respective packet traffic is less than a respective threshold, or in a restricted state when the respective traffic is above the respective threshold;

means for making for each VLAN request when that VLAN has packets to transmit on said link; and

selector means which makes an arbitration between requests from the VLANs to control access to said link from the VLANs;

wherein said selector accords preference in said arbitration to a request from any VLAN which is in a priority state over any VLAN which is in a restricted state.

11. A device as in claim 10 wherein said selector means comprises:

means for producing a priority signal for each VLAN in a priority state;

means for gating each request for a VLAN with any priority signal from the same VLAN to provide a set of priority request signals indicating those VLANs which have made a request and which are in a priority state;

means for detecting the presence of any priority request signal; and

a selector operative in the presence of any priority request signal to arbitrate between the priority requests in the set of priority requests and in the absence of any priority request signal to arbitrate between requests from VLANs which are in the restricted state.

12. A device as in claim 10 wherein the means for monitoring comprises for each VLAN a counter which is decremented at a fixed rate and is incremented in accordance with the respective traffic so as to produce a priority signal when a resultant count denotes packet traffic below the respective threshold for that VLAN.