Dynamically adjusting frame MTU to support low-latency communication

• US 9,973,596 B2
• Filed: 06/19/2013
• Issued: 05/15/2018
• Est. Priority Date: 06/19/2013
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Hui, Jonathan W., Vasseur, Jean-Philippe
• Primary Examiner(s): Beharry, Noel R
• Assistant Examiner(s): Mak, Rodrick
• Application Number:
  US13/921,651
• Publication Number:
  US 20140376427A1
• Time in Patent Office: 1,791 Days
• CPC Class Codes: H04L 47/24 Traffic characterised by specific attributes, e.g. priority or QoS
• CPC Class Codes: H04L 47/245 using preemption
• CPC Class Codes: H04L 47/365 Dynamic adaptation of the packet size
• CPC Class Codes: H04L 5/16 Half-duplex systems; Simplex/duplex switching; Transmission of break signals non-automatically inverting the direction of transmission
• CPC Class Codes: H04L 69/04 Protocols for data compression, e.g. ROHC
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

In one embodiment, a sender in a shared-communication network determines whether a pending frame is low-latency or high-throughput, and sets a maximum transmission unit (MTU) of the pending frame as a first MTU in response to a low-latency frame and a longer second MTU in response to a high-throughput frame. In another embodiment, a receiver receives a data frame from a sender according to an MTU, and determines a trigger for adjusting the MTU based on latency requirements. In response to the trigger, the receiver sets an interrupt flag in a link-layer acknowledgment for the received data frame. In still another embodiment, a sender determines a pending low-latency data frame to send to a receiver operating according to an MTU, and sends a control message to the receiver to indicate the pending low-latency data frame and an adjusted MTU.

Claims

1. A method, comprising:

receiving, by a receiver, a data frame from a sender over a shared-communication network, the frame sent according to a maximum transmission unit (MTU), wherein the MTU is a frame MTU that limits an amount of time that the data frame occupies a particular channel;

determining, by the receiver, whether the MTU needs to be dynamically adjusted by the sender based on latency requirements of flows that the receiver or a neighboring device of the receiver is servicing, wherein the receiver and sender operate in either a half-duplex mode or a full-duplex mode;

based on a determination that the MTU needs to be dynamically adjusted by the sender, adjusting the MTU by setting an interrupt flag in a link-layer acknowledgment for the received data frame, wherein the MTU is reduced when urgent traffic needs to be serviced by the receiver or a neighboring device and the MTU is increased when urgent traffic does not need to be serviced by the receiver or a neighboring device; and

replying to the sender with the link-layer acknowledgment and interrupt flag, wherein replying occurs in response to completion of the received data frame from the sender in half-duplex mode, and prior to completion of the received data frame from the sender in full-duplex mode.

2. The method as in claim 1, wherein the urgent traffic is a critical low-latency frame.

3. The method as in claim 1, wherein determining whether the MTU needs to be dynamically adjusted by the sender comprises:

receiving a control frame from a third device indicating a pending low-latency transmission by the third device for the receiver.

4. The method as in claim 1, further comprising:

receiving the MTU from a management device.

5. The method as in claim 1, further comprising:

setting the MTU individually.

6. The method as in claim 1, wherein the MTU is different for each neighbor pair in the network.

7. A method, comprising:

determining, by a sender, whether a pending data frame to send to a receiver over a shared-communication network is low-latency, the receiver operating according to a maximum transmission unit (MTU), wherein the MTU is a frame MTU that limits an amount of time that the data frame can occupy a particular channel, wherein the receiver operates in either a half-duplex mode or a full-duplex mode;

in response to the pending data frame being an urgent data frame, dynamically adjusting, by the sender, the MTU to account for the pending data frame, wherein the MTU is reduced when urgent traffic exists and is increased when urgent traffic does not exist;

sending a control message to the receiver to indicate the pending data frame is latency critical and an adjusted MTU, wherein sending the control message occurs in response to hearing an acknowledgment sent from the receiver to a remote transmitting device in half-duplex mode, and prior to completion of a transmission from a remote transmitting device to the receiver in full-duplex mode;

receiving an acknowledgment for the received control message; and

sending the urgent data frame to the receiver at the adjusted MTU in response to the acknowledgment.

8. The method as in claim 7, wherein the acknowledgment is a link-layer acknowledgment having a set interrupt flag sent from the receiver to a remote transmitting device and overheard by the sender.

9. The method as in claim 7, wherein sending the control message is in response to hearing an acknowledgment sent from the receiver to a remote transmitting device.

10. The method as in claim 7, further comprising:

receiving the MTU from a management device.

11. The method as in claim 7, further comprising:

setting the MTU individually.

12. The method as in claim 7, wherein the MTU is different for each neighbor pair in the network.

13. A method, comprising:

determining whether a pending frame is urgent or not by a sender in a shared-communication network;

dynamically adjusting a maximum transmission unit (MTU) of the pending frame as a first MTU in response to the pending frame being urgent and a second MTU in response to the pending frame not being urgent, wherein the first MTU is shorter than the second MTU, wherein the first MTU reduces the overall throughput and the second MTU increases the overall throughput and wherein the first and second MTUs are frame MTUs that limit an amount of time that the pending frame can occupy a particular channel;

setting the second MTU individually, wherein the second MTU is different for each neighbor pair in the network; and

transmitting the pending frame to a receiver at the dynamically adjusted MTU.

14. The method as in claim 13, further comprising:

waiting until completion of a current frame being transmitted by the sender prior to transmitting the pending frame.

15. The method as in claim 13, further comprising:

receiving the second MTU from a management device.

16. The method as in claim 13, wherein determining whether the pending frame is urgent or not is based on a neighboring device receiving on a same channel as the frame at the same time.

17. An apparatus, comprising:

one or more network interfaces to communicate in a shared-media communication network;

a processor coupled to the network interfaces and adapted to execute one or more processes; and

a memory configured to store a process executable by the processor, the process when executed operable to;

determine whether a pending frame of the apparatus is urgent or not;

in response to a determination that the pending frame is urgent, dynamically adjust a maximum transmission unit (MTU) of the pending frame as a first MTU in response to the pending frame being urgent and as a second MTU in response to the pending frame not being urgent, wherein the first MTU is shorter than the second MTU, wherein the first MTU reduces the overall throughput and the second MTU increases the overall throughput and wherein the first and second MTUs are frame MTUs that limit an amount of time that the pending frame can occupy a particular channel;

set the second MTU individually, wherein the second MTU is different for each neighbor pair in the network; and

transmitting the pending frame to a receiver at the dynamically adjusted MTU.

18. The apparatus as in claim 17, wherein the process when executed is further operable to:

receive an incoming data frame from a sender according to the sender'"'"'s MTU;

determine whether to adjust the sender'"'"'s MTU based on latency requirements;

based on a determination that the sender'"'"'s MTU needs adjustment, set an interrupt flag in a link-layer acknowledgment for the incoming data frame; and

reply to the sender with the link-layer acknowledgment and interrupt flag.

19. The apparatus as in claim 17, wherein the process when executed is further operable to:

determine that the pending frame is urgent;

determine that the receiver is currently receiving a transmission from a remote sender;

send a control message to the receiver to indicate the pending urgent frame and the first MTU; and

sending the urgent frame to the receiver at the first MTU in response to an acknowledgment for the control message.

20. The apparatus as in claim 17, wherein the process when executed to determine whether the pending frame is urgent or not is further operable to:

determine whether the pending frame is urgent or not based on a neighboring device receiving on a same channel as the frame at the same time.