The Patent Act 1970
(39 of 1970)
&
The Patent Rules, 2005

COMPLETE SPECIFICATION
(SEE SECTION 10 AND RULE 13)

TITLE OF THE INVENTION

“Deterministic MTU setting on Link aggregation ports”

APPLICANTS:
Name Nationality Address
Alcatel Lucent France Alcatel-Lucent
3 av. Octave Gréard
75007 Paris, France

The following specification particularly describes and ascertains the nature of this invention and the manner in which it is to be performed:-

TECHNICAL FIELD
[001] The present invention relates to communication protocols and, more particularly, to the IEEE 802.3ad communication protocol.

BACKGROUND
[002] 802.3ad (Link Aggregation Control Protocol (LACP) describes the mechanism of using multiple network cables/ports in parallel to increase the link speed beyond the limits of any one single cable or port, and to increase the redundancy for higher availability. LACP was proposed to overcome bandwidth limitations in existing networking ports by providing a method to control the bundling of several physical ports together to form a single logical channel. LACP allows a network device to negotiate an automatic bundling of links by sending LACP packets to the peer (directly connected device that also implements LACP). LACP works by sending frames down all links that have the protocol enabled. If it finds a device on the other end of the link that also has LACP enabled, it will also independently send frames along the same links enabling the two units to detect multiple links between themselves and then combine them into a single aggregated link.
[003] LACP assumes that all the links in an aggregated link have the same MTU (Maximum Transmission Unit), which is the maximum size of data packet that may pass through the link. However, in practice, all the links in an aggregated link may not have the same MTU size. This can result in an error in the aggregated link, which may result in a loss in data, when they are sent across the aggregated link. For example, consider two pairs of links, one pair having an MTU of 1518 bytes and the second pair having an MTU of 1700 bytes. As per LACP, the MTU of the aggregated link may be assumed to be 1700 bytes, but in reality the MTU of the aggregated link is less than 1700 bytes due to the presence of the pair of links with an MTU of 1518 bytes. So, when a data packet which is 1650 bytes in size (which is greater than 1518 bytes but less than 1700 bytes) is sent across the aggregated link by being redirected to the link whose MTU is 1518 bytes, the data packet may act in an unpredictable manner due to the mismatch between the size of the data packet and the actual MTU of the aggregated link.

SUMMARY
[004] In view of the foregoing, an embodiment herein provides a method for adding a link in a device to an aggregated link in a communication network, the method comprising of the device tuning maximum transmission unit of the link to a configured value of maximum transmission unit; and the device adding the link to the aggregated link. The configured value of maximum transmission unit may be configured by an operator in the communication network, the operator at a network management system present in the communication network or the operator at the device. The configured value of maximum transmission unit may be configured by the operator using a CLI/MIB instruction. The method further comprises steps of the device tuning maximum transmission unit of the link to the configured value of maximum transmission unit if the configured value of maximum transmission unit has been configured by the operator.
[005] Embodiments herein further disclose a device in a communication network, the device comprising at least one means configured for tuning maximum transmission unit of a link to a configured value of maximum transmission unit; and adding the link to the aggregated link. The device is configured for receiving the configured value of maximum transmission unit from an operator in the communication network, through a network management system or from the operator directly. The device may be configured for accepting the configured value of maximum transmission unit from the operator using a CLI/MIB instruction. The device is configured for tuning maximum transmission unit of the link to the configured value of maximum transmission unit if the configured value of maximum transmission unit has been configured by the operator.
[006] These and other aspects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings.

BRIEF DESCRIPTION OF THE FIGURES
[007] The embodiments herein will be better understood from the following detailed description with reference to the drawings, in which:
[008] FIG. 1 depicts a network, according to embodiments as disclosed herein;
[009] FIG. 2 is an exemplary implementation, according to embodiments as disclosed herein.
[0010] FIG. 3 depicts a device, according to embodiments as disclosed herein; and
[0011] FIG. 4 depicts a flowchart, according to embodiments as disclosed herein.

DETAILED DESCRIPTION OF EMBODIMENTS
[0012] The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
[0013] The embodiments herein disclose a method and system to ensure a predictable packet size coming out of each of the member links of an aggregated link in accordance with a configured MTU parameter of the aggregated link. Referring now to the drawings, and more particularly to FIGS. 1 through 4, where similar reference characters denote corresponding features consistently throughout the figures, there are shown embodiments.
[0014] FIG. 1 depicts a network, according to embodiments as disclosed herein. The network, as depicted, comprises of a plurality of devices 101, 102 and a Network Management System (NMS) 103. The devices 101, 102 may be a network switch, router, hub or any similar device in the communication network. Each of the devices comprise of a plurality of communication links. The devices, device-A 101 and device-B 101 comprise of 3 links each; A1, A2 and A3 in device-A 101 and B1, B2 and B3 in device-B 102. Links A1, A2 and A3 of device-A 101 have MTUs of C1. C2 and C3 respectively. Links B1, B2 and B3 of device-B 102 have MTUs of C1, C2 and C3 respectively. Both the devices 101, 102 are connected to the NMS 103 using a suitable connection means.
[0015] The operator of the network may set a value of the MTU using an appropriate instruction. The operator may use using a management CLI/MIB to set the MTU value. An example of the format of the management CLI/MIB may be
Linkagg MTU
[0016] The MTU value may be set in term of bytes. The operator may set the MTU value at the NMS 103. The NMS 103 may communicate the MTU value to all the appropriate devices connected to it. Here, the NMS 103 communicates the MTU value to device-A 101 and device-B 102. In another embodiment herein, the operator may set the MTU value at each of t he devices present in the network.
[0017] When one of the links in device-A 101 is to be added to the aggregated link, the device-A 101 checks if an MTU value has been configured. If an MTU value has been configured, then the device-A 101 tunes the MTU of the link to the MTU value. The device-A 101 then adds the link to the aggregated link.
[0018] As depicted in figure 1, suppose operator has configured the MTU value as C. When link A1 with a MTU of C1 wants to be added to the aggregated link, the device A1 tunes the MTU of A1 to C, before adding A1 to the aggregated link. In a similar manner, the MTU of link B2 may also be tuned to the MTU value of C.
[0019] When either of the devices 101, 102 has to transmit a data packet, data packets with a size equal to or less than the MTU will be utilized. For example, if the MTU is C bytes, then the devices 101, 102 ensure that each of the transmitted data packets is equal to or less than C bytes. In another example, if the MTU is 1518 bytes, then the devices 101, 102 ensure that each of the transmitted data packets is equal to or less than 1518 bytes.
[0020] FIG. 3 depicts a device, according to embodiments as disclosed herein. The device 101, 102 may be any device present in the network and having links for communication and capable of using LACP. The device 101, 102 as depicted comprises of a controller 301, a transceiver 302, a plurality of links 303 and a memory 304. The controller 301 may initiate formation of an aggregated link between a link 303 and a link in another device present in the same network.
[0021] The MTU value as set by the operator in term of bytes or any other suitable units may be received by the devices 101, 102. The operator may set the MTU value at the NMS 103 and the NMS 103 may communicate the MTU value to the controller 301 present in the devices 101, 102 using the transceiver 302. In another embodiment herein, the operator may set the MTU value at the devices 101, 102 present in the network. The MTU value is stored by the controller 201 in the memory 304.
[0022] When one of the links 303 in the device 101, 102 is to be added to the aggregated link, the link 303 informs the controller 301. The controller 301 checks if any MTU value has been configured. If an MTU value has been configured, then the controller 301 fetches the MTU value from the memory 304. The controller 301 tunes the MTU of the link 303 to the MTU value. The controller 301 then adds the link 303 to the aggregated link.
[0023] FIG. 4 depicts a flowchart, according to embodiments as disclosed herein. When one of the links 303 in the device 101, 102 wants to join the aggregated link, the link 303 initiates (401) the process of joining the aggregated link and negotiates (402) with aggregated link. If the link 303 satisfies (403) the criteria to join the aggregated link, the device 101, 102 checks (405) if any MTU parameter has been configured. If the device 101, 102 detects that no MTU parameters for the aggregated link have been configured, then the device 101, 102 adds (408) the link 303 to the aggregated link. If the device 101, 102 detects that a MTU parameter has been set, then the device 101, 102 checks (406) if the link can be tuned to the configured MTU value. If the link can be tuned to the configured MTU value, the device 101, 102 tunes (407) the MTU of the link 303 to the MTU parameter and adds (408) the link 303 to the aggregated link. If the link cannot be tuned to the configured MTU value, the device 101, 102 informs (409) the NMS 103. The various actions in method 400 may be performed in the order presented, in a different order or simultaneously. Further, in some embodiments, some actions listed in FIG. 4 may be omitted.
[0024] Embodiments disclosed herein ensure consistent behaviour across all the member links of the aggregated link to provide a deterministic behaviour and provides a consistent MTU size coming out of each of the member link of the aggregated link.
[0025] The embodiments disclosed herein can be implemented through at least one software program running on at least one hardware device and performing network management functions to control the network elements. The network elements shown in Figs. 1, 2 and 3 include blocks which can be at least one of a hardware device, or a combination of hardware device and software module.
[0026] The embodiment disclosed herein specifies a mechanism to ensure a consistent MTU size coming out of each of the member link of the aggregated link. Therefore, it is understood that the scope of the protection is extended to such a program and in addition to a computer readable means having a message therein, such computer readable storage means contain program code means for implementation of one or more steps of the method, when the program runs on a server or mobile device or any suitable programmable device. The method is implemented in a preferred embodiment through or together with a code written in e.g. Very high speed integrated circuit Hardware Description Language (VHDL) or any other coding language, or implemented by one or more VHDL or several software modules being executed on at least one hardware device. The hardware device can be any kind of device which can be programmed including e.g. any kind of computer like a server or a personal computer, or the like, or any combination thereof, e.g. one processor and two FPGAs. The device may also include means which could be e.g. hardware means like e.g. an ASIC, or a combination of hardware and software means, e.g. an ASIC and an FPGA, or at least one microprocessor and at least one memory with software modules located therein. The method embodiments described herein could be implemented in pure hardware or partly in hardware and partly in software. Alternatively, the invention may be implemented on different hardware devices, e.g. using a plurality of CPUs.
[0027] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the claims as described herein.


WE CLAIM:-
1. A method for adding a link in a device to an aggregated link in a communication network, said method comprising of
Said device tuning maximum transmission unit of said link to a configured value of maximum transmission unit; and
Said device adding said link to said aggregated link.

2. The method, as claimed in claim 1, wherein said configured value of maximum transmission unit is configured by an operator in said communication network.

3. The method, as claimed in claim 2, wherein said configured value of maximum transmission unit is configured by said operator at a network management system present in said communication network.

4. The method, as claimed in claim 2, wherein said configured value of maximum transmission unit is configured by said operator at said device.

5. The method, as claimed in claim 2, wherein said configured value of maximum transmission unit is configured by said operator using a CLI/MIB instruction.

6. The method, as claimed in claim 1, wherein said method further comprises steps of said device tuning maximum transmission unit of said link to said configured value of maximum transmission unit if said configured value of maximum transmission unit has been configured by said operator.
7. A device in a communication network, said device comprising at least one means configured for
tuning maximum transmission unit of a link to a configured value of maximum transmission unit; and
adding said link to said aggregated link.

8. The device, as claimed in claim 7, wherein said device is configured for receiving said configured value of maximum transmission unit from an operator in said communication network.

9. The device, as claimed in claim 8, wherein said device is configured for receiving said configured value of maximum transmission unit from said operator through a network management system.

10. The device, as claimed in claim 8, wherein said device is configured for receiving said configured value of maximum transmission unit from said operator directly.

11. The device, as claimed in claim 10, wherein said device is configured for accepting said configured value of maximum transmission unit from said operator using a CLI/MIB instruction.

12. The device, as claimed in claim 7, wherein said device is configured for tuning maximum transmission unit of said link to said configured value of maximum transmission unit if said configured value of maximum transmission unit has been configured by said operator.

Dated this 07th day of Dec 2010
Dr. Kalyan Chakravarthy
Patent Agent