FIELD OF INVENTION
[0001] The present subject matter relates to routing protocols and,
particularly, but not exclusively, to open shortest path first (OSPF) routing
protocol.
BACKGROUN5 D
[0002] Network devices, such as routers, gateways, and switches, typically
communicate amongst each other using routing protocols. Based on a type of the
communication network in which the network devices are deployed, a suitable
routing protocol may be implemented for facilitating communication between the
10 network devices.
[0003] Open Shortest Path First (OSPF) is a type of routing protocol
implemented in autonomous systems. An autonomous system may be understood
as a network or collection of networks managed by a single organization, for
example, an educational institution. The OSPF facilitates the network devices
15 present in an autonomous system to communicate amongst each other using
shortest possible communication path.
SUMMARY
[0004] This summary is provided to introduce concepts related to establishing
Open Shortest Path First (OSPF) adjacency between network devices. This
20 summary is not intended to identify essential features of the claimed subject
matter nor is it intended for use in determining or limiting the scope of the
claimed subject matter.
[0005] In one implementation, a method for establishing OSPF adjacency
between network devices is described. The method comprises, receiving, by a first
25 network device having a first maximum transmission unit (MTU), a second
Database Descriptor (DBD) packet from a second network device, wherein the
DBD packet comprises a second MTU associated with the second network device.
The method further comprises, on determining the second MTU to be less than the
first MTU, generating, by the first network device, an updated first DBD packet to
3
be transmitted to the second network device for establishing the OSPF adjacency
with the second network device, the updated first DBD packet comprising an
updated first MTU associated with the first network device, the updated first
MTU being equal to the second MTU.
[0006] In another implementation, a first network device having a firs5 t
maximum transmission unit (MTU) is described. The first network device
comprises a processor and a communication module coupled to the processor. In
one implementation, the communication module receives a second Database
Descriptor (DBD) packet from a second network device, wherein the DBD packet
10 comprises a second MTU associated with the second network device. The first
network device further comprises a configuration module coupled to the
processor. In an implementation, the configuration module, on determining the
second MTU to be less than the first MTU, generates, by an updated first DBD
packet to be transmitted to the second network device for establishing the OSPF
15 adjacency with the second network device, the updated first DBD packet
comprises an updated first MTU associated with the first network device, the
updated first MTU being equal to the second MTU.
[0007] In accordance with another implementation of the present subject
matter, a computer-readable medium having embodied thereon a computer
20 program for executing a method for establishing OSPF adjacency between
network devices is described. The method comprises, receiving, by a first network
device having a first maximum transmission unit (MTU), a second Database
Descriptor (DBD) packet from a second network device, wherein the DBD packet
comprises a second MTU associated with the second network device. The method
25 further comprises, on determining the second MTU to be less than the first MTU,
generating, by the first network device, an updated first DBD packet to be
transmitted to the second network device for establishing the OSPF adjacency
with the second network device, the updated first DBD packet comprising an
updated first MTU associated with the first network device, the updated first
30 MTU being equal to the second MTU.
4
BRIEF DESCRIPTION OF THE FIGURES
[0008] The detailed description is described with reference to the
accompanying figures. In the figures, the left-most digit(s) of a reference number
identifies the figure in which the reference number first appears. The sam5 e
numbers are used throughout the figures to reference like features and
components. Some embodiments of system and/or methods in accordance with
embodiments of the present subject matter are now described, by way of example
only, and with reference to the accompanying figures, in which:
10 [0009] Figure 1 illustrates an exemplary network environment implementation
for establishing OSPF adjacencies between network devices, according to an
embodiment of the present subject matter;
[0010] Figure 2 illustrates an exemplary call flow diagram for establishing
OSPF adjacencies between network devices; and
15 [0011] Figure 3 illustrates a method for establishing OSPF adjacencies
between network devices, according to an embodiment of the present subject
matter.
DESCRIPTION OF EMBODIMENTS
[0012] Routing protocols facilitate network devices, such as routers and
20 gateways, to communicate with each other. For instance, a routing protocol, such
as Open Shortest Path First (OSPF) is implemented in communication networks,
such as autonomous systems, for facilitating communication amongst a plurality
of network devices present in the communication network. The OSPF enables
each of the network devices to determine a shortest path to other network devices
25 by facilitating exchange of routing information, such as link-state database
(LSDB), amongst the network devices. Based on the routing information the
shortest paths may be determined using known techniques.
[0013] For exchanging the routing information, two network devices initially
establish an OSPF adjacency between themselves. The OSPF adjacency may be
5
understood as a session, upon establishment of which, the two network devices
may exchange the routing information. To establish the OSPF adjacency, the two
network devices exchange their corresponding maximum transmission unit
(MTU) with each other. An MTU indicates a largest packet size transmittable by a
network device over the communication network. The exchange of the MTUs 5 is
also referred to as an exstart state of the OSPF adjacency establishment. In a case
where the MTU size of the two network devices do not match, the two network
devices are not able to proceed further from the exstart state. As a result, the
OSPF adjacency between the two network devices may not be established, and
10 exchange of the routing information may not take place. In such a case, the
network devices may have to be reconfigured manually, say by an administrator,
to ensure that the two network devices have the same MTU size.
[0014] The present subject matter describes system and method for
establishing OSPF adjacency between network devices. According to an aspect, a
15 first network device, being configured with a first MTU, upon receiving a second
MTU of a different size from a second network device, may reconfigure the first
MTU. The first MTU may be reconfigured to obtain an updated MTU in a manner
such that the updated MTU matches the second MTU. The updated MTU may
then be transmitted to the second network device, as the applicable MTU for the
20 first network device, for establishing the OSPF adjacency. Thus, in accordance
with the present subject matter, two network devices with different MTU sizes
may establish OSPF adjacency.
[0015] In order to establish the OSPF adjacency, the first network device and
the second network device may transmit their corresponding MTU to each other
25 through Database Descriptor (DBD) packets. For instance, the first network
device may transmit a Database Descriptor (DBD) packet comprising a MTU
associated with the first network device to the second network device. Similarly,
the second network device may transmit another DBD packet comprising a MTU
associated with the second network device to the first network device. The DBD
30 packet transmitted by the first network device may interchangeably be referred to
6
as a first DBD packet and the DBD packet transmitted by the second network
device may interchangeable be referred to as a second DBD packet. The MTU
associated with the first network device may interchangeably be referred to as a
first MTU. The MTU associated with the second network device may
interchangeably be referred to as a second MTU5 .
[0016] Upon receiving the MTU corresponding to the other network device,
each of the first and the second network devices may inspect the received MTU to
determine if a reconfiguration of their own MTU is to be performed or not. For
ease of explanation, the inspection of the received MTU is described below in
10 reference to the first network device. However, it will be understood by a person
skilled in the art, that the second network device may also inspect the MTU
packet received from the first network device in a similar manner, as described
below in conjunction with the first network device.
[0017] In an example, upon receiving the second MTU form the second
15 network device, the first network device may compare the second MTU with the
first MTU. In case the second MTU is less than the first MTU, the first network
device may reconfigure the first MTU to obtain an updated MTU which matches
the second MTU. The first network device may then transmit an updated first
DBD packet comprising the updated MTU to the second network device for
20 establishing the OSPF adjacency. In case the first MTU is equal to the second
MTU, the first network device may proceed to establish the OSPF adjacency
using known conventional techniques. Thus, the present subject matter provides a
scalable solution for establishing the OSPF adjacency between the network
devices. Further, in case, the second MTU is greater than the first MTU, the first
25 network device may discard the second MTU. In such a case, the first network
device may receive an updated second MTU from the second network device for
establishing the OSPF adjacency.
[0018] The present subject matter thus facilitates in dynamic reconfiguration
of MTU of a network device for establishing OSPF adjacency with another
30 network device. As will be clear from the foregoing description, the network
7
device may reconfigure its MTU upon receiving an MTU of a different size from
the other network device. As a result, the network devices, despite the different
MTU sizes, successfully passes the exstart state and successfully establish OSPF
adjacency between themselves. Further, since the MTU are being automatically
reconfigured by the network devices, manual intervention by syste5 m
administrators is avoided, thus reducing network monitoring costs. Thus, the
present subject matter facilitates OSPF adjacency establishment between two
network devices having different MTU size.
[0019] The manner in which the systems and the methods for establishing
10 OSPF adjacency between network devices shall be implemented has been
explained in details with respect to the Figures 1, 2, and 3. While aspects of
described systems and methods for dynamic load balancing can be implemented
in any number of different computing systems, transmission environments, and/or
configurations, the embodiments are described in the context of the following
15 exemplary system(s).
[0020] Figure 1 illustrates a network environment 100 for establishing
OSPF adjacency between network devices. The network environment 100
includes a plurality of network devices 102-1, 102-2, …., and 102-N, hereinafter
collectively referred to as the network devices 102 and individually referred to as
20 the network device 102, interconnected with each other through a network 104,
according to an embodiment of the present subject matter. Examples of the
network device 102 include, but are not limited to devices, such as network
switches and network routers, implemented in communication networks, such as
autonomous systems, for the purpose of transferring data packets. In an example,
25 the network devices 102 may communicate with each other using the OSPF
protocol. As may be understood, in accordance with the OSPF protocol, two
network devices 102 may establish an OSPF adjacency between themselves for
exchanging routing information with each other.
[0021] The network 104 may be a wireless network, a wired network, or a
30 combination of wired and wireless network. The network 104 can be a collection
8
of individual networks, interconnected with each other and functioning as a single
large network (e.g., internet or an intranet). Examples of such individual networks
include, but are not limited to, autonomous systems, internet, Local Area Network
(LAN), Wide Area Network (WAN), and the like.
[0022] In an implementation, each of the network devices 102 ma5 y
include processor(s) 106. For example, the network device 102-1 and the network
device 102-2 include processor(s) 106-1 and 106-2, respectively. The processor
106 may be implemented as one or more microprocessors, microcomputers,
microcontrollers, digital signal processors, central processing units, state
10 machines, logic circuitries, and/or any devices that manipulate signals based on
operational instructions. Among other capabilities, the processor(s) 106 is
configured to fetch and execute computer-readable instructions stored in a
memory of the network device 102.
[0023] The functions of the various elements shown in the figure,
15 including any functional blocks labeled as “processor(s)”, may be provided
through the use of dedicated hardware as well as hardware capable of executing
software in association with appropriate software. When provided by a processor,
the functions may be provided by a single dedicated processor, by a single shared
processor, or by a plurality of individual processors, some of which may be
20 shared. Moreover, explicit use of the term “processor” should not be construed to
refer exclusively to hardware capable of executing software, and may implicitly
include, without limitation, digital signal processor (DSP) hardware, network
processor, application specific integrated circuit (ASIC), field programmable gate
array (FPGA), read only memory (ROM) for storing software, random access
25 memory (RAM), and non-volatile storage. Other hardware, conventional and/or
custom, may also be included.
[0024] Also, the network devices 102 include I/O interface(s) 108. For
example, the network device 102-1 and the network device 102-2 include I/O
interface(s) 108-1, 108-2, respectively. The I/O interface(s) 108 may include a
30 variety of software and hardware interfaces that allow the network devices 102 to
9
communicate with each other. Further, the I/O interface(s) 108 may enable the
network device 102 to communicate with other communication and computing
devices, such as web servers and external repositories (not shown in figure). The
I/O interface(s) 108 may facilitate multiple communications within a wide variety
of networks and protocol types, including wire networks, for example, LAN5 ,
cable, etc., and wireless networks, for example, WLAN, cellular, satellite-based
network, etc.
[0025] The network devices 102 may include memory 110. For example,
the network device 102-1 and the network device 102-2 may include memory
10 110-1, and 110-2, respectively. The memory 110-1 and 110-2 may be coupled to
the processor 106-1, and the processor 106-2, respectively. The memory 110 may
include any computer-readable medium known in the art including, for example,
volatile memory (e.g., RAM), and/or non-volatile memory (e.g., EPROM, flash
memory, etc.).
15 [0026] In one implementation, the network devices 102 include module(s)
112 and data 114. For example, the network device 102-1 and the network device
102-2 include modules 112-1, 112-2 and data 114-1, 114-2, respectively. The
module(s) 112, amongst other things, include routines, programs, objects,
components, data structures, etc., which perform particular tasks or implement
20 particular abstract data types. The module(s) 112 may also be implemented as,
signal processor(s), state machine(s), logic circuitries, and/or any other device or
component that manipulate signals based on operational instructions.
[0027] Further, the modules 112 can be implemented in hardware,
instructions executed by a processing unit, or by a combination thereof. The
25 processing unit can comprise a computer, a processor, such as the processor 106, a
state machine, a logic array or any other suitable devices capable of processing
instructions. The processing unit can be a general-purpose processor which
executes instructions to cause the general-purpose processor to perform the
required tasks or, the processing unit can be dedicated to perform the required
30 functions.
10
[0028] In another aspect of the present subject matter, the module(s) 112
may be machine-readable instructions (software) which, when executed by a
processor/processing unit, perform any of the described functionalities. The
machine-readable instructions may be stored on an electronic memory device,
hard disk, optical disk or other machine-readable storage medium or 5 nontransitory
medium. In one implementation, the machine-readable instructions can
be also be downloaded to the storage medium via a network connection. The data
114 serves, amongst other things, as a repository for storing data that may be
fetched, processed, received, or generated by one or more of the modules 112.
10 [0029] In an implementation, the module(s) 112-1 of the network device
102-1 includes a communication module 116-1, a configuration module 118-1,
and other module(s) 120-1. In said implementation, data 114-1 of the network
device 102-1 includes network data 122-1 and other data 124-1.
[0030] Similarly, in an implementation, the module(s) 112-2 of the
15 network device 102-2 include a communication module 116-1, a configuration
module 118-2, and other module(s) 120-2. In said implementation, data 114-2 of
the network device 102-2 includes network data 122-2 and other data 124-2. The
other module(s) 120-1 and 120-2 may include programs or coded instructions that
supplement applications and functions, for example, programs in the operating
20 system of the network device 102-1 and the network device 102-2, respectively.
The other data 124-1 and 124-2 comprise data corresponding to one or more other
module(s) 120-1 and 120-2, respectively.
[0031] In operation, the network device 102-1 may seek to establish an
OSPF adjacency with the network device 102-2. In order to establish the OSPF
25 adjacency, the network device 102-1 and the network device 102-2 may exchange
their corresponding MTU with each other. For example, the communication
module 116-1 may transmit a first DBD packet comprising a first MTU associated
with the network device 102-1 to the communication module 116-2. While, the
communication module 116-2 may transmit a second DBD packet comprising a
30 second MTU associated with the network device 102-2 to the communication
11
module 116-1. The communication module 116-1 may store the second DBD
packet in the network data 122-1. The communication module 116-2 may store
the first DBD packet in the network data 122-2.
[0032] Upon receiving the second DBD packet, the configuration module
118-1 may analyze the second MTU to determine if the first MTU is to 5 be
reconfigured or not. Similarly, the configuration module 118-2 may analyze the
first MTU to determine if the second MTU is to be reconfigured or not. For the
sake of brevity, the inspection of the MTU has been described below with
reference to the configuration module 118-1. As may be understood, the
10 configuration module 118-2 may inspect the first MTU in a similar manner.
[0033] In order to determine if the first MTU is to be reconfigured or not,
the configuration module 118-1 may compare the second MTU with the first
MTU. In a case where the configuration module 118-1 ascertains that the second
MTU is less than the first MTU, the configuration module 118-1 may reconfigure
15 the first MTU. In an implementation, the configuration module 118-1 may
reconfigure the first MTU in a manner so as to obtain an updated first MTU equal
to the second MTU. Upon obtaining the updated first MTU, the configuration
module 118-1 may generate an updated first DBD packet, comprising the updated
first MTU, to be transmitted to the communication module 116-2. Thereafter, the
20 communication module 116-1 may transmit the updated first DBD packet to the
communication module 116-2 for facilitating establishment of the OSPF
adjacency between the first network device 102-1 and the network device 102-2.
The communication module 116-2 may receive and store the updated first MTU
packet in the network data 122 and, thereafter, may proceed to establish the OSPF
25 adjacency.
[0034] In another case where the second MTU is more than the first MTU,
the configuration module 118-1 may discard the second DBD packet. In yet
another case where the second MTU is equal to the first MTU, the configuration
module 118-1 may transmit a trigger to the communication module 116-1. The
12
trigger may indicate the communication module 116-1 to proceed with the
establishment of the OSPF adjacency with the network device 102-2.
[0035] Thus, the present subject matter provides a scalable solution for
establishing OSPF adjacencies between the network devices 102.
[0036] Figure 2 illustrates an exemplary call flow diagram 200 5 0 for
establishing OSPF adjacencies between network devices 102, according to an
embodiment of the present subject matter. The various arrow indicators used in
the call-flow diagram 200 depict the transfer of OSPF packets between the
network device 102-1 and the network device 102-2.
10 [0037] In an implementation, the network device 102-1 and the network
device 102-2 may seek to establish OSPF adjacency between themselves. In said
implementation, the network device 102-1 may transmit a first DBD packet 202
comprising its corresponding MTU to the network device 102-2. Similarly, the
network device 102-2 may transmit a second DBD packet 204 comprising its
15 corresponding MTU to the network device 102-1. As explained earlier in the
description of Figure 1, each of the network device 102-1 and 102-2 may inspect
the received MTU for determining whether their corresponding MTU is to be
reconfigured or not. As explained earlier, in a case where the network 102-1
ascertains that its MTU is greater than the MTU of the network device 102-2, the
20 network device 102-1 may reconfigure its MTU to obtain an updated MTU. The
network device 102-1 may then transmit an updated first DBD packet 206
comprising the updated MTU to the network device 102-2 for establishing the
OSPF adjacency.
[0038] Figure 3 illustrates a method 300 for establishing OSPF adjacencies
25 between network devices, in accordance with an embodiment of the present
subject matter. The order in which the method 300 is described is not intended to
be construed as a limitation, and any number of the described method blocks can
be combined in any order to implement the method 300, or an alternative method.
Additionally, individual blocks may be deleted from the method without departing
30 from the spirit and scope of the subject matter described herein. Furthermore, the
13
method can be implemented in any suitable hardware, software, firmware, or
combination thereof.
[0039] The method(s) may be described in the general context of computer
executable instructions. Generally, computer executable instructions can include
routines, programs, objects, components, data structures, procedures, modules5 ,
functions, etc., that perform particular functions or implement particular abstract
data types. The method may also be practiced in a distributed computing
environment where functions are performed by remote processing devices that are
linked through a communication network. In a distributed computing
10 environment, computer executable instructions may be located in both local and
remote computer storage media, including memory storage devices.
[0040] A person skilled in the art will readily recognize that steps of the
method can be performed by programmed computers. Herein, some embodiments
are also intended to cover program storage devices, for example, digital data
15 storage media, which are machine or computer readable and encode machineexecutable
or computer-executable programs of instructions, wherein said
instructions perform some or all of the steps of the described method. The
program storage devices may be, for example, digital memories, magnetic storage
media, such as a magnetic disks and magnetic tapes, hard drives, or optically
20 readable digital data storage media. The embodiments are also intended to cover
all the communication networks and communication devices configured to
perform said steps of the exemplary method.
[0041] At block 302, a first network device having a first MTU receives a
second DBD packet comprising a second MTU from a second network device. An
25 MTU indicates largest packet size transmittable by a network device. In order to
establish an OSPF adjacency, the first network device and the second network
device may transmit their corresponding MTU to each other. In an
implementation, the communication module 116-1 of the network device 102-1
may transmit a first MTU, associated with the first network device 102-1, to the
30 communication module 116-2 of the second network device 102-2. Similarly, the
14
communication module 116-2 of the second network device 102-2 may transmit a
second MTU, associated with the second network device 102-2, to the
communication module 116-1.
[0042] At block 304, it is ascertained whether the first MTU is greater than
the second MTU or not. In a case, the configuration module 118-1 may ascertai5 n
whether the first MTU is greater than the second MTU or not. In a case where it is
ascertained that the first MTU is not greater than the second MTU, the method
proceeds to block 306, which is the 'NO' path. At block 306 the second DBD
packet is discarded. In an example, the configuration module 118-1 may discard
10 the second DBD packet.
[0043] In another case where it is ascertained that the first MTU is greater
than the second MTU, the method proceeds to block 308, which is the 'YES' path.
At block 308, the first MTU is reconfigured by the first network device to obtain
an updated first MTU equal to the second MTU. In an example, the configuration
15 module 118-1 may reconfigure the first MTU to obtain the updated first MTU.
[0044] At block 310, an updated first DBD packet comprising the updated
first MTU is transmitted by the first network device to the second network device
for establishing OSPF adjacency with the second network device. In an example,
the communication module 116-1 may transmit the updated first DBD packet to
20 the communication module 116-2.
[0045] Although implementations for establishing OSPF adjacency between
network devices have been described in a language specific to structural features
and/or methods, it is to be understood that the appended claims are not necessarily
limited to the specific features or methods described. Rather, the specific features
25 and methods are disclosed as exemplary implementations for establishing OSPF
adjacency between network devices.

CLAIMS:1. A method for establishing open shortest path first (OSPF) adjacency between network devices present in a communication network, the method comprising:
receiving, by a first network device being configured with a first maximum transmission unit (MTU), a second Database Descriptor (DBD) packet from a second network device, wherein the DBD packet comprises a second MTU associated with the second network device;
on determining the second MTU to be less than the first MTU, generating, by the first network device, an updated first DBD packet to be transmitted to the second network device for establishing the OSPF adjacency with the second network device, the updated first DBD packet comprising an updated first MTU associated with the first network device, the updated first MTU being equal to the second MTU.
2. The method as claimed in claim 1, wherein the method further comprises comparing, by the first network device, the first MTU and the second MTU.
3. The method as claimed in claim 1, wherein the method further comprises reconfiguring, by the first network device, the first MTU to obtain the updated first MTU.
4. The method as claimed in claim 1, wherein the method further comprises transmitting, by the first network device, a first DBD packet to the second network device, the first DBD packet comprising the first MTU associated with the first network device.
5. The method as claimed in claim 1, wherein the first MTU indicates a maximum size of data unit transmittable by the first network device, and wherein the second MTU indicates a maximum size of data unit transmittable through the second network device.
6. The method as claimed in claim 1, wherein the method further comprises discarding, by the first network device, the second DBD packet on determining the second MTU packet to be greater than the first MTU packet.
7. A first network device configured with a first maximum transmission unit (MTU), the first network device comprising:
a processor;
a communication module coupled to the processor to, receive a second Database Descriptor (DBD) packet from a second network device, the DBD packet comprising a second MTU associated with the second network device; and
a configuration module coupled to the processor to, generate, on determining the second MTU to be less than the first MTU associated with the first network device, an updated first DBD packet based on the determining, the updated first DBD packet comprising an updated first MTU associated with the first network device, the updated first MTU being equal to the second MTU.
8. The first network device as claimed in claim 7, wherein the configuration module further is to compare the first MTU and the second MTU.
9. The first network device as claimed in claim 7, wherein the configuration module further is to reconfigure the first MTU to obtain the updated first MTU.
10. The first network device as claimed in claim 7, wherein the configuration module further is to discard the second DBD packet on determining the second MTU to be greater than the first MTU.
11. The first network device as claimed in claim 7, wherein the communication module further is to transmit the updated first DBD packet to the second network device for establishing open shortest path first (OSPF) adjacency with the second network device.
12. The first network device as claimed in claim 7, wherein the communication module further is to transmit a first DBD packet to the second network device, the first DBD packet comprising the first MTU associated with the network device.
13. A non-transitory computer-readable medium having embodied thereon a computer program for executing a method comprising:
receiving, by a first network device being configured with a first maximum transmission unit (MTU), a second Database Descriptor (DBD) packet from a second network device, wherein the DBD packet comprises a second MTU associated with the second network device; and
on determining the second MTU to be less than the first MTU, generating, by the first network device, an updated first DBD packet to be transmitted to the second network device for establishing the OSPF adjacency with the second network device, the updated first DBD packet comprising an updated first MTU associated with the first network device, the updated first MTU being equal to the second MTU.