Method and arrangement for determining transmission delay

A network element comprising:

• a first ingress port and a second ingress port for to receive protocol data units each of which is associated with an order indicator arranged to indicate the position of that protocol data unit in a mutual sequential order of said protocol data units, and each of which is sent earlier than or simultaneously with the protocol data unit next in said sequential order, wherein the network element has a processor unit arranged to:
• determine, based on a first order indicator associated with a first protocol data unit received earlier and a second order indicator associated with a second protocol data unit received later, whether the first protocol data unit is later in said sequential order than said second protocol data unit, said first protocol data unit being a protocol data unit received at the first ingress port of the network element, and said second protocol data unit being a protocol data unit received at the second ingress port of the network element,
• in response to a situation in which said first protocol data unit is later in said sequential order than said second protocol data unit, calculate a time difference of receiving moments of said second protocol data unit and said first protocol data unit, said time difference representing a lower limit for a difference between transmission delays experienced by said second protocol data unit and said first protocol data unit, and
• remove said second ingress port from among ingress ports available to a routing protocol in response to a situation where said first protocol data unit is later in said sequential order than said second protocol data unit and an indicator value updated on the basis of said time difference exceeds a predetermined threshold value.

A method for determining mutual differences of transmission delays experienced by received protocol data units and for performing control actions related to ingress ports of a network element, each protocol data unit being associated with an order indicator arranged to indicate the position of that protocol data unit in a mutual sequential order of said protocol data units, and each protocol data unit being sent earlier than or simultaneously with the protocol data unit next in said sequential order, the method comprising:

• determining, based on a first order indicator associated with a first protocol data unit received earlier and a second order indicator associated with a second protocol data unit receiver later, whether the first protocol data unit is later in said sequential order than said second protocol data unit, said first protocol data unit being a protocol data unit received at a first ingress port of the network element and said second protocol data unit is a protocol data unit received at a second ingress port of the network element,
• in response to a situation in which said first protocol data unit is later in said sequential order than said second protocol data unit, calculating a time difference of receiving moments of said second protocol data unit and said first protocol data unit, said time difference representing a lower limit for a difference between transmission delays experienced by said second protocol data unit and said first protocol data unit, and
• removing said second ingress port from among the ingress ports available to a routing protocol if said first protocol data unit is later in said sequential order than said second protocol data unit and an indicator value updated on the basis of the time difference of said receiving moments exceeds a predetermined threshold value.

A non-transitory computer readable medium encoded with a computer program for controlling a programmable processor to determine mutual differences of transmission delays experienced by protocol data units received and to perform control action related to ingress ports of a network element, each protocol data unit being associated with an order indicator arranged to indicate the position of that protocol data unit in a mutual sequential order of said protocol data units, and each protocol data unit being sent earlier than or simultaneously with the protocol data unit next in said sequential order, the computer program comprising:

• software means for controlling said programmable processor to determine, based on a first order indicator associated with a first protocol data unit received earlier and a second order indicator associated with a second protocol data unit received later, whether the first protocol data unit is later in said sequential order than said second protocol data unit, said first protocol data unit being a protocol data unit received at a first ingress port of the network element to be controlled, and said second protocol data unit being a protocol data unit received at a second ingress port of the network element,
• software means for controlling said programmable processor to calculate, in response to a situation in which said first protocol data unit is later in said sequential order than said second protocol data unit, a time difference of receiving moments of said second protocol data unit and said first protocol data unit, said time difference representing a lower limit for a difference between the transmission delays experienced by said second protocol data unit and said first protocol data unit, and
• software means for controlling said programmable processor to remove said second ingress port from among ingress ports available to a routing protocol in response to a situation where said first protocol data unit is later in said sequential order than said second protocol data unit and an indicator value updated on the basis of said time difference exceeds a predetermined threshold value.