Why an even number of frames should be received at the receiver?

[mad_mavula]

I'm new to the computer networks. Can someone please answer this?

[Joseph W. Doherty]

Where did you read there was such a requirement?

Possibly you were reading about TCP which normally ACKs every other packet?  If so, such was done to reduce overhead, but even TCP will, eventually, ACK an odd number of packets.

[mad_mavula]

I was searching about alignment errors, and I was able to find out an error which is taken as an alignment error when an odd number of frames are received.

https://community.cisco.com/t5/networking-documents/alignment-error-counter-increments-due-to-a-misconfiguration-or/ta-p/3131451#:~:text=Alignment%20errors%20are%20the%20count,Cyclic%20Redundancy%20Check%20(CRC).&text=On%20a%20Cisco%20IOS%20-based,to...

[Joseph W. Doherty]

You misunderstand that document.  It notes "Alignment errors are the count of the number of frames received that do not end with an even number of octets and have a bad Cyclic Redundancy Check (CRC).", i.e. not the number of odd number of frames received.

[mad_mavula]

yeah that was my mistake.