The IPv4 protocol has several limitations, which include:

• Scarcity of IPv4 Addresses: The IPv4 addressing system uses a 32-bit address space, which allows for 4,294,967,296 IPv4 addresses. However, the previous and current IPv4 address allocation practices limit the number of available public IPv4 addresses. This has created a scarcity of IPv4 addresses, and many organizations have implemented Network Address Translation (NAT) to map multiple private IPv4 addresses to a single public IPv4 address to conserve IPv4 addresses.

• Weak Protocol Extensibility: The IPv4 header has an insufficient size that does not accommodate the required number of additional parameters, which limits the protocols extensibility.

• Lack of End-to-End Connectivity: IPv4 does not provide end-to-end connectivity, which means that the communication between two hosts may require multiple network hops, and each hop may introduce additional latency and packet loss.

• Security Related Issues: IPv4 was not designed with security in mind, and the current network security threats were not anticipated at the time of its publication. This has created security-related issues that need to be addressed.

• Lack of Quality of Service Support: IPv4 does not support the placement of information about bandwidth and delays required for the smooth operation of some network applications.

• Geographic Limitations: Since the Internet was created in the USA, this country is also involved in the distribution of IP addresses. Almost 50% of all addresses are reserved for the United States, which creates geographic limitations.

In summary, the limitations of the IPv4 protocol include scarcity of IPv4 addresses, weak protocol extensibility, lack of end-to-end connectivity, security-related issues, lack of quality of service support, and geographic limitations.