Topic of discussion: Class D & Class E in IP addressing.
Classful Addressing consists of 5 classes: A, B, C, D, and E.
Previous classes discussed: A, B, and C.
Class D
Definition & Characteristics
Class D consists of 32-bit IP addresses divided into 4 octets (8 bits each).
The first octet is crucial for determining the class of the IP address.
Fixed binary prefix for Class D: 1110.
If the first octet's binary representation starts with 1110, then it belongs to Class D.
Range of Class D
Decimal range for Class D: 224 to 239.
First octet values: 224 (11100000) to 239 (11101111).
Total number of unique addresses in Class D: 2^28 addresses (approximately 250 million).
Purpose and Limitations
Class D addresses are reserved for multicasting and group broadcasting.
No network or host addresses because all Class D IPs are reserved, leading to a waste of IP addresses since many are unused.
Approximately 6.25% of total IP addresses fall under Class D.
Class E
Definition & Characteristics
Similar structure to Class D with 32-bit IP addresses and 4 octets.
Fixed binary prefix for Class E: 1111.
Decimal range for Class E: 240 to 255.
First octet values: 240 (11110000) to 255 (11111111).
Total number of unique addresses in Class E: 2^28 addresses (approximately 250 million).
Purpose
Class E addresses are reserved exclusively for military purposes.
No network or host addresses similar to Class D.
Observations on Classes D & E
Both classes result in a significant waste of IP addresses due to their reservation.
Historical context: Classful Addressing was replaced by Classless Addressing post-1993 due to increasing user demand and the need for more flexible address allocation.
Examples
Given example of Class D: 239.1.2.3 belongs to Class D.
Given example of Class E: 245.0.1.2 belongs to Class E.
Important to note that there is no network or host allocation for both classes due to the reserved nature of the addresses.
Conclusion
Class D and E addresses serve important specific purposes but contribute to IP address wastage. The transition to Classless Addressing has provided more efficient IP address management.