Multicast - GLOP address space

The GLOP multicast address space is an experimental public statically assigned multicast address space for ISPs and other entities to source multicast content on the Internet. The GLOP address space consists of the IPv4 address range.

GLOP addressing defines a multicast address allocation method that provides a block of 255 addresses that are determined by their 16-bit autonomous system number (ASN) allocation. The middle two octets of the GLOP address are formed by the assigned ASN.

For example, an ASN of 5670 would result in the following GLOP multicast address:

  • 5670 in binary is 0001011000100110‬
  • Separate that into two octets: 00010110.00100110‬
  • Write that in decimal: 22.38
  • Use those values for the middle to octets of the GLOP address:

Thus the resulting GLOP address space for this particular ASN is

GLOP does not support 32-bit ASNs.

GLOP was only experimental and was never implemented on the Internet. With only 256 multicast addresses available to each ASN, it was inadequate for large scale broadcasters.