TP-Link T1500G-8T T1500G-10PSUN V1 User Guide - Page 102

IPv4 Multicast Address, Multicast IP address range, Description

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3. Each user can join and leave the multicast group at any time; 4. Real time is highly demanded and certain packets drop is allowed.  IPv4 Multicast Address 1. IPv4 Multicast IP Address: As specified by IANA (Internet Assigned Numbers Authority), Class D IP addresses are used as destination addresses of multicast packets. The multicast IP addresses range from 224.0.0.0~239.255.255.255. The following table displays the range and description of several special multicast IP addresses. Multicast IP address range Description 224.0.0.0~224.0.0.255 Reserved multicast addresses for routing protocols and other network protocols 224.0.1.0~224.0.1.255 Addresses for video conferencing 239.0.0.0 239.255.255.255 ~ Local management multicast addresses, which are used in the local network only Table 8-1 Range of the special multicast IP 2. IPv4 Multicast MAC Address: When a unicast packet is transmitted in an Ethernet network, the destination MAC address is the MAC address of the receiver. When a multicast packet is transmitted in an Ethernet network, the destination is not a receiver but a group with uncertain number of members, so a multicast MAC address, a logical MAC address, is needed to be used as the destination address. As stipulated by IANA, the high-order 24 bits of a multicast MAC address begins with 01-00-5E while the low-order 23 bits of a multicast MAC address are the low-order 23 bits of the multicast IP address. The mapping relationship is described as Figure 8-2. Figure 8-2 Mapping relationship between multicast IPv4 address and multicast MAC address The high-order 4 bits of the IP multicast address are 1110, identifying the multicast group. Only 23 bits of the remaining low-order 28 bits are mapped to a multicast MAC address. In that way, 5 bits of the IP multicast address is not utilized. As a result, 32 IP multicast addresses are mapped to the same MAC addresses. 92

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3.
Each user can join and leave the multicast group at any time;
4.
Real time is highly demanded and certain packets drop is allowed.
IPv4 Multicast Address
1.
IPv4 Multicast IP Address:
As specified by IANA (Internet Assigned Numbers Authority), Class D IP addresses are used as
destination addresses of multicast packets. The multicast IP addresses range from
224.0.0.0~239.255.255.255. The following table displays the range and description of several
special multicast IP addresses.
Multicast IP address range
Description
224.0.0.0
224.0.0.255
Reserved multicast addresses for routing protocols
and other network protocols
224.0.1.0
224.0.1.255
Addresses for video conferencing
239.0.0.0
239.255.255.255
Local management multicast addresses, which are
used in the local network only
Table 8-1 Range of the special multicast IP
2.
IPv4 Multicast MAC Address:
When a unicast packet is transmitted in an Ethernet network, the destination MAC address is
the MAC address of the receiver. When a multicast packet is transmitted in an Ethernet
network, the destination is not a receiver but a group with uncertain number of members, so a
multicast MAC address, a logical MAC address, is needed to be used as the destination
address.
As stipulated by IANA, the high-order 24 bits of a multicast MAC address begins with 01-00-5E
while the low-order 23 bits of a multicast MAC address are the low-order 23 bits of the
multicast IP address. The mapping relationship is described as Figure 8-2.
Figure 8-2 Mapping relationship between multicast IPv4 address and multicast MAC address
The high-order 4 bits of the IP multicast address are 1110, identifying the multicast group. Only
23 bits of the remaining low-order 28 bits are mapped to a multicast MAC address. In that way,
5 bits of the IP multicast address is not utilized. As a result, 32 IP multicast addresses are
mapped to the same MAC addresses.
92