Method and system for determining path maximum transfer unit for IP multicast
AssigneeCisco Technology, Inc.
InventorsSrinivas Subramanian, Anand Jayaraman, Balaji Venkataswami
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Abstract
A method and system for determining path maximum transfer unit (PMTU) in an Internet Protocol (IP) multicast is described. If a packet of a size greater than the MTU of any link of a path, with its Don't Fragment (DF) bit set, is sent by the source, the packet is dropped and an ICMP message, stating “Destination unreachable, DF bit set”, is sent to the source. The rate of messages to the source is controlled to avoid implosion of traffic. In response to the messages, the source sends multicast probe packets of multiple sizes to multicast distribution tree to determine its PMTU.
Claims18
A method for determining path maximum transmission unit (PMTU) for an internet protocol multicast which enables transfer of packets from a source device to a plurality of destination devices in a network, the method comprising:
- receiving a message at a source device when a packet transmitted from the source device has a size greater than the MTU of a link in a path to at least one destination device receiving the packet and don't fragment (DF) bit is set, the link comprising a connection between two adjacent nodes in the IP multicast;
- and
- determining PMTU of a multicast distribution tree comprising a set of paths from the source device to the destination devices and along which the packet is delivered to the destination devices.
A system for determining path maximum transmission unit (PMTU) for an internet protocol multicast enabling transfer of packets from a source device to a plurality of destination devices in a network, the system comprising:
- means for receiving a message at a source device when a packet transmitted from the source device has a size greater than the MTU of a link in a path to at least one destination device receiving the packet and don't fragment (DF) bit is set, the link comprising a connection between two adjacent nodes in the IP multicast;
- and
- means for determining PMTU of a multicast distribution tree having a set of paths from the source device to the destination devices and along which the packet is delivered to the destination devices.
A system for determining path maximum transmission unit (PMTU) for an internet protocol multicast, the internet protocol multicast enabling transfer of packets from a source device to a plurality of destination devices in a network, the system comprising:
- a message receiver for receiving a message at the source device when a packet transmitted from the source device has a size greater than the MTU of a link in a path to at least one destination device receiving the packet and don't fragment (DF) bit is set, the link comprising a connection between two adjacent nodes in the IP multicast;
- and
- a PMTU calculator for determining PMTU of a multicast distribution tree, the multicast distribution tree comprising a set of paths, from the source device to the destination devices, along which the packet is delivered to the destination devices.
A system for determining path maximum transmission unit (PMTU) for an internet protocol multicast, the internet protocol multicast enabling transfer of packets from a source device to a plurality of destination devices in a network, the system comprising:
- a message receiver for receiving a message at the source device when a packet transmitted from the source device has a size greater than the MTU of a link in a path to at least one destination receiving the packet and don't fragment (DF) bit is set, the link comprising a connection between two adjacent nodes in the IP multicast;
- and
- a PMTU calculator for determining PMTU of a multicast distribution tree, the multicast distribution tree comprising a set of paths, from the source device to the destination devices, along which the packet is delivered to the destination devices, the PMTU calculator comprising:
- a probe packet generator for generating a multicast probe packet by the source device at pre-defined time intervals, the multicast probe packet being packet of a certain size with DF bit set;
- and
- a probe packet sender for sending the multicast probe packet to each path in the multicast distribution tree.
An apparatus for determining path maximum transmission unit (PMTU) for an internet protocol multicast, the internet protocol multicast enabling transfer of packets from a source device to a plurality of destination devices in a network, the apparatus comprising:
- a processing system including a processor coupled to a display and user input device;
- a machine-readable medium including instructions executable by the processor comprising
- one or more instructions for receiving a message at the source device when a packet transmitted from the source device has a size greater than the MTU of a link in a path to at least one destination device receiving the packet and don't fragment (DF) bit is set, the link comprising a connection between two adjacent nodes in the IP multicast;
- and
- one or more instructions for determining PMTU of a multicast distribution tree, the multicast distribution tree comprising a set of paths, from the source device to the destination devices, along which the packet is delivered to the destination devices.
A machine-readable medium including instructions executable by the processor comprising:
- one or more instructions for receiving a message at the source device when a packet transmitted from the source device has a size greater than the MTU of a link in a path to at least one destination device receiving the packet and don't fragment (DF) bit is set, the link comprising a connection between two adjacent nodes in the IP multicast;
- and
- one or more instructions for determining PMTU of a multicast distribution tree, the multicast distribution tree being a set of paths, from the source device to the destination devices, along which the packet is delivered to the destination devices.
Dependencies are inferred from the claim text.