Congestion handling in multicast networks
The invention relates to techniques for traffic handling in congestion situations in a point-to-multipoint (‘PTM’) enabled network. A method embodiment of the inventive technique is performed in an egress node of the network and comprises the steps of detecting marked packets, the marking being indicative of a congestion situation in a core node of the PTM-enabled network; selecting, based on the detected markings, a particular PTM flow from one or more PTM flows passing the egress node for termination; and indicating the selected PTM flow in an upstream direction of the selected flow.
1. A method of traffic handling in congestion situations in a point-to-multipoint (“PTM”) enabled network, the method being performed in an egress node of the network and comprising the steps of:
detecting marked packets, the marking being indicative of a congestion situation in a core node of the PTM-enabled network;
distinguishing between marked packets belonging to a unicast flow and marked packets belonging to a multicast flow;
selecting, based on the detected markings and based on the distinguishing between unicast and multicast flows, a particular PTM flow from one or more PTM flows passing the egress node for termination; and
indicating the selected PTM flow in an upstream direction of the selected flow.
2. The method according to claim 1 , wherein the step of detecting the marked packets is performed separately for each of one or more interfaces of the egress node.
3. The method according to claim 1 , wherein the step of selecting a particular PTM flow comprises determining, based on the detected marked packets, one or more traffic flows affected by the marking.
4. The method according to claim 3 , wherein the step of selecting the particular PTM flow comprises determining one or more PTM flows among the one or more traffic flows affected by the marking.
5. The method according to claim 4 , wherein the step of selecting a particular PTM flow comprises selecting, based on the determined overload level, a particular PTM flow from the one or more PTM flows which have been determined to be affected by the marking.
6. The method according to claim 1 , wherein the step of selecting the particular PTM flow comprises determining, based on the marked packets, an overload level.
7. The method according to claim 1 , wherein the step of indicating the selected PTM flow comprises sending a termination indication related to the selected PTM flow in the upstream direction.
8. The method according to claim 7 , wherein the termination indication, according to the Protocol Independent Multicast (“PIM”) standard, comprises a PIM prune message.
9. An egress node adapted for traffic handling in congestion situations in a point-to-multipoint (“PTM”) enabled network, comprising:
a first component adapted to detect marked packets, the marking being indicative of a congestion situation in a first core node of the PTM-enabled network;
a second component adapted to distinguish between marked packets belonging to a unicast flow and marked packets belonging to a multicast flow and adapted to select, based on the detected markings and based on the distinguishing between unicast and multicast flows, a particular PTM flow from one or more PTM flows passing the egress node for termination; and
a third component adapted to indicate the selected PTM flow in an upstream direction of the selected flow.
10. The egress node according to claim 9 , wherein the first component is adapted to detect marked packets associated with one of one or more interfaces of the egress node.
11. The egress node according to claim 9 , wherein the second component is adapted to determine, based on the marked packets, one or more PTM flows affected by the marking.
12. A point-to-multipoint (“PTM”) enabled network, comprising multiple egress nodes wherein in each of the egress nodes a component adapted for selecting a particular PTM flow from one or more PTM flows is identically implemented, each egress node comprising:
a first component adapted to detect marked packets, the marking being indicative of a congestion situation in a first core node of the PTM-enabled network;
a second component adapted to distinguish between marked packets belonging to a unicast flow and marked packets belonging to a multicast flow and adapted to select, based on the detected markings and based on the distinguishing between unicast and multicast flows, a particular PTM flow from one or more PTM flows passing the egress node for termination; and
a third component adapted to indicate the selected PTM flow in an upstream direction of the selected flow.
13. The PTM-enabled network according to claim 12 , further comprising one or more second core nodes adapted to forward marked packets received from the congested first core node to the one or more egress nodes by identically replicating the marked packets in case the marked packets belong to one or more PTM flows.