Transport of aggregated client packets
View Patent ↗The invention relates to a method for transmitting one or more client signals via a packet transport network. According to the method, packets of the one or more client signals are received at an ingress node of the network. Timing information characterizing the timing of the received packets is determined and the received packets are mapped into a container. The container and the timing information are transmitted via the network. At an egress node of the network, the packets are extracted from the container and the packets are timed for further transmission based on the transmitted timing information.
1. A method of transmitting packets via a packet transport network, the method comprising the steps of: at an ingress node of the network, receiving and accumulating packets of one or more client signals, with a variable traffic load of said packets; determining timing information characterizing the timing of the received packets; and mapping the accumulated packets into a container so that in case of low traffic load, packets that are well separated upon arrival at the ingress node are accumulated together in the container and appear to an egress node of the network as a burst of packets after transmission of the container via the transport network, and so that said variable traffic load at the ingress node results in variable times for accumulating packets for the containers, with variations of delay between containers, and in jitter of packet arrival at the egress node; wherein the earliest received packet to be transmitted in a respective container waits during the accumulation of packets for a first time period at the ingress node; transmitting the container and the timing information via the network; and at said egress node of the network, receiving the container, extracting the packets from the container and timing the packets for further transmission based on the timing information; and causing the earliest received packet to wait at the egress node for a second time period such that the sum of the first and second periods is an essentially constant time period, the ratio between the first time period at the ingress node and the second time period at the egress node being dependent on the load of the ingress node.
2. The method of claim 1 , further comprising the step of:
monitoring whether a predetermined time-out period is reached at the ingress node for the earliest received packet to be transmitted in the container.
3. The method of claim 2 , further comprising the step of:
monitoring whether the accumulated packets at the ingress node reach a predetermined portion of the container capacity;
wherein at the ingress node the container is prepared for transmission when the predetermined time-out period is reached for the earliest packet, or when the accumulated packets reach a predetermined portion of the container capacity; and
wherein at the egress node the earliest packet is timed based on the non-elapsed portion of the time-out period and the remaining packets in the container are timed based on the timing information, thereby essentially reproducing the relative timing of the packets to each other.
4. The method of claim 2 , further comprising the steps of:
at the ingress node, storing the packets in a first buffer; and
at the egress node, storing the content of the received container in a second buffer,
wherein it is monitored whether the predetermined time-out period is reached for the earliest packet for the container in the first buffer, and
wherein the content of the first buffer for the container is prepared for transmission when the predetermined time-out period has lapsed for the earliest packet.
5. The method of claim 4 , further comprising the step of:
monitoring whether the first buffer reaches a predetermined filling size;
wherein the content of the first buffer is processed for transmission when the first buffer reaches the predetermined filling size, and
wherein the earliest packet is released from the second buffer timed based on the non-elapsed portion of the time-out period and the remaining packets of the container are released from the second buffer timed based on the timing information, thereby essentially reproducing the relative timing of the packets to each other.
6. The method of claim 3 , wherein the transmitted timing information related to the earliest packet indicates the non-elapsed portion of the time-out period.
7. The method of claim 1 , wherein the container is an Ethernet jumbo frame.
8. The method of claim 1 , wherein the determining and mapping steps comprise the steps of:
encoding the received packets by means of a modified Generic Framing Procedure, GFP, wherein GFP specific idle frames are left out; and
counting left out idle frames.
9. The method of claim 8 , wherein the encoding step comprises the steps of:
generating a data stream essentially pursuant to the GFP, with the data stream having GFP specific idle frames; and removing the idle frames.
10. The method according to claim 8 , wherein the determining and mapping steps comprise the step of
storing the numbers of left out idle frames in spare fields of GFP headers.
11. The method of claim 10 , wherein the number of left out idle frames is stored in the GFP header of the packet directly following the respective left out idle frames.
12. The method of claim 8 , wherein the timing step comprises the step of inserting idle frames as indicated by the numbers of left out idle frames.
13. A packet transport network, comprising: at an ingress node of the network, a first network element comprising: means for receiving and accumulating packets of one or more client signals, with a variable traffic load of said packets, to be transmitted via the network; determining means for determining timing information characterizing the timing of the received packets; mapping means for mapping the accumulated packets into a container so that in case of low traffic load, packets that are well separated upon arrival at the ingress node are accumulated together in the container and appear to an egress node of the network as a burst of packets after transmission of the container via the transport network, and so that said variable traffic load at the ingress node results in variable times for accumulating packets for the containers, with variations of delay between containers, and in jitter of packet arrival at the egress node, wherein the earliest received packet to be transmitted in a respective container waits during the accumulation of packets for a first time period at the ingress node; transmitting means for transmitting the container and the timing information via the network; and at said egress node of the network, a second network element comprising: receiving means for receiving the container as generated by the first network element at the ingress node of the network; and extracting means for extracting the packets from the container and timing means for timing the packets for further transmission based on the timing information, said timing means causing the earliest received packet to wait a second time period at the egress node such that the sum of said first and second time periods is an essentially constant time period, the ratio between the first time period at the ingress node and the second time period at the egress node being dependent on the load of the ingress node.