MLPPP Subscriber Accounting Statistics Overview

Client-to-Internet Traffic Statistics

When the client sends IP packets towards the Internet, they may be fragmented. For example, packet P1 is fragmented into F1 and F2, and the fragments belonging to a single packet can be sent on different links (Figure 1).

• F1 is sent on Link 1

• F2 is sent on Link 2

When Link 1 on the MX Series receives fragment F1, it is identified as an MLPPP encapsulated fragment. Because IPv4 or IPv6 families are indicated on the first fragment, all of the incoming fragments are counted using a protocol-agnostic method before the fragment is forwarded to the bundle for reassembly.

• The protocol-agnostic incoming packet count is incremented by 1.

• The protocol-agnostic incoming byte count is incremented by the size of the fragment.

Similarly on Link 2, fragment F2 is also counted using a protocol-agnostic method, and then forwarded to the bundle for reassembly.

Fragment F1 arrives at the bundle and is stored along with its MLPPP header containing the sequence number with the begin flag set to 0, and the end flag set to 1.

Fragment F2 arrives at the bundle and is stored along with its MLPPP header containing the sequence number with the begin flag set to 1, and the end flag set to 0.

The pattern of monotonically increasing sequence numbers, begin flag set to 1 and end flag set to 1, causes fragments F1 and F2 to be reassembled into a single packet.

After the packet has been reassembled, the packet's Layer 3 type (either IPv4 or IPv6) is determined at the bundle. Then, the packets and bytes are counted according to its Layer 3 type at the bundle based on accurate accounting statistics:

• bundleA_ipv4_packets_from_client += 1

• bundleA_ipv4_bytes_from_client += packet_size

Or

• bundleA_ipv6_packets_from_client += 1

• bundleA_ipv6_bytes_from_client += packet_size

Internet-to-Client Traffic Statistics

In the reverse direction, Layer 3 packets come from the Internet to the bundle.

The packets and bytes are counted according to its Layer 3 type at the bundle:

• bundleA_ipv4_packets_to_client += 1

• bundleA_ipv4_bytes_to_client += packet_size

Or

• bundleA_ipv6_packets_to_client += 1

• bundleA_ipv6_bytes_to_client += packet_size

If the packets are fragmented, the fragments belonging to the same packet can be sent out different links. Because no IPv4 or IPv6 families are indicated on the links, all of the outgoing fragments are counted using a protocol-agnostic method.

• The protocol-agnostic outgoing packet count is incremented by 1.

• The protocol-agnostic outgoing byte count is incremented by the size of the fragment.