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Network layers define a hierarchy of services delineated by functionality. Each layer can use the functionality of the next layer below, and offers services to the next layer above. The packet accelerator sub-system examines and routes packets based on fields in up to three layers of the Ethernet packets or L0-L2 header of the SRIO packets.
In layer 2, the MAC (Media Access Control) layer, the sub-system classifies IEEE 802.3 packets based on (optionally) the destination MAC, source MAC, Ethertype, and VLAN tags.
In Layer 3, the network layer, IPv4 (Internet Protocol Version 4) and IPv6 (Internet Protocol Version 6) packets are routed based (optionally) on source IP address, destination IP address, IPv4 protocol, IPv6 next header, IPv4 Type of Service (recently changed to IPv4 differentiated service in RFC 2474), IPv6 traffic class, and IPv6 flow label. For IP packets with security services the SPI (Security Parameters Index) is also included in the classification information. For IP packets with SCTP (Stream Control Transmission Protocol) the SCTP destination port is also included in the classification information.
In layer 4, the transport layer, UDP (User Datagram Protocol) and TCP (Transmission Control Protocol) packets are routed based on the destination port. However, the GTP-U (GPRS Tunnelling Protocol User Plane) over UDP packets are routed based on its 32-bit TEID (Tunnel ID).
For SRIO (Serial RapidIO), L0-L2 header information the sub-system classifies SRIO packets based on (optional) the source ID, destination ID, transport type, priority, message type, SRIO type 11 mailbox and letter, SRIO type 9 stream ID and class of service.