Dell Force10 C150 Configuration Manual page 486

Traffic Class (8 bits)
The Traffic Class field deals with any data that needs special handling. These bits define the packet priority
and are defined by the packet Source. Sending and forwarding routers use this field to identify different
IPv6 classes and priorities. Routers understand the priority settings and handle them appropriately during
conditions of congestion.
Flow Label (20 bits)
The Flow Label field identifies packets requiring special treatment in order to manage real-time data
traffic. The sending router can label sequences of IPv6 packets so that forwarding routers can process
packets within the same flow without needing to reprocess each packet's head separately.
Note: All packets in the flow must have the same source and destination addresses.
Payload Length (16 bits)
The Payload Length field specifies the packet payload. This is the length of the data following the IPv6
header. IPv6 Payload Length only includes the data following the header, not the header itself.
The Payload Length limit of 2 bytes requires that the maximum packet payload be 64 KB. However, the
Jumbogram option type Extension header supports larger packet sizes when required.
Next Header (8 bits)
The Next Header field identifies the next header's type. If an Extension header is used, this field contains
the type of Extension header
is the same as for IPv4. The Extension header is located between the IP header and the TCP or UDP
header.
Table 22-1. Next Header field values
Value
0
4
6
8
41
43
44
50
51
486 | IPv6 Addressing
(Table 22-1). If the next header is a TCP or UDP header, the value in this field
Description
Hop-by Hop option header following
IPv4
TCP
Exterior Gateway Protocol (EGP)
IPv6
Routing header
Fragmentation header
Encrypted Security
Authentication header