QoS

IP 封包中的欄位

In RFC2474, these fields are interpreted as 8-bit Differentiated Services (DS)

• bits 0-1 (2 lowest bits) of separate data
• bits 2-7 (highest 6 bits) of Differentiated Services Codepoint (DSCP).

In RFC2481 and RFC3168, bits 0-1 are used for ECN.

Historically (RFC1349, obsoleted by RFC2474), these were interpreted as: bit 0 (lowest bit) for reserved (currently being redefined as congestion control), 1-4 for Type of Service and bits 5-7 (highest bits) for Precedence.

tos 值對應 DSCP 對應表：

"CS0", 0x00 },

{ "CS1", 0x08 },

{ "CS2", 0x10 },

{ "CS3", 0x18 },

{ "CS4", 0x20 },

{ "CS5", 0x28 },

{ "CS6", 0x30 },

{ "CS7", 0x38 },

{ "AF11", 0x0A },

{ "AF12", 0x0C },

{ "AF13", 0x0E },

{ "AF21", 0x12 },

{ "AF22", 0x14 },

{ "AF23", 0x16 },

{ "AF31", 0x1A },

{ "AF32", 0x1C },

{ "AF33", 0x1E },

{ "AF41", 0x22 },

{ "AF42", 0x24 },

{ "AF43", 0x26 },

{ "EF", 0x2E

設 IP ToS

• IPv4 或 any address 的 IPv6
• setsockopt(sockfd, IPPROTO_IP, IP_TOS, &tos, sizeof(tos))
• IPv6
• setsockopt(sockfd, IPPROTO_IPV6, IPV6_TCLASS, &tos, sizeof(tos))