Zyxel NXC5500 [146/469] Assured forwarding af phb for diffserv

Zyxel NXC5500 [146/469] Assured forwarding af phb for diffserv
Chapter 9 Policy and Static Routes
NXC Series User’s Guide
146
NAT and SNAT
NAT (Network Address Translation - NAT, RFC 1631) is the translation of the IP address in a packet
in one network to a different IP address in another network. Use SNAT (Source NAT) to change the
source IP address in one network to a different IP address in another network.
Assured Forwarding (AF) PHB for DiffServ
Assured Forwarding (AF) behavior is defined in RFC 2597. The AF behavior group defines four AF
classes. Inside each class, packets are given a high, medium or low drop precedence. The drop
precedence determines the probability that routers in the network will drop packets when
congestion occurs. If congestion occurs between classes, the traffic in the higher class (smaller
numbered class) is generally given priority. Combining the classes and drop precedence produces
the following twelve DSCP encodings from AF11 through AF43. The decimal equivalent is listed in
brackets.
WMM
Wi-Fi Multimedia (WMM) provides basic Quality of Service (QoS) features to wireless networks. The
four categories of QoS described by WMM are: voice (VO), video (VI), best effort (BE), and
background (BK). These categories, known as a “access categories” (AC), are mapped to 802.1D
priority values which can then be mapped to their corresponding DSCP hex values.
The WMM ACs as implemented on the NXC have the following functions:
VOICE: All wireless traffic to the SSID is tagged as voice data. This is recommended if an SSID is
used for activities like placing and receiving VoIP phone calls.
VIDEO: All wireless traffic to the SSID is tagged as video data. This is recommended for activities
like video conferencing.
Table 71 Assured Forwarding (AF) Behavior Group
Class 1 Class 2 Class 3 Class 4
Low Drop Precedence AF11 (10) AF21 (18) AF31 (26) AF41 (34)
Medium Drop Precedence AF12 (12) AF22 (20) AF32 (28) AF42 (36)
High Drop Precedence AF13 (14) AF23 (22) AF33 (30) AF43 (38)
Table 72 WMM to DiffServ Conversion on the NXC
Priority WMM AC 802.1D Priority DSCP Hex Value
Lowest
Highest
BK 1 0x08
BK 2 0x10
BE 0 0x00
BE 3 0x18
VI 4 0x20
VI 5 0x28
VO 6 0x30
VO 7 0x38

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