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D-Link DSL-500B User Manual
Web Configuration
QoS-DSCP Setting
In order to understand what is differentiated services code point (DSCP), you should be familiar with the differen-
tiated services model (Diffserv).
Diffserv is a class of service (CoS) model that enhances best-effort Internet services via differentiating traffic by
users, service requirements and other criteria. Packets are specifically marked, allowing network nodes to provide
different levels of service via priority queuing or bandwidth allocation, or by choosing dedicated routes for specific
traffic flows.
As displayed in following diagram, the IPV4 packet has a TOS filed. Diffserv defines TOS field in IP packet headers
referred to as DSCP. Hosts or routes that pass traffic to a Diffserv-enabled network typically mark each trans
-
mitted packet with an appropriate DSCP. The DSCP markings are used by Diffserv network routers to appropriately
classify packets and to apply particular queue handing or scheduling behavior.
Layer 3 IPV4 Packet
Version/
Length
TOS
(1 Word)
Length
ID
Offset/
Mark
TTL
Protocol
Checksum
IP-SA
IP-DA
Data
TOS Filed-IP priority (TOS front 3 bit) or DSCP (front 6 bit)
7
6
5
4
3
2
1
0
IP Priority
Undefined
DSCP
Flow Control
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D-Link DSL-500B User Manual
Web Configuration
For example, mark each transmitted ICMP packet which passes
traffic to 0-35class with an appropriate DSCP (CS1).
After proper modifications, click
Save/Apply
and the following
page will appear.
Click
Save/Apply
. This configuration takes effective at once.
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D-Link DSL-500B User Manual
Web Configuration
Mark
TPID
(0x8100)
Priority
(3bit)
CFI
(1bit)
VLAN ID
(12bit)
For example: Mark the frame of 802.1p that queued to Queue 9 on
value 2.
After proper modifications, click
Save/Apply
to show the following
interface.
QoS-802.1p Setting
The IEEE 802.1p priority marking method is a standard for prioritizing network traffic at the data link/Mac sub-layer
802.1p traffic is simply classified and sent to the destination, with no bandwidth reservations established.
The follow diagram shows the structure of 802.1Q Frame. The 802.1Q header includes a 3-bit prioritization field,
which allows packets to be grouped to be grouped into eight levels of priority (0-7), where level 7 is the highest one.
In addition, DSL maps these eight levels to priority queues, where queue 1 has the highest priority.
Layer 2 802.Q Frame
Preamble
SFD DA SA
Mark
(4 word)
Len/Etype
(2 word)
DATA
FCS
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D-Link DSL-500B User Manual
Web Configuration
Select
Advanced Setup
>
Routing
. The
Routing - Default
Gateway
page will appear.
Routing - Default Gateway
In this page, you can modify the default gateway settings.
If you select
Enable Automatic Assigned Default Gateway
, this
router can accept the first received default gateway assignment
from one of the PPPoA, PPPoE or MER/DHCP enabled PVC(s).
If the check box is not selected, you must enter the static default
gateway and/or a WAN interface. Then, click
Save/Apply
.
Note:
If the
Automatic Assigned Default Gateway
check box is
changed from deselected to selected, you must reboot the router to
obtain the automatic assigned default gateway.
Routing
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D-Link DSL-500B User Manual
Web Configuration
Routing - Static Route
On this page you can modify the static route settings. You can
query the preset static routes, delete an existing static route, or add
a new static route. By default, the system has no static route infor-
mation.
Click
Add
and the following page will appear. Enter the destination
network address, subnet mask, gateway AND/OR available WAN
interface, then click
Save/Apply
to add the entry to the routing
table.
Destination:
The IP address to which packets are transmitted.
Subnet Mask:
The subnet mask of the destination IP address.
Gateway:
The gateway that the packets pass by during trans-
mission.
Interface:
The interface that the packets pass through on the
modem.
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