Moby Dick Consolidated System Integration Plan

D0103v1.doc Version 1 6.7.2003
4.2.2.7.2 DMS location
Application 1 Application 2
Application level module
DSCP
matching
table
Fast Handover
module
Enhanced IPv6 stack
Standard IPv6 stack
MIPL
DSCP marking software
Network devicedrivers
TDCDMA WLAN Ethernet
Figure 48: Location of the DSCP marking software in the IP stack
The previous figure shows where the DMS will be located in the protocol stack. It « intercepts » packets
just before transmitting them to the lower layer. Thus, all the packets generated by both the IP stack and
the upper layers can be filtered and marked.
4.2.2.7.3 DMS Architecture
The DMS contains five components, as in figure 49:
• a DSCP Matching Table (DMT): this table contains the definition of every filter and the DSCP
associated with it in the Linux kernel space,
• a DSCP Marking Function (DMF): this is the DMS engine, which consults the fields in the different
headers of each packet, compares it with the filters in the DMT, and decides to mark or not the
packet with a new DSCP; it is located in the Linux kernel (in the IPv6 code),
• a Filters Database (FD): this file (or set of files) contains the definitions of all the filters, in the user
space,
• a Table Update Module (TUM): this is a Linux module in charge of updating the DSCP Matching
Table with the data stored in the Filters Database,
• a Service Table (ST): this table, only used by the TUM, associates a DSCP with each service.
4.2.2.7.4 DSCP Matching
The packet marking process is based on the search of a table containing all the filters definitions
whenever a packet is ready to be transmitted. In this section, we describe how these filters are introduced
by a user, and how the DMT is built and updated.
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