PDN Gateway Overview
▀ Features and Functionality - Base Software
▄ Cisco ASR 5x00 Packet Data Network Gateway Administration Guide
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MS may request for DNS server IPv4 or IPv6 addresses using the Protocol Configurations Options IE (as a container or
as part of IPCP protocol configuration request) in PDP Context Activation procedure for PDP Type IPv4, IPv6, or
IPv4v6. In that case, the P-GW may return the IP address of one or more DNS servers in the PCO IE in the PDP
Context Activation Response message. The DNS address(es) shall be coded in the PCO as specified in 3GPP TS 24.008.
For PDP Type IPv4v6, if MS requested DNS server IPv4 address, it did not return anIPv4 address. Support is now
added to respond with address requested by MS.
AAA server may also provide DNS Server IP Address in Access-Accept Auth Response. In such cases, AAA provided
DNS server IPs takes priority over the one configured under APN.
When DNS server address is requested in PCO configuration, the following preference would be followed:
1.
DNS values received from RADIUS Server.
2.
DNS values locally configured with APN.
3.
DNS values configured at context level with
ip name-servers
CLI.
Domain Based Flow Definitions
This solution provides improved flexibility and granularity in obtaining geographically correct exact IP entries of the
servers by snooping DNS responses.
Currently, it is possible to configure L7 rules to filter based on domain (m.google.com). Sometimes multiple servers
may serve a domain, each with its own IP address. Using an IP-rule instead of an http rule will result in multiple IP-
rules; one IP-rule for each server “behind” the domain, and it might get cumbersome to maintain a list of IP addresses
for domain-based filters.
In this solution, you can create ruledefs specifying hostnames (domain names) and parts of hostnames (domain names).
Upon the definition of the hostnames/domain names or parts of them, the P-GW will monitor all the DNS responses sent
towards the UE and will snoop only the DNS response, which has q-name or a-name as specified in the rules, and
identify all the IP addresses resulted from the DNS responses. DNS snooping will be done on live traffic for every
subscriber.
DSCP Marking
Provides support for more granular configuration of DSCP marking.
For Interactive Traffic class, the P-GW supports per-gateway service and per-APN configurable DSCP marking for
Uplink and Downlink direction based on Allocation/Retention Priority in addition to the current priorities.
The following matrix may be used to determine the Diffserv markings used based on the configured traffic class and
Allocation/Retention Priority:
Table 1.
Default DSCP Value Matrix
Allocation Priority
1
2
3
Traffic Handling Priority
1
ef
ef
ef
2
af21
af21
af21
3
af21
af21
af21
