DNS Basics in LTE EPC: Records Explained (A, AAAA, SRV, NAPTR)

This page describes DNS basics in LTE. DNS stands for Domain Name System. LTE stands for Long Term Evolution. It mentions DNS records used in LTE EPC viz. A record, AAAA record, SRV record and NAPTR record. It provides a link to functions of DNS and DHCP. EPC (Evolved Packet Core) in LTE depends on DNS to find critical services.

We know that EPC services are referenced by their names. DNS is the directory service to provide mapping of service addresses to names.

When the connection (Attach request) is initiated by subscriber (here smartphone) it goes through eNodeB, MME and reaches DNS. The DNS resolves the IP address which is to be used for the packet gateway.

The DNS server replies to MME with a list of IP addresses in order to pick a Gateway for forwarding or routing the IP packets. Usually DNS provides a static list of packet gateways. This list often includes failed or out-of-service packet gateways also.

These gateways are running with unequal network loads. This leads to poor customer satisfaction, dropped connections and higher CAPEX/OPEX. To avoid above problems, intelligent DNS have been developed in order to provide DNS reply with only available and healthy packet gateways. Moreover subscribers are evenly distributed among available packet gateways so that load is equally balanced.

DNS Records used in LTE EPC | A record, AAAA record, SRV record, NAPTR record

The DNS records used in LTE EPC are A record, AAAA record, SRV record and NAPTR record. Each of these have specific meanings as described below.

• DNS A Record: This record is used to map hostnames to IPv4 Addresses.
• DNS AAAA Record: This record is used to map hostnames to IPv6 Addresses.
• DNS SRV Record: This is known as a resource record. It is used to specify the location of services. Due to this record, a client can request a specific protocol or service for a specific domain. Moreover, due to this resource record, clients get back names of the available servers.
• DNS NAPTR Record: This resource record is specified in RFC 3403. NAPTR stands for Name Authority Pointer. This NAPTR record allows DNS to be used for lookup services for a variety of resource names. These resource names are not even in domain name syntax. This record can be used by a client program in order to re-write a string into a domain name. The re-write process is controlled by the flags. These flags provide information on communication with the host at the domain name which was the result of the re-write operation.