Connectivity¶

Ella Core uses 4 different interfaces by default:

Interface	Role	Transport	`name`	`address`	Address families
API	The HTTP API and UI	TCP, `interfaces.api.port`	Yes	Yes	IPv4, IPv6
N2 / S1-MME	Control plane between Ella Core and the radio	SCTP, `38412` (5G) and `36412` (4G) by default	Yes	Yes	IPv4, IPv6.
N3 / S1-U	User plane between Ella Core and the radio	UDP `2152`	Yes	Yes	IPv4, IPv6.
N6 / SGi	User plane between Ella Core and the internet	—	Yes	No	Not configurable

Combining interfaces¶

It is possible to combine interfaces in the following manners.

Combined N2 and N3¶

Many radios can use a single network link towards the core. In this case, N2 and N3 can be combined by using the same interface name for both of them in the configuration file.

Combined API and N6¶

The API interface is often the network interface with internet access, and the N6 interface also requires internet access. They can be combined by using the same interface name for both in the configuration file.

Combined API/N6 and combined N2/N3¶

It is possible to use both combination together to reduce the requirements to 2 interfaces.

One or both of these interfaces can be virtual interfaces, with veth. See Datapath constraints.

Combined on one interface¶

Ella Core can also be run with a single network interface. It can be achieved by using the same interface name in the configuration file, or by using VLANs.

Using VLANs¶

It is possible to use VLAN interfaces, with or without combining interfaces as described previously. In this case, the configuration file should contain the name of the VLAN interface, not the parent interface.

Datapath constraints¶

The datapath attaches to N3 and N6 at the hook set by datapath.attach-mode. The shape of those interfaces constrains which modes work.

veth, xdp-native: an XDP program must be attached to the peer interface, see the explanation and the setup guide.
veth, xdp-generic: TX checksum offload must be disabled on both ends (ethtool -K <veth> tx off), or decapsulated packets are silently corrupted.
Any interface, tcx or xdp-generic: the interface must not deliver merged packets, see Disable merged packets.

NAT¶

Property	Behaviour
Default	Enabled
Address family	IPv4 only
Scope	Uplink traffic leaving N6, sourced from the N6 address
Translated protocols	TCP, UDP, and ICMP
Source ports	`1024`-`32767`
Downlink traffic	Delivered only when it matches a translation the subscriber's own traffic created.
Untranslatable traffic	IP fragments (`nat_fragment`) and protocols without ports, such as ESP and GRE (`nat_unsupported_proto`), are dropped. Protocols that embed addresses in their payload, such as FTP in active mode, do not work
Configuration	The `Networking` page of the UI, or the Networking API.