Network terms and further reading

In this chapter

Internet and access, explained
Mobile and voice, explained

Internet and access, explained

These are some of the terms behind our public addresses, tunnel services and connections between networks. They describe different jobs along the same journey.

SDR and eNB

A software-defined radio, or SDR, uses software to perform radio functions. The BladeRF xA4 in my first setup was an SDR. An eNB, or eNodeB, is an LTE base station: the radio side that connects phones to the mobile core.

ASN and BGP

An ASN identifies a network's routing domain. BGP exchanges reachability information between networks. Our ASN is AS218388.

Prefix and default route

A prefix is an address block, written with a length such as /24 or /48. A default route is the next hop used when no more specific route applies.

IPv4, IPv6 and NAT

IPv4 and IPv6 are Internet address families. NAT translates addresses, often allowing private devices to share one public IPv4. CGNAT puts shared translation inside a provider's network.

RPKI and ROA

RPKI helps check which network is authorised to originate a route. A ROA records that origin permission and the permitted prefix length.

Tunnel, IPsec and WireGuard

A tunnel carries traffic inside another connection. IPsec and WireGuard provide protected transport. Plain L2TP carries PPP and needs a separate protection layer when encryption is required.

MTU, latency, jitter and loss

MTU limits packet size. Latency is travel time, jitter is variation in that time, and loss is traffic that fails to arrive. All affect the experience of using a connection.

Mobile and voice, explained

VoLTE and SMSoIP

VoLTE is Voice over LTE, using IMS to provide a mobile telephone service over 4G. SMSoIP is SMS over IP, carrying text messages through that IMS platform.

A phone connection brings together radio access, subscriber control, packet forwarding and telephone services. These names help identify the part doing each job.

eNodeB, backhaul and EPC

An eNodeB is a 4G base station. Backhaul connects its site to the wider network. EPC is the Evolved Packet Core behind LTE access.

MME and HSS

The MME manages attachment and mobility. The HSS holds subscriber and authentication information, helping the network recognise a SIM and its service.

SGW, PGW and CUPS

Serving and packet gateways handle the mobile data path. CUPS separates their control decisions from packet forwarding. The C and U suffixes identify those roles.

GTP-U and PFCP

GTP-U carries encapsulated mobile traffic. PFCP lets control functions install the rules used by user-plane gateways to forward it.

IMS and CSCF

IMS supplies the service layer for IP voice and messaging. Its proxy, interrogating and serving call control functions provide entry, subscriber lookup and service routing.

SIP, SDP and RTP

SIP controls a call. SDP describes its proposed media. RTP carries the audio packets. Keeping these jobs separate helps explain ringing, connection and sound.

PLMN

A PLMN identifies a mobile network through country and network codes. It has a different purpose from an Internet ASN.

Earlier chapters of our story

AzurePCS was the beginning of the project that became Lodestar. These early pages and updates show how the ideas and infrastructure developed.