Service Provider & Internet

The documents on this page pertain core Service Provider technology that don’t fit into the other document categories listed on the overview page.

6to4 Tunnelling

A visual guide to 6to4 Automatic Tunnels, breaking down details like how IPv4 addresses are embedded in IPv6 addresses and how tunnels are formed.

Carrier Supporting Carrier

When a Service Provider needs to connect two separate parts of its network together, sometimes it needs to call on another Service Provider to help. This document covers just such a scenario known as CsC or Carrier Supporting Carrier. An accompanying downloadable lab and full configs can be downloaded from here.

DNS Basics

This gives a broad overview of how the Domain Name System works and offer quick reference for anyone new to its workings.

EVPN Concepts

Shows the basic principle involved in EVPN, including Route Type, forwarding planes and multihoming features.

Inter-AS MPLS Options

MPLS communications between Autonomous Systems can be achieved a number of ways and can sometimes be confusing to get your head around. This document outlines the different possibilities, giving diagrams of the overall concepts as well as CLI output from the downloadable labs that can be downloaded from here.

L2TP Overview

Summary diagram of the fundamentals of L2TP along with its connection establishment and operation with PPP.

LDP Basics

A brief overview of LDP Discovery, Neighborships and Modes.

MPLS TE Database & RSVP Process

This document shows three basic concepts of MPLS Traffic Engineering: (1) How the Topology Database is populated, (2) How the RESV and PATH messages are used to signal an MPLS TE tunnel and (3) The contents of the RSVP messages.

NAT64

NAT64 is a common method of IPv4/IPv6 co-existence, that implements translation of IPv6 address into IPv4 addresses. This document addresses both stateful and stateless methods.

NAT Types

Inside and Outside NAT vs. Local and Global NAT is a bit confusing. Use this diagram as a quick reference to keep it straight in your head:

OSPF Sham Links

Sham links are used across Service Provider cores in scenarios whereby intra vs inter area routes might cause routing issues for OSPF in MPLS solutions. This diagram shows such a scenario and summarises the configuration of a sham link.

Packet Path through QinQ & PBB Network

It’s often difficult to understand a concept until you look at the “life of a packet” as it goes through the network. This doc is designed to explore, step by step, how a packet would traverse a QinQ and then a PBB network.

Pseudowire Overview

Shows a conceptual overview of what an MPLS pseudowire (or xconnect) is, as well as how it is signalled.

SSL Operation

This shows the sequence of events that takes place behind the scenes when your PC browses to a website using HTTPS with SSL.

Unified MPLS

This document shows the principles involved in setting up Unified MPLS and the life of a packet from one CE to another.

VPLS with BGP Signalling

A breakdown of how labels are communicated in BGP when VPLS signalling is used.

VRF Routing Leaking using Import & Export maps

This documents shows how traffic passes from one VRF to another and where all the config sits, using import and export maps.

VxLAN Packet & Basic Operation

Shows the header structure of a VxLAN packet down to layer two, in conjunction with how it might be forwarded within a VxLAN fabric.