Networking

Layers, packets and addresses.

1. Interactive

   Coming soon

   The network layers

   OSI and TCP/IP: what each layer adds.

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   Coming soon

   Packets and encapsulation

   Wrap data in headers, layer by layer.

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   Coming soon

   IP addresses and subnets

   Addresses, masks and which machines are local.

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   Coming soon

   MAC addresses and ARP

   Finding the next machine on the local network.

5. Interactive

   Live

   NAT and private networks

   Many devices behind one public address.

   Open session →

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   Coming soon

   IPv6

   Why we need it and what changes.

Getting bytes there reliably, or quickly.

1. Interactive

   Live

   The TCP handshake

   SYN, SYN-ACK, ACK, and what it costs in round trips.

   Open session →

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   Coming soon

   Retransmission and acknowledgements

   How TCP recovers a lost packet.

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   Live

   Flow control

   The receive window stops a fast sender drowning a slow receiver.

   Open session →

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   Live

   Congestion control

   Slow start, backing off on loss, and sharing the link.

   Open session →

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   Coming soon

   UDP

   Send and forget: no handshake, no retries.

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   Coming soon

   TCP vs UDP

   Which to use for web, games, video and DNS.

How networks find each other.

1. Interactive

   Live

   How routers forward packets

   Routing tables and the next hop.

   Open session →

2. Interactive

   Coming soon

   BGP

   How the networks that make up the internet share routes, and how that breaks.

3. Interactive

   Coming soon

   Anycast

   One address, many locations, nearest one answers.

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   Live

   Traceroute and latency

   See every hop and where the time goes.

   Open session →

5. Interactive

   Coming soon

   ISPs, peering and exchanges

   Who carries your traffic and who pays.

Finding the server.

Already live in other tracks: DNS, TCP, TLS and HTTP: one request

1. Interactive

   Live

   DNS resolution, hop by hop

   Stub resolver, recursive resolver, root, TLD, authoritative.

   Open session →

2. Interactive

   Coming soon

   DNS caching and TTLs

   Why a DNS change takes time to reach everyone.

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   DHCP

   How a device gets its address when it joins a network.

How browsers and servers talk.

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   Coming soon

   HTTP/1.1

   Requests, responses, headers and keep-alive.

2. Interactive

   Live

   HTTP/2 multiplexing

   Many requests on one connection.

   Open session →

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   Coming soon

   HTTP/3 and QUIC

   HTTP over UDP, and why that helps on bad networks.

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   The TLS handshake

   Agree on keys and check the certificate before any data flows.

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   Coming soon

   WebSockets

   Upgrade an HTTP connection to a two-way channel.

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   Coming soon

   gRPC and protobuf

   Binary messages over HTTP/2 with a typed contract.

Why the network feels slow.

Already live in other tracks: CDNs: caching at the edge

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   Live

   Latency vs bandwidth

   A wider pipe doesn't make the first byte arrive sooner.

   Open session →

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   Coming soon

   Head-of-line blocking

   One lost packet holds up everything behind it.

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   CDNs and edge networks

   Move content closer to cut round trips.

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   Wi-Fi and mobile networks

   Radio, signal loss and why mobile latency jumps around.

Protecting traffic in transit.

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   Firewalls

   Allow and deny rules, stateful and stateless.

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   VPNs and tunnels

   Wrap traffic inside an encrypted tunnel.

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   DDoS attacks

   Floods at different layers, and how they're absorbed.

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   Coming soon

   Man-in-the-middle attacks

   Intercepting traffic, and how TLS stops it.

Tools for when it doesn't connect.

1. Interactive

   Coming soon

   curl, dig and friends

   Check each step of a request from the command line.

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   Coming soon

   Packet capture with Wireshark

   See the actual packets on the wire.

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   Coming soon

   Open ports and connections

   Which process is listening, and who is connected.