CS338 Computer Security
Monday, 16 May 2022

+ Today
- Questions
- Local networks (Ethernet, 802.11, etc.)
- Address Resolution Protocol (ARP)
- Network Address Translation (NAT)
- Network routing

+ Questions

+ Local networks: focus on Ethernet (IEEE 802.3)
- Medium Access Layer & shared medium
- Medium Access Control Address
    - Global uniqueness (ha!)
    - 48 bits (2^48 ~ 250 trillion)
    - Typically written as 6 colon-separated bytes
       (EC:26:51:23:E9:B4)
- Yet another header (search for "ethernet header"
    or "ethernet frame") but also a footer!
- Controlling who speaks when
- Broadcast messages
    - my IP & MAC
    - which MAC has this IP?
- Non-broadcast messages

+ ARP
- 

+ Routing
- Hierarchical network structures
- IP (mostly)
- Routing tables (netstat -r, netstat -rn)
- Routing algorithms

+ Think "abstract data types"
- What is the data? (routing table, ARP cache, DNS cache, etc.)
- What are the operations?

+ What happens when my computer wants to send a packet?

+ NAT