Kinda silly name for a layer

Yet another note about the dual nature of this class
	Network programmers here, not IT folks
	Understand enough to get by

Network Layer:
	"Internet Layer" in TCP/IP model

Challenges:
	Now we have multiple subnets connected together
	Addressing
	Routing!
	MTU and fragmentation
	Connectionless (TCP will provide connections in layer 4)
	Traffic flow	
	
Reminder:  What the layers do, picture on Wikipedia IP page
Reminder:  Datagram naming

Encapsulation:
	Layers encapsulate data from the layer above

Virtual Circuits:
	Imaging each router is programmed with the route from each place to each other place
	Circuits are a phone-company solution
		- Reliability is assured unless equipment fails
		- Circuits are allocated as used
		- "All circuits busy"
		- Price is per circuit-hour
		- Guaranteed latency
	This is NOT how IP works!

Routing:
	IP address indicates destination
	Routing tables
	Draw graph or routers
		- Dijkstra's Algorithm
		- Cost function, ISPs, links and saturation
	Equipment failure:  Amend table

Speed discrepancy:
	Router Memory
		
Layer 3 switches
	We've got one.  What does it do?

IPv4:  Let's look at a header:
	https://en.wikipedia.org/wiki/IPv4#Header

Netmasks:
	MLH310 
	isoptera
	
Special blocks:
	192.168.*
	172.16.*
	10.*
	127.0.0.*
		There's no place like 127.0.0.1
	255.255.255.255
	Stanford returned 36.*

List of /8 blocks
	Apple has one
	Apparently Ford does too

Evil bit:
	https://tools.ietf.org/html/rfc3514

IPv6:
	128 bit addressing
		This is really quite a lot!
		How many?
	Extension headers and simplified "basic" header

What if you want to switch to IPv6?
	Your ISP has to support it
	Have I checked on this yet?