asm: lec 4 fixed

cst311/lec/lec14.md

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+# lec14
+
+IP Address: 32 bit identifier for a host, router interface
+The interface is that part of a router that connect between a host router and the physical link.
+
+## Global Addresses
+
+3 Types of Formats for the addresses
+
+Type A: 
+
+|1-bit  |  7-bits 	| 24-bits	|
+|-------|-----------|-----------|
+|0 		| network 	| host		|
+
+Typb B:
+
+## Subnets
+
+If we split the ip address into two (parts) 16-bit portions:
+
+* subnet - high bits
+* host  part - low order bits
+
+### Subnet mask
+
+usually we'll have `x.x.x.x/mask` where the mask is also some 1-byte value.
+
+We can determine the class of a subnet from `mask` value, hereby referred to by subnet mask.
+First we split the 32-bit mask into two portions of 1's and 0's respecctively.
+
+Example: `255.240.0.0` = `11111111 11110000 00000000 0000000`
+
+In our example the split happens at offset 12, meaning our x value from before in this case is just 12.
+
+## Addressing: CIDR
+
+Classless InterDomain Routing
+
+This says that any address say: `a.b.c.d./x` will tell us that x is the bit offset in the subnet portion of an address.
+
+