L1-7 technologies, protocols, apps
  L2 Forwarding 
  ARP
  MAC Addresses
  Broadcast Domain
  VLANs
    broadcast 
    Are VLANs required?
    When do I need a VLAN?
    Why not just subnet my network?
    How can devices on different VLAN’s communicate?
    What is a trunk port?  trunking protocols
    What do VLAN’s offer?
    Link aggregation
      To increase bandwidth
      to provide link failover
      LACP
  Network Layer
    Understanding IP Addresses
      Classes
      Network Masks
      Understanding Subnetting /Math 
    Route Tables
    Routing Protocols
      static 
      Dynamic
        RIP 
        IGRP, EIGRP 
        OSPF 
        IS-IS
        BGP
    Why does fragmentation occur?
    How are the packets reassembled? at tcp udp L4
    TTL
    Packet Traversing
    IPv6
      types: 
        IPv4  unicast, broadcast and multicast.
        IPv6  unicast, multicast and anycast.
        
        2001:0db8:3c4d:0015:0000:0000:abcd:ef12
        2001:0db8:3c4d:0015:0:0:abcd:ef12
        2001:0db8:3c4d:0015::abcd:ef12
        
        0000:0000:0000:0000:0000:0000:192.168.1.25
        ::192.168.1.25
        
        0000:0000:0000:0000:0000:0000:0000:0001   localhost address
        ::1
  Transport layer
    MTU
    MSS
    TCP
    UDP
    Protocol Ports
    TCP Timeout and Retransmission
    What are TCP RST Packets?
    TCP Options
    TCP Checksum
    TCP Error Correction
    Flow Control
    Congestion control
    Delayed Binding
    
  Application layer
    HTTP Protocol
    HTTP versions: GET, POST, HEAD, OPTIONS, PUT, DELETE, TRACE and CONNECT
    Structure of HTTP Transactions
      A request line has three parts: a method name, the local path of the requested resource, version of HTTP,
                             example GET /           path/to/file/index.html                   HTTP/1.0
      The initial response line: the HTTP version, a response status code and an English reason phrase
                             example HTTP/1.0      200 OK                     or HTTP/1.0 404 Not Found
    status codes
    1xx indicates an informational message only
    2xx indicates success of some kind
      200 OK The request succeeded
    3xx redirects the client to another URL
      301 Moved Permanently
      302 Moved Temporarily
      303 Moved to another URL
      304 Not Modified
    4xx indicates an error on the client’s part 
      401 Authorization Required
      403 Forbidden The request was a valid request, but the server is refusing to respond to it.
      404 Not Found The requested resource doesn’t exist.
    5xx indicates an error on the server’s part
      500 Internal Server Error	  An unexpected server error.
      503 Service Unavailable  The server is currently unavailable
      
    The HEAD Method
      A HEAD request is just like a GET request, except it asks the server to return the response headers only,
    The POST Method
    HTTP Keep-alives
    HTTP Headers
    DNS
    SIP
    FTP, Active FTP vs. Passive
    SMTP 
    How HTTP Cookies Work? How do Web sites use cookies?
    URL