Nameserver

• Assume we registered google.com domain.
• Most domain registrars have their own ns
• NS makes authoritative response to google.com
• Glue Records

Activity

• install bind9
• out of box recursion is on
• tld
• resolv.conf

Activity

• set zone example.google.com 

Types of Records

1. A record
2. PTR record  dig -x 8.8.8.8 @8.8.8.8
   
3. CNAME
4. NS
5. SPF DKIM

Where else dns can be used?

1.    To geographically distribute traffic
2.     Load balancing
3.     Both a and b
4.     none

HTTP States

• Stateless
• Cookie
• Web Proxy (cache headers)
• Man in the middle
  tcpdump

HTTPS

TLS

End to End Encryption

sysctl values

• tcp_rmem,tcp_wmem
• tcp_max_syn_backlog
• tcp_recycle,tcp_fintimeout
  Connection Tearing Phase

What if somebody spoofs Syn and send to me?

1.      Syn+Ack goes to spoofed ip
2.      Syn+Ack goes to correct ip
3.      Syn+Ack is dropped
4.      Hodor

Network + Data Link Layer

Q From your system to Access point what part of the packet addresses the access point when you open google.com?

1.       Source IP Address
2.       Dest IP Address
3.       Dest Port
4.       Mac Address

NAT

• Port based nat
  Activity
• Setup Nat using iptables masquerade and ip_forwarding on one vm and change routing table on another vm to use the nat
  http://www.revsys.com/writings/quicktips/nat.html
• Tcp recycle