rev

symmetric key- 128bit
asymmetric key-1096 minimum size..
disadvantage of asymmetric key is longer time to encrypt..
hashfunction used in digital signature forauthentication..
hash is one way.. cant be decoded so nt used for encryption..
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ssl..protocol- process.. symmetric and asymmetric used together..
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computer networks and internet:
1.OSI
2.TCP/IP
3.Each layer and there protocol, use.
4.Routing algorithms.
5.Packet header,packet data-hex format.
6.IP addressing,classes,non routable ip addresses..eg:192.168...
7.ARP..link between ip and mac address
8.Subnet,ip subnetting,subnet calculation..
DNS:
classless ip addressing
supernetting
NAT- network address translation protocol
NAT-static/dynamic mapping..
PAT-port address translation/
DNS->uses UDP
uses of UDP
DNS Zones:
authorative/iterative..
Resource REcords(RR)-types
dnsstuff.com
SOA field in dns record.
MX records..
DNS packet..
DNS cache poisoning- avoid by random query id and using pik

RR

Common DNS RR types-record in the dns
RR type value 1
:text code A

RR type-address
contains ip addressess


Type2
gives details of name server
text code NS
its gives infor authorative server
the ip addres of dns is also given

RR type 5

Text code Cname or canonical name node name
it masks changes from outside users

RR type value 6

Text code SOA
Start of authority

Provides info in detail of that zone

RR type 12
PTR
pointer
Reverse domain mapping
IP address is mapped to domain name


RR type 15
MX

Mail exchange

Specifies name of device responsible for handling emails sent to the domain


RR type 16

TXT
gives additonal text of domain to be stored


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Zone transfer

updates are dont at primar dns
and the secondary dns roll back and looksup in primary

checking condition is done when serial no in primary changes
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recursive and iterative resolution
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