Category Archives: Protocol

Understanding HTTP methods

HTTP connect method: One of the HTTP request is CONNECT method.  When you have a client with explicit proxy configured at that time when the client tries to connect to some https website then the client send a HTTP CONNECT … Continue reading

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Layer 2 Frame

A layer 2 frame contain following field: +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++ | preamble | SFD | DMAC | SMAC | Type/Length | Data + padding | CRC | | 7 byte | 1 byte | 6 byte | 6 byte | 2 byte … Continue reading

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How tracert works in windows:

When we do tracert in windows it uses “echo request”, “Time exceeded TTL expired”, echo reply. Time exceeded TTL expired is type 11 code 0 echo request is type 8 code 0 echo reply is type 0 code 0 When … Continue reading

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Understanding Fragmentation

Lets take a example to understand fragmentation. I have two system Host A and Host B. IP address of host A is 192.168.3.1 and IP address of host B is 192.168.3.134 I am ping from Host A to Host B … Continue reading

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ESP[Encapsulating Security Payload ] and AH [Authentication Header ]

ESP provides confidentiality, Authentication, Integrity, Anti replay ESP packet format: +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Security Parameters Index (SPI) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sequence Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Payload Data* (variable) | ~ ~ | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | Padding (0-255 bytes) | … Continue reading

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ICMP

Echo request and Echo reply: When we ping to a destination the source sends echo request to the destination and destination replies with echo reply. Echo request is type 8 code 0, Echo reply is type 0 code 0 Echo … Continue reading

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SSL/TLS

SSL/TLS protocol consist of two protocol: 1> SSL handshake protocol: 2> Record protocol: Record protocol is used to encrypt the user data. For key exchange we can have RSA, DH, DHE. In RSA a pre-master secret is sent over network … Continue reading

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