3Com 4500 PWR 26-Port Configuration Manual page 669

Cu ently, the switch supports only SSH2 Version. rr
Versi on negotiation
The server opens port 22 to listen to connection requests from clients.
The client sends a TCP connection request to the server. After the TCP connection is established,
the server sends t
format of "SSH-<primary
number>-<software version number>". The primary and secondary protocol version numbers
constitute the protocol version number, wh
The client receives and resolves the packet. If the protocol version of the server is lower but
supportable, the client uses the protocol versi
protocol version.
The clie nt sends to the server a packet that contains the number of the protocol version it decides
to use. Th e server compares the version carried in the packet with that of its own to determine
wheth er it ca n cooperate with the client.
If the negotiation is successful, the server and t
If not, the server breaks the TCP connection.
All the packets above are transferred in plain text.
Key n egotiation
The server and the client send algorithm negotiation packets to each other, which contain public
key algorithm lists supported by the serv
authentication code (MAC
The server and the client cal
The server and the client generate
exchange algorithm and the host key pair.
Then, the server and the client get the same session key and use it for data encryption and
decryption to secure data communication.
A uth ntication negotiation e
The negotiatio n steps are as follows:
The client sends an authentication request to the server. The authentication request contai
username, authentication type, and authentication-related information. For example, if the
authentication type is password, the content is
The server starts to authenticate the user. If authentication fails, the server sends an authenticat
failure message to the client, which contains the list of methods used for a new authentication
process.
he first packet to the client, which includes a version identification string in the
protocol
) algorithm list, and compressed algorithm list.
culate the final algorithm according to the algorithm lists supported.
the session key and session ID based on the Diffie-Hellman (DH)
version number>.<secondary
ile the software version number is used for debugging.
on of the server; otherwise, the client uses its own
he client go on to the key and algorithm negotiation.
er and the client, encrypted algorithm list, message
the password.
protocol version
ns
ion