Protocols vs. network layers? |
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EXPERT RESPONSE FROM: Puneet Mehta
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QUESTION POSED ON: 18 February 2002
I want to know how actually the protocols are embedded in the
layers of network architectures(OSI/TCP/IP)?Are there any algorithms of
transport layer? Or whether protocols themselves are converted to suitable
algorithms and coded in the layers?
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EXPERT RESPONSE
Every Layer in the Network Architecture (OSI) defines its own method of Framing the data packets, its flow and
the way it has to be served to the layer above it. This whole process definition is taken care by the Protocols.Protocols
are embedded inside the layers as stack of streams.The principle behind layering is that each layer hides its implementation
details from the layers below and the layers above. Each layer on the transmitting machine has a logical peer-to-peer connection
with the corresponding layer in the receiving machine and this is accomplished through the use of encapsulation. If Talking specifically of
Transport Layer- Yes, Transport Layer Protocols use different algorithms ,like the new IETF standard TLS 1.0 ,which is based on SSL.
In TLS , the security context is negotiated in the client and server hello messages. For example: TLS_RSA_WITH_RC4_MD5 means the initial
authentication will be done using the RSA public key algorithm, RC4 will be used for the session key, and MACs will be based on the MD5
algorithm. Furthermore these protocols consists of embedded Sub Protocols.For example: Addition of Kerberos inside the TLS Protocol.Kerberos credentials are used to achieve mutual authentication and to establish a master secret which is subsequently used to secure
client-server communication. For Kerberos authentication option, new cipher suites are defined including DES, 3DES,RC4, IDEA etc.
Also another example is:The SSL protocol which includes two sub-protocols: the SSL record protocol and the SSL handshake protocol.
The SSL record protocol defines the format used to transmit data. The SSL handshake protocol involves using the SSL record protocol to exchange a series of messages between an SSL-enabled server and an SSL-enabled client when they first establish an SSL connection. The use of embedded sub protocols avoids the overheads like Latency, weak connection,
handshake, identification,authentication, maintaining session information etc.from the original protocol.
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