CCENT Concepts Pt. 1 Flashcards
Same-layer interaction on different
computers
The two computers use a protocol to communicate with the same layer on
another computer. The protocol defined by each layer uses a header that is
transmitted between the computers, to communicate what each computer
wants to do.
Adjacent-Layer interaction on the
same computer
On a single computer, one layer provides a service
to a higher layer. The software or hardware that
implements the higher layer requests that the next
lower layer perform the needed function.
OSI Reference Model Layers
Application, Presentation, Session,
Transport, Network, Data Link Physical
TCP/IP Reference Model Layers
Application, Transport, Internet,
Network Access
NetWare Reference Model Layers
HTTP, SMTP, POP3, VoiP;
IPX(SPX); Mac Protocols;
OSI Layering Benefits
Less Complex,Standard Interfaces, Easier to learn, Easier to develop, Multivendor interoperability, Modular Engineering Decapsulation On a computer that receives data over a network, the process
Decapsulation
On a computer that receives data over a network, the process in which the
device interprets the lower-layer headers and when finished with each header,
removes the header, revealing the next-higher-layer PDU.
Encapsulation
The placement of data from a higher-layer protocol behind the header (and in
some cases, between a header and trailer) of the next-lower-layer protocol.
For example, an IP packet could be encapsulated in an Ethernet header and
trailer before being sent over an Ethernet.
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Protocol data unit (PDU)
An OSI term to refer generically to a grouping of
information by a particular layer of the OSIO mode.
More specifically, an LxPDU would imply the data
and headers as defined by Layer x.
Segment
In TCP, a term used to describe a TCP header and its encapsulated data
(also called an L4PDU). Also in TCP, the process of accepting a large chunk
of data from the application layer and breaking it into smaller pieces that fit
into TCP segments. In Ethernet, a segment is either a single Ethernet cable to
a single collision domain (no matter how many cables are used).
Application Layer (OSI)
Interfaces between network and
application software. Also includes
authentication services.
Presentation Layer (OSI)
Defines the format and
organization of data. Includes
encryption.
Session Layer (OSI)
Establishes and maintains end-to-end
bidirectional flows between endpoints.
Includes managing transaction flows.
Transport Layer (OSI)
Provides a variety of services between two host computers, including
connection establishment and termination, flow control, error recovery, and
segmentation of large data blocks into smaller parts for transmission.
Network Layer (OSI)
Logical addressing, routing, and
path determination.
