datagram confusion
My buddy and i are studying for the network exam, and we are having some confusion with the term datagram.
I am using Sybex's network+ exam, and on page 60 it references datagram as being used at the application layer.
On page 111 it specifies the total length of a datagram when refering to a tcp/ip header, and that to me is substituted for a packet, like this site says on the OSI layer section and uses datagram/packet.
On page 112 is refers to the datagram as an ICMP message, again at the network layer.
Wikipedia refers to it as: In general, the term packet applies to any message formatted as a packet, while the term datagram is generally reserved for packets that are not transmitted reliably.
To me that references UDP, and is refering to the Transport layer (segments).
My buddy thinks the book is using the term datagram as a wide and general term, and if so, it really makes reading confusing, especially to someone that might not understand computers as much as (we think) we do.
Please help with clearing up this confusion.
I am using Sybex's network+ exam, and on page 60 it references datagram as being used at the application layer.
On page 111 it specifies the total length of a datagram when refering to a tcp/ip header, and that to me is substituted for a packet, like this site says on the OSI layer section and uses datagram/packet.
On page 112 is refers to the datagram as an ICMP message, again at the network layer.
Wikipedia refers to it as: In general, the term packet applies to any message formatted as a packet, while the term datagram is generally reserved for packets that are not transmitted reliably.
To me that references UDP, and is refering to the Transport layer (segments).
My buddy thinks the book is using the term datagram as a wide and general term, and if so, it really makes reading confusing, especially to someone that might not understand computers as much as (we think) we do.
Please help with clearing up this confusion.
Comments
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Danman32
Member Posts: 1,243
Datagram is one of those things that can be very general. I was going to say that a datagram was originally defined for the layer 2, but then I remembered layer 2 set of bits is a frame. Layer 3 set of bits is definitely a packet. So datagram would be above layer 3.
The net+ test won't go that far though that you HAVE to know where a datagram lies. Do know where a packet is, and possibly also a frame. -
WindowsLM
Member Posts: 39 ■■□□□□□□□□
Well i'm glad that it doesn't go that in depth in the test, thanks for the advice and response.
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bighornsheep
Member Posts: 1,506
In data communications:
A datagram is a segment without *much* overhead. Whereas
a packet is a segment with overhead.
ie. error checking, error recovery and etc.Jack of all trades, master of none