From 510d5b083863c1ff514bafdafbda65baffb167ad Mon Sep 17 00:00:00 2001 From: Richard Whitehouse Date: Wed, 20 Apr 2011 01:13:46 +0100 Subject: [PATCH] Added introduction with overview, background and description of layers --- introduction.tex | 35 +++++++++++++++++++++++++++++++++++ 1 file changed, 35 insertions(+) diff --git a/introduction.tex b/introduction.tex index a81b272..17dcb41 100644 --- a/introduction.tex +++ b/introduction.tex @@ -1,2 +1,37 @@ \chapter{Introduction} +% Identify additional link layer protocols to incorporate + +Data Link Layer protocols are responsible for data transfer between adjacent nodes, routing of data within a local network segment and providing and regulating access to the physical network layer and allowing services to be run on top. Ethernet, the dominant protocol in this area, has been around since the early 1970s \cite{ethernet}. Research has indicated that Ethernet has a number of issues as the size of networks scale up. A number of different proposals have been made replace Ethernet, notably SEATTLE \cite{seattle} and MOOSE \cite{moose1}. Due to the large numbers of hosts and data involved in performing such a simulation, and the variety of different network topologies I shall analyse, the only suitable mechanism in order to perform this evaluation is under simulation. + +In this paper, I aim to compare one of these proposals to Ethernet in order to provide qualatative evidence to show the differences between the networks, and how MOOSE identifies the deficiencies identifed. In order to do this, I set out to create a representative implementation of Ethernet and MOOSE for a modern network simulator. + +\section{Background} + +When designing for use in a computer network architecture, it is common to divide the functions into layers, with each layer providing services to the layer above, and requiring services from the layer below. By doing this we can provide separation of concerns in forms of an abstraction of what the layer above and below require and provides us. This reduces the complexity of the network stack. Splitting up the different layers also allows the system to be modular, allowing us to specify different sets of protocols for different architecture and applications. + +Several different proposals have been made for the different layers of the network stack, the seven layer ISO OSI Model \cite{osi} and the four layers in the Internet Protocol Suite \cite{rfc1122}. In practice the model used by the Internet Protocol is largely represenative, along with a addition physical layer. + +The layers described below operate on packets, also known as frames and datagrams. Each layer may add headers to the front of the packet and trailers to the end in order to add routing information and checksums as necessary. A protocol may choose to split up a packet, in which case it is required to rejoin it at the other end. + +\subsection{Physical Layer} + +The stack starts at the bottom with the physical layer. This is primarily concerned with the physical interconnection of the two computers and how the basic signalling works in terms of cabling or radio. Standards on this layer include 100BASE-T \cite{ieee802-3y} and 1000BASE-T \cite{ieee802-3ab} - commonly known as Fast Ethernet amd Gigabit Ethernet respectively. + +\subsection{Data Link Layer} + +The data link layer layer providees basic addressing and controlling access to the physical layer. The dominant protocol in this area is Ethernet as part of IEEE 802.3. + +\subsection{Network Layer} + +The network layer provides large scale routing, control over network traversal and identification of hosts. The primary protocol in this area is IP - Internet Protocol, in particular IPv4 \cite{rfc791} although IPv6 \cite{rfc1883} is starting to gain traction due to impending address exhaustion \cite{icann-030211}. + +\subsection{Transport Layer} + +The transport layer provides multiplexing of data between end hosts. On this level also exists the capability for connection setup, reliability and ordering. Examples of protocols on this layer are UDP \cite{rfc768} and TCP \cite{cerf74}. + +\subsection{Application Layer} + +The top layer of the protocol stack in the Internet Protcol Suite model and the top three layers in the OSI Reference Model, Application, Presentation and Session, can be considered as a singular discrete layer - the application layer. These provide user level services situated on end hosts. Examples include HTTP \cite{rfc2616} and DNS \cite{rfc1035}. These provide for the transmission of material in the form of hypertext documents and other media and a distributed directory of names and addresses. + + -- 2.34.1