Introduction to Network Servers

Introductie

• Vandana G. Bandhoesingh BSc, MBA is the instructor.
• Students will introduce themselves by stating name, age, work and personal technical interests.

Course Outline

• Topics covered include networking components, TCP/UDP/IP network protocols, subnetting, and basic network troubleshooting.
• Assessment consist of 25 multiple-choice questions (70%) and a class practical assignment (30%) in English.

Network Components - Servers

• Servers are software running on robust hardware with enough capacity.
• Servers coordinate multiple client requests.
• Server requirements include bandwidth capacity, storage, and physical or virtual infrastructure.
• Examples of servers:
  • Web servers host websites.
  • Email servers facilitate sending and receiving emails through IMAP, POP, or SMTP.
  • FTP servers handle file transfer protocols and file sharing through a LAN intranet.
  • Identity servers (AAA, TACACS) handle authentication, authorization, and accounting purposes.
• Securing servers is important.

Network Basic Elements

• Key elements of a network include routers, firewalls, switches/hubs, and wireless modems.

Network Components - Router

• A router connects several network components to each other.
• Routers route traffic from one network to another.
• Routers learn about neighbors.
• Access lists can be created.
  • Access lists include whitelists and blacklists.
• Each port on a router has another broadcast domain.

Network Components - Switch

• A switch connects devices from one specific network to each other.
• Switches send traffic to specific devices connected to a specific port/interface.
• The bandwidth of each port is limited to 100Mbps.
• Traffic can be defined through VLANs.
• A switch creates a redundant network through Spanning Tree.

Network Components - Switch - Spanning Tree

• Spanning Tree decides the best path for data transmission which is the shortest path with less delay.
• Spanning Tree prevents loops in a network, while maintaining backup connections within.

Switching - Keeping Track of Hosts

• A switch learns MAC addresses and maps them to an IP address.
  • MAC addresses are unique physical addresses of a device.
• A switch keeps track of an ARP table per port.

Network Components - Hub

• A hub is a basic switch that sends traffic to everyone within that network.
• The bandwidth capacity of 100Mbps is distributed to all connections.
• Hubs forward all incoming packets to everyone in the network, regardless of the intended recipient.
• Hubs cause a lot of unnecessary traffic and load on the network.

Network Components - Access Points

• An access point is a wireless router that connects several hosts.

Network Components - Firewall

• The firewall establishes a barrier between a trusted internal network and an untrusted external network, such as the Internet.
• Firewalls act as a router, connecting the external network with the internal network.
• Access rules are created by Firewalls.
• Firewalls monitor incoming and outgoing traffic based on security rules.

Client - Server vs Peer-to-Peer

• A diagram visually outlines the setup for both client and peer networks.

OSI and Other Network Models

• The OSI (Open Source Interconnection) model is a seven-layer model.
• Layer 7 - Application Layer: End user layer for programs that open or create content.
  • Functions include resource sharing, remote file access, remote printer access, directory services, and network management.
  • The central device or protocol used is SMTP.
• Layer 6 - Presentation Layer: Syntax layer that encrypts and decrypts.
  • Functions include Character code translation, data conversion, data compression, data encryption, and character set translation.
  • Common protocols include JPEG/ASCII, EBDIC/TIFF/GIF, and PICT.
• Layer 5 - Session Layer: Synchronizes and sends to ports.
  • Session establishment, maintenance, termination, support, security, name recognition, and logging.
  • Common Protocols: RPC/SQL/NFS, NetBIOS Names
• Layer 4 - Transport Layer: TCP (Host to Host), and flow control.
  • Message segmentation, acknowledgement, message traffic control, and session multiplexing. -TCP/SPX/UDP
• Layer 3 - Network Layer: Packets (Letters), contains IP addresses.
  • Routing, subnet traffic control, frame fragmentation, and logical-physical address mapping, and subnet usage accounting.
  • Routers
  • Protocols: IP/IPX/ICMP
• Layer 2 - Data Link Layer: Frames ("envelopes") contains MAC address.
  • Functions: Establishes and terminates logical links between nodes, ensures frame traffic control, sequencing, acknowledgment, delimiting, error checking, and controls media access.
  • This layer is the most related to Switch, Bridge, WAP, PPPSLIP, Land Based Layers
• Layer 1 - Physical Layer: concern with transmission and reception of raw bits.
  • Data encoding, physical medium attachment, and transmission technique.
  • Cables, Hubs

Communication on the Network

• A data diagram represents communication on the network.

Packet Details

• A visual diagram outlines the details of TCP/IP packets.

TCP Three-Way Handshake

• A three-way handshake establishes a connection between client and server.

Encapsulation and De-encapsulation

• Data from the APPLICATIE layer (layer 5) such as web browsing data, receives the HTTP header and this is called "DATA".
• Data arrives at the TRANSPORT layer (layer 4), a TCP header is added (ENCAPSULATED)
  • The packets are now called SEGMENTS.
  • With UDP packets, they would be called DATAGRAMMEN.
• Data reaches the NETWORK layer (layer 3), the IP protocol works and the IP header is added.
  • The packets are then called PACKETS
• Packets arrive at layer 2, the DATA LINK layer and are called FRAMES.
  • A data link header and trailer is added.
  • Examples include Ethernet, Frame-relay, ATM.
• They arrive on the PHYSICAL layer, layer 1 where the frames are changed into BITS to be sent.

Connectionless vs Connection-Oriented Data Communication

• Connectionless (UDP):
  • Data is sent without setup or breakdown of the connection.
• Connection-oriented (TCP):
  • A connection is first made, maintained, and then broken down.
  • Possible scenarios:
    • Without Virtual Circuit:
      • TCP on the internet - Packets are broadly routed but tracked.
    • With Virtual Circuit:
      • Packets follow the same route.
• Tthree-way handshake is something to investigate further.

Bandwidth; Data Rate and Throughput

• Data Rate is the speed at which data is transmitted.
  • Data Rate comes in kilobits per second (kbps) or megabits per second (Mbps).
• Throughput: volume of data consumed, such as mobile data plan usage.

Physical Layer

• Wired Network:
  • Uses copper Cat 5e or Cat 6 cables.
  • May use fiber optic cables.
• Wireless Network:
  • Outdoor cellular technologies include GSM, MicrowaveWiMAX, LTE, Satellite, etc.
  • Indoor wireless technologies are utilized, such as Wireless LAN (WiFi) or Bluetooth.

Types of Networks

• A visual graph with the differences in networks (WAN, PAN, LAN, MAN)

Types of Wireless Networks

• Wireless tech types based on range: WWAN, WMAN, WLAN, WPAN

Physical Layer - Wired vs Wireless

• A table compares wired and wireless networks.
• Provides a comparison of specifications, wired network and wireless network.
• Speed of operation: wired is higher, but wireless tech is catching up.
• System Bandwidth: higher in wired, but lower in wireless, as Frequency Spectrum is scarce.
• Cost: less in wired. More for wireless due to stations, routers and adapters.
• Mobility: limited in wired, not limited in wireless.
• Transmission medium: copper wires, optical fiber cables, ethernet VS radiowaves

Wired vs Wireless

• A table compares wired network with a wireless network in relation to Interference, QoS and Reliability.
• Channel Interference is more susceptible to interference in a wireless setting.
• QoS (Quality of Service) is better with wired networks.
• Reliability - failure of a router in the wired network will affect the entire network.

Data Link Layer - Switchports

• Ethernet ports support:
  • Half Duplex: Transmitting data in one direction at a time.
  • Full Duplex: Transmitting data in both directions simultaneously.
  • 10 Mbps half/full duplex.
  • 100 Mbps fast ethernet.
  • 1000 Mbps (1Gb).

Data Link Layer - VLANs

• Virtual LANs split networks on a logical/software/configuration level, but remain physically connected to one node/wire.
• VLANs typically use IEEE 802.1Q protocol for packet-tagging.
• S1 and S3 each have both red and blue ports and the switch network S1-S4 deliver traffic when source and destination ports share the same color.
• Red packets can be forwarded to the blue VLAN only only by passing through the router R, entering R's red port and leaving its blue port.
• R may apply firewall rules to restrict red–blue traffic.
• When the source and destination ports are on the same switch, nothing needs to be added to the packet
• Switch can track the ports
• Swith-to-switch traffic be tagged with source traffic in order to be delivered