Transcript Network Structures - Pravin Shetty > Resume

Network Structures
Refer: Burgess Ch 3
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Why Network ??
Networks appear when several computers in organization. Why?
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Resource Sharing
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Hardware
Data storage & retrieval
Software
Processing power
Internet Access
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Efficient Cooperation
Security
– Centralized
– Common backup
– Also a Risk!
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Costs
– Costly to install
– but savings later
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Networks contain….
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Hosts that run Clients and Services
Media and equipment that connect Hosts
Protocols that govern connections
Users (Vendors or Customers !?!)
Networks allow cooperation
Cooperation leads to Communities of Users
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Clients and Servers
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The Hosts and their services need an Identity
Identities are usually names
However protocols use numeric addresses
Addresses can be associated with names using resolver
services and directories
• This is an Infrastructure service
• SysAdmins maintain these too….
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Host Identities & Name Services
A host has many different names used in various contexts:
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HostID – NIC or CPU serial#
Install Name - /etc/hostname.*
Application Names – eg Oracle database name
Local name list - /etc/hosts
Network Information Service – “yellow pages”
Transport level addresses – TCP/UDP port# + IP#
Physical level addresses – NIC address
DNS names – IP names & info
WINS names – IP, NetBIOS & WfW names
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Establishing Network Identity
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Identity = Address = Name
Some addresses are fixed (eg HostID, NIC#)
Some must be initialised (eg during startup)
– Internet Addresses must be Globally Unique therefore can’t use NIC#
(IPv6 excepted?)
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Static Allocation
– continuous identity (RARP,BOOTP,DNS)
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Dynamic Allocation
– transient identity (BOOTP,DHCP)
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Naming Services
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Used to convert Address to Name or vice-versa
A Performance and Security nexus
DNS or bind used world-wide
NIS or NIS+ used in Unix
WINS used in Windows
Authentication (Kerberos,Radius)
Directory (X500,ldap,NDS,ActiveServer)
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Network Operating Systems
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Peer-to-Peer .vs. Server-Workstation
Unix – most general, open and variant
Windows NT/2000/XP – Workgroups or Domains
Novell - NDS
Macintosh – now like Unix (System X)
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NOS Functions
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I/O optimisation – Various forms of Cache
Fault Tolerance
Directory – Manage server resources
User Sessions – Directory, history & preferences
Multi-Processing - Concurrency
Print Spooling
Backup
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Network Sharing models
Based on Synchronous Request/Reply protocols (RPC)
• Drive mapping
• File System Mount
• Resource Share & Subscribe
• Terminal session – CLI or shell based
• GUI interface – X11,Windows
• Web-based
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Network Hardware
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Ethernet, Fast Ethernet, Gigabit Ethernet
Token Ring
Wireless (IEEE 802.11b)
Fibre Distributed Data interface (FDDI)
ATM
Fibre Channel
High Performance Parallel Interface (HIPPI)
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Ethernet Hardware
• Network Interface Cards (NIC)
– Connector, RAM, DMA, I/O port, IRQ
• Workstations – PCs or “Thin Clients”
• Cables & Connectors
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Network Connections
-- Repeaters, Bridges and Routers
• An Ethernet is a single collision domain
ie a single shared medium (segment)
• Bus topology (physical or logical)
• Media Access Control (MAC) “contest” based
– CSMA/CD
• Ethernet Frame format
– Ethernet, EthernetII and SNAP
• Ethernet cable characteristics: Min.Frame size, Signal
propagation speed, Max.Segment length = Collision window size
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Network Design with Ethernet
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Uses repeaters, hubs, bridges, switches
Repeaters copy incoming bit-stream to all outputs
Bridges filter (MAC address) – isolate local traffic
Both extend range (4 repeats max.) or adapt different
media and connectors
• Router also, but uses network (IP) address
• Switch forwards packet only to target address
• Switching Hubs create virtual private cables
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Network Segments
• In a single network, devices share a media access protocol (eg
CSMA/CD in ethernet)
• A packet being transmitted usually occupies the medium
exclusively over the entire cable
• To reduce the traffic density in large networks,
they need to be divided into separate
media areas or segments
• Segments can then be joined using bridges, switches or routers
which forward appropriately
• What about Broadcasts? Switches usually forward them but
Routers usually don’t
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Network Analysis Checklist
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Topology
Subnets
Network addresses
Default routes
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Netmask
What’s connected
Host Functions
Locate key services
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