Why Cisco internetworking
required?
To sort out the problems in LAN like
à Too many
hosts in a broadcast domain,
à Broadcast Storm
à Multiplexing
à Low Bandwidth
Routers, Switches, Bridges and Hubs are used
Routers are used to break the broadcast domain,
Routers can filter the network based on IP Address and forwards the
packet to other network
Switch breaks collision domain (every port is collision domain), but
one broadcast domain
Switches are used to optimize the performance
of LAN,
Switch switches frames from one port to another, does not forward it to
other network
More manageable with VLANS, STP etc. than Bridge
100s of ports available
Bridge breaks collision domain (each port is collision domain like switch),
but one broadcast domain, same function as switch
16 ports maximum
Not manageable like switch
Hub does not break any domain. One Broadcast domain, one collision
domain
Not manageable
Seven
Layers & its Functions
Layer
Name
|
alias
|
Layer
Function
|
Type
of Application / Protocols Used
|
|
Application
|
Upper
Layers
|
Provides a User Interface / file, print, message, database and
application services
|
WWW, E-mail gateways (SMTP or X.400)
|
|
EDI (Electronic data interchange – flow control of accounting,
shipping, inventory tracking)
|
|||
|
Special Interest bulleting boards – chat rooms
|
|||
|
Internet navigation utilities – Google & Yahoo! Search engines,
Gopher, WAIS
|
|||
|
Financial transaction services – currency exchange rates, market
trading,commodities etc.
|
|||
|
Presentation
|
Presents Data, Handles processes of encryption, compression and
translation services
|
PICT, TIFF, JPEG, MIDI, MPEG, RTF, Quick Time (manages audio and
video applications of Macintosh programmes)
|
|
|
Session
|
Setting up, managing and ending up sessions between presentation
layer entities,
Keeps different applications’ data separate / Dialog Control
|
NFS, SQL, RPC, X Window (GUI based protocol – like GUI interface in
Linux), Apple Talk Session Protocol (ASP), Digital Network Architecture
Session Control Protocol (DNA SC) – DECnet session layer protocol
|
|
|
Transport
|
Lower
Layers
|
End to End Connectivity / Provides reliable or unreliable deliver,
Performs error correction before retransmit. Known as Communication Layer also
|
(TCP/UDP) Flow Control: prevents buffer from overflowing in receiving
host – no loss of data, Connection Oriented Protocol, Windowing –
Acknowledgement
|
|
Network
|
Routing / Provides logical addressing, which routers use for path
determination
|
Passes User Data Packets – routed protocols (IP/IPX)
|
|
|
Passes Route Update Packets – routing protocols (RIP, IGRP, EIGRP,
OSPF, BGP)
|
|||
|
Routing Tables : Protocol-specific network address, Exit Interface,
Metric (load, reliability, bandwidth, MTU, hop count – distance), Access
lists, VLAN Connections, QoS for specific network traffic
|
|||
|
Data Link
|
Framing / Combines packets into bytes and bytes into frames, Provides
access to media using MAC address, Performs error detection not correction
|
Provides physical transmission of data and handles error
notification, network topology and flow control.
|
|
|
MAC Layer (802.3):
Defines how packets are placed on media. Physical addressing, logical
topologies (signal path through physical topology), line discipline, error
notification (not correction), ordered delivery of frames, optional flow
control.
|
|||
|
LLC Layer (802.2):
Identify the network layer protocols and then encapsulate them. Decides where
to destined the packed when frame received (IP Protocol at the network
layer), flow control and sequencing of control bits.
|
|||
|
Layer 2 Switches and Bridges work here.
|
|||
|
Physical
|
Physical topology / Moves bits between devices, specifies voltage,
wire speed and pin-out of cables
|
Sends / receives bits. (0s/1s). Different signaling methods for
different type of medias. We can identify the interface between DTE (attached
device) and DCE (located at service provider) DTE can be accessed through
modem or CSU/DSU.
|
Ethernet Networking:
à A media access method that allows all hosts
on a network to share the same bandwidth of a link
à It is scalable to Fast Ethernet and Giga
Ethernet
à Easy to implement and troubleshoot
à Use Data Link and Physical layer
specifications
à Uses CSMA/CD protocol to avoid collision of
data being transferred by two devices at the same time
à Effect of CSMA/CD network sustaining heavy
collision like Delay, Low throughput and Congestion
à Half Duplex (802.3) uses one pair of wire
with a signal running in both directions on the wire
à Full Duplex uses two pairs of wire and sends
and receives the data on separate pair makes data transfer faster
à Full Duplex can be used between Switch to
host, Switch to Switch, Host to Host
à When powered on, first connects to remote
end, negotiate with the other end (called auto detect mechanism method) which
decides the exchange capability (10/100/1000 Mbps).
Ethernet at the Data Link
Layer :
MAC Addressing and data transfer takes place through the form of frames
like Ethernet II frame, 802.3 Ethernet frame, 802.2 SNAP frame and 802.2 SAP
frame.
10 Base 2 : 10 Mbps, baseband technology, 185 Mtrs.
length, thinnet, supports up to 30 nodes on a single segment. Use BNC (British
Naval Connector) and T-connectors. Use logical and physical bus with AUI (15
pins) connectors. (Attachment Unit Interface allows one bit-at-a-time transfer
to the physical layer from data link media access method.)
10 Base 5 : 10 Mbps, baseband technology, 500 Mtrs.
length, thicknet, up to 1024 users with 2500 meters with repeaters. Use logical
and physical bus with AUI connectors.
10 Base T : 10 Mbps using Cat 3 UTP wiring, each device
must connect to hub/switch so one host per segment or wire. Uses RJ-45
connector (8 pin modular connector) with physical star and logical bus
topology.
100 Base TX : EIA/TIA Cat 5,6,or 7 UTP two-pair wiring.
One user per segment, up to 100 Mtrs. long. RJ-45 Connector with a physical
star and a logical bus topology. Use MII -- Media Independent Interface (uses
nibble, defined as 4 bits) which provides 100 Mbps throughput.
100 Base FX : Use fiber cabling 62.5/125-micron multimode
fiber. Point-to-point technology, up to 412 Mtrs. long, ST or SC connector
which are MII.
1000 Base CX : Copper twisted-pair called twinax (a
balanced coaxial pair) that can run up to only 25 meters. GMII interface.
1000 Base T : Cat 5 UTP four pair wiring up to 100 meters
long.
1000 Base SX : MMF using 62.5/50 micron core, uses 850
nano-meter laser, and range is from 3 Kms to 10 Kms
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