Transcript New Bulgarian University

Routing
A world without networks and routing
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No connection between offices, people and
applications
Worldwide chaos because of the lack of
centralized configurations and support
Limited possibilities of communications on
vocal and visual levels
No further technical progress achievements
Hardware requirements
Network hardware:
 Cables
 Lan cards
 Routers
 Switches
 Hubs
 Repeaters
Broadcast & Collision domains
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Broadcast Domain
A broadcast domain is a
logical division of a
computer network, in which
all nodes can reach each
other by broadcast at the
data link layer. A broadcast
domain can be within the
same LAN or it can be
routed towards other LAN
segments.
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Collision Domain
A collision domain is a
physical network segment
where data packets can
"collide" with one another
for being sent on a shared
medium, in particular in the
Ethernet.
The routing table
The routing table consists of at least three
information fields:
the network id: i.e. the destination
network id
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cost: i.e. the cost or metric of the path
through which the packet is to be sent
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next hop: The next hop, or gateway, is
the address of the next station to
which the packet is to be sent on the
way to its final destination
Depending on the application and
implementation, it can also contain
additional values that refine path
selection:
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quality of service associated with the
route. For example, the U flag
indicates that an IP route is up.
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links to filtering criteria/access lists
associated with the route
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interface: such as eth0 for the first
Ethernet card, eth1 for the second
Ethernet card, etc.
Routing protocols - RIP
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Defined in RFC 1058
Two versions 1 and 2
Uses hops as metric
Maximum 15 hops
allowed
No VLSM support in V1
Slow convergence
Advantage: Easy to
configure
Disadvantage: Limited
scalability
Routing protocols - EIGRP
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CISCO proprietary
Based on DUAL (Diffusing
Update Algorithm)
Crates three tables – neighbor,
topology and routing
Relies on triggered updates
Uses five different metrics:
bandwidth
load
delay
reliability
MTU
Advantage: Load balancing
possibility
Disadvantage: Extremely
complicated metric for calculating
Routing protocols – OSPF
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Defined in RFC 2328
Single/Multi area OSPF
Uses SPF (shortest path first algorithm)
Several router types – ABR, ASBR, IR
(internal router), BR (backbone router)
Works with subnet masks, but uses
wildcard bits for configuration
Advantage: Once properly configured,
the network is very stable and wellscalable, just adding the new routers
(members) to an existing area.
Disadvantage: Redistributing OSPF
processes can be painful, due to the
large number of requirements – type,
metric, metric-type, matching external
types and internal type routes
Very fast convergence, thanks to the
fast hello packets
Routing protocols – IS-IS
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NOT an interned
standard
Published in RFC 1142
Uses Dijkstra’s algorithm
Uses levels instead of
pure areas (compared to
OSPF)
More suitable for ISP
infrastructure than
enterprise networking
Routing protocols - BGP
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The CORE protocol for the
internet
Can withstand heavy load and
enormous traffic
Defined in RFC 4271
Uses simple FSM (Finite state
machine) that uses six states –
idle, connect, active, OpenSent,
OpenConfirm, established
Advantage – supports almost
limitless number of addresses in
the routing table and can shift
between them very fast
Disadvantage – these big,
heavily-loaded routes require
powerful hardware and this
makes the routers doing the BGP
routing a bit more expensive
The future of networks
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NGN (Next generation
networks) plan for unifying all
kinds of services via single
carrier
Installing fiber-optic cables and
replacing the existing LAN
cables
Implementing IPv6 due to the
limited availability of IPv4
addresses
Thanks to a faster network,
implementation of QoS will be
easier
Centralization of the network will
ensure buying less amount of
network hardware, reducing the
price of the total packet
(internet, TV, radio, telephony)