Routing Basics

Internet Routing Basics

Back to basics Application Presentation

Data

Application (HTTP, DNS, FTP)

Transport Header

Data

Transport (TCP/UDP)

Transport Header

Data

Internet (IPv4/IPv6)

Application (HTTP, DNS, FTP)

Session E2E connectivity (app-to-app) Transport

Transport (TCP/UDP)

Network

Internet (IPv4/IPv6)

Data Link

Network

Physical

Access (Ethernet, PPP)

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Por t n u m be r s (s oc ke t s )

Device to device  !

IPv4 /IPv6 a ddr e s s

Media access control  !

IP Header

Frame Header

IP Transport Header Header

Data

Network Access (Ethernet, PPP)

MAC address

0011010100000111

Addressing is the key!

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Internet/Network Layer !

Host to host communication across networks  "

Addressing !

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Routing !

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unique and hierarchical network-w network-wide ide address the best path to the destination

Current protocols  "

IPv4 and IPv6

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L3 Device/Router !

L3 device gets the packet one step closer  "

The next hop to reach the destination!

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Router Exchanges network information

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Finds the best path to a destination, and

Forwards the packet to the next hop (a step closer) to reach the destination

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Best Be st pat path h look lookup up – Rou outin ting g Decision !

Inspects the destination address of the packet  "

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best match”  Looks up its routing table for a ““best match”   "

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Network portion

Longest matching left-most bits

If no match, checks for default route  "

If no default route, drop the packet!

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