Fragmentation is the process of splitting large packets into smaller fragments to accommodate networks with smaller maximum transmission unit sizes. This allows packets to travel across multiple networks without being dropped. There are two types of fragmentation: transparent, where fragments are reassembled at exit gateways, and non-transparent, where fragments are treated as individual packets and reassembled only at the destination host, as used in the Internet Protocol. Key challenges include ensuring all fragments are received for reassembly and minimizing overhead from fragmenting and reassembling packets.

1. FRAGMENTATION
- An Internetworking concept
Shashwat Shriparv
dwivedishashwat@gmail.com
InfinitySoft

2. What is fragmentation?
Splitting up things into smaller more
manageable entities for incorporating
ease in use and flexibility in transport.
Where could it possibly come in
Networks ?

3. Each n/w imposes some maximum
size on its packets, the reason being;
 Hardware (frame size)
 Operating System (buffers size 512 bytes)
 Protocols (no. of bits in packet length field)
 Compliance with some standard
 To reduce error-induced retransmission to
some level
 Prevent packet from choking channel

4. Problems
 A large packet wants to travel through
a network whose maximum packet
size is small.
 What if the original source packet is
too large to be handled by the
destination network?
 Routing algorithms to prevent such
situation (not applicable)

5. Fragmentation in networks
 Allow gateways to break up packets
into fragments, sending each packet
as a separate internet packet
 Breaking up a thing is easy, but fixing
it back is not that easy

6. Types of fragmentation
 Transparent
 Non transparent

8. Transparent Fragmentation
 Caused by a “small packet” network
transparent to any subsequent networks
through which the packet may pass on its
way to the destination
 Gateways fragment oversized packets,
each addressed to the same exit gateway,
where they are recombined
 The process carries on until destination is
reached

9. Problems
 Exit gateway should know that it has
received all fragments to start
combination sequence
 All packets must exit via the same
gateway, else data loss occurs
 Overhead required to fragment and
reassemble at each gateway

10. Non transparent Fragmentation
 Refrain from recombining fragments
at intermediate gateways
 Fragments are considered as packets
and are passed through the gateways
 Recombination occurs only at the
destination host
 IP follows this methodology

11. Problems
 Requires all hosts to do Reassembly
 Increases overhead, larger the
packet, more the headers
 An advantage being multiple exit
gateways can be employed increasing
the efficiency of the transmission

12. Schemes
 Fragments should be numbered in a way
that aids recombination
 Trees can be used
 0 can be split as 0.1, 0.2, 0.3 …..
 These can be again fragmented as 0.0.0,
0.0.1, 0.0.2, …….., 0.1.0, 0.1.1 etc.
 Only if enough space is reserved in header
such terminology can be employed
 Sufficient to reorder fragments

13. THANK YOU
Shashwat Shriparv
dwivedishashwat@gmail.com
InfinitySoft