An Investigation into Transport Protocols and Data Transport ...

5.1. TCP Hardware Requirements 80
for systems that do not implement the setsockopt() call can be given default
socket buffer settings as defined in the net.core.rmem_default and
net.core.wmem_default sysctl variables.
One may be tempted to assign large default and maximum values to the
socket memory to enable high speed TCP transfers over high BDP paths.
However, this could lead to performance degradation on servers as physical
memory may need to be swapped to and from disk if many such connections
are used. Servers can often have hundreds to thousands of simultaneous
network connections.
5.1.2 Network Framing and Maximum Segment Size
As the TCP/IP paradigm requires the transport of data packets across the
Internet, a fundamental question arises upon the size of each packet or segment.
However, there is an overhead cost due to framing and encapsulation
upon of each packet.
As the IP, TCP and underlying Layer 2 headers are often static in size, by
imposing a larger packet size it is possible to increase the raw data throughput
due to the relative decrease in header overheads. Large packets also result in
fewer interrupts at then end systems which can result in higher throughput
(See Section A.2.4).
However, with larger packet sizes, and with constant Bit Error Rate
(BER), the probability of packet corruption increases - although this issue
only becomes serious with wireless networks [BPSK96, Che01, CKPC03].
The Maximum Segment Size (MSS) [Pos83] is the size of the raw data
which TCP is allowed to store in each packet. To prevent problems due to
fragmentation at the IP level, the Maximum Transfer Unit (MTU) [MD90]