An Investigation into Transport Protocols and Data Transport ...

3.2. Network Monitoring 42
(TCP) [Pos81b]. The former offers a unreliable way of transferring information,
i.e. it does not know explicitly that a sent packet has been received,
whilst the latter offers a reliable service - for every packet of information
that is sent and consequently received by the receiving host, some kind of
acknowledgment is sent by the receiver and received by the sending host.
UDP can offer a greater raw performance as it does not require the extra
overhead of acknowledging information and maintaining state. However, as
UDP offers no kind of signaling from the network to discover the current network
conditions, it can be potentially dangerous if used maliciously (Denial
of Service attacks [MVS01, HHP03]).
As the Internet is based mainly on the connectionless communication
model of the IP protocol, in which UDP and TCP segments are encapsulated
before transfer across the internet, IP has no inherent mechanisms to
provide delivery guarantees according to traffic contracts and hence mechanisms
to reserve network resources have to be implemented via other means
(See Section 9.2). Because of this, IP routers on a given data path from
source to destination may suffer from congestion when the aggregated input
rate exceeds the output capacity.
3.2 Network Monitoring
3.2.1 Networking Metrics
Networking performances are broadly classified into both latency and throughput.
Moreover, other metrics such as the internet path (e.g. with traceroute)
[Jac89], the connectivity (whether the Internet host is reachable) [MP99] and
the jitter (AKA interpacket-delay variance) [DC02] may be important.