This paper has two main contributions. First the extremely high latency
of the GSM link is revealed which through measurements is determined to
have a magnitude usually only known from satellite links. This greatly
impacts the link configuration time of packet framing protocols for serial
links like the Point-to-Point Protocol (PPP). The key idea of the proposed
solution - Quickstart-PPP - is to break the strict sequential order of the
different signalling phases while ensuring that protocol semantics are not
violated and interoperability with existing PPP implementations is
preserved. As a result the link configuration delay can be completely
eliminated. The second contribution uncovers a fundamental problem which
is that the GSM circuit-switched data service is not capable of satisfying
different reliability requirements simultaneously. More precisely it is
not possible to use applications requiring the GSM link to operate in
reliable mode together with loss-tolerant but delay-sensitive applications
at the same time. The developed solution - Link Sniffer - suggests a
mechanism that can be added to the implementation of GSM's reliable link
layer protocol which allows to "sniff" on packet headers to determine the
reliability mode to be used. The key advantage of this solution is that
the link layer protocol itself does not have to be changed.