Proposed How Ossified is the Protocol Stack? Research Group
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How Ossified is the Protocol Stack? (HOPS)
There has been long term and increasing interest in deploying transport
protocols with alternate dynamics and behaviors to TCP and UDP. The IETF has
standardized several new protocols including DCCP, UDP-lite, SCTP and several
changes to TCP including ECN and LEDBAT. All of these new technologies have
resulted in deployment challenges blamed on intentional and unintentional
interference by middleboxes such as NATs and firewalls. This has lead to
approaches such as building new protocols over UDP or HTTP to make traffic look
like something a middlebox would expect. However, both these approaches have
shortcomings and a variety of ameliorating engineering approaches are being
What is missing is a study with more than anecdotal evidence of the nature of
the problem and the portions of the network in which it manifests. One of the
best analyses to date is  which measures from a very small number of
locations: 49 residential, 17 enterprise, and 142 locations in total. There are
two more recent studies:  is focusing on TCP in-band testing while using
PlanetLab as a measurement testbed;  use crowd-sourcing with in total 1,165
workers from 53 different countries covering a larger set of access networks
including mobile access for TLS testing . However, to be able to draw
conclusions about the significance of a certain middlebox interference problem
more data form a large variety of access networks is needed. In the interest of
getting ground-truth data about the nature of the problem, the HOPS research
group will provide a discussion forum to coordinate efforts in research and
industry -- such as network stack, browser, and middlebox vendors, as well as
network and service operators -- on collecting and reporting statistics about
middlebox impact on transport sessions.
 M. Honda, Y. Nishida, C. Raiciu, A. Greenhalgh, M. Handley, and H. Tokuda.
Is it still possible to extend tcp? In Proc. ACM IMC, 2011.
 R. Craven, R. Beverly, and M. Allman.
A middlebox-cooperative TCP for a non end-to-end Internet. In Proc. ACM
SIGCOMM, 2014. <http://doi.acm.org/10.1145/2619239.2626321>
 A. M. Mandalari, M. Bagnulo, A. Lutu.
Informing Protocol Design Through Crowdsourcing: the Case of Pervasive
Encryption. ACM SIGCOMM Workshop on Crowdsourcing and crowdsharing of Big
(Internet) Data (C2B(I)D), 2015.
The HOPS research group follows from the successful BarBoF meeting organized by
Aaron Falk at IETF92 in Dallas to bring more data on the nature and extent of
middlebox interference to protocol design and engineering efforts. To this end,
we aim to provide a forum for discussion and exchange of measurement insights,
data, and techniques co-located with IETF meetings. The BarBoF identified the
need for this forum, with many participants wanting a place to continue these
In addition, we have identified two near-term goals to be completed within the
research group in support of this work.
First is the definition of a common format for reporting on middlebox
impairments observed in the network, whether these observations are made
passively, actively, or as a side effect of some other operation, e.g. taken
from application or network stack error logs. This common format must provide
for correlation and comparison among data from disjoint observations, and
address end-user privacy and business confidentiality concerns, e.g. using path
pseudonyms instead of paths identified by AS number and/or IP address where
necessary. These measurements should be useful not only for detecting
impairments but also for assessing the likelihood that a certain impairment
will be experienced by traffic on certain types of networks and in the Internet
as a whole. For this purpose aggregated statistics on the prevalence of certain
middblebox behaviors are useful, even without revealing the underlying
Second is the specification of methods for analysis of middlebox interference,
and associated active measurement techniques, that can scale to much larger
numbers of measured paths than those presently in the literature, while
minimizing network measurement traffic load on the network. Similar techniques
could be used for middlebox benchmarking. Focusing on active measurements that
are considered feasible for inclusion in well-known end-systems (e.g. in
browsers or the OS) has been identified as way forward to collect more data and
reach a high coverage of different access networks, specifically including
mobile and fixed, residential, as well as enterprise network. These active
measurements will be useful for targeted questions about specific paths as well
as to fill in data not available from passive measurement. Further, providing
guidelines on with measurement and analysis techniques are needed to detect and
classify certain impairments may increase the willingness of industry to share
data that is already available.
Membership in the HOPS RG is open.
The HOPS RG will meet one to three times per year, initially always co-located
with IETF meetings, to foster exchange among researchers and between research
and industry on middlebox measurement topics. Meetings may in the future be
scheduled to provide additional interaction with the network operations
community, should operationally relevant and useful results warrant this.