37,539 research outputs found
Source-specific routing
Source-specific routing (not to be confused with source routing) is a routing
technique where routing decisions depend on both the source and the destination
address of a packet. Source-specific routing solves some difficult problems
related to multihoming, notably in edge networks, and is therefore a useful
addition to the multihoming toolbox. In this paper, we describe the semantics
of source-specific packet forwarding, and describe the design and
implementation of a source-specific extension to the Babel routing protocol as
well as its implementation - to our knowledge, the first complete
implementation of a source-specific dynamic routing protocol, including a
disambiguation algorithm that makes our implementation work over widely
available networking APIs. We further discuss interoperability between ordinary
next-hop and source-specific dynamic routing protocols. Our implementation has
seen a moderate amount of deployment, notably as a testbed for the IETF Homenet
working group
Joint Routing and STDMA-based Scheduling to Minimize Delays in Grid Wireless Sensor Networks
In this report, we study the issue of delay optimization and energy
efficiency in grid wireless sensor networks (WSNs). We focus on STDMA (Spatial
Reuse TDMA)) scheduling, where a predefined cycle is repeated, and where each
node has fixed transmission opportunities during specific slots (defined by
colors). We assume a STDMA algorithm that takes advantage of the regularity of
grid topology to also provide a spatially periodic coloring ("tiling" of the
same color pattern). In this setting, the key challenges are: 1) minimizing the
average routing delay by ordering the slots in the cycle 2) being energy
efficient. Our work follows two directions: first, the baseline performance is
evaluated when nothing specific is done and the colors are randomly ordered in
the STDMA cycle. Then, we propose a solution, ORCHID that deliberately
constructs an efficient STDMA schedule. It proceeds in two steps. In the first
step, ORCHID starts form a colored grid and builds a hierarchical routing based
on these colors. In the second step, ORCHID builds a color ordering, by
considering jointly both routing and scheduling so as to ensure that any node
will reach a sink in a single STDMA cycle. We study the performance of these
solutions by means of simulations and modeling. Results show the excellent
performance of ORCHID in terms of delays and energy compared to a shortest path
routing that uses the delay as a heuristic. We also present the adaptation of
ORCHID to general networks under the SINR interference model
A General Class of Throughput Optimal Routing Policies in Multi-hop Wireless Networks
This paper considers the problem of throughput optimal routing/scheduling in
a multi-hop constrained queueing network with random connectivity whose special
case includes opportunistic multi-hop wireless networks and input-queued switch
fabrics. The main challenge in the design of throughput optimal routing
policies is closely related to identifying appropriate and universal Lyapunov
functions with negative expected drift. The few well-known throughput optimal
policies in the literature are constructed using simple quadratic or
exponential Lyapunov functions of the queue backlogs and as such they seek to
balance the queue backlogs across network independent of the topology. By
considering a class of continuous, differentiable, and piece-wise quadratic
Lyapunov functions, this paper provides a large class of throughput optimal
routing policies. The proposed class of Lyapunov functions allow for the
routing policy to control the traffic along short paths for a large portion of
state-space while ensuring a negative expected drift. This structure enables
the design of a large class of routing policies. In particular, and in addition
to recovering the throughput optimality of the well known backpressure routing
policy, an opportunistic routing policy with congestion diversity is proved to
be throughput optimal.Comment: 31 pages (one column), 8 figures, (revision submitted to IEEE
Transactions on Information Theory
The Bernardi process and torsor structures on spanning trees
Let G be a ribbon graph, i.e., a connected finite graph G together with a
cyclic ordering of the edges around each vertex. By adapting a construction due
to O. Bernardi, we associate to any pair (v,e) consisting of a vertex v and an
edge e adjacent to v a bijection between spanning trees of G and elements of
the set Pic^g(G) of degree g divisor classes on G, where g is the genus of G.
Using the natural action of the Picard group Pic^0(G) on Pic^g(G), we show that
the Bernardi bijection gives rise to a simply transitive action \beta_v of
Pic^0(G) on the set of spanning trees which does not depend on the choice of e.
A plane graph has a natural ribbon structure (coming from the
counterclockwise orientation of the plane), and in this case we show that
\beta_v is independent of v as well. Thus for plane graphs, the set of spanning
trees is naturally a torsor for the Picard group. Conversely, we show that if
\beta_v is independent of v then G together with its ribbon structure is
planar. We also show that the natural action of Pic^0(G) on spanning trees of a
plane graph is compatible with planar duality.
These findings are formally quite similar to results of Holroyd et al. and
Chan-Church-Grochow, who used rotor-routing to construct an action r_v of
Pic^0(G) on the spanning trees of a ribbon graph G, which they show is
independent of v if and only if G is planar. It is therefore natural to ask how
the two constructions are related. We prove that \beta_v = r_v for all vertices
v of G when G is a planar ribbon graph, i.e. the two torsor structures
(Bernardi and rotor-routing) on the set of spanning trees coincide. In
particular, it follows that the rotor-routing torsor is compatible with planar
duality. We conjecture that for every non-planar ribbon graph G, there exists a
vertex v with \beta_v \neq r_v.Comment: 25 pages. v2: numerous revisions based on referee comments. v3:
substantial additional revisions; final version to appear in IMR
Recommended from our members
SLAM : an automated structure to layout synthesis system
SLAM is a structure to layout synthesis system. It incorporates parameterisable bit-sliced and glue-logic generators to produce high density layout. In this paper, we describe a sliced layout architecture and SLAM system. In addition, we present partitioning algorithms for generating the floorplan for such an architecture. The algorithms partition the netlist into component sets best suited for different layout styles such as bit-sliced or strip-oriented logic. Each group is partitioned further into clusters to achieve better area utilization. Several experiments demonstrate that highly dense layouts can be achieved by using these algorithms with the sliced layout architecture
Lower Bounds in the Preprocessing and Query Phases of Routing Algorithms
In the last decade, there has been a substantial amount of research in
finding routing algorithms designed specifically to run on real-world graphs.
In 2010, Abraham et al. showed upper bounds on the query time in terms of a
graph's highway dimension and diameter for the current fastest routing
algorithms, including contraction hierarchies, transit node routing, and hub
labeling. In this paper, we show corresponding lower bounds for the same three
algorithms. We also show how to improve a result by Milosavljevic which lower
bounds the number of shortcuts added in the preprocessing stage for contraction
hierarchies. We relax the assumption of an optimal contraction order (which is
NP-hard to compute), allowing the result to be applicable to real-world
instances. Finally, we give a proof that optimal preprocessing for hub labeling
is NP-hard. Hardness of optimal preprocessing is known for most routing
algorithms, and was suspected to be true for hub labeling
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