memory overhead of switches and sets up a remote collector to decode the flows and counters network-
wide. They both ignore the misalignment of upstream and downstream time windows caused by clock offset
and variable transmission delay, leading to biased packet loss analysis in a short time window. LossRadar
[6] is a seminal work, which marks the time window ID in the packet header upstream to identify the
source of packets and thus counter the impact of time window misalignment. Despite its success in data
center networks, it is not applicable and uneconomic to the backbone network we focus on. Specifically, the
data center’s egress devices and ingress devices are often non-programmable commercial switches, hard to
add packet headers efficiently. Moreover, routers beyond the control of CSPs may not support forwarding
non-standard packets with headers added.
This paper proposes SketchDecomp, a novel detection method for packet loss between data centers.
Based on sketch decomposition and matrix optimization, it does a high-accuracy job at the flow level
without modification of packets or other hardware operations. Thus, it is easy to deploy and economical
compared to previous methods. Concretely, in SketchDecomp, several count-min sketches [7], a particular
data structure represented as a matrix, are deployed upstream and downstream to count flows in the
send and receive windows. Given that packets sent may be branched to multiple receive windows due to
delay jitter, we regard the sketches as the sum of several unknown sub-sketches. After some equality and
inequality constraint are derived, a matrix optimization model following low-rank property is subsequently
developed to solve these sub-sketches. In particular, we design a symmetric Gauss–Seidel alternating
direction method in order to solve it efficiently. Finally, SketchDecomp identifies the packet loss and
computes the loss rate by comparing the sub-sketches recovered and sketches observed.
The rest of the paper is organized as follows: In Section 2, we give the precise problem statement and
detail the deployment and optimization problem modeling of SketchDecomp. In Section 3. we present the
sGS-ADMM algorithm to solve the optimization model and cover its convergence. Extensive experiments
in Section 4 highlight the efficiency and accuracy of SketchDecomp. Finally, we conclude the work in
Section 5.
2 SketchDecomp
In this section, we briefly describe the packet loss detection problem to be solved and then develop our
proposed method.
2.1 Problem Statement
Consider communication between two data centers DC1and DC2, bridged by a WAN link L. Their clocks
have been synchronized using certain synchronization methods of the WAN. In a certain period, streaming
data consisting of several types of flows are continuously sent from upstream DC1to downstream DC2
through L. The forward delay varies with time, and its rough range is known. Dividing the upstream time
into multiple windows of length T, we aim to check for each flow whether the packet loss occurs in each
window and estimate the packet loss rate accurately.
2.2 Count-min Sketch
The count-min sketch (CM sketch) is a particular data structure to count and record the frequency of each
type of flow in stream data, with a certain confidence level. Unlike traditional hash tables, it utilizes mul-
tiple, say d, mutually independent hash functions {hi}d
i=1 to against the overcounting caused by collisions.
Basically, CM-Sketch is a d×wmatrix denoted as C, whose i-th row is the count created by hi. There is
2