Advanced satellite infrastructures in
future global Grid computing: network
solutions to compensate delivery delay
Blasco Bonito, Alberto Gotta and Raffaello Secchi
ISTI – CNR
Advanced satellite infrastructures in
future global Grid computing: network
solutions to compensate delivery delay
Blasco Bonito, Alberto Gotta and Raffaello Secchi
ISTI – CNR
Outline
Outline
Introduction
Grid Networks Architecture to Access Remote
Equipments
Technology Overview
DVB-RCS overview and
TCP-friendly protocols and their related startup
problems
Numerical Results
Current TFRC performance
TFRC performance using Quick Start Integration between QS and DAMA
Introduction
Grid Networks Architecture to Access Remote
Equipments
Technology Overview
DVB-RCS overview and
TCP-friendly protocols and their related startup
problems
Numerical Results
Current TFRC performance
TFRC performance using Quick Start Integration between QS and DAMA
Introduction
Introduction
Grid Network typically require high speed
connection to transfer significant amount of data
Remote equipments may be difficult to reach with
high speed connections
New satellite links (DVB-RCS) may provide reliable
and high speed connectivity to these sites
Grid Network typically require high speed
connection to transfer significant amount of data
Remote equipments may be difficult to reach with
high speed connections
New satellite links (DVB-RCS) may provide reliable
and high speed connectivity to these sites
GEO SATELLITE
DVB-RCS architecture
DVB-RCS architecture
DVB-RCS (ETSI EN 301)
DVB-RCS is maintained by the DVB
project is an industry-led consortium of broadcasters, manufacturers,
network operators and regulatory bodies in over 35 countries
DVB-RCS defines MAC and PHY
specifications for a satellite network
DVB-RCS permits bidirectional
channels over satellite links (Meshed Networks) with a generic MF-TDMA access scheme
DVB-RCS (ETSI EN 301)
DVB-RCS is maintained by the DVB
project is an industry-led consortium of broadcasters, manufacturers,
network operators and regulatory bodies in over 35 countries
DVB-RCS defines MAC and PHY
specifications for a satellite network
DVB-RCS permits bidirectional
channels over satellite links (Meshed Networks) with a generic MF-TDMA access scheme
RETURN LINK
DVB-RCS
FORWARD LINK
Concept of Demand
Assignment Multiple Access
Concept of Demand
Assignment Multiple Access
Internet congestion control algorithm (e.g. TCP
or TFRC) may suffer of long end-to-end delay
due to DAMA latency
Internet congestion control algorithm (e.g. TCP
or TFRC) may suffer of long end-to-end delay
due to DAMA latency
DAMA steps
1. The Traffic Terminal (TT) sends a Bandwidth request
2. The Master Station (MS) receive the message, computes the value of the bandwidth to be allocated and broadcast the BTP
3. Once the TT has received the reply from the MS, it waits its turn of transmission allocation delay BW req B T P Processing time safe frame period Master Station Traffic Terminal
DVB-RCS Bandwidth Allocation Methods
DVB-RCS Bandwidth Allocation Methods
Constant Rate Assignment (CRA)
Bandwidth is negotiated between the traffic terminal and the allocator
at the beginning of each connection
Rate Based Dynamic Capacity (RBDC)
Each Traffic terminals submits to the allocator a bandwidth request message based on the rate of local incoming traffic
Volume Based Dynamic Capacity (VBDC)
Each terminal dynamically signals the data volume needed to empty its buffer
Free Capacity Assignment (FCA)
No explicit request comes from the terminals. Unused bandwidth is
assigned automatically by the allocator to the traffic terminals according to some fairness criteria
Constant Rate Assignment (CRA)
Bandwidth is negotiated between the traffic terminal and the allocator
at the beginning of each connection
Rate Based Dynamic Capacity (RBDC)
Each Traffic terminals submits to the allocator a bandwidth request message based on the rate of local incoming traffic
Volume Based Dynamic Capacity (VBDC)
Each terminal dynamically signals the data volume needed to empty its buffer
Free Capacity Assignment (FCA)
No explicit request comes from the terminals. Unused bandwidth is
assigned automatically by the allocator to the traffic terminals according to some fairness criteria
TCP-friendly Rate Control
TCP-friendly Rate Control
TFRC is an equation-based & paced-based protocol that providescongestion control to multimedia applications. It is designed to be reasonably fair when competing for bandwidth with TCP connections. In TFRC, the receiver periodically sends a feedback report informing
the sender of received throughput and recent loss event rate that a connection experiences.
TFRC slow start phase
Initial Slow Start: TFRC starts with 4 packets per RTT and doubles the rate at each RTT. Due to satellite delays, the sending rate reaches the encoding rate in a long time (without congestion).
Sending rate limit: TFRC sending rate can be at most twice the current receiver rate. This growth rate is not sufficient to keep up with the encoding rate when the application oscillates between silence and talk periods.
TFRC is an equation-based & paced-based protocol that provides
congestion control to multimedia applications. It is designed to be reasonably fair when competing for bandwidth with TCP connections.
In TFRC, the receiver periodically sends a feedback report informing
the sender of received throughput and recent loss event rate that a connection experiences.
TFRC slow start phase
Initial Slow Start: TFRC starts with 4 packets per RTT and doubles the rate
at each RTT. Due to satellite delays, the sending rate reaches the encoding rate in a long time (without congestion).
Sending rate limit: TFRC sending rate can be at most twice the current receiver rate. This growth rate is not sufficient to keep up with the encoding rate when the application oscillates between silence and talk periods.
Quick Start (RFC 4782)
Quick Start (RFC 4782)
Quick Start is a protocol that provides a lightweightsignaling of congestion level between the routers of a network and a pair of communicating end hosts.
QS was proposed to work with TCP but it can be used
with any congestion control protocol that would prefer to inflate their sending rates without effectively slow starting from a small initial rate.
Using QS with Internet protocols can effectively and
efficiently work over a wide range of links including those with satellite delay. QS may also be useful for multimedia flows.
Quick Start is a protocol that provides a lightweight
signaling of congestion level between the routers of a network and a pair of communicating end hosts.
QS was proposed to work with TCP but it can be used
with any congestion control protocol that would prefer to inflate their sending rates without effectively slow starting from a small initial rate.
Using QS with Internet protocols can effectively and
efficiently work over a wide range of links including those with satellite delay. QS may also be useful for multimedia flows.
Basic QS mechanism
Basic QS mechanism
QS request sent QS response sent the sender can transmit data up to the approved rate QS request accepted QS routerTFRC Performance (with/without QS) in
terms of end-to-end delay
TFRC Performance (with/without QS) in
terms of end-to-end delay
QS improves performance but we want more!!
QS improves performance but we want more!!
QS request sent
QS request accepted
QS problems due to the interaction with
DAMA (Skyplex Data
®platform)
QS problems due to the interaction with
DAMA (Skyplex Data
®platform)
BTP Source quick starts Receiver sends low feedback report BW req Packets queued Receiver sends QS resp TFRC sender TFRC receiver Source reduces Tx rate
Proposed Solution: Delaying the QS
request
Proposed Solution: Delaying the QS
request
QS request sent QS request accepted BTP Source quick starts BW req Receiver sends QS respT
q TFRC sender TFRC receiverTFRC Performance (with/without QS +DAMA
improvement) in terms of end-to-end delay
TFRC Performance (with/without QS +DAMA
improvement) in terms of end-to-end delay
Delay further reduced!!
Delay further reduced!!
QS QS with
