Upload
destiny-henry
View
214
Download
0
Tags:
Embed Size (px)
Citation preview
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
OutlineOutline
IntroductionGrid Networks Architecture to Access Remote
EquipmentsTechnology Overview
DVB-RCS overview and TCP-friendly protocols and their related startup
problemsNumerical Results
Current TFRC performanceTFRC performance using Quick StartIntegration between QS and DAMA
IntroductionGrid Networks Architecture to Access Remote
EquipmentsTechnology Overview
DVB-RCS overview and TCP-friendly protocols and their related startup
problemsNumerical Results
Current TFRC performanceTFRC performance using Quick StartIntegration between QS and DAMA
IntroductionIntroduction
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
HOST B
DVB-RCS architectureDVB-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 allows 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 allows bidirectional channels over satellite links (Meshed Networks) with a generic MF-TDMA access scheme
RETURN LINK
DVB-RCS
FORWARD LINK
DVB-S/S2
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
TP
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 ControlTCP-friendly Rate Control 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.
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
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.
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 mechanismBasic QS mechanism
QS request sent QS
response sent
the sender can transmit
data up to the approved rate
QS request accepted
QS router
TFRC Performance (with/without QS) in terms of end-to-end delayTFRC 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!!
NO QS QS
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
BWreq
Packets queued
Receiver sends
QS resp
TFRC sender TFRC receiver
Source reduces Tx rate
Proposed Solution: Delaying the QS requestProposed Solution: Delaying the QS request
QS request sent
QS request accepted
BTP
Source quick starts
BWreq
Receiver sends
QS resp
Tq
TFRC sender TFRC receiver
TFRC 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 Forward Delay
Delayed QS requestDelayed QS request
Estimation of the minimum delay to impose to QS request
Estimation of the minimum delay to impose to QS request
Conclusions and Future worksConclusions and Future works
Congestion control algorithms will be probably a MUST in future internet and Grid networksQS protocol supply a considerable support to networks with large propagation delay (such in case of SAT networks) The proposed solution really improves the performance of a DAMA base satellite platform when QS is adopted
Find an analytical backing of the imposed delay in relation with the satellite architecture
Congestion control algorithms will be probably a MUST in future internet and Grid networksQS protocol supply a considerable support to networks with large propagation delay (such in case of SAT networks) The proposed solution really improves the performance of a DAMA base satellite platform when QS is adopted
Find an analytical backing of the imposed delay in relation with the satellite architecture