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