Toby Moncaster

Toby Moncaster (PhD Student)

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Transport Protocols

I have done a lot of work in teh Transport Areaa of the IETF. Most of my work has concentrated on congestion exposure, pre-congestion notification and congestion control.

Congestion Exposure is a simple technique designed to close teh information gap between end systems and the network. It involves getting senders to include an estimate of the congestion they expect their traffic to cause in every packet they send. As their traffic traverses the network every interemediate host is able to see the congestion the traffic has actually caused and work out how much congestion is still to come. The simplest version of the system is called re-ECN. It relies on the sender and receiver being ECN-compliant and on intermediate routers performing ECN marking. Effectively for every ECN mark the receiver tells the sender it has caused, the sender must send a re-ECN mark. At any point in the network a router can see how many ECN marks it is seeing and subtract this from the number of re-ECN marks to see how much downstream congestion the traffic will cause if it forwards it.

Pre-congestion notification (PCN) is a technique to make efficient use of network capacity for real-time traffic such as voice calls. At the ingress to the network all traffic bound for the same egress is added to an ingress-egress aggregate. As traffic crosses the network intermediate nodes may mark it if they are becoming congested. All these marks are collected at the egress, fed back to the ingress and used to determine whether or not to admit new traffic. The marking is done using a virtual queue with a capacity slightly lower than the link capacity. Two thresholds are provided. If the traffic exceeds the first threshold then the link is becoming pre-congested and no more flows shoudl be admitted. If the second threshold is passed then that indicates incipient congestion and flows will need to be terminated to minimise the overall damage.


Data Centre Networks

My PhD is concentrating on the field of data centre networks. {ToDo} Add some details here.