MaxNet is:

1
MaxNet Quick Overview

• MaxNet is
• A Fully distributed flow control architecture
  for large networks (no per-flow state in
  router)
• Max-Min fair in principle.
• Stable for networks of arbitrary topology,
  number of users, capacity and delay.
• Fast convergence properties.
• Addresses short-flow control.
• Low queuing delay, drastically reduces router
  buffer size requirements.
• Based on similar analysis as FAST TCP
• Incrementally deployable Integrates with FAST
  TCP

2
MaxNet Packet Format
MaxNet requires N bits in the packet to carry an
explicit signal about the path congestion level.
The routers along the packets path modify this
congestion signal. The congestion signal controls
the sources rate.
Data
Congestion Signal N Bits
IPV6
IPV4 TCP
3
MaxNet System
Maxnet requires the participation of the Source,
Router and Receiver. The sourcerate is
controlled by a feedback value in the ACK packet.
This feedback value is obtained from routers as
the packet passes through MaxNet links on their
way to the receiver. Each routers only remarks
the packet if its congestion value is higher than
in the packet, hence MaxNet. At the end of the
path, the packet holds the highest congestion
value off all routers along the path.
TCP sender
TCP receiver
Data packets
P
P
P
P
p1
p2
Xmit Rate
Router
Router
P
P
P
P
ACK packets
Source 1. Transmits packets at ratecontrolled by
feedback value in ACK Pj

• Router
• 2. Computes congestion level
• Remarks packet if routers congestionlevel is
  higher than level in packet

Receiver 4. Relays P value and sends it back to
sender in an ACK packet.
4
MaxNet Source Link Algorithm
Source Algorithm
D(Pj)
Source receives ACK j with feedbackvalue Pj and
determines transmissionrate by demand function
D(Pj)
Xi D(Pj)
Link Algorithm

• Router monitors aggregate input traffic rate
  Yl(t) destined for link l which has capacity
  Cl(t)
• Every 10 ms router l computes its congestion
  level pl
• pl(t1) pl(t) b(Y(t)-aC(t))
• a control target link utilization
• b controls convergence rate
• 2. For every data packet k with signal Pk router
  conditionally remarks it
• if (Pk lt pl(t)) Pkpl(t)

5
MaxNet XCP Properties
Criteria MaxNet XCP
Rate Allocation MaxMin Fair if all sources have the same demand function. Weighted MaxMin if sources weight their demand function. Constrained MaxMin (less than MaxMin)
Stability Provable stability for networks of arbitrary topology, RTTs, capacity and arbitrary number of flows. (Linear analysis). Single link and aggregate of flows, all with same RTT only shown. No general proof exists.
Convergence Speed Linear analysis shows faster convergence than ECN, loss (RENO), delay (FAST,VEGAS) based schemes. No control analysis available. Some simulation results show faster than TCP-RENO.
Router operations per packet 2 1 addition 1 max 12 3 multiplications 1 division 6 additions 2 comparisons
6
MaxNet XCP Properties
Criteria MaxNet XCP
Bits per Packet Naïve encoding 40 Bits/pkt with naïve linear encoding. Exponential encoding Even 20 bits per packet would give huge dynamic range. 96 Bits/pkt from BSD implementation.
Incremental Deployment Yes, MaxNet can be thought of as an explicit version of FAST-TCP (where the congestion signal is implicit- delay). A combined protocol with FAST-TCP is possible which uses explict signal, delay and loss, allowing operation on paths with no explicit signal ability. Unknown
Implementation progress TCP-FAST can be adopted. Linux MaxNet module in development. NS2 BSD
Lossy environments Decouples loss from congestion measurement. Recent improvements to loss recovery for FAST-TCP apply equally to MaxNet. FAST-TCP was recently shown to achieve around 6Mbps goodput at 30 loss rate, on a 70ms 10Mbps link. Unknown
For more information go to http//www.cs.caltech.
edu/bartek/