Discussion of Transport Protocol and Network Monitoring Advances

1
Discussion of Transport Protocol and Network
Monitoring Advances

• Deb Agarwal (DAAgarwal_at_lbl.gov)
• Lawrence Berkeley National Laboratory
• Berkeley, CA USA
• NOTE The views expressed in this presentation
  are the authors and not necessarily those of the
  United States Government

2
Outline

• Reliable Multicast status
• TCP flow and congestion control advances
• Network performance testing and monitoring

3
What is Multicast Communication?

• Group communication mechanism
• Provides one-to-many and many-to-many
  communication
• Efficient dissemination of messages
• Network-based duplication (when needed)
• Targeted retransmissions
• Bandwidth savings
• Parallel delivery at multiple locations
• Components
• IP Multicast (hosts and routers)
• Reliable multicast (application level)

4
IP Multicast Communication
Multicast
Unicast
5
Internet Protocol (IP) Multicast

• Efficient group communication mechanism
• provides one-to-many communication
• Best-effort delivery to the group members
  (unreliable)
• Implemented in the network routers and hosts
• Class D addresses used for multicast (224.x.x.x -
  239.x.x.x)
• Network components manage routing and duplicate
  the message as needed
• Co-exists with TCP and UDP communication
  mechanisms

6
Example IP Multicast Use (Access Grid )
7
What is Reliable Multicast?

• Properties similar to TCP
• Application-level program (runs on end systems)
• Uses IP Multicast as the underlying communication
  mechanism
• Reliable and ordered delivery of messages within
  a group (negative acknowledgments and
  retransmissions)
• Tracks group membership

8
Example Reliable Multicast Use
9
CD-1.1 Multicast Capability

• Motivation
• efficient transmission of data to multiple sites
• reliability (minimize single points of failure)
• allow as-needed use of multicast
• Designed and implemented by SAIC
• data provider multicasts data and provides
  retransmissions (small look back window only)
• reliability host requests any required catch-up
  from data provider (unicast)
• reliability host responsible for catch-up of data
  consumers (unicast)
• easy to use either unicast or multicast

10
Design Constraints

• All system-level CD-1.1 unicast requirements
  apply
• 99.99 reliability requirement has been retained
• Application level reliability provided by a
  combination of multicast and point-to-point
  transmission mechanisms
• Minimize perturbations to CD-1.1 Formats and
  Protocols IDC 3.4.3 Rev. 0.2
• Compatible with CDS CD-1.1 unicast
• A data provider must be able to service both
  multicast and point-to-point data consumers
  simultaneously

1. Adapted from Cordova and Bowman, CD-1.1
Reliable MulticastingRequirements and
Preliminary Design.
11
Design Features for the Multicast Capabilities

• Up to 20 data consumers in a single multicast
  group.
• Supports increases and decreases in the size of
  the multicast group without the need to restart
  the sending activity of the data provider.
• Transmission rates are constant and configurable
  to mitigate network congestion.
• The size of multicast data packets is
  configurable to support small MTU networks
  (frames broken into packets)
• Retransmission of missing multicast data packets,
  availability limited by configurable data buffer
  size.
• Reliability hosts provide unicast catch-up of
  frames missed by multicast data consumers

12
CD-1.1 Reliable Multicast - Normal Operation
e.g., Data Center
Consumer 3
Reliability Host 1
Multicast
Multicast

IMS Station
Multicast
Consumer 4
Reliability Host 2
Multicast
Multicast
e.g., Backup Data Center
1. Adapted from Cordova and Bowman, CD-1.1
Reliable MulticastingRequirements and
Preliminary Design.
13
CD-1.1 Reliable Multicast -Catch-Up Operation
e.g., Data Center
Reliability Host 1
Consumer 3
Multicast
Multicast
Pt to Pt
Pt to Pt

IMS Station
Multicast
Reliability Host 2
Consumer 4
Multicast
Multicast
Pt to Pt
Pt to Pt
e.g., Backup Data Center
1. Adapted from Cordova and Bowman, CD-1.1
Reliable MulticastingRequirements and
Preliminary Design.
14
Conceptual Design
Data Provider
Data Consumers
Multicast Sender
Multicast Receiver
Point-to-Point Receiver
Point-to-Point Sender
Multicast Receiver
Point-to-Point Sender
Reliability Hosts
Point-to-Point Receiver
1. Adapted from Cordova and Bowman, CD-1.1
Reliable MulticastingRequirements and
Preliminary Design.
15
Reliability Hosts

• Policies
• Any site may provide a reliability host for
  catch-up data transmission
• Data consumers may select the reliability host to
  connect to
• CD-1.1 Access Control

1. Adapted from Cordova and Bowman, CD-1.1
Reliable MulticastingRequirements and
Preliminary Design.
16
Design Approach

• System level
• Custom reliable multicast solution (based on
  CD1.1)
• Point-to-point mechanism for application level
  reliability
• Separate multicast (real-time) and point-to-point
  (catch-up) transmission into separate subsystems
• Multicast subsystem
• Modify connection sequence to generalize
  initiation of a connection after an outage
• Multicast transmission initiated by pull from
  data consumer
• Use CD-1.1 procedure (in reverse) to establish
  connection
• Multicast transmission begins at data provider
  time (current time - small look back) - no
  attempt to catch up
• Data provider provides packet-level reliability
  host

1. Adapted from Cordova and Bowman, CD-1.1
Reliable MulticastingRequirements and
Preliminary Design.
17
CD-1.1 Formats and Protocols

• Extension to connection options
• Data consumer requests connections for
• multicast transmission
• point-to-point catch-up of missing frames
• Data provider initiated connections for unicast
  unchanged
• Minor changes required to IDC 3.4.3 Rev. 0.2
• Use some fields that had been reserved for
  multicasting
• Defined a new type of Option Request Frame
• Changed miscellaneous text descriptions to be
  valid for both unicast and multicast

1. Adapted from Cordova and Bowman, CD-1.1
Reliable MulticastingRequirements and
Preliminary Design.
18
SAIC - CD-1.1 Reliable Multicast Testing

• Test phases
• 1. Local area testing on San Diego Testbed -
  complete
• 2. Wide area testing between San Diego Testbed
  and CMR - complete
• 3. Wide area testing between IS56US and San Diego
  Testbed and CMR - complete
• 4. Wide area testing between I56US and AFTAC, CMR
  and San Diego Testbed - ongoing
• Example test cases
• Multicast Data Transmission
• Gap Notification and Unicast Catchup
• Change of Multicast Group Address
• Multicast Layer Network Usage
• Data Timeliness
• Multicast Connectivity Fails

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Outline

• Reliable Multicast status
• TCP flow and congestion control advances
• Network performance testing and monitoring

20
Standard TCP - Background

• Sliding window-based flow and congestion control
• Number of outstanding packets in the path
• Slow start
• Probe the network at start-up
• Quickly find operating throughput range (minimal
  congestion)
• Additive Increase Multiplicative Decrease (AIMD)
• Steady state algorithm
• Continually strive to improve throughput
• React quickly to congestion
• Congestion measured by lost packets

21
Standard TCP Algorithms

• Slow start window size
• Initially one segment
• Size increased by one for each acknowledgement
• Exponential growth
• Continues until loss of a packet or reach a set
  threshold
• AIMD
• Loss of a packet cuts the window size in half
• Each acknowledgement increases the window by
  1/cwind
• Acknowledgements
• Receiver sends acknowledgement for highest in
  sequence packet received (3 duplicates cause a
  retransmission)
• Selective acknowledgement SACK
• Allow acknowledgement of packets beyond a gap

22
Standard TCP Congestion Control
23
Problems With Standard TCP

• Large bandwidthdelay product
• Connection must have bandwidthdelay packets in
  flight to fully utilize a connection
• Random loss
• Interpreted as congestion
• Bursty transmission
• Window size jumps cause bursts of packets
• Small MTU (Maximum Transmission Unit)
• Window increases and decreases are in MSS
• Small default buffer sizes in end hosts (8KB
  versus 4MB)

24
Currently Proposed Solutions

• TCP Tuning
• Appropriate values for the TCP buffers at the
  sender and receiver
• HighSpeed TCP/Scalable TCP
• Makes AIMD more aggressive
• Non-linear increase and decrease parameters based
  on current window size
• FAST TCP
• TCP Vegas-like algorithm
• Congestion measured as a function of round trip
  time
• Jumbo Frames
• Increase the MTU of the network
• Web 100 Work Around Daemon
• Provides work-arounds for several TCP problems

25
TCP Tuning
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TCP/HSTCP Response Function
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Performance Comparison
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Outline

• Reliable Multicast status
• TCP flow and congestion control advances
• Network performance testing, monitoring, and
  diagnosis

29
Network Testing Goals

• Network path to destination
• Roundtrip time/one way delay
• Capacity of each segment of a path
• Bottleneck in the path
• Available bandwidth
• Achievable bandwidth
• TCP throughput
• Appropriate TCP parameters
• UDP throughput
• Loss rate
• IP Multicast capabilities
• Identify router and host mis-configuration
• Jitter
• Packet reordering

30
Network Testing Tools

• Ping
• ICMP packets
• Reachability and response time
• Traceroute
• ICMP packets
• List of routers along the path and response time
  for each router
• Iperf
• TCP and UDP throughput
• Delay, jitter, and loss
• Client/server
• Pchar/pathchar
• Series of UDP packets of varying sizes
• Bottleneck link capacity
• Per hop bandwidth, propagation delay, queue time,
  and drop rate

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Testing Cont.

• Treno
• UDP packets to an unused port
• Expected TCP throughput
• Pathrate
• UDP packet trains
• Capacity of a path
• Pathload
• UDP packet trains
• Available bandwidth of a path
• Network Characterization Service (NCS)
• UDP packet trains
• Available bandwidth, maximum burst size, and
  bottleneck
• TCP and UDP achievable throughput
• Network Internet Measurement Infrastructure
  (NIMI)
• Framework for launching network testing tools
• Internet2 Performance Improvement Performance
  Environment

32
Network Monitoring Goals

• Track performance of network paths
• Detect problems
• Understand application and protocol behaviors
• Test new applications and protocols
• Predict future performance
• Resource scheduling

33
Network Monitoring Tools - Active

• PingER
• ICMP ping-based (periodically send a set of
  pings)
• Response time
• Packet loss
• Reachability
• TCP Bulk transfer rate
• Traceroute
• Used to track High Energy Physics sites

34
Cont.

• Multicast Beacon
• Periodic IP Multicasts from all sites
• Multicast connectivity/loss matrix
• Used by Access Grid community

35
Network Monitoring Tools - Passive

• Tcpdump/tcptrace/xplot
• Capture traffic headers at an end host
• Protocol and application behavior
• CoralReef
• Capture traffic headers from inside the network
• Self-Configuring Network Monitor
• Secure capture of traffic headers inside the
  network
• Configuration based on request
• Protocol and network behavior
• NeTraMet A Network Traffic Flow Measurement
  Tool
• CoralReef packet capture
• Provides a flow meter
• NetFlow
• Flow statistics from routers (SNMP)
• Multi Router Traffic Grapher (MRTG)
• Graph statistics from routers (SNMP)

36
Self-Configuring Network Monitor
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Network Diagnosis

• Netlogger
• Event triggered monitoring
• User specified monitoring points
• End-to-end monitoring of application performance
• Net 100
• TCP parameter visibility and recording
• Can be analyzed for problematic behaviors
• Traffic Analysis and Automatic Diagnosis (TAAD)
• CoralReef flow collection
• Analyze aggregated traffic flows for problematic
  signatures

38
Web100/Iperf/Netlogger
39
Netlogger Debugging of an Application
40
Network Intrusion Detection

• Bro
• Passively monitor network link
• Filters traffic to produce higher level events
• Uses a policy language to express site security
  policy
• Real-time detection and notification of attacks
• Ability to contact border router and block
  attacker
• Used at Lawrence Berkeley Lab (LBNL) and National
  Energy Research Supercomputing Center (NERSC)
  extensively

41
Relevant Working Groups

• Reliable Multicast
• IETF Reliable Multicast Transport Working Group
• IRTF Reliable Multicast Research Group
• Network Measurement/Monitoring
• IETF IP Performance Metrics Working Group
• IRTF Internet Measurement Research Group
• GGF Grid High-Performance Networking Research
  Working Group
• GGF Network Measurements Working Group

42
URLs

• AMP - http//amp.nlanr.net/AMP/
• CoralReef - http//www.caida.org/tools/measurement
  /coralreef/
• FAST TCP - http//netlab.caltech.edu/FAST/
• GGF Network Measurements Working Group -
  http//www-didc.lbl.gov/NMWG/
• HSTCP - http//www.icir.org/floyd/hstcp.html and
  http//www-itg.lbl.gov/evandro/hstcp/index.html
• IETF IP Performance Metrics working group -
  http//www.ietf.org/html.charters/ippm-charter.htm
  l
• Iperf - http//dast.nlanr.net/Projects/Iperf/
• NCS - http//www-didc.lbl.gov/NCS/
• Net100 - http//www.net100.org/
• Netlogger - http//www.itg.lbl.gov/Netlogger/homep
  age.html
• Netperf - http//www.netperf.org/netperf/NetperfPa
  ge.html
• NeTraMet - http//www2.auckland.ac.nz/net/NeTraMet
  /
• NIMI - http//www.ncne.nlanr.net/nimi/
• Pathrate/pathload - http//www.cc.gatech.edu/fac/C
  onstantinos.Dovrolis/bw.html
• Pathchar - ftp//ftp.ee.lbl.gov/pathchar/
• PingER - http//www-iepm.slac.stanford.edu/pinger/
  
• SCNM - http//www-itg.lbl.gov/Net-Mon/Self-Config.
  html
• TAAD - http//ncne.nlanr.net/research/taad/
• TCP tuning guide - http//www-didc.lbl.gov/TCP-tun
  ing/TCP-tuning.html