Lightweight Flow Setup Wirespeed Flow Reservation

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Lightweight Flow SetupWirespeed Flow Reservation
Jon Turner Fred Kuhnsjst,fredk_at_cs.wustl.eduhtt
p//www.arl.wustl.edu/arl
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Resource Reservation in Internet?

• Bandwidth reservation can provide dramatically
  better performance for some applications.
• Obstacles to resource reservation in Internet.
• distaste for signaling protocols
• perceived complexity of IntServRSVP
• requires end-to-end deployment
• little motivation for service providers
• How to get resource reservation in Internet?
• keep it simple
• focus on top priorities - one-way unicast flows
• avoid complex signaling - leverage hardware
  routing mechanisms
• make it useful when only partially deployed
• provide motivation for ISPs to deploy it

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Context Extreme Networking

• The Lightweight Flow Service is one of two
  interrelated services provided within the Extreme
  Networking framework.
• Lightweight Flow Setup (LFS)
• one-way unicast flow with reserved bandwidth,
  soft-state
• no complex signaling, wire-speed setup, easy to
  deploy
• Network Access Service (NAS)
• provides controlled access to LFS
• registration/authentication of hosts, users
• resource usage data collection for monitoring,
  accounting

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Lightweight Flow Setup Service

• Sender initiated, one-way, unicast flow
• Soft-state that responds to transmission of
  packets between endpoints
• Arrival of first packet triggers creation of
  per flow state - no advance signaling required
• Reservation request embedded in application
  packets
• flow rate(s) specified in packet header using IP
  options
• Routers independently process reservations and
  allocate resources
• No global coordination required
• Flow detected and route selection triggered as
  needed
• Route for flow pinned until flow is released or
  times out
• Prefer routes with ample unreserved bandwidth
• allocate requested rate if/when sufficient
  bandwidth

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Service Models

• Firm rate - Basic Service Model
• Applications required minimum guaranteed rate
• Client may alter reservation up or down - limits
  may be placed on rate of reservation change
• Allocate bandwidth on a FCFS basis as available
• Partial allocations - congested links forward
  packets as datagrams until sufficient bandwidth
  is released by other flows
• Soft Reservations
• Can be intermixed with firm requests
• Applications maximum desired rate
• Congested links allocate bandwidth fairly among
  competing flows, proportional to their firm rate
• Requires minimum firm rate of 64Kbps

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Basic LFS Operation
Select path and attempt to reserve
Reserve bandwidth
Reserve 8 Mb/s to B
Complete reservation
A
20 Mb/s available
B
Select best next hop
Select path and reserve

• One way, unicast setup with partial reservation.
• complete reservations locally when bandwidth
  released
• Optional Status Report returned by far-end access
  router.
• Reservation may terminate explicitly with a
  Release message or timed out.
• May alter reserved bandwidth but not route.

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Example Application

• Web site specifies stable rate in outgoing
  streaming media packets
• Use feedback to adjust sending rate if necessary.
• Note no action required by receivers.

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Example Application - Continued
Network
2) server receives request prepares to send
video
Service Provider
AR
End System (source)
TR
TR
4) each router allocates rate and binds flow to
route.
3) Sends video with embedded LFS reservation
requests, user identifier U1.
Service User
5) Receives video clip at guaranteed rate.
TR
TR
End system (destination)
AR
1) request video clip from service provider.
TR
TR
AR - Access Router TR - Transit Router
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Regulating LFS Use

• Assumes the existence of a Network Access Service
  (NAS)
• client (user or host) must register prior to
  using LFS service
• binds client-specific privileges
• limit rates, reserved flows, frequency of
  changes, total bandwidth
• establishes an access pipe between an access
  router and an authenticated client
• Records usage for monitoring, accounting.
• record reservation periods, rates, bytes
  delivered
• Regulation and monitoring at network access
  points by NAS or its proxy
• for fixed access, just use physical interface
• access router keeps record and enforces limits
• for roaming access to ISP or corporate network
• registration protocol executed when host connects
  to network
• IP tunnel for data transfers between host and
  access point
• all data to/from host passes through that point

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Source Network and SAR
NAS
user dB
user
info
limits
id
...
...
...
...
Establish access pipe and client usage limits
register user
Authenticate user, return credentials
SAR
NAS verify user and request LFS process request
End system (Source)
All traffic from Client to Access Router goes
through the established Access Pipe. Access pipes
are simplex.
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Status Reporting and Usage Monitoring

• If a router can not allocate the requested rate
  it updates a field in the LFS request
• DAR maintains a usage database by recording the
  flow, user and current reservation status
• Client may request end-to-end status reports from
  the DAR
• DAR sends report directly to client
• Status reporting mechanism for use by network
  provides (ISPs).
• reporting to routers within a domain, reporting
  across the public network portion of the path and
  end-to-end reporting for private networks at the
  ends of a path

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Destination Network and DAR
Record usage, remove LFS requests if destination
does not support LFS
End system Destination
IP
data
AR
Usage dB
time
reservation
flow identifier
user
id
requested
allocated
duration
start
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Example Application - Continued
user dB
SAR NAS - Verify user and request. LFS - Process
request
AR - Access Router TR - Transit Router
NAS
user auth. info and usage rights. Create Access
Pipe.
register
AR
Source Host (NAS and LFS Client)
TR
TR
Access Pipe
TR process request and update LFS option showing
minimum allocation along path
Source LAN
DAR record reservation status (requested and
minimum rates). Remove LFS option.
TR
TR
Destination Host (Not required to register with
NAS)
AR
Access Pipe (Not Supported!)
TR
TR
usage dB
Destination LAN
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Partial LFS

• LFS to Non-LFS networks
• Boundary router between last LFS network and
  first non-LFS network terminates LFS flow. Status
  messages sent from this node. Assumes LFS role of
  the DAR.
• non-LFS LAN to LFS network through a single
  access point
• Assume bandwidth plentiful within LANs.
• Use LFS capable router at access point
• Intermediate Non-LFS networks
• Terminate LFS flow at the first LFS to Non-LFS
  network boundary router.
• Suggests policy of routing LFS flows through
  LFS-capable networks.

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Partial LFS

• WAN supports LFS but LANs do not.
• Ample LAN bandwidth can make partial reservation
  worthwhile.
• Sending LAN router (and perhaps switches) give
  LFS flows high priority.
• Sending WAN router processes reservation.

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Partial LFS in WANs

• Partial LFS useful from A to B if only A supports
  it.
• If only B supports LFS, not clear if its
  worthwhile.
• route changes can cause orphan reservations
• avoid orphan reservations by configuring
  inter-WAN routers to mark packets to disable LFS
  processing
• but if time between route changes is gtgt
  reservation timeout, orphan reservations not
  serious problem

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The LFS IP Option
op (2b)
flags (6 bits)
type (8 bits)
length (8 bits)
rate 1 (8 bits)
rate 2 (8 b its)
trace field (24 bits)
Client Network Status Recipient (32 bits,
optional)
Public Network Status Recipient (32 bits,
optional)
Intradomain Status Recipient (32 bits, optional)
Operations 00 Firm Rate Request 01 Soft Rate
Request 10 Release 11 Undefined
Flags (XXHCPI) H Host Status Request C Client
Network Status Request P Public Network Status
Request I Intradomain Network Status
Request XX Undefined
Status Recipient - 32 bit IP Address
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LFS Option- Flags

• Host Status Request - Requests router terminating
  the LFS portion of the path to send status report
  directly to the source host (source address in IP
  header).
• Client Network Status Request - Requests router
  terminating the LFS portion of the path to send
  status report to the Client Network Status Report
  Recipient.
• Public Network Status Request - Requests router
  terminating the LFS portion of the path to send
  status report to the Public Network Status Report
  Recipient. The recipient forwards the status
  report along the path of the flow. Report removed
  by the router that terminates the LFS section of
  the path, i.e. the reporting router.
• Intradomain Network Status Request - The report
  is sent by the last router on the path within the
  domain, to the intradomain status report
  recipient. Removed at outgoing BR

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Remaining LFS Option Fields

• Rate1 and Rate2 - Rates expressed using a
  floating point representation with a 4 bit
  mantissa and a 4 bit exponent.
• if m first 4 bits, x last 4 bits, then the
  rate is m ?2x?64 Kb/s.
• Permits reservation rates ranging from 64 Kb/s to
  over 4 Gb/s.
• Successive rates differ by no more than a factor
  of 1.0625.
• Rate 1 contains the desired rate, Rate 2 contains
  the minimum rate allocated along the path
• Trace field - Enables a network to determine
  where a flow entered the network for purposes of
  monitoring and accounting. Domains free to define
  own specific use.
• Status report target recipients - Optional list
  of up to three status report recipients. Each is
  associated with one of the status request flags
  and is present if and only if the corresponding
  status request flag is present. The order in
  which they appear (if present) is Client Network,
  Public Network then Intradomain.

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LFS Control and Status Messages
Hdr
operation(8 bits)
flags (8 bits)
undefined (2 Bytes)
source IP address (32 bits)
Flow Identifier
destination IP address (32 bits)
Status Record (20 Bytes)
source port (16 bits)
destination port (16 bits)
firm (8 bits)
soft (8 bits)
protocol (8 bits)
undefined (8 bits)

• LFS Status report are encapsulated within an IP
  datagram with a unique protocol type field.
• Currently, only this status message is envisioned
  so we do not need the LFS header.

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Internet Different ISPs
user database
NAS
ISP A
authenticate/ authorization
user authorization and constraints
register
user identifer
SAR
BR
TR
End system Source
usage dB
application flow LFS trace AX
application flow LFS trace AX to BX
Source Network
remove LFS option for trace BX
BR
TR
End system Client
DAR
BR
TR
usage dB
usage dB
Destination Network
ISP B
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Source Access Router - LFS Processing

• SW manages FPX reserved queues.
• Always reclassify packets.
• New or updated reservation must return bandwidth
  allocated.

Define access pipe, set usage limits/trace ID,
get usage table
CP
NAS (IKE, Accounting)
Return usage table, current and history.
NAS Register
Route Update
Add Exact Match Filter with Reservation
New LFS Flow. Allocate QID
Command Interface
Classify after filter added
Delete Exact Match Filter/Reservation
Release or error. Free QID
Route DB
Classify before delete filter
Forward No option or no change
No option or no change
Queue, Flow, and Access Pipe Table
Change LFS flow reservation
FPX Classifier
Change rate or style.
Classify after rate change
Dst Local, Proto LFS (status report)
Packet/Event Dispatcher
NAS (Authentication)
Access Pipe
Authorized
Non-LFS or Error drop LFS option
LFS Processing
Send status report to next hop
Encapsulated Status Report, send to next hop for
flow
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Transit Router
CP
Route Update
Add Exact Match Filter with Reservation
New LFS Flow. Allocate QID
Command Interface
Classify after filter added
Delete Exact Match Filter/Reservation
Release or error. Free QID
Route dB
Classify before delete filter
Forward No option or no change
No option or no change
Queue and Flow Table
Change LFS flow reservation
FPX Classifier
Change rate or style.
Classify after rate change
Dst Local, Proto LFS (status report)
Packet/Event Dispatcher
IP Option Processing
Packets with IP Options
LFS Options Present
LFS Processing
Send status report to next hop
Encapsulated Status Report, send to next hop for
flow
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Boundary or Destination Access Router

• No specialized routing needed since either the
  destination host is directly connected or peers
  with a Non-LFS network.
• Also needs output port bandwidth reservations.

CP
Get Usage Report
NAS (Accounting)
Return Usage Report
Add Exact Match Filter with Reservation
New LFS Flow. Allocate QID
Command Interface
Classify after filter added
Delete Exact Match Filter/Reservation
Release or error. Free QID
Usage dB
Classify before delete filter
Forward No option or no change
No option or no change
Queue and Flow Table
Change LFS flow reservation
FPX Classifier
Change rate or style.
Classify after rate change
Dst Local, Proto LFS (status report)
Packet/Event Dispatcher Remove LFS options Do
not forward status reports. Can destination
register? If so we forward options and reports.
IP Option Processing
Packets with IP Options
LFS Options Present
LFS Processing
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FPX - LFS Issues

• Shims input and output VINs included, SID
  changed to QID or Queue identifier
• Interfacing to FPX
• Queue Identifier for reserved flows allocated by
  software on the SPC.
• Add/removing/modifying exact match filters,
  including reservations and QID. Should return
  rate allocated.
• Do we need to request current firm and soft rate
  allocation for specific flow?
• Rely on LFS options to expose current allocation
  to SPC - when SPC updates filter the current
  allocation is returned.
• All packets with IP options are sent to SPC.
• Sent to SPC before classification.
• What about timing out LFS soft state on TR or
  DAR? Application must send LFS option in every X
  packets.

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NAS - LFS Issues

• Access pipe is used by LFS for authorizing
  requests
• NAS assigns usage limitations on a per access
  pipe basis
• LFS then verifies request against access pipe
  limits. If request exceeds limit then drop should
  we drop request, drop packet or reduce rate to
  max allowed?
• NAS may request LFS to release all reservations
  associated with a given access pipe.
• LFS obtains access pipe designator by
• inVIN ! default, then arrived on an access pipe
  with ID sub-port ID.
• IPSec - what do we use for an access pipe ID?
• Usage database reporting to NAS
• SPC/FPX sends to NAS instance on local CP
• LFS to NAS usage push or pull? AAL0 or AAL5? JDD
  data channels?
• IKE on SPC?! Not supported now. Implement on CP.
• Access Pipes are simplex - only on source end.

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Implementation -Transit Router Input

• If flow table entry present, use stored next hop.
• If no flow table entry, lookup route create
  entry
• store selected next hop in flow table entry
• next hop selected from list of candidates, based
  on outgoing link status

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Implementation - Transit Router Output

• If flow table entry present, use it to find
  queue, otherwise create an entry allocate
  queue.
• If firm reservation specified, update entry.
• keep list of unsatisfied reservation requests to
  process as bandwidth becomes available
• If soft reservation, update fair share, pacing
  rate.

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Implementation - Access Router Ingress

• If entry for user present in access table.
• check privileges and record usage in access table
• Otherwise, first retrieve user data from
  database.
• implies delay on first use of any given access
  link
• When multiple concurrent access points.
• users allocation divided - periodic updates

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Implementation - Access Router Egress
FlowTable
RouteTable
FlowTable
FlowProcessor
FlowProc.
. . .
StatusTable
AccessTable

• Flow status recorded in status table.
• Record usage data for accounting.
• reserved amount, time of reservation changes
• Periodically transfer accounting data to CP.
• need to do data reduction, first?

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Routing Flow Reservations

• May use standard datagram routing for flows.
• QoS routing can produce better results.
• Shortest path routing with suitable cost metric.

• Link cost proportional to length when link not
  busy.
• When margin is small, link cost grows to reflect
  uncertainty in link state.
• Parameter a chosen to balance cost of false
  positive and false negative.
• Interdomain routing?

sample parameter valuesR5 Mb/s, k5,
a500/(kR)2