802 Handoff A Technical Preview

1
802 HandoffA Technical Preview

• David Johnston
• david.johnston_at_ieee.org
• dj.johnston_at_intel.com

2
Purpose (of these slides)

• To date, a lot has been said about scope,
  purpose, goals, interworking, liason, PARs and
  other such things
• This presentation skips rapidly through that and
  gets to the meat of some technical aspects of 802
  handoff that could become part of the standard

3
Problem Statements

• Three problem statements approved as findings of
  the group
• 1 Detection of a useable attachment to a network
  is impacted by the ambiguous indicators of
  network attachment in certain 802 MACs. Thus
  there is a need to develop a standard that allows
  a mobile terminal to optimize detection of a
  useable attachment to a network above the LLC.
• 2 The information necessary to make effective
  handoff decisions is lacking in part because 802
  networks provide insufficient information to the
  upper layers. Thus there is a need to develop a
  standard that permits information exchange
  between mobile terminals and/or networks to
  enable mobile terminals and/or networks to make
  more effective handoff decisions.
• 3 There is no standardized mechanism in 802 for
  information exchange between mobile terminals and
  network attachment points. This impacts the
  ability to make informed decisions to select
  between disparate network attachment points or to
  initiate handoffs between heterogeneous network
  types or between administrative domains within a
  single network type. Thus there is a need to
  develop a standard that permits mobile terminals
  and network attachment points to access
  information on which to base effective handoff
  decisions.

4
Draft Scope

• For the purposes of converging towards a
  consensus on purpose and scope, the group
  approved the following text as a working copy of
  the scope for discussion prior to the September
  interim

The scope of this project is to develop a
standard that shall define mechanisms that may be
adopted into implementations so that handoff of
handoff-capable upper layer entities, e.g.
MobileIP sessions, can be optimized between
homogeneous or heterogeneous media types both
wired and wireless, where handoff is not
otherwise defined. Consideration will be made to
ensure compatibility with the 802 architectural
model. Consideration will be made to ensure that
compatibility is maintained with 802 security
mechanisms including 802.1x. Neither security
algorithms nor security protocols shall be
defined in the specification.
5
Draft Purpose

• For the purposes of converging towards a
  consensus on purpose and scope, the group
  approved the following text as a working copy of
  the purpose for discussion prior to the September
  interim

The scope of this project is to develop a
standard that shall define mechanisms that may be
adopted into implementations so that handoff of
handoff-capable upper layer entities, e.g.
MobileIP sessions, can be optimized between
homogeneous or heterogeneous media types both
wired and wireless, where handoff is not
otherwise defined. Consideration will be made to
ensure compatibility with the 802 architectural
model. Consideration will be made to ensure that
compatibility is maintained with 802 security
mechanisms including 802.1x. Neither security
algorithms nor security protocols shall be
defined in the specification.
6
Relevant Elements in Network
7
Handoff Cases
8
What Can We Do?

• Easy
• Enable make before break handoffs
• Reduce length of break before make handoffs
• Prevent inappropriate attachment attempts
• Improve scanning speed
• Prevent unnecessary DHCP attempts
• Hard
• Pre authenticate via backbone
• Transfer QoS context
• Remotely interrogate base stations
• Media independent handoff decisions on network
  side
• L2 end to end triggers

9
How do we do it

• Easy
• Provide an information base with defined
  structure and semantics
• Provide access via the top (API, MAC SAP
  messages, management interface (oids, ndis snmp)
• Provide access via link (extended 802.1x model,
  encapsulation)
• Hard
• Define new media independent inter base protocols
• Other (Left as exercise to the reader)

10
L1,2 L3 Triggers

• Meets emerging requirements in IETF for fast
  mobile IP and for effective DNA (Detection of
  Network Attachment)
• Maps elsewhere (non IP, handoff-able L3 nets)
• Sends events upwards from L2 to L3
• Indicated specific states or state changes
• Link Up, Handoff decision, etc
• May contain per trigger metadata
• Link ID, VLAN etc.

11
The 802.1x Model
12
Extending The 802.1x Model
13
Extending the 802.1x model

• 2 Handoff ethertypes, one for secure, one for
  insecure
• Device on other end of link can interrogate the
  information bases using packets marked with the
  appropriate ethertypes
• Packets passed are traditional MSDUs common to
  all 802 MACs
• Thus information can be made available
  independent of media type

14
Define Handoff Decision Data

• Pre defined information to support handoff
  decisions
• Network vendor
• Auth types supported
• L3 network media (internet/PSTN/ATM etc)
• Etc
• Make it extensible
• Supports proprietary vendor codes/extensions
• Supports playpen data types

15
Transporting The Decision Data

• It needs a coding and encapsulation for
  transmission
• Ethertypes to map into extended 802.1x model
• ASN.1 or XML or canonical S expressions
• I prefer canonical S expressions due to
  opportunities for easy parsing, signing and
  stateless expression
• XML canonicalisation needed for signing
• VERY compute intensive

16
Define Media Independent HO Decision Data
Encapsulation
EG ltbase_descriptorgt ltmedia_typegt802.11lt/media_t
ypegt ltauth_requiredgt ltauth_vendorsgt ipass
boingo lt/auth_vendorsgt ltbackbone_pre_authgt
yes lt/backbone_pre_authgt ltCS_descriptorgt ltty
pegtmIPv6lt/typegt ltaddressgt192.168.0.1lt/addressgt
lt/CS_descriptorgt ltadjacent_basesgt base1 base2
etc. lt/adjacent_basesgt lt/base_descriptorgt

• Pick XML/ ASN.1/ Canonical S Expressions
• Make it suitably extensible

17
More out there ideas

• Make link signaling carry more elaborate
  semantics than fetch
• Get/Set, Forward, Remote Request
• Enable end to end triggers through information
  conduit
• Allows remote triggering, network side handoff
  commands to mobile part