Use of Overbooking in

Diffserv-aware MPLS Traffic Engineering<draft-wlai-tewg-overbook-00.txt>

IETF’57 TEWG Meeting

Vienna, July 14, 2003

Jerry Ash, Wai Sum Lai

AT&T Labs

Overbooking in DS-TE

• Per-domain per-CT overbooking

– Specified in current PROTO, MAM, and RDM drafts

– Based on existing techniques for aggregate TE:

Link size overbooking

LSP size overbooking

• Per-link per-CT overbooking

– Addressed by this draft

– Two methods compared:

Components-based approach (based on the LOM)

Integrated approach

Components-Based Approach (the LOM Method)

New concepts

• LOM = local overbooking multiplier

• Normalized bandwidth = reserved bandwidth / LOM

Bandwidth Constraints

• Unaffected by LOM

Unreserved Bandwidth

• Needs to be adjusted to account for LOM

Maximum Reservable Bandwidth

• Relationship with LOM currently unspecified

Impact on operations

• Different formulas for different overbooking scenarios

Integrated Approach

Single concept, single formula

• Maximum reservable bandwidth = maximum link bandwidth

• OB = overbooking factor

• OB = LSOM * LSPOM * LOM

LSOM = link size overbooking multiplier

LSPOM = LSP size overbooking multiplier

LOM = local overbooking multiplier

Impact on router operations

• Reserved bandwidth = Tspec / OB

Integrated Approach

Issues under discussion

• router interpretation of Tspec to determine ‘reserved bandwidth’

• relationship to current overbooking models– validity of Maximum reservable bandwidth = maximum link bandwidth