IS-IS and OSPF: Network Design Comparisons and ... - JANOG

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Metrics: OSPF • Dimensionless metric • Large metric field • Cost • Type 1 LSA = 16 bits • Type 3, 4, 5, and 7 LSA = 24 bits • Cost = Reference BW / Interface BW • Default Reference BW = 100 Mbps • If (Ref BW / Interface BW) > 1, Cost = 1 • Cost can also be set arbitrarily • External Metrics • Type 1 (E1) = Assigned cost + cost to ASBR • Type 2 (E2) = Assigned cost only
Metrics: IS-IS • Dimensionless metric • ISO 10589 defines 4 metric fields • Only default used in practice • Small 6-bit metric field • Default = 10 for all interfaces • Maximum interface value = 64 • Maximum route metric = 1,023 • Possible limited metric granularity in large networks • Originally intended to simplify SPF calculation (irrelevant with modern CPUs) • Wide Metrics • Extends metric field to 32 bits • Metrics tagged as internal or external (I/E bit)
Page 1 and 2: IS-IS and OSPF: Network Design Comp
Page 3 and 4: Agenda • Overview of link-state p
Page 5 and 6: In the Beginning Was Distance Vecto
Page 7 and 8: Problems with Distance Vector • S
Page 9 and 10: Fundamental Link-state Concepts •
Page 11 and 12: SPF Calculation Example Link-state
Page 17 and 18: Problems with Link State • Inform
Page 19 and 20: In the Beginning Was DECnet... •
Page 21 and 22: Protocol History • (Disclaimer—
Page 23 and 24: Protocol History • 1991 • OSPF
Page 25 and 26: Protocol History • 1996-1998 •
Page 27 and 28: ISOspeak 101 • Intermediate Syste
Page 29 and 30: Message Types: IS-IS • Hello PDU
Page 31 and 32: IS-IS Level 1 LSPs • Single LSP,
Page 33 and 34: Message Encoding: OSPF • Runs ove
Page 35 and 36: Media Support • OSPF • Broadcas
Page 37 and 38: Router and Area IDs: IS-IS 1-13 byt
Page 39 and 40: Neighbor Discovery and Maintenance:
Page 41 and 42: Database Synchronization: IS-IS •
Page 43 and 44: Database Refresh: IS-IS • LSP ref
Page 45 and 46: Designated Routers (DIS): IS-IS •
Page 47 and 48: Area Structure: IS-IS • Area boun
Page 49: Agenda • Overview of link-state p
Page 53 and 54: LSP Scalability: IS-IS • Single L
Page 55 and 56: IS-IS Inter-Area Route Leaking •
Page 57 and 58: NBMA Networks • OSPF • Point-to
Page 59 and 60: Overload Bit • IS-IS feature •
Page 61 and 62: Security • Both protocols support
Page 65 and 66: Optimality • Optimality • OSPF
Page 67 and 68: Writing OSPF Code • OSPF spec is
Page 71: Thank You http://www.juniper.net

IS-IS and OSPF: Network Design Comparisons and ... - JANOG

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