Packet-Switching. Programme authors and contributors. Switching, Part II. Chapter 7: Router Hardware Architectures. Material: Diederich,, Piotr Pacyna

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1 Switching, Part II Packet-Switching Chapter 7: Router Hardware Architectures Material: David Larrabeiti,, Pedro Reviriego, Jörg Diederich,, Piotr Pacyna Programme authors and contributors Lecturers (Spanis course): David Larrabeiti López José Félix Kukielka Supporting lecturers (English course): Jorg Diederich Huw Oliver Mónica Cortés (circuit switching) Piotr Pacyna (intro, packet switching, ATM, IP, QoS, MPLS) 2 1

2 Contact Piotr Pacyna Visiting professor at UC3M Office: 4.1 A16 Phone: Outline of the Chapter Introduction to routers What is a router? Types of routers and design criteria Hardware architectures Shared memory Shared bus Switching fabric 4 2

3 What is a Router? Router: A device that switches (routes) IP packets MTU Enterprise Branch SMB & Small Branch Small Business & Telecommuter Network Enterprise ISP 5 Types of Networks & Routers I Access Network Layer 3 Core Network Access Network Metro IP Regional Metro IP IP Core Regional Metro IP Metro IP Network Users Network Users 6 3

4 Types of Networks & Routers II CPE (Customer Premises Equipment) SOHO (Small Office / Home Office) Enterprise routers Network routers Access concentrators MAN routers Core routers 7 Design Criteria for Routers Performance: Number of packets per second (pps) to switch. Packet processing complexity (Route lookup, but also NAT, security..). Modularity: Reuse the same router to do more or different things. Adding more interfaces. Changing the type of interfaces (Example: ISDN to ADSL). Cost Reliability / support: Cost of downtime SOHO vs. network operator. Different priorities for different type of routers 8 4

5 Example for CPE () 2600/ 3600 MTU Enterprise Branch 1700 SMB & Small Branch SOHO 77 Small Business & Telecommuter 6400 IP+ATM Enterprise ISP SOHO 77 9 CPE SOHO Routers Example: Ethernet to ADSL ( SOHO 77) Design Criteria: Performance low ( pps and small routing table) Cost very important (main differentiation factor) Modularity low (changes do not occur often) Reliability low (downtime has a limited cost) 10 5

6 CPE: Enterprise Teldat Atlas 7500 Small Branch Office Corporate Office 3660 Large Branch Office T1/E1 IMA 7200/7500 Regional Office 11 CPE Enterprise Routers: Example Example Teldat Altas (Small Branch Office) 3660 (Large Branch Office) 12 6

7 CPE Enterprise Routers: Design Criteria Enterprise routers: Comprise a wide category ranging from a small branch router to a corporate office routers. The design criteria are difficult to quantify General trend for design criteria: Performance medium pps Medium routing table sizes Cost somewhat important (not the only differentiating factor) Modularity medium to high (bigger offices require more changes) Reliability medium to high (example: router in a bank corporate office) 13 Access Concentrator: Example

8 Access Concentrators: Design Criteria Access concentrators: Include other requirements such as support for service provisioning and network management. Not discussed here Following our criteria we get: Performance medium high ( pps, depends on the number of users) Cost somewhat important (not the only differentiating factor) Modularity high (add users as needed, add new access technologies) Reliability medium to high (again, depending on the number and category of users) 15 Network Routers Access Network Layer 3 Core Network Access Network Series Series Series Series Metro IP Regional Metro IP IP Core Regional Metro IP Metro IP Network Users Network Users 16 8

9 MAN/Regional Routers: Example Example: MAN/Regional Routers: Design Criteria MAN/Regional routers: Include a wide range of performance requirements. Design criteria (summary) Performance high 1-10 million packets per second Routing tables with entries Cost somewhat important (not the only differentiating factor) Modularity high (Evolve with the network needs more speed) Reliability high very high (example: Route processor redundancy (RPR)) Similar to enterprise routers 18 9

10 Core Routers: Example (Juniper) Juniper T Core Routers: Design Criteria Core routers: Designed for extreme performance Evolve rapidly with advances in CMOS VLSI technology Design criteria: Performance Æ very high million packets per second 9 Routing tables with more than entries Cost Æ somewhat important Modularity Æ very high (Enable network flexibility / evolution) Reliability Æ very high (Again depending on the number of users) 20 10

11 Outline of the Chapter Introduction to routers What is a router? Types of routers and design criteria Hardware architectures Shared memory Shared bus Switching fabric 21 Hardware Architectures: Shared Memory Routers Three basic components: CPU Interface controllers (controlling I/O devices) Memory Connected via a bus CPU I/O Device I/O Device Memory I/O Device 22 11

12 Shared Memory Routers CPU: Switches packets (no offload processors) Example: Motorola family ( in cisco 1600, 2500) MIPS RISC ( in cisco 4500, 4700) Memory: DRAM for routing tables, caches, operating system data (IOS), packet buffers,... Split into regions: Local (route table, cache, IOS) and Iomem (packets) Interface controllers Transfer packets from / to the physical media Move packets between I/O memory and the media May have own processors (media controllers) No switching tasks performed, no packet processing. Basic procedure: Packet copied from input device to memory After the routing decision: Copy packet from memory to output device 23 Shared Memory Routers: Discussion Low cost Low performance Limited by CPU and memory speed Must send data twice over the bus Input Port Memory Output Port System Bus Limited modularity Low costs: Use of standard processors (Motorola 68360, 860,...) 24 12

13 Shared Memory Routers: Example Console 25 Hardware Architectures: Shared Bus Routers Same components as for shared memory routers: Memory Connected via a bus Main CPU CPU Interface controllers difference: Memory I/O Device I/O Device I/O Device Shared Bus Packet are directly copied from input to output 9 After the switching decision 26 13

14 Shared Bus: Discussion Low medium cost (bus controllers) Low medium performance (limited by CPU and mainly the shared bus) Bus contention Medium modularity Use of communication processors in low end routers to reduce costs. 27 Shared Bus Routers: Example I

15 Shared Bus Routers: Example II Teldat Atlas 29 Switching Fabric-Based Routers Control Processor Interface Interface Interface Interface Switch Fabric Interface Interface Interface Interface 30 15

16 Switch Fabric Switch Fabric 31 Switching Fabric-Based Routers: Characteristics Bus no longer limiting factor: Use interconnection network Comparable to multi-stage circuit switches Example: Banyan networks, or other interconnection networks Initially developed to connect processors in multiprocessor designs 32 16

17 Switching Fabric-Based Routers: Discussion High costs High performance High modularity Massive use of specialized hardware Network processors (Intel, AMCC). TCAM memories (Sibercore, ISSI). Switching fabrics (Vitesse, Agere) 33 Switching Fabric-Based Routers: Example: Line Card Line Card Line Card Line Card Multigigabit Crossbar Fabric Line Card Line Card Route Processor Route Processor Maintenance Bus Fan System Power Supply 34 17

18 References R. White, V. Bollapragada, and C. Murphy, Inside IOS Software Architecture. Press 2000 (Available in the library). A. Pattavina, Switching theory (Chapters 2 and 3), Wiley 1998 (Available in the library). H. J. Chao, Next Generation Routers in: Proceedings of the IEEE September ( C. Semeria, Internet Backbone Routers and Evolving Internet Design, Juniper Networks ( C. Semeria, Implementing a Flexible Hardware-based router for the new IP infrastructure, Juniper Networks ( F. Baker, Requirements for IPv4 Routers, RFC 1812, IETF (