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SmartARP: Making Gigabit Networks Cheap

Learn how SmartARP technology helps build affordable gigabit networks efficiently. Explore advantages & disadvantages of interconnecting LANs in university campus using routers, switches, and VLANs. Discover SmartARP implementation details and features for advanced network configurations.

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SmartARP: Making Gigabit Networks Cheap

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  1. SmartARP: Making Gigabit Networks Cheap Andris Sidorovs, Riga Technical UniversityJanis Lacis, LatnetKarlis Ogsts, Tieto Konts Financial Systems Ltd.Guntis Barzdins, Taide Network ASJanis Dzerins, University of Latvia

  2. Most popular LAN technology nowadays 10Mb/s - 1Gb/s Each host has unique 48bit MAC address (factory assigned) Frames sent to MAC addresses Broadcasts widely used To find destination MAC address, ARP protocol is used IP: 10.0.0.10 MAC: 00:00:aa:aa:aa:aa IP: 10.0.0.11 MAC: 00:00:bb:bb:bb:bb A B IP: 10.0.0.12 MAC: 00:00:cc:cc:cc:cc IP: 10.0.0.13 MAC: 00:00:dd:dd:dd:dd C D Ethernet frame Dest MAC Source MAC IP packet DestIP SourceIP Data Ethernet

  3. ARP Query Host A Host B Broadcast Host B MAC ? Host B IP ARP Response Unicast Host B MAC Host B IP ARP: finding the MAC Address RFC 826: Address Resolution Protocol, 1982

  4. Interconnecting Ethernet LANs Requirements • Interconnections must be fast • Departmental Novell and MS Windows networks should be isolated • Misconfiguration in one department should not disrupt network in another department • Easy to configure ? ? ? ? Departmental LANs in University Campus

  5. Interconnecting by Routers Advantages • Contain broadcasts • Filtering possible by protocol Disadvantages • Slow (each packet intensively processed) • Complex • Expensive (especially for 100Mbps and 1Gbps) Departmental LANs in University Campus

  6. Interconnecting by LAN Switches Advantages • Fast (wire speed) • Cheap • Simple to install Disadvantages • Do not scale, because broadcasts are not contained • No filtering by protocol Departmental LANs in University Campus

  7. Bottleneck Interconnecting by VLANs Advantages • Single powerful router interconnects many VLANs • Cisco Netflow and Routing Switches shortcut traffic Disadvantages • Bottleneck is router • Only expensive switches and routers support that VLAN 1 VLAN 2 VLAN 4 VLAN 3

  8. Interconnecting by SmartARP MAC Broadcast filter Advantages • Contains Broadcasts • Effectively stops all protocols • Fast (wire speed) • Cheap (standard switches used) Disadvantages • Nothing works ...... unless smartARP used

  9. SmartARP • Server based ARP • Transparent to hosts • Uses queries instead of broadcasts • Easy to configure (stateless) • Only one needed per broadcast domain • Available for free (runs on Win95 & Linux) • Supports 10Mb/s, 100Mb/s, 1Gb/s, ...

  10. MAC Broadcast filter SmartARP Server 1 SmartARP Server ARP Query 4 Broadcast 2 ARP Reply Y X Unicast 3 SmartARP Server SmartARP Server SmartARP operation A B D C

  11. MAC Broadcastfilter SmartARPServer B SmartARPServer A SmartARPServer D SmartARPServer C SmartARP configuration B A Workgroups are assigned smaller continuous ranges of IP addresses 10.1.2.0 - 10.1.2.255 10.1.1.0 - 10.1.1.255 10.1.4.0 - 10.1.4.255 10.1.3.0 - 10.1.3.255 C D Whole network is one big IP subnet 10.1.0.0/16

  12. SmartARP config file MAC addressof smartARP server B Configuration file of SmartARP server A: 10.1.1.0 255.255.255.0 local 10.1.2.0 255.255.255.0 forward 00:01:3a:4c:12 10.1.3.0 255.255.255.0 forward 00:73:18:a5:62 10.1.4.0 255.255.255.0 forward 00:0c:63:52:7a MAC addressof smartARP server C MAC addressof smartARP server D Ranges of IP addressesassigned to workgroups

  13. SmartARP implementation Win95

  14. SmartARP implementation Linux • Source code available • Runs on multiple interfaces • Can be used with Linux bridge • Convenient pre-compiled version: • boots from single 1.44MB FDD (no HDD needed) • optionally acts as bridge with MAC broadcast filter • supports up to six NE2000 PCI compatible 10/100Mbps Ethernet cards • “Cisco IOS like” interface for easy use

  15. Advanced SmartARP features IP Address and Mask Action Parameter 10.1.1.0 255.255.255.0 LOCAL 10.1.2.0 255.255.255.0 FORWARD 00:00:00:11:11:11 10.1.7.2 255.255.255.255 CONST 00:00:22:d5:e6:f7 10.1.3.0 255.255.255.0 IP 00:11 10.1.3.1 255.255.255.255 SILENT 10.2.2.0 255.255.255.0 DNS mac.mydomain.com 10.3.3.0 255.255.255.0 PROXY 10.1.1.2 Like in routing, IP network number with longest prefix is preferred when selecting a SmartARP rule to be applied

  16. no ip routing bridge 1 protocol ieee bridge 1 address ffff.ffff.ffff discard interface Ethernet0 no ip address bridge-group 1 interface Ethernet1 no ip address bridge-group 1 How to filter broadcasts in switches? • None of configurable Cisco, Bay, 3Com switches has such option (!!!) • Use Linux bridge code - modify one line in source code to filter Broadcasts • Use any Cisco router as Ethernet bridge:

  17. Cheap Scaleable Ethernet: HANE Hierarchically Addressed Non-broadcast Ethernet • Ethernet without MAC broadcasts • 48bit MAC addresses are not factory assigned, but are configurable like IP addresses (32bit IP address can be part of 48bit MAC address) • Ethernet switches use prefix based MAC switching tables HANE is the way to go: it is cheap, fast, scales to global networks, and is compatible with existing networks.

  18. 24 bits 24 bits Vendor Code Serial Number 0000.3c12. 3456 ROM RAM How to change MAC address? Interface driver copies MAC address from ROM into RAM by default, if no explicit MAC address is supplied to the driver • Factory assigned unique MAC address is burned into ROM, but the MAC address actually used by the card is stored in RAM • MAC address is configurable in Win95, NT, UNIX, Cisco routers (instructions provided in Full Paper)

  19. Final • More details appear in Full Paper (TNNC’99 Conference Proceedings) • SmartARP software available at:http://www.ltn.lv/~guntis/smarp02.zip • Contact authors for latest smartARP versions:guntis@taide.net, asid@lmt.lv, janis@latnet.lv, k.ogsts@konts.lv, jonis@mt.lv

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