Implementation of Virtual Router Redundancy Protocol

1
Implementation of Virtual Router Redundancy
Protocol

• By
• Divya Mukundan Muthuvelan KP
• Directed by Dr. Joseph B. Evans
• EECS 801 - Directed Graduate Reading - Spring
  2002
• University of Kansas, Lawrence.

2
Introduction

• Routing inside a local area network
• End-host configuration options
• Dynamic routing protocol.
• Statically configured default route better
  solution.

3
Motivation

• Problems with statically configured default
  route.
• Single point of failure.
• Inability to find alternate path.
• Solution Redundancy using VRRP.

4
Elements of VRRP

• Virtual Router (VR)
• abstract object which acts as a default router.
• VRRP Router
• manages multiple Virtual Routers.
• Virtual Router Master
• VRRP Router with forwarding responsibility of a
  VR.
• Virtual Router Backup
• Set of VRRP Routers available to assume
  forwarding responsibility when VR Master fails.

5
VRRP - Introduction

• An Election protocol.
• Uses IP multicasting in Multi-Access Medium.
• Uses a Periodic VRRP advertisement message.
• Dynamic fail-over in the forwarding
  responsibility.
• Preferred Path Indication.
• Operation over Extended LANs.
• Extensible Security.

6
Implementation

• User Level implementation using Socket API
  provided by Linux 2.4.x kernel.
• VRRP Interface Functions.
• IsRealIPAddress(IP Addr, IfName, Options)
• GetHwAddress(IfName, Mac) SetHwAddress(IfName,
  Mac)
• GetPrimaryIPAddress(IfName, IPAddr)
• AddToMulticast(SockFd, IpAddr, MCastAddr)
• RemoveFromMulticast(SockFd, IpAddr, MCastAddr)
• AddAliasInterface(AliasIp, IfName, AliasNo)
• RemoveAliasInterface(IfName, AliasNo)
• CalculateIPChecksum(Buffer)
• VerifyChecksum(Buffer, Size)
• CreateAsyncRawSocket(SockFd, IpAddr)

7
Virtual Router Parameters

• struct VR
• uint8_t VRId
• uint8_t N / Number of virtual IP
  addresses. /
• uint32_t VRIp / Virtual IP address in host
  byte order. /
• uint8_t VRMacMAC_ADDR_SIZE /
  00-00-5E-00-01-ltVRIDgt /
• uint8_t Priority
• uint8_t AdvertInt / Advertizement
  Internval /
• uint8_t Timer / Currently Active Timer/
• uint8_t AuthType / Authetication Type /
• uint8_t AuthDataVRRP_AUTH_SIZE /
  Authentication Data /
• uint8_t PreemptMode
• uint8_t CurrentState
• int SockFd / Sending Socket /
• int McastSockFd / Receiving Socket /
• struct VRIF VRIf / Interface Information/

8
VRRP Packet Format
9
Protocol State Machine
10
VRRP Events
11
Implementation Details

• Initialization
• Set defaults to a Virtual Router.
• Read configuration file.
• Check if configuration is complete.
• Registration of signal handlers.
• Catch_SIGUSR1 - StartUp Event
• Catch_SIGUSR2 - ShutDown Event
• Catch_SIGALRM - Timer Expiration
• Catch_SIGIO - Packet Reception

12
Implementation Details

• Sending gratuitous ARP
• Done in Master State.
• Protocol State Machine
• State Event Matrix.
• CallSEM(CurrentState, Event)
• Reception/ transmission of packets

13
Implementation Details

• De-Initialization
• Remove from multicast group.
• Remove timers.
• Free memory.

14
Testing - Scenarios

• Unequal Priority Without Preemption.
• Unequal Priority With Preemption.
• Equal Priority Without Preemption.
• Equal Priority With Preemption.
• Unequal Priority Without Preemption, One of the
  VRRP Routers is IP Address Owner.
• Unequal Priority With Simple Authentication.

15
Conclusion Future Work

• Multiple Virtual Routers in a VRRP router.
• IP Authentication HeaderAH support for VRRP
  advertisement packets.
• Kernel-level implementation.
• Provide Command Line Interface (CLI).

16
References

• S. Knight, D. Weaver, D. Whipple, R. Hinden, et
  al, Virtual Router Redundancy Protocol,
  draft-ietf-vrrp-spec-v2-05.txt, Work in Progress.
• IP Aliasing, http//www.tldp.org/HOWTO/mini/IP-Ali
  as/.
• Packet Headers, http//www.networksorcery.com/enp/
  protocol/ip.htm.
• Linux Man Pages, http//linux.ctyme.com/.
• Multicast over TCP/IP, http//www.tldp.org/HOWTO/M
  ulticast-HOWTO.html
• Virtual Router Redundancy Protocol, Cisco White
  Paper.
• Gratuitous ARP, http//martinh.net/Linux2001/talk/
  slide11.html.