Route Servers

Super Sparrow obtains BGP information that is used to determine which point of presence is closest to a client by accessing existing route servers. At this stage three route server types are supported, GNU Zebra, Gated and Cisco IOS. The current implementation obtains routing information by establishing a TCP/IP connection to the route server and issuing a query, in the same way that a user may manually query a route.

By using existing route servers Super Sparrow is able to leverage existing BGP technologies. This has the added advantage that a number of route server types can be supported maximising the flexibility of Super Sparrow in fitting into existing infrastructure.

GNU Zebra

GNU Zebra is a routing daemon, released under the GNU General Public Licence, available from www.zebra.org. GNU Zebra is copyright DML Networks, Inc. GNU Zebra is able to manage many TCP/IP routing protocols including BGP. GNU Zebra is configured interactively via telnet using an interface similar to that of Cisco IOS.

Super Sparrow obtains information by making a TCP/IP connection to the bgpd component of GNU Zebra, issuing a query, and parsing the output. This can be done manually using telnet as follows:

$ telnet 192.168.192.13 bgpd
Trying 192.168.192.13...
Connected to 192.168.192.13.
Escape character is '^]'.

Hello, this is zebra (version 0.89.horms.pre.2)
Copyright 1996-2000 Kunihiro Ishiguro


User Access Verification

Password: 
jasmine> sho ip bgp 192.168.193.15
BGP routing table entry for 192.168.193.0/24
Paths: (2 available, best #2, table Default-IP-Routing-Table)
  64600 64601 64602
    192.168.192.12 from 192.168.192.12 (192.168.192.12)
      Origin IGP, metric 1, localpref 100, valid, external
      Last update: Fri Oct  6 15:47:28 2000
                                           
  64702
    192.168.193.11 from 192.168.193.11 (192.168.193.11)
      Origin IGP, metric 1, localpref 100, valid, external, best
      Last update: Fri Oct  6 15:44:05 2000


jasmine> exit
Connection closed by foreign host.

This indicates that there are two valid routes to 192.168.195.15 from 192.168.192.13 and that the second route listed is preferred. The AS path for the preferred route is 64702. It is the AS path of the preferred route that Super Sparrow uses to determine if a point of presence in the Super Sparrow network is closer to the address begin queried than the route server being queried. More details of the topology being shown by this query are shown in the configuration section along with details of how to configure GNU Zebra. A discussion of how the AS path can be used to determine the best point of presence for a client is given in the BGP section.

Gated

Gated is a routing daemon available from www.gated.org. Gated is copyright Merit Network, Inc. Gated is able to speak many TCP/IP routing protocols including BGP. Gated has two main releases, a public release which is freely downloadable, and a private release which requires are licencing agreement. The public version is supported by Super Sparrow. Gated is configured by editing a configuration file and changed take effect by either restarting or sending a SIGHUP to the daemon.

Status information is available by telneting to GII, the Gated Interactive Interface. This is the method that Super Sparrow obtains information from Gated by making a TCP/IP connection to GII. This can be simulated manually using telnet as follows:

$ telnet 192.168.193.11 gii
Trying 192.168.193.11...
Connected to 192.168.193.11.
Escape character is '^]'.
Password? 
100 Gated Interactive Interface. Version gated-public-3_6
GateD-roger> sho ip walkup 192.168.192.10
100 BGP     192.168.192/24 192.168.193.14  (64702) 64700 IGP (Id 29)
100 Sta         0.0.0.0/0  192.168.193.14  IGP (Id 1)
GateD-roger> quit
Connection closed by foreign host.

This shows that the preferred route to 192.168.192.10 from 192.168.193.11 has the AS path (64702) 64700. 192.168.192.10 is also covered by a less specific static route as designated by Sta. The AS number in brackets represents the AS number of 192.168.193.11 itself. Super Sparrow uses the AS path to determine the best point of presence for a client to connect to. More information on configuring Gated for the topology shown can be found in the configuration section. For a discussion on how AS paths are used to determine the best point of presence for a given IP address see the BGP section.

Cisco IOS

IOS is the operating system that runs on Cisco routers and is synonymous with BGP and routing in general. Cisco and IOS are trademarks of Cisco Systems, Inc. IOS can be configured and queried using a command line interface via telnet.

Super Sparrow is able to obtain information from cisco routers by making a TCP/IP connection to the telnet port of the router. This can be demonstrated using telnet:

$ telnet 192.168.128.3
Trying 192.168.128.3...
Connected to 192.168.128.3.
Escape character is '^]'.


User Access Verification

Password: 
cisco>sh ip bgp 192.168.0.2
BGP routing table entry for 192.168.0.0 255.255.255.0, version 36
Paths: (2 available, best #1, advertised over EBGP)
  64800
    192.168.128.1 from 192.168.128.1
      Origin IGP, metric 1, valid, external, best
  64900 64800
    192.168.128.2 from 192.168.128.2
      Origin IGP, valid, external
cisco>exit
Connection closed by foreign host.

This shows that the preferred route to 192.168.0.2 from 192.168.128.3 has the AS path 64800. 192.168.0.2 is also covered by a route with AGS path 64900 64800. Super Sparrow uses the AS path to determine the best point of presence for a client to connect to. For a discussion on how AS paths are used to determine the best point of presence for a given IP address see the BGP section.

Notes on Commands

$ echo flim
flim