http://en.wikipedia.org/wiki/Quagga_%28software%29
The Quagga architecture consists of a core daemon (zebra) which is an abstraction layer to the underlying Unix kernel and presents the Zserv API over a Unix-domain socket or TCP socket to Quagga clients. The Zserv clients typically implement a routing protocol and communicate routing updates to the zebra daemon. Existing Zserv clients are:
ospfd, implementing Open Shortest Path First (OSPFv2)
ripd, implementing Routing Information Protocol (RIP) version 1 and 2;
ospf6d, implementing Open Shortest Path First (OSPFv3) for IPv6
ripngd, implementing Routing Information Protocol (RIPng) for IPv6
bgpd, implementing Border Gateway Protocol (BGPv4+), including address family support for IP multicast and IPv6
babeld, implementing the Babel routing protocol, including support for both IPv4 and IPv6 and for both wired networks and wireless mesh networks.
Additionally, the Quagga architecture has a rich development library to facilitate the implementation of protocol and client software with consistent configuration and administrative behavior.
Linux 路由軟件 Quagga包含一個核心守護進程zebra，它作爲Unix底層核心的一個抽象層，表示爲Unix上的一些Zserv API或Linux Quagga客戶端的TCP流。這些Linux Quagga客戶端實現路由協議並和zebra守護程序交換路由更新信息。
這些Zserv客戶端包括：
ospfd：實現OSPFv2
ripd：實現RIPv1和RIPv2
ospf6d：實現OSPFv3（IPv6）
ripngd：實現RIPv3（IPv6）
bgpd：實現BGP4+（包括對組播地址族和IPv6地址族的支持）
// TODO
