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Re: 请问ERO是什么?

Each hop (LSR) that the TE tunnel should cross is put into an ERO, which is basically an ordered

list of interface IP addresses, with one IP address per LSR. The PATH message is sent from the

head end router to the next-hop router. This next-hop router removes his own IP address from the

ERO, sees what the next IP address is, and sends the PATH message to that next hop. This

continues until the tail end router of the TE tunnel receives the PATH message. Upon receipt of

the PATH message, the tail end router returns a RESV (or reservation) message along the same

path that the PATH message took, but in the opposite direction. Only when the head end receives

the RESV message without an RSVP error message is the path set up or signaled and is the TE

tunnel up.

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Re: 请问ERO是什么?

在MPLS TE隧道的首端路由器通过CSPF算法计算出TE路径之后,首端路由器需要将TE隧道本身属性(例如所需带宽、本地优先级、所希望得到的本地保护、TE所经过的路径)等相关信息通过RSVP告知给TE隧道的下游路由器以申请资源,RSVP使用PATH消息进行相关信息的通告和资源的申请,在PATH消息中包含若干个RSVP对象,分别对TE的相关信息进行描述,其中就包括ERO对象,ERO对象描述了首端路由器通过CSPF算法计算出来的TE路径信息,即TE隧道所要经过的每一跳ip地址,当下游路由器收到PATH消息之后,首先会根据PATH消息中所描述的TE相关信息进行资源的预留,如果下游路由器能够满足TE建立的需求,那么,他会产生一个PATH消息,发送给ERO对象TE下一条地址列表中所指定的该下游路由器的下一跳路由器,同时将ERO中自己的地址移除。如果希望详细了解RSVP相关消息及携带的对象,可以去看看《Traffic Engineering with MPLS》,相关知识点在该书第四章有详细的描述。

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