SRv6 学习笔记 -- RFC 8402

Background

• 在基于IGP的分布式控制平面的上下文中，有两个拓扑段定义：IGP邻接段和IGP-Prefix段。
• 在基于BGP的分布式控制平面的上下文中，有两个拓扑段定义：BGP对等段和BGP前缀段。
• The headend of an SR Policy binds a SID (called a Binding segment or BSID) to its policy.When the headend receives a packet with active segment matching the BSID of a local SR Policy, the headend steers the packet into the associated SR Policy. 【那么一开始的BSID是谁给的= =】 answer：见：SRv6 学习笔记 – draft of segment routing policy architecture

IGP 前缀

三元组

• 算法

  • 目前只定义了两种
    • SPF SSPF

• 分类

  • Adj - SID p16
    • 本地必须是IGP node 远程可以是non-adjacent neighbour
    • FIB 条目

BGP segment

• prefix
  • 只有 IGP不用的时候采用
• peering
  • peerNode
  • peerAdj
  • peerSet

Binding Segment p21

• 对应一个segment policy
• 使用BSID允许将策略的实例化（SID列表）仅存储在需要施加策略的节点上。 然后，到支持该策略的节点的流量的方向仅需要强加BSID。如果策略更改，这也意味着只需要更新强制策略的节点。 策略的用户不受影响。Use of a BSID allows the instantiation of the policy (the SID list) to be stored only on the node or nodes that need to impose the policy. Direction of traffic to a node supporting the policy then only requires imposition of the BSID. If the policy changes, this also means that only the nodes imposing the policy need to be updated. Users of the policy are not impacted.

SRv6的操作

• N addvertsing an IPv6 address R usable as a segment identifier MUST mantain the following FIB entry:

Incoming Active Segment: R 
Ingress Operation: NEXT 
Egress interface: NULL

• 独立于SR支持，任何远程IPv6节点都将为任何前缀维护普通的IPv6 FIB条目，无论前缀是否表示段。这允许甚至通过不支持SR的节点将分组转发到拥有SID的节点。Independent of SR support, any remote IPv6 node will maintain a plain IPv6 FIB entry for any prefix, no matter if the prefix represents a segment or not. This allows forwarding of packets to the node that owns the SID even by nodes that do not support SR.