RFC 5661 - Network File System (NFS) Version 4 Minor Version 1 Protocol¶
读完了 RFC 7530，抓包时却发现 NULL 后接的 EXCHANGE_ID 操作找不到，才知道这是 NFSv4.1 的内容。
NFSv4.1 introduces Sessions
Major extensions introduced in NFS version 4 minor version 1 include Sessions, Directory Delegations, and parallel NFS (pNFS).
NFS version 4 minor version 1 has no dependencies on NFS version 4 minor version 0, and it is considered a separate protocol.
接下来，我们针对 NFSv4.1 引入的 Sessions 进行学习
Session¶
目录中，可以看到有关 Session 的改变：
- 第二章：核心基础设施
- 第八章：状态管理（新增章节）
第二章详细介绍了 Session 的概念：
Limited trunking over multiple network paths.
The NFSv4.1 client can associate an arbitrary number of connections with the session, and thus provide trunking (Section 2.10.5).
先前的协议不能充分利用多条网络路径。NFSv4.1 客户端可在会话中联结任意数量的连接以实现多条网络路径的聚合。
A session is a dynamically created, long-lived server object created by a client and used over time from one or more transport connections.
会话的定义：为一个客户端动态分配，长期保持，在多个传输连接中复用。
A client may have one or more sessions associated with it so that client-associated state may be accessed using any of the sessions associated with that client's client ID, when connections are associated with those sessions
客户端可以建立多个会话，连接和会话之间也没有一一对应的限制。
Client ID and Session Association