IS-IS 数据包类型 | 实验_is is协议报文封装与封装的区别和联系问题-优快云博客

本文链接：https://blog.youkuaiyun.com/u013669912/article/details/145409440

注：本文为 “IS-IS” 相关文章合辑。

英文引文，机翻未校。

IS-IS Packet Types

IS-IS 数据包类型

isis-helllos-ipcisco

Network protocols uses different packets. Here we will focus on the packets used by IS-IS Protocol. We will learn IS-IS Packet Types.

网络协议使用不同的数据包。在这里，我们将重点介绍 IS-IS 协议使用的数据包。我们将学习 IS-IS 数据包类型。

IS-IS Protocol uses L2 encapsulation Ethernet 802.3/802.2. It do not use Ethernet II. Ethernet II is used for IP traffic. You can check the lesson that we have exmpained different Ethernet Packets on IPCisco.

IS-IS 协议使用 L2 封装以太网 802.3/802.2。它不使用以太网 II。以太网 II 用于 IP 流量。您可以查看我们在 IPCisco 上解释不同以太网数据包的课程。

IS-IS Protocol exchanges protocol information by using Link-State PDUs (Protocol Data Units).

IS-IS 协议使用链路状态 PDU（协议数据单元）交换协议信息。

There are four types of PDU packets in IS-IS Protocol. These IS-IS packets are given below:

IS-IS 协议中有四种类型的 PDU 数据包。这些 IS-IS 数据包如下所示：

IS-IS Hello PDU (IIH)
Link State PDU (LSP)
Partial Sequence Number PDU (PSNP)
Complete Sequence Number PDU (CSNP)

In IS-IS PDUs there is a TLV (Type, Length, Value) field. According to the need, these fields are added to the PDUs. This TLV field makes IS-IS extendable and it is the major advantage of IS-IS over OSPF. There are several TLVs in IS-IS packets. IS-IS Header always same, but according to the type of the packet, added TLV fields change.

在 IS-IS PDU 中，有一个 TLV（类型、长度、值）字段。根据需要，这些字段将添加到 PDU 中。此 TLV 字段使 IS-IS 可扩展，这是 IS-IS 相对于 OSPF 的主要优势。IS-IS 数据包中有多个 TLV。IS-IS 报头始终相同，但根据数据包的类型，添加的 TLV 字段会发生变化。

TLVs are maximum 256 bytes and they contains sub-TLVs.

TLV 最大为 256 字节，包含子 TLV。

IS-IS Header Format, ISIS TLVs

IS-IS Header Format

IS-IS discovers the IS-IS neighbours and IS-IS adjacency via Hello PDUs. DIS election is also done with these PDUs. There are three types Hello PDUs in IS-IS Protocol:

ESH: ES sent to IS
ISH: IS sent to ES
IIH: Between two ISs

IS-IS Hellos, ESH, ISH, IIH

IS-IS Hellos, ESH, ISH, IIH

IS-IS Hello interval is 10 seconds and the dead interval is 30 seconds by default.

IS-IS Hello 间隔为 10 秒，死区间隔默认为 30 秒。

In IS-IS Hello packet, 6 types of data can be included with TLVs. These are:

在 IS-IS Hello 数据包中，TLV 可以包含 6 种类型的数据。这些是：

Area Addresses TLV
区域地址 TLV
Padding TLV
填充 TLV
IP Interface Address TLV
IP 接口地址 TLV
Authentication Information TLV
认证信息 TLV
Protocols Supported TLV
支持的协议 TLV
Intermediate System Neighbors TLV
中间系统邻居 TLV

For more information about IS-IS TLVs, you can check Intermediate System-to-Intermediate System (IS-IS) TLVs article on Cisco Website.

有关 IS-IS TLV 的详细信息，您可以在 Cisco 网站上查看中间系统到中间系统（IS-IS） TLV 一文。

IS-IS LSPs are like LSAs in OSPF and contains many information about the neighbour ISIS Routers and links. They are flooded periodically in IS-IS network. L1 and L2 PDUs use different formats LSPs are stored in IS-IS LSDBs. Seperate datababses are used for L1 and L2 LSPs. Each LSP has sequence number that shows its version.

IS-IS LSP 类似于 OSPF 中的 LSA，包含有关邻居 ISIS 路由器和链路的许多信息。它们会定期在 IS-IS 网络中泛洪。L1 和 L2 PDU 使用不同的格式，LSP 存储在 IS-IS LSDB 中。单独的 Datababs 用于 L1 和 L2 LSP。每个 LSP 都有显示其版本的序列号。

In LSPs, below TLVs are supported:

在 LSP 中，支持以下 TLV：

Area Addresses TLV
区域地址 TLV
Originating LSP Buffer Size TLV
始发 LSP 缓冲区大小 TLV
Intermediate System Neighbors TLV
中间系统邻居 TLV
End System Neighbor TLV
终端系统邻居 TLV
Authentication Information TLV
认证信息 TLV
Prefix Neighbor TLV
前缀邻居 TLV
Protocols Supported TLV
支持的协议 TLV
IP Interface Address TLV
IP 接口地址 TLV
IP Internal Reachability Information TLV
IP 内部可达性信息 TLV
IP External Reachability Information TLV
IP 外部可达性信息 TLV

PDU Type field shows the level of PDU. Level 1 PDU is showed with the value 18, Level 2 PDU is showed with the value 20.

ATT bit is the bit that set if the IS is connected to another area.

PDU Type 字段显示 PDU 的级别。1 级 PDU 显示值 18，2 级 PDU 显示值 20。 ATT 位是 IS 连接到另一个区域时设置的位。

OL bit is set to show that the link-state database of IS is overloaded.

OL bit 设置为表示 IS 的链路状态数据库过载。

IS Type shows the level of the IS. For level 1, it is 1. For level 2 it is set as 3.

IS Type 显示 IS 的级别。对于级别 1，它是 1。对于级别 2，它设置为 3。

CSNP (Complete Sequence Number PDU) provides LSP to be sent reliably. CSNPs are like Database Description (DD) packets in OSPF and they used to synronize the LSDBs.

CSNP（完整序列号 PDU）提供可靠发送的 LSP。CSNP 类似于数据库描述（DD）数据包，它们用于同步 LSDB。

CSNPs are exchange at the beginning, at the router initialization. And every 10 seconds after this, they are sent. In point to point links, both end routers send CSNPs. But for broadcast networks, only DIS sends CSNPs.

CSNP 在路由器初始化开始时进行交换。在此之后每 10 秒发送一次。在点对点链路中，两端路由器都发送 CSNP。但对于广播网络，只有 DIS 发送 CSNP。

IS-IS CSNPs carry two types of TLVs . These are :

IS-IS CSNP 携带两种类型的 TLV。这些是：

Authentication TLVs
身份验证 TLV
Entries TLVs
条目 TLV

Entries TLVs are identify the LSPs and CSNPs include the below TLVs for all LSPs in its database:

条目 TLV 用于标识 LSP，CSNP 包括其数据库中所有 LSP 的以下 TLV：

The remaining life of LSP
LSP 的剩余寿命
The ID of LSP
LSP ID
The Sequence number of LSP
LSP 序列号
Checksum Value
校验和值

PSNPs (Partial Sequence Number PDU) are sent when there is a missing information. With PSNP, this specific missing information is requested. And it is also sent for acknowledgement of the receipt. So PSNPs are like LSAcks and LSRs ( Link State Request) in OSPF.

当缺少信息时，将发送 PSNP（部分序列号 PDU）。使用 PSNP 时，将请求此特定的缺失信息。并且它还被发送以确认接收。因此，PSNP 类似于 OSPF 中的 LSAck 和 LSR（链路状态请求）。

IS-IS CSNPs and PSNPs

IS-IS CSNPs and PSNPs

In IS-IS Protocol, PSNPs are used in point-to-point links. PSNPs also includes the TLVs like CLNPs. (The remaining life of LSP, the ID of LSP, the Sequence number of LSP, Checksum Value)

在 IS-IS 协议中，PSNP 用于点对点链路。PSNP 还包括 CLNP 等 TLV。（LSP 的剩余寿命、LSP 的 ID、LSP 的序列号、校验和值）