diff --git a/src/.vuepress/public/assets/image/article/network/comparing-ipv4-and-ipv6-headers.png b/src/.vuepress/public/assets/image/article/network/comparing-ipv4-and-ipv6-headers.png new file mode 100644 index 00000000..d0528140 Binary files /dev/null and b/src/.vuepress/public/assets/image/article/network/comparing-ipv4-and-ipv6-headers.png differ diff --git a/src/.vuepress/public/assets/image/article/network/ip.png b/src/.vuepress/public/assets/image/article/network/ip.png new file mode 100644 index 00000000..c170f244 Binary files /dev/null and b/src/.vuepress/public/assets/image/article/network/ip.png differ diff --git a/src/.vuepress/public/assets/image/article/network/ip_zh.png b/src/.vuepress/public/assets/image/article/network/ip_zh.png new file mode 100644 index 00000000..9701658d Binary files /dev/null and b/src/.vuepress/public/assets/image/article/network/ip_zh.png differ diff --git a/src/en/guide/concepts/network/2-ip.md b/src/en/guide/concepts/network/2-ip.md new file mode 100644 index 00000000..18da9d2f --- /dev/null +++ b/src/en/guide/concepts/network/2-ip.md @@ -0,0 +1,143 @@ +--- +order: 2 +title: "IP" +--- + +## IP + +IP (Internet Protocol) and TCP together form the TCP/IP protocol stack, which is one of the core protocols of the Internet. + +IP has the following characteristics: + +- **Stateless**: It does not store any state information, which means that IP packets can be unordered and duplicated. +- **Connectionless**: It does not require establishing a connection, and both the sender and receiver do not need to store information about each other. The destination IP address needs to be specified for each transmission. +- **Unreliable**: IP cannot guarantee that packets will always be delivered. They may be lost or discarded due to timeouts. + +### **IPv4** Structure + +![ipv4 header](/assets/image/article/network/ip.png) + +::: tip Field Descriptions + +| Field | Description | +| ---------------------------- | ----------------------------------------------------------------------------------------------------------------------------- | +| Version | Occupies 4 bits and is used to identify the version number of the IP header. The IPv4 version number is 4. | +| Header Length | Represents the size of the IP header, with a minimum value of 5 (5*4 = 20 bytes) and a maximum value of 15 (15*4 = 60 bytes). | +| Differentiated Services (DS) | Used to represent the type of service. It can be divided into DSCP and ECN (Explicit Congestion Notification). | +| Total Length | Represents the total number of bytes of the IP header and the data section combined. | +| Identification | Used for fragmentation and reassembly. This field is incremented by 1 for each generated datagram during fragmentation. | +| Flags | Represents the relevant information about packet fragmentation. | +| Fragment Offset | Used to identify the position of each segment being fragmented relative to the original data, in units of 8 bytes. | +| Time to Live (TTL) | Decreases by one for each router the packet passes through. When it reaches zero, the packet is discarded. | +| Protocol | The protocol used in the data section of the packet. | +| Header Checksum | Used to check if the packet is damaged. | +| Source Address | Represents the IP address of the sender. | +| Destination Address | Represents the IP address of the receiver. | +| Options | Additional information. | +| Data | The content of the transmitted data. | + + +::: + +::: details Version Number Corresponding to Digits + +| Version | Description | Status | +| ------- | ------------------------------------- | ---------- | +| 0 | Pre-Internet Protocol, before v4 | Reserved | +| 1–3 | Unassigned | | +| 4 | Internet Protocol version 4 (IPv4) | Active | +| 5 | Internet Stream Protocol or ST | Deprecated | +| 5 | Internet Stream Protocol or ST-II | Deprecated | +| 6 | Simple Internet Protocol (SIP) | Deprecated | +| 6 | Internet Protocol version 6 (IPv6) | Active | +| 7 | TP/IX Next Generation Internet (IPv7) | Deprecated | +| 8 | P Internet Protocol (PIP) | Deprecated | +| 9 | TCP and UDP Large Addresses (TUBA) | Deprecated | +| 10–14 | Unassigned | | +| 15 | Version field reserved value | Reserved | + +::: + +::: details Flags Description +This 3-bit field is used to control and identify fragmentation. They are: +| Bit | Description | +| --- | -------------------------- | +| 0 | Reserved, must be set to 0 | +| 1 | Don't Fragment (DF) | +| 2 | More Fragments (MF) | + +::: warning +- **If the DF flag is set to 1 but the route requires the packet to be fragmented, the packet will be discarded.** + +- **For fragmented packets, except for the last fragment, the MF flag is set to 1, and the fragment offset field of the last fragment is not 0.** +::: + +::: details Common IP Options + +- **Security Options**: Used to provide network security functions, such as data encryption, authentication, and access control. + +- **Record Route Option**: Enables the IP datagram to record the IP addresses of the routers it passes through in the transmission path, for diagnosing network problems or tracing the path of packets. + +- **Loose Source Routing**: Specifies the transmission path of the data packet, requiring the packet to pass through specified intermediate nodes, but allowing other nodes on the path to make certain choices. + +- **Strict Source Routing**: Specifies the transmission path of the data packet, requiring the packet to be delivered in the specified node order, and other nodes cannot participate. + +- **Timestamp Option**: Inserts timestamp information into the packet to measure the time required for the packet to be transmitted from the source to the destination. + +::: + +### Fragmentation + +::: tip MTU +Maximum Transmission Unit (MTU) refers to the maximum packet size (in bytes) that can be transmitted at the data link layer. +::: + +When an `IP` packet is transmitted over a link layer and the packet size exceeds the link layer's `MTU`, the packet needs to be fragmented. The length of each fragment must be less than or equal to the MTU minus the IP header length. + +::: important Fragmentation Process +Each fragmented data segment is placed in an independent IP datagram, and the corresponding fields in the datagram need to be modified: + +- Modify the total length field to the length of the current fragment. +- Except for the last fragment, set the More Fragments (MF) flag to 1. +- Adjust the fragment offset. +- Recalculate the checksum. + +::: + +::: details Example + +An IP datagram with a header length of `20` bytes and a data payload of `4000` bytes (total length: `4020` bytes) is transmitted over a link with an `MTU` of `2500` bytes. It will be divided into two fragments: + +| Total Length | Header | Data | More Fragments (MF)? | DF | Fragment Offset | +| ------------ | ------ | ---- | -------------------- | --- | --------------- | +| 2500 | 20 | 2480 | Yes | 0 | 0 | +| 1540 | 20 | 1520 | No | 0 | 310 (2480/8) | + +Similarly, when the MTU becomes smaller, the cut fragments will be further divided. + +::: + +### Reassembly + +::: tip How to Determine if Data is Fragmented? +- DF flag is 0 +- Fragment offset field is not 0 +::: + +The receiver collects the fragments and sorts them based on the offset. Once all the fragments are collected, they are reassembled and submitted to the upper protocol stack. + +### IPV6 + +![IPV6](/assets/image/article/network/comparing-ipv4-and-ipv6-headers.png) + +::: tip Differences between IPv4 and IPv6 + +| Feature | IPv4 | IPv6 | +| :--------------------------- | :--------------------------------------------- | :------------------------------------------------------------------------------------ | +| **Address Length** | 32 bits, providing about 4.3 billion addresses | 128 bits, providing a vast number of addresses | +| **Address Notation** | Dotted decimal notation, e.g., 192.168.0.1 | Colon hexadecimal notation, e.g., 2001:0db8:85a3:0000:0000:8a2e:0370:7334 | +| **Header Length** | Fixed, 20 bytes | Fixed, 40 bytes | +| **Quality of Service (QoS)** | Limited native support | Native support, including flow labels and flow priorities | +| **Security** | Requires the use of IPSec | Native support for IPSec | +| **Configuration** | Manual or DHCP | Manual, automatic (based on link-local addresses and router announcements), or DHCPv6 | +::: \ No newline at end of file diff --git a/src/en/guide/concepts/network/2-tcp-udp.md b/src/en/guide/concepts/network/3-tcp-udp.md similarity index 99% rename from src/en/guide/concepts/network/2-tcp-udp.md rename to src/en/guide/concepts/network/3-tcp-udp.md index 06001a27..12db2b37 100644 --- a/src/en/guide/concepts/network/2-tcp-udp.md +++ b/src/en/guide/concepts/network/3-tcp-udp.md @@ -1,5 +1,5 @@ --- -order: 2 +order: 3 title: "TCP/UDP" --- ### TCP diff --git a/src/guide/concepts/network/2-ip.md b/src/guide/concepts/network/2-ip.md new file mode 100644 index 00000000..e4951080 --- /dev/null +++ b/src/guide/concepts/network/2-ip.md @@ -0,0 +1,143 @@ +--- +order: 2 +title: "IP" +--- + +## IP + +IP (Internet Protocol) 协议和 TCP 组成的 TCP/IP 协议栈是互联网的核心协议之一。 + +IP 协议有以下特点： + +- **无状态**： 不储存状态信息，意味着 IP 协议传递的数据包可能是无序的、重复的。 +- **无连接**： 不需要建立连接，发送方和接收方都不需要存储对方的信息，每次发送都需要指定目标的 IP 地址。 +- **不可靠**： IP 协议不能保证数据包一定能送达，可能会丢包，或者因超时而被丢弃。 + +### **IPV4** 结构 + +![ipv4 header](/assets/image/article/network/ip_zh.png) + +::: tip 字段介绍 + +| 字段 | 描述 | +| ------------- | -------------------------------------------------------------------------- | +| 版本 | 占用 4 bit，用来标识 IP 首部的版本号。IPv4 版本号是 4 | +| 首部长度 | 表示 IP 首部的大小，最小值为5 (5*4 = 20 byte)，最大值为 15 (15*4 = 60byte) | +| 区分服务(DS) | 用来表示服务的类型。可划分为 DSCP 和 ECN (显式拥塞通告) | +| 总长度 | 表示的是 IP 首部与数据部分合起来的总字节数 | +| 标识 | 用于分片重组，分片时每产生一个数报文该字段就加1 | +| 标志 | 表示包被分片的相关信息 | +| 片偏移 | 用来标识被分片的每一个分段相对于原始数据的位置，单位为 **8** 字节 | +| 生存时间(TTL) | 每经过一个路由器该字段就会减一，当为零的时候会被丢弃 | +| 协议 | 该报文数据区使用的协议 | +| 首部校验和 | 用于检测报文是否损坏 | +| 源地址 | 表示发送端的 IP 地址 | +| 目标地址 | 表示接收端的 IP 地址 | +| 选项 | 附加的信息 | +| 数据 | 传输的数据内容 | + + +::: + +::: details 版本对应数字列表 + +| 版本 | 描述 | 状态 | +| ----- | ------------------------- | ---- | +| 0 | 互联网协议，v4 之前 | 保留 | +| 1–3 | 未分配 | | +| 4 | 互联网协议版本 4 (IPv4) | 活跃 | +| 5 | 互联网流协议或 ST | 废弃 | +| 5 | 互联网流协议或 ST-II | 废弃 | +| 6 | 简单互联网协议 (SIP) | 废弃 | +| 6 | 互联网协议版本 6 (IPv6) | 活跃 | +| 7 | TP/IX 下一代互联网 (IPv7) | 废弃 | +| 8 | P 互联网协议 (PIP) | 废弃 | +| 9 | TCP 和 UDP 大地址 (TUBA) | 废弃 | +| 10–14 | 未分配 | | +| 15 | 版本字段标记值 | 保留 | + +::: + +::: details 标志 (Flags) 介绍 +这个3位字段用于控制和识别分片，它们是： +| 位 | 描述 | +| --- | ------------------------------ | +| 0 | 保留，必须为0 | +| 1 | 禁止分片（Don’t Fragment，DF） | +| 2 | 更多分片（More Fragment，MF） | + +::: warning +- **如果DF标志位被设置为1，但路由要求必须分片报文，则此报文会被丢弃。** + +- **被分片的报文除了最后一个分片以外其他分片的 MF 标志位都为 1，且最后一个分片的分片偏移字段不为 0** +::: + +::: details 常见的 IP 选项有哪些？ + +- **安全性选项（Security Options）**：用于提供网络安全功能，例如数据加密、身份验证和访问控制。 + +- **记录路由选项（Record Route Option）**：启用IP数据报在传输路径上记录途经的路由器的IP地址，以便诊断网络问题或跟踪数据包的路径。 + +- **宽松源站选路（Loose Source Routing）**：指定数据包的传输路径，要求数据包经过指定的中间节点，但允许在路径上的其他节点进行一定的选择。 + +- **严格源站选路（Strict Source Routing）**：指定数据包的传输路径，要求数据包必须按照指定的节点顺序传递，其他节点不能参与。 + +- **时间戳选项（Timestamp Option）**：在数据包中插入时间戳信息，用于测量数据包从源到目的地传输所需的时间。 + +::: + +### 分片 + +::: tip MTU +最大传输单元 (MTU, Maximum Transmission Unit) 指的是在数据链路层能通过的最大数据包大小（单位： 字节）。 +::: + +当 `IP` 数据包在链路层传输的时候，若数据包大于链路层的 `MTU`， 则需要对数据包进行分片。分片的长度需小于等于 MTU 减去 IP 首部长度。 + +::: important 分片过程 +分片后的每一个数据分片都会放到独立的 IP 报文中，报文中的对应字段需要进行修改： + +- 修改总长字段为此时分片的长度 +- 除了最后一片分片外，其他分片的更多分片（MF）标志位被设置为 1 +- 调整分片偏移量 +- 重新计算校验和 + +::: + +::: details 例子 + +一个IP报文首部长度 `20` 字节且有 `4000` 字节的数据载荷（总长：`4020` 字节），在 `MTU` 为 `2500` 字节的链路上传输，他将被分割成两个分片： + +| 总长 | 首部 | 数据 | 更多分片（MF）？ | DF | 分片偏移量 | +| ---- | ---- | ---- | ---------------- | --- | ---------------- | +| 2500 | 20 | 2480 | 是 | 0 | 0 | +| 1540 | 20 | 1520 | 否 | 0 | 310 （2480/8） | + +同理，切割后的分片在 MTU 变小时会被再次切割。 + +::: + +### 重组 + +::: tip 如何判断数据已被分片? +- DF 标志位为 0 +- 分片偏移字段不为 0 +::: + +接收者会将分片收集起来，并通过偏移量进行排序，一旦收集齐就会组装起来提交给上传协议栈。 + +### IPV6 + +![IPV6](/assets/image/article/network/comparing-ipv4-and-ipv6-headers.png) + +::: tip IPV4 和 IPV6 区别 + +| 特性 | IPv4 | IPv6 | +| :------------------ | :---------------------------------- | :---------------------------------------------------------------- | +| **地址长度** | 32位，提供约43亿个地址 | 128位，提供极大数量的地址 | +| **地址表示** | 点分十进制表示法，例如：192.168.0.1 | 冒号十六进制表示法，例如：2001:0db8:85a3:0000:0000:8a2e:0370:7334 | +| **头部长度** | 固定，20字节 | 固定，40字节 | +| **服务质量（QoS）** | 原生支持有限 | 原生支持，包括流标签和流优先级 | +| **安全性** | 需要使用 IPSec | 原生支持 IPSec | +| **配置** | 手动或 DHCP | 手动，自动（基于链接的本地地址和路由公告）或 DHCPv6 | +::: \ No newline at end of file diff --git a/src/guide/concepts/network/2-tcp-udp.md b/src/guide/concepts/network/3-tcp-udp.md similarity index 99% rename from src/guide/concepts/network/2-tcp-udp.md rename to src/guide/concepts/network/3-tcp-udp.md index 0eb6717b..1178b6f7 100644 --- a/src/guide/concepts/network/2-tcp-udp.md +++ b/src/guide/concepts/network/3-tcp-udp.md @@ -1,5 +1,5 @@ --- -order: 2 +order: 3 title: "TCP/UDP" ---