S1 C5 OSI Network Layer

Network layer use 4 basic process:

  • Addressing//Gan dia chi
  • Encapsulation//Dong goi
  • Routing //Tim duong di den dich dua tren dia chi
  • Decapsulation //

Network Layer Protocols:

  • Internet Protocol version 4 (IPv4)
  • Internet Protocol versionn 6 (IPv6)
  • Novell Internetwork Packet Exchange (IPX)
  • Apple Talk
  • Connectionless Network Service (CLNS/DECNet)

Basic characteristics:

  • Connectionless //Phi ket noi (giong UDP
  • Best Effort//Khong tin cay, khong can truyen lai
    an unreliable protocol, does not have the capability to manage, and recover from, undelivered or corrupt packets.
  • Media Independent//Doc lap voi moi truong truyen phia duoi-moi truong nao cung hoat dong va giu nguyen dinh dang, cau truc goi tin va du lieu
    Thay doi khi truyen tu Private IP<->Public IP
    Thay doi khi MTU # nhau

IPv4 Header

  • Ver //Cho biet v4 hay 6
  • IHL //Do dai
  • Service Type //Xac dinh kieu dich vu (QoS)
  • Packet Length //Do dai cua ca Packet (H4+Data)
  • Identification //Xac dinh mieng nho du lieu da chia thuoc goi nao ban dau
  • Flag //co 3 bit
    R: reserved
    DF: cho biet goi tin co fragment ko
    MF: cho biet mieng day co phai mieng cuoi cung hay chua
  • Fragment Offset //Cho biet vi tri cua mieng nho du lieu trong goi tin ban dau
  • Time to Live //So luong tram trung gian dc phep di qua cua goi tin. -1 di qua 1 tram. Den 0 thi huy.
    Windows 128, Unix 255, Linux 64
  • Protocol //Giao thuc cua lop =4 hoac 6
  • Header Checksum //Kiem tra tinh toan ven
  • Source Address //IP nguon
  • Destination Address //IP Dich
  • Options //Truong cau hinh them
  • Padding //Phan bu cua Option boi cua 32 bit

Segmenting //Chia nho du lieu o tang 4
Fragmenting //Chia nho goi tin o tang 3

Nmap zenmap

Group Devices

  • De quan ly
  • De bao mat
  • De gan dia chi IP cho de hon
  • Dua vao vi tri dia ly
  • Muc dich
  • Quyen han nguoi dung & may tinh
  • Tranh xung dot khi gui nhieu ban tin Broadcast

Routing Metrics //Chi phi cua tuyen duong

Routed protocol:

Routing protocol: giao thuc cai tren router giup xac dinh duong di

Gateway: Dia chi cua router ma la noi cac goi tin trong 1 he thong mang di qua de sang mang khac. 1 mang co the co nhieu Gateway

Default Gateway: Gateway dc chi dinh duoc di ra

Next hop address: dia chi cua router tiep theo tren tuyen duong toi dich

Exit interface (out going interface): la cong de day goi tin ra //interface la cong cua router

Direct connected C

Static S

Dynamic D

Default route: la tuyen duong dung cho moi dich, thuong su dung khi o noi chi co 1 tuyen duong de di ra