Major functions:
- Tracking the individual communication between applications on the source and destination hosts. //Khoi tao duy tri va giam sat cac ket noi rieng biet
- Segmenting data and managing each piece. //Chia nho du lieu thanh cac phan (Phan lon cac du lieu se duoc chia nho)
Du lieu duoc chia tai tang 7: VoIP, Video, DNS
Du lieu khong duoc chia tai tang 7: Mail, Web, FTP, Telnet
->Chia nho du lieu de truyen duoc du lieu cua nhieu loai ung dung khac nhau + Multiplexing (+nhanh hon, truyen lai phan du lieu bi loi …) - Reassembling the segments into streams of application data. //Lap rap lai du lieu
- Identifying the different applications. //Nhan dang va phan biet cac loai ung dung khac nhau bang cach nhan dang Port Number
Controlling the Conversation:
- Establishing a Connection // Khoi tao 1 ket noi
- Reliable delivery//Ho tro truyen tin cay
- Same order delivery//Den dich tuan tu
- Flow Control //Dieu khien luong – tin hieu thong nhat giua ben luong va ben dich (tang giam kich thuoc khoi luong truyen tranh tran bo nho)
TCP Header format:
- Source port //Cong nguon
- Destination port //Cong dich
- Sequence number //So thu tu
- Acknowledgement number
- Hlen (Header Length)
- Reserved //Du phong
- Code bits //Co nhu ACK, FIN
- Window //Kich thuoc se cho biet ben nguon duoc truyen bao nhieu du lieu de ben dich co the xu ly
- Checksum //Kiem tra tinh toan ven cua goi tin
- Urgent pointer //Ket hop voi co Urgen se chi vao cho du lieu can duoc uu tien xu ly truoc
- Option (if any) //Noi chua cac thong so cac cau hinh them
- Padding //Don them cac bit thieu cua Option de du 32 bit
UDP Header format
- Source Port
- Destination Port
- Length
- Checksum
Port number = 2^16 = 65536 = 0->65535
- 0->1023 //Cac ung dung pho bien hay duoc dung tren mang
- 1024->49151 //Dung cho phep cac nha phat trien dich vu ung dung
- 49152->65535 //Random cho truong Source port
TCP and UDP port number
- FTP 21-TCP
- Telnet 23-TCP
- SMTP 25-TCP
- DNS 53-TCP/UDP //DNS cung ca 2 TCP va UDP
Khi query & reply thi dung UDP (vi toc do nhanh)
Khi cau hinh DNS Server can bao mat an toan va chac chan thi dung TCP - TFTP 69
- SNMP 161
- RIP 520
Datagram //Du lieu duoc chia o tang 7
Segment //Du lieu duoc chia o tang 4
IP + Port = Socket/Proxy //Dai dien tao nen 1 connection
3 way hand shake
Truyen lai het: Go back N
Thoi gian truyen lai: Time out, xac dinh = thoi gian dua tren thiet lap ket noi bat tay 3 buoc
