In this assignment, you will build a simple reliable transport protocol, RTP, on top of UDP
RTP sends data in the format of a header, followed by a chunk of data. RTP has four header types: ST ART, END, DAT A, and ACK, all following the same format:
typedef s t r u c t RTP_header {
uint8_t type ; // 0 : START; 1 : END; 2 : DATA; 3 : ACK
uint16_t length ; // Length of data ; 0 for ACK, START and END packets
uint32_t seq_num ;
uint32_t checksum ; // 32−b i t CRC
} rtp_header_t ;
- Establish connection. To initiate a connection, sender starts with a ST ART mes�sage along with a random seq_num value, and wait for an ACK for this ST ART message.
- Data transmission. After establishing the connection, additional packets in the same connection are sent using the DAT A message type, adjusting seq_num appropriately. sender will use 0 as the initial sequence number for data packets in that connection.
- Terminate connection. After everything has been transferred, the connection should be terminated with sender sending an END message, and waiting for the correspond�ing ACK for this message.
- ACK for START & END. The ACK seq_num values for ST ART and END messages should both be set to whatever the seq_num values are that were sent by sender.
- Packet Size. An important limitation is the maximum size of your packets. The UDP protocol has an 8 byte header, and the IP protocol underneath it has a header of 20 bytes. Because we will be using Ethernet networks, which have a maximum frame size of 1500 bytes, this leaves 1472 bytes for your entire packet structure (including both the header and the chunk of data)
sender should be invoked as follows:
. / sender [ Receiver IP ] [ Receiver Port ] [ Window Size ] [ Message ]
receiver should be invoked as follows:
. / receiver [ Receiver Port ] [ Window Size ] [ File Name]
- receiver will not send cumulative ACKs anymore; instead, it will send back an ACK with seq_num set to whatever it was in the data packet (i.e., if a sender sends a data packet with seq_num set to 2, receiver will also send back an ACK with seq_num set to 2). It should still drop all packets with seq_num greater than or equal to N+ window_size, where N is the next expected seq_num.
- sender must maintain information about all the ACKs it has received in its current window. In this way, packet 0 having a timeout would not necessarily result in a retransmission of packets 1 and 2.
In this assignment, you will implement the distance vector routing protocol.
The router location file maps a unique router ID to a router process. Each router is
defined by a 3-tuple:<router IP,router port,router id>
Each router is assigned a unique identifier router id. It runs on IP router IP,
and listens on port router port for two pieces of information: (i) commands from the
agent and (ii) messages from other routers.
The topology configuration file specifies the router topology. Here, the distance between
two neighboring routers is unidirectional, i.e., the distance from router 1 to router 2 may
be different from the distance from router 2 to router 1. The topology configuration
file is a text file composed of a number of topology tuples. The format of a topology
tuple is shown below:<RouterID1,RouterID2,weight>
.router <router location file> <topology conf file> <router id>
| Name | Example of commands | Description |
|---|---|---|
| dv | dv | All routers are triggered to propagate dis�tance vectors to neighboring routers until |
| the link costs become stable | ||
| update | update:1,6,4 | Change the link weight of link (1,6) to 4. If |
| the link weight is -1, then it means that the | ||
| link is deleted. If the link is absent before, | ||
| then it means that the link is added with | ||
| the update command | ||
| show | show:2 | Display the routing table of router 2. |
| reset | reset:2 | Reset the number of distance vectors of |
| router 2 to zero. This helps us easily de�bug your assignment |
.agent <router location file>
- Messages between the agent and a router.
- Messages between two routers