在安裝好ion環境後，要開啟ION應用程式並通過DTN協議棧傳輸資料，最重要的就是通過ionstart命令配置rc檔案來配置應用程式的環境，

一般而言，ionstart開啟rc檔案的命令如下：

ionstart -I host1.rc

其中host1.rc就是rc檔名，要注意的是，在終端輸入ionstart命令，當前路徑必須是rc檔案所在路徑。

接下來具體分析rc檔案的組成：

首先給出一份rc檔案：

在分析之前，要知道一點：以單個“#”開頭的行表示註釋以方便了解相應配置所起的作用,而以兩個“##”開頭的行即表示此行為註釋號,同時也起到識別不同管理程序的作用,如ionadmin, ionsecadmin, ltpadmin, bpadmin, ipnadmin。

host1.rc

## begin ionadmin
# ionrc configuration file for host3 in a 3node ltp test.
#This uses ltp as the convergence layer.
#command: % ionadmin host3.ionrc
#This command should be run FIRST.
#
#Soochow University, April 2012
# Initialization command (command 3).
#Set this node to be node 3 (as in ipn:3).
#Use sdr configuration of “ionconfig” file.

1 1 ionconfig
# start ion node
s
# Add some contacts.
#They will start at +0 seconds from now, ending +86400 seconds from now.
#They will connect node 1 to node 2, and connect node 2 to node 3.
#They will transmit 125000 bytes/second.
#Note that contacts are unidirectional, so order matters.

a contact +0 +86400 1 2 125000
a contact +0 +86400 2 1 125000

# Add some ranges. These are the physical distance between nodes.
#They will start at +0 seconds from now, ending +86400 seconds from now.
#They will connect node 1 to node 2, and connect node 2 to node 3.
#We will assume every range is one second. Data on the link is expected to take 1 second
#to reach the other end (One Way Light Time).
#Note that ranges cover both directions, so you only need define one range for any
#combination of nodes.

a range +0 +86400 1 2 1

# set this node to consume and produce a mean of 1000000 bytes/second.

m production 1000000
m consumption 1000000
m horizon +0
## end ionadmin
## begin ionsecadmin

1
e 1
## end ionsecadmin
## begin ltpadmin
# ltprc configuration file for host1 in a 3node ltp test.
#Command: % ltpadmin host3.ltprc
#This command should be run AFTER ionadmin and BEFORE bpadmin.
#
#Soochow University, April 2012
#
#A warning: the ltp configuration is not ideal in this case.
#please consult manual pages and other documentation for a better description.
# Initialization command (command 1).
# Establishes the LTP retransmission window.
# (Prohibiting LTP from seizing all available storage).
#A maximum of 5 sessions. A session is assumed to be around one second of
#transmission. This value should be estimated at the sum of maximum round-trip
#times(in seconds) for all "spans." Suggest throwing 20% higher number of sessions
#to account for extra- long sessions which contain an actual retransmission. Set a total
#LTP memory space usage limit of 1200000 as the sum of the memory space usage of
#all spans (more or less the number of bytes in transit on all links for their duration).

1 5 1200000
# Add a span. (a connection)
#Identify the span as engine number 2. That is the ipn node number of the node on
#the other end of this span. Use 5 as the maximum number of export sessions.
#Use 120000 as the maximum size of an export block. This more or less limits the
#maximum size of a bundle in the system. The next two items are the maximum
#number of import sessions and the maximum size of an imported block.
#Since this is connect, we just copy the export numbers here.
#1400 is the maximum segment size- more or less, the amount of data that can be
#held in a single frame of the underlying protocol. In this case, UDP packets are
#the frame, and we will give a conservative limit.
#Limit the aggregation size to 120000 bytes, and set a time limit on aggregation to 1
#second. Use the command 'udplso 10.0.0.4:1113' to implement the link itself.
#In this case, we use udp to connect to host2 (10.0.0.4 is host2's ipaddr) using port 1113
#(defined by IANA as the default UDP port for Licklider Transmission Protocol).
#The single quote is important, don't use double quotes.
a span 2 5 120000 5 120000 1400 120000 1 'udplso 10.0.0.4:1113'
# Start command.
#This command actually runs the link service output commands
#(defined above, in the "a span" commands).
#Also starts the link service INPUT task 'udplsi 10.0.0.5:1113' to
#listen locally on UDP port 1113 for incoming LTP traffic.
s 'udplsi 10.0.0.3:1113'
m screening n
w 1
## end ltpadmin
## begin bpadmin
# bprc configuration file for host3 in a 3node ltp test.
#Command: % bpadmin host3.bprc
#This command should be run AFTER ionadmin and ltpadmin and
#BEFORE ipnadmin or dtnadmin.
#
#Soochow University, April 2012
# Initialization command (command 1).

1

# Add an EID scheme.
#The scheme's name is ipn.
#This scheme's forwarding engine is handled by the program 'ipnfw.'
#This scheme's administration program (acting as the custodian daemon) is 'ipnadminep.'

a scheme ipn 'ipnfw' 'ipnadminep'

# Add endpoints.
#Establish endpoints ipn:3.1 and ipn:3.2 on the local node.
#The behavior for receiving a bundle when there is no application currently accepting
#bundles, is to queue them 'q', as opposed to immediately and silently discarding
#them (use 'x' instead of 'q' to discard).
#Note that the custodian endpoint ipn:3.0 is automatically generated.
a endpoint ipn:1.0 q
a endpoint ipn:1.1 q
a endpoint ipn:1.2 q
# Add a protocol.
#Add the protocol named ltp.
#Estimate transmission capacity assuming 1400 bytes of each frame (in this case, udp
#on ethernet) for payload, and 100 bytes for overhead.
a protocol ltp 1400 100
# Add an induct. (listen)
#Add an induct to accept bundles using the ltp protocol.
#The duct's name is 3 (this is for future changing/deletion of the induct).
#The induct itself is implemented by the 'ltpcli' command.
a induct ltp 1 ltpcli
# Add an outduct. (send to host2)
#Add an outduct to send bundles using the ltp protocol.
#The duct's name is 2(this is for future changing/deletion of the outduct).
#The outduct itself is implemented by the 'ltpclo' command.
a outduct ltp 2 ltpclo
#Start bundle protocol engine, also running all of the induct, outduct, and
#administration programs defined above
s
#w 1
## end bpadmin
## begin ipnadmin
# ipnrc configuration file for host3 in a 3node ltp test.
#Essentially, this is the IPN scheme's routing table.
#Command: % ipnadmin host1.ipnrc
#This command should be run AFTER bpadmin (likely to be run last).
#
#Soochow University, April 2012
# Add an egress plan.
#Bundles to be transmitted to element number 2 can be transmitted directly to host2
#using ltp outduct identified as ‘2.’
#See your bprc file or bpadmin for outducts/protocols you can use.
a plan 2 ltp/2
## end ipnadmin
 

接下來分段分析：

1 2 ionconfig

這行命令是選取ionconfig配置檔案，該檔案主要是指定了ion執行的記憶體空間，1代表是命令1 ，2代表是節點2，也就是如果你是為了節點1配置rc檔案，那麼這裡應該改成1 1 ionconfig，要注意的是，這裡ionconfig檔案應該和rc檔案在同一路徑下。

# start ion node
s

該行命令無需多解釋

a contact +0 +86400 1 2 125000
a contact +0 +86400 2 1 125000

這兩行命令是新增傳輸的時間和節點，傳輸將從0s開始，結束於86400s，將連線從節點1到節點2，傳輸速度是125000 bytes/second

a range +0 +86400 1 2 1
 

新增一些範圍。 這些是節點之間的物理距離，連線節點1到節點2，我們假設這些節點之間的距離時間為1s，也就是說資料從節點1到節點2要花費1s時間，由於range包含了雙向，因此只需要定義一個range即可。

m production 1000000
m consumption 1000000
m horizon +0

設定該節點消耗和生產的均值為1000000 bytes/second

1
e 1

不多解釋

a protocol ltp 1400 100

1 5 1200000

1表示命令1，5表示會話程序最大值為5，1200000（單位byte）表示LTP記憶體空間的使用上限，，也就是所有span的使用記憶體空間總和。

a span 2 5 120000 5 120000 1400 120000 1 'udplso 10.0.0.4:1113'
 

新增一個span也就是一個連線，2表示連線另一端的節點號碼，5表示最大數目的輸出會話程序，120000是最大的輸出塊尺寸，後面的5和120000表示輸入的最大數目會話程序和最大塊尺寸，這裡設定和輸出一樣。1400是segment的尺寸，也就是1400byte資料在一個幀中，比如udp包，120000是限制聚合層大小，並設定聚合層時間為1s，命令'udplso 10.0.0.4:1113‘是設定連線本身性質，在這個rc檔案中，利用udp連線host2（ip地址：10.0.0.4）埠1113。

s 'udplsi 10.0.0.3:1113'
m screening n
w 1

這裡設定input task。用udp埠1113進行監聽，本節點地址為10.0.0.3。

m screening n 此命令啟用或禁用接收的LTP的篩選，n表示禁用。預設是禁用。

a scheme ipn 'ipnfw' 'ipnadminep'

不做解釋

a endpoint ipn:1.0 q
a endpoint ipn:1.1 q
a endpoint ipn:1.2 q

新增終端節點，ipn:1.0 1表示本節點的number，0表示service number，servicenumber 類似於埠號之類的，每個number提供一個服務，q表示對於每一個接收到的bundle進行排隊，而x表示立即丟棄這個bundle，也就是a endpoint ipn:1.0 q 改成a endpoint ipn:1.0 x，常用在loopback測試中。

a protocol ltp 1400 100

新增ltp協議，每個frame有1400bytes資料，100個位元組的開銷。

a induct ltp 1 ltpcli

新增監聽induct，duct的名字為1

a outduct ltp 2 ltpclo

添加發送outduct，duct名字為2

s

開始bundle 協議，開啟所有的induct和outduct。

a plan 2 ltp/2

新增輸出計劃，也就是bundle要傳輸到node number為2的節點，使用標識為“2”的ltp輸出。

以上就是對rc檔案的分析，可以說正確的配置好rc檔案那麼ion就成功了一半，那麼rc檔案中，有幾個需要注意的地方，

比如bp的啟動命令

s，很多情況下由於並不顯眼，可能會漏寫該命令，會直接導致bp層執行失敗。本人就曾經因為漏了s命令，調了一天的bug。

還有就是ltp協議的兩個主要引數，block和session。也就是這條命令：a span 1 5 120000 5 120000 1400 120000 1 'udplso 10.0.0.3:1113'

Block 的尺寸決定著一次會話最多可以傳輸多少資料(以位元組為單位)。會話的量(或數目)決定著同時最多可以進行多少個會話。Block 的實際尺寸與通道的速率( Channel rate )決定了傳輸 Block 所需的時間。