[docs]:effective-gas-price

[krlosMata]

Effective Gas Price (EGP)

Motivation

• Add a mechanism to compute and charge L1 data-availability costs in L2 transactions
• The user signs a gasPrice (provided by the RPC) which must cover the L1 data-availability and L2 execution costs
• Mechanism will charge the user fair gasPrice to cover above costs
• Therefore, a reduction in the user signed gasPrice will be applied

Specification

• Single byte [0 - 255] to indicate reduction in the gasPrice by a percentage

Formula

effectiveGasPrice = Floor((signedGasPrice * (effectivePercentage + 1)) / 256)

where:

• effectiveGasPRice: the gas price applied when executing the transaction
• signedGasPrice: gas price signed by the user
• effectivePercentage: percenttage index to apply that specifies the reduction

Table

note that no reduction is achieved with 0xff byte. Therefore, effectiveGasPRice = signedGasPrice

index	Reduction applied (%)
0	99.61
1	99.22
2	98.83
3	98.44
4	98.05
5	97.66
6	97.27
7	96.88
8	96.48
9	96.09
10	95.70
11	95.31
12	94.92
13	94.53
14	94.14
15	93.75
16	93.36
17	92.97
18	92.58
19	92.19
20	91.80
21	91.41
22	91.02
23	90.63
24	90.23
25	89.84
26	89.45
27	89.06
28	88.67
29	88.28
30	87.89
31	87.50
32	87.11
33	86.72
34	86.33
35	85.94
36	85.55
37	85.16
38	84.77
39	84.38
40	83.98
41	83.59
42	83.20
43	82.81
44	82.42
45	82.03
46	81.64
47	81.25
48	80.86
49	80.47
50	80.08
51	79.69
52	79.30
53	78.91
54	78.52
55	78.13
56	77.73
57	77.34
58	76.95
59	76.56
60	76.17
61	75.78
62	75.39
63	75.00
64	74.61
65	74.22
66	73.83
67	73.44
68	73.05
69	72.66
70	72.27
71	71.88
72	71.48
73	71.09
74	70.70
75	70.31
76	69.92
77	69.53
78	69.14
79	68.75
80	68.36
81	67.97
82	67.58
83	67.19
84	66.80
85	66.41
86	66.02
87	65.63
88	65.23
89	64.84
90	64.45
91	64.06
92	63.67
93	63.28
94	62.89
95	62.50
96	62.11
97	61.72
98	61.33
99	60.94
100	60.55
101	60.16
102	59.77
103	59.38
104	58.98
105	58.59
106	58.20
107	57.81
108	57.42
109	57.03
110	56.64
111	56.25
112	55.86
113	55.47
114	55.08
115	54.69
116	54.30
117	53.91
118	53.52
119	53.13
120	52.73
121	52.34
122	51.95
123	51.56
124	51.17
125	50.78
126	50.39
127	50.00
128	49.61
129	49.22
130	48.83
131	48.44
132	48.05
133	47.66
134	47.27
135	46.88
136	46.48
137	46.09
138	45.70
139	45.31
140	44.92
141	44.53
142	44.14
143	43.75
144	43.36
145	42.97
146	42.58
147	42.19
148	41.80
149	41.41
150	41.02
151	40.63
152	40.23
153	39.84
154	39.45
155	39.06
156	38.67
157	38.28
158	37.89
159	37.50
160	37.11
161	36.72
162	36.33
163	35.94
164	35.55
165	35.16
166	34.77
167	34.38
168	33.98
169	33.59
170	33.20
171	32.81
172	32.42
173	32.03
174	31.64
175	31.25
176	30.86
177	30.47
178	30.08
179	29.69
180	29.30
181	28.91
182	28.52
183	28.13
184	27.73
185	27.34
186	26.95
187	26.56
188	26.17
189	25.78
190	25.39
191	25.00
192	24.61
193	24.22
194	23.83
195	23.44
196	23.05
197	22.66
198	22.27
199	21.88
200	21.48
201	21.09
202	20.70
203	20.31
204	19.92
205	19.53
206	19.14
207	18.75
208	18.36
209	17.97
210	17.58
211	17.19
212	16.80
213	16.41
214	16.02
215	15.63
216	15.23
217	14.84
218	14.45
219	14.06
220	13.67
221	13.28
222	12.89
223	12.50
224	12.11
225	11.72
226	11.33
227	10.94
228	10.55
229	10.16
230	9.77
231	9.38
232	8.98
233	8.59
234	8.20
235	7.81
236	7.42
237	7.03
238	6.64
239	6.25
240	5.86
241	5.47
242	5.08
243	4.69
244	4.30
245	3.91
246	3.52
247	3.13
248	2.73
249	2.34
250	1.95
251	1.56
252	1.17
253	0.78
254	0.39
255	0.00

Examples

• transaction bytes: rlp(nonce, gasprice, gaslimit, to, value, data, chainId, 0, 0) # r # s # v # effectivePercentage
• assumptions:
  • simplified calldata cost: 16 GAS each byte
  • L1GasPrice = 100 Gwei

Ethereum transfer

• summary table

Bytes L1 DATA	Cost ETH L1 Data	gas used	fair gasPrice	priceSigned	Redution to apply	effectiveGasPrice
113	0.0001808	21000	8.6 GWei	15 Gwei	42.97 %	8.55 GWei

• operations
  • transaction bytes: 113 bytes
  • transaction gas used: 21000 GAS
  • simplified breakeven gas price
    • data-availability costs: 16 GAS/byte * 113 bytes * L1GasPrice = 1808 GAS * 100 Gwei = 0.0001808 ether
    • fairGasPrice = 0.0001808 ether / 21000 = 8.6 Gwei
  • assumption: the user has signed a signedGasPrice = 15 GWei
  • Sequencer compute effectiveGasPercentage to reduce gasPrice applied from 15 Gwei to 8.6 Gwei
    • percentage = (8.6 GWei / 15 gWei) * 100 = 56.66 %
      • reduction applied = 100 - 56.66 = 43.34 %
    • sequencer select the closest percentage from the table --> select an effectivePercentage = 145 which correspond to a 42.97 % reduction
    • compute final gas price to apply to the transaction: effectiveGasPrice = Floor((15 gWei * (145 + 1)) / 256) = 8.55 GWei